Talks
Kepler-1656b’s Eccentricity: Signature of a Gentle Giant – Isabel Angelo
Highly eccentric orbits are one of the major surprises of exoplanets relative to the Solar System and indicate rich and tumultuous dynamical histories. One system of particular interest is Kepler-1656, which hosts a sub-Jovian planet with an eccentricity of 0.8. Sufficiently eccentric orbits will shrink in semi-major axis due to tidal dissipation of orbital energy during periastron passage. Here our goal was to assess whether Kepler-1656b is currently undergoing such high-eccentricity migration, and to further understand the system’s origins and architecture. We confirm a second planet in the system with Mc =0.40±0.09Mjup and Pc =1919±27 days. We simulated the dynamical evolution of planet b in the presence of planet c and find a variety of possible outcomes for the system, such as tidal migration and engulfment. The system is consistent with an in situ dynamical origin of planet b followed by subsequent Eccentric Kozai Lidov (EKL) perturbations that excite Kepler-1656b’s eccentricity gently, i.e. without initiating tidal migration. Thus, despite its high eccentricity, we find no evidence that planet b is or has migrated through the high-eccentricity channel. Finally, we predict the outer orbit to be mutually inclined in a nearly perpendicular configuration with respect to the inner planet orbit based on the outcomes of our simulations, and make observable predictions for the inner planet’s spin- orbit angle. Our methodology can be applied to other eccentric or tidally locked planets to constrain their origins, orbital configurations and properties of a potential companion.
An Exploration of Constraining Chemistry in Three-Dimensional Eclipse Mapping – Lucas Brefka
Eclipse mapping is a useful tool for understanding the composition, temperature, and dynamics of the atmospheres of transiting extrasolar planets, by measuring the flux emitted by the planet as it passes behind its star, subsequently mapping its temperature as a function of longitude and latitude. The open source Three-dimensional Exoplanet Retrieval from Eclipse Spectroscopy of Atmospheres (ThERESA) code utilizes these spectral observations, building two-dimensional maps at individual wavelengths, stacking and interpolating them to create a fully three-dimensional temperature-pressure model of the atmosphere. In this work, we relax many of ThERESA’s simplifying assumptions and allow for metallicity and other individual atomic abundance ratios to vary, accounting for thermal disequilibrium in the process. We expect true planetary atmospheres to be in disequilibrium, existing with varying compositions and complexities; this work is thus a step toward more robust exoplanet atmospheric characterization, and will be a powerful tool for studying observations from JWST in the near future, as well as planning observations for exoplanet characterization.
Kepler’s Greatest Hits: Revising Occurrence Rate Benchmarks – Anne Dattilo
We present exoplanet occurrence rates for planets between 0.4-22 Re and between 1-500 days. We apply a non-parametric method via a kernel density estimator to measure occurrence and use Monte Carlo methods for uncertainty estimation. We use a full characterization of completeness and reliability measurements from the Kepler DR25 catalog, including detection efficiency, vetting completeness, astrophysical- and false alarm reliability. We also include more accurate and homogeneous stellar radii from Gaia DR2. We revisit benchmark exoplanet occurrence rate measurements from the literature. Because these benchmarks were calculated on intermediate or independent catalogs, our comparison both tests the method and identifies the differences in measurement values due to the different catalogs. We examine occurrence dependencies on planet radius and orbital period, and reproduce benchmarks within one-sigma confidence for all literature values, except for measurements below 1.3 Re. We then explore the shape of the occurrence cliff (2.5- 4 Re) in period-radius space and perform preliminary photoevaporation models to explain the structure. Input distributions used to replicate the radius valley can replicate the structure of the occurrence cliff marginalized over orbital period but cannot replicate the full structure in the period-radius plane, exemplifying the need to retain the 2D shape information. Future work will incorporate full Bayesian inference population inference.
Examining Planet-Star Interactions in HAT-P-2 b to Understand Stellar Pulsations and Hot Jupiters’ Migration – Zoe de Beurs
The role of planet-star interactions in stellar pulsations and in the inward migration of Hot Jupiters is not well understood. One possible migration mechanism proposed is that high-eccentricity gas giants experience tidal interactions with their host star that cause them to lose orbital energy and migrate to a close-in orbit. Here, we study these types of tidal interactions in an eccentric Hot Jupiter called HAT-P-2 b, which is the first system where planet-induced tidal pulsations in a host star were measured and a trend in orbital parameters was found. An additional three years of RV measurements were taken by the California Planet Search (CPS) team on HIRES and 10 new transits of HAT-P-2b have also been observed with TESS. In this talk, we will discuss our pipeline that has confirmed a rapid change argument of periastron (ω) and eccentricity (e) from the CPS observations. These orbital parameter changes are significantly larger than what would be expected from general relativity alone and this rapid orbital evolution could be explained by tidal planet-star interactions. Thus, we will also discuss our models of the tidal pulsations observed in the star using MESA and GYRE and how these tidal pulsations relate to the rapid orbital evolution seen in HAT-P-2 b.
Stable or Not: Constraining the Stability of Hidden Super-Short Period Planets – Thea Faridani
Recent ground and space-based observations show that stars with multiple planets are common in the galaxy. Most of these observational methods are biased toward detecting large planets near to their host stars. Because of these observational biases, these systems can hide small, close-in planets inward of observed planets. These hidden planets with short periods are influenced dynamically by their companions. In certain configurations, this influence can destabilize the system; in others, the star’s gravitational influence through both general relativity can instead further stabilize the system. Additionally, the stellar quadrupole moment (J2) can, depending on initial conditions, act to both stabilize and destabilize the system. We derive criteria for hidden planets orbiting within known planets that quantify how strongly general relativistic and J2 effects can stabilize systems that would otherwise be unstable. Furthermore, we show the regions of parameter space that possible hidden planets lie in if they are to be stable.
Stellar Variability: Star-Planet Connections – Tara Fetherolf
Characterizing exoplanets first requires precise measurements of their host star’s properties. In addition to revealing possible companions, the shape and periodic nature of a star’s light curve can uncover important information about its intrinsic properties. Stellar pulsations and rotational modulations, for example, are inherently linked to a star’s evolutionary stage and thus can be used to infer stellar ages. Furthermore, stellar variability may induce false planetary signals in radial velocity measurements or hide transit events of small exoplanets. The TESS spacecraft obtained high-precision space-based time-series photometry of nearly the entire sky during its primary mission, allowing for a large-scale study of stellar variability that is not sensitive to the diurnal limitation of ground-based surveys. We have developed a stellar variability catalog that includes ~40,000 stars that exhibit significant photometric variability on timescales of 0.01-13 days, which could be attributed to rotational modulations, stellar pulsations, or binarity. We will discuss the characteristics of the stars in our stellar variability catalog, which will serve as a valuable resource to the stellar astrophysics and exoplanet communities. The variability catalog will aid in 1) studying the characteristics of periodic variable stars; 2) understanding interactions between host star variability and planetary atmospheres; and 3) identifying exoplanets that are actually false positives caused by stellar variability. Overall, this work also encompasses understanding “worlds and Suns in context,” which has been identified as a high-priority area of research by the Astronomy 2020 Decadal Survey.
Atmospheric composition of the Super-Earth 55 Cancri e and its future observability with JWST – Priyankush Ghosh
One of the primary goals of exoplanetary science is to confirm the presence of an atmosphere along with its composition for small exoplanets. Until today, we have understood the presence of an atmosphere for only one rocky exoplanet known as 55 Cancri e, which lacks an H2-dominated atmosphere. We study the chemistry of this nitrogen-dominated ultra-short period super-Earth exoplanet 55 Cancri e based on observations that favor a high mean molecular mass atmosphere. We initiate our analysis by considering Titan’s atmospheric composition and using photo-chemical kinetics to obtain possible compositional behavior of the planet that should agree with observational constraints. We observe the behavior of the planetary atmosphere by generating synthetic spectra on varying C/O, N/O ratios, and the vertical mixing parameter. We also study the potential observability of such spectra with the James Webb Space Telescope (JWST). We find that the HCN molecule is a tracer of high C/O ratios with higher concentrations of CN and CO in such atmospheres. At low N/O ratios, we find that CH4 and C2H4 dominate the spectral absorption features, and at high N/O ratios, ammonia becomes abundant. We predict a possibility of depletion of hydrogen and other volatiles from such atmospheres due to its proximity to the host star that results in high mean molecular mass atmospheres dominated by nitrogen with CN, NO and CO as strong absorbers. Our models suggest that future observations by JWST favor the detections of distinct atmospheric compositional signatures.
Generalized Peas-in-a-Pod: Extending Intra-System Mass Uniformity to Non-TTV Systems via the Gini Index – Armaan Goyal
Among the most intriguing recent discoveries regarding extrasolar systems at large has been the tendency for planets orbiting the same star to be surprisingly uniform in their sizes and masses, often called the “peas-in-a-pod” phenomenon. However, while size uniformity has been generalized across a wide array of multiple-planet systems, studies of mass uniformity have largely been limited to systems whose planetary masses were determined via their transit timing variations (TTVs), signals that are particularly prominent for systems near mean motion resonance (MMR). Given the general dearth of radial velocity (RV) mass measurements of similar precision at the time of these initial studies, it remained unclear if intra-system mass uniformity was unique to resonant configurations. However, widespread RV follow-up of various K2 and TESS systems in the past several years has bolstered the available catalog of well-defined planetary masses such that a sample of uniquely non-resonant systems may be assessed for the first time. In this talk, I will present a novel analysis of mass uniformity for 17 systems whose planets exhibit no measurable TTVs. By quantifying mass uniformity via the Gini index, an economic metric often used to assess wealth inequality, this sample exhibits intra-system mass uniformity with 2.5 sigma confidence. I will discuss how our result confirms a theoretical prediction that mass uniformity may a minimum-energy state for multiple-planet systems regardless of resonance. I will also demonstrate via construction of minimum-mass extrasolar nebulae (MMEN) that systems with more unequal planet masses may have formed from more massive disks.
Fishing for Planets: Analyzing the Fisher Information Content of EPRV Exoplanet Surveys – Arvind Gupta
With dedicated exoplanet surveys underway for multiple extreme precision radial velocity (EPRV) instruments, the near-future prospects of RV exoplanet science are promising. These surveys’ generous time allocations are expected to facilitate the discovery of Earth analogs around bright, nearby Sun-like stars. But survey success will depend critically on the choice of observing strategy, which will determine the survey’s ability to mitigate known sources of noise and extract low-amplitude exoplanet signals. Here, we present an analysis of the Fisher information content of EPRV survey simulations, accounting for the most recent advances in our understanding of stellar variability on both short and long timescales (i.e., oscillations and granulation within individual nights, and activity-induced variations across multiple nights). In this analysis, we capture the correlated nature of stellar variability by parameterizing these signals with Gaussian Process kernels. We describe the underlying simulation framework as well as the physical interpretation of the Fisher information content, and we evaluate the efficacy of EPRV observing strategies that have been presented in the literature.
The Role of Exoplanet Photometry in Orbit-Fitting of Directly Imaged Multi-Planet Systems – Sammy Hasler
Planned and future direct imaging missions, such as the Large space-based IR/O/UV Telescope prioritized in Astro2020, will directly image Earth-like planets around Sun-like stars. Determining whether a planet is in the habitable zone of its star may be difficult in multi-planet systems, which are now known to occur frequently. Previous work (Keithly et al. 2021) has shown that planets in multi-planet systems can be “confused” in direct images of a system taken over multiple epochs due to lack of prior knowledge about orbital parameters or planetary characteristics. This confusion problem arises when it is not clear which point source in an image belongs to which planet. Differentiating planets in multi-planet systems is necessary in order to determine orbital parameters, schedule observations, characterize atmospheres, and determine habitability. In this work, we address the confusion problem using photometric considerations in a “deconfusion” algorithm to help differentiate between multiple planets in an image. The deconfusion algorithm (“deconfuser”) that our team has developed accepts unlabeled astrometric measurements of planets and generates a list of orbit parameter matches. The orbit combinations are then ranked based on how well they explain the data (e.g., orbits matching more observations are ranked higher). However, this method of ranking alone may not be enough to solve the confusion problem. We introduce orbital phase considerations in the deconfuser to further differentiate the matched orbit combinations. With a large number of simulated planetary systems, we are investigating the utility of orbital phase (intensity and color) information for each planet to reduce the rate of confusion in a multi-planet system. We present confusion rates for systems that include simulated photometric information. Our results will be used to determine the ability of photometric information to mitigate confusion and improve observation scheduling techniques.
The Discovery of a Rare Planetary Companion Interior to Hot Jupiter WASP-132 b – Ben Hord
Hot Jupiters are generally observed to lack close planetary companions, a trend that has been interpreted as evidence for high-eccentricity migration. We present the discovery and validation of WASP-132 c (TOI-822.02), a 1.85 +/- 0.10 REarth planet on a 1.01 day orbit interior to the hot Jupiter WASP-132 b. Transiting Exoplanet Survey Satellite (TESS) and ground-based follow-up observations, in conjunction with vetting and validation analysis, enable us to rule out common astrophysical false positives and validate the observed transit signal produced by WASP-132 c as a planet. Running the validation tools VESPA and TRICERATOPS on this signal yield false positive probabilities of 9×10-5 and 0.0107, respectively. Analysis of archival CORALIE radial velocity data leads to a 3
Thermal Torques on Low Mass Planets Embedded in Protoplanetary Disks – Fergus Horrobin
The evolution of protoplanetary systems during the first few millions of years of their life is largely driven by the dynamical interactions with the gaseous protoplanetary disk. For instance, as a planet grows in mass, it can gravitationally perturb the flow in the disk, and if the perturbation becomes asymmetric, the disk may in turn apply a torque to the planet. The effect of this torque is that the planet may migrate inwards or outwards in the disk. Recently, it has been proposed that another mechanism by which the planet perturbs the disk is through thermal feedback, where energy from accretion is deposited into the nearby gas, leading to an under-density in the vicinity of the planet. This under-density may become asymmetric due to the disk shear, if the planet is slightly offset from corotation, which can lead to a torque analogous to that from the gravitational perturbation. In this work, we present the first fully three dimensional radiation hydrodynamic simulations of this effect. We show that under the right conditions, the thermal torque may be similar in magnitude to the gravitational torque. We also show that under certain conditions, the thermal torque may be able to stop or even reverse the migration of the planet. We propose that this effect may provide a mechanism to slow or stop runaway migration which would otherwise destroy planetary systems.
The Roman Microlensing Survey in a Galactic Context with SynthPop – Macy Huston
The microlensing method for exoplanet detection is unique in its sensitivity to planets around stars at very large distances from the Sun, as well as low mass, cold planets. The Roman microlensing survey is estimated to detect ~1,400 new exoplanets, greatly increasing our understanding of planetary demographics in a Galactic context. In this work, we explore estimated microlensing event rates for the Roman Galactic Bulge Time Domain Survey using the SynthPop Galactic modeling software. We examine Roman’s predicted events as a function of Galactocentric distance and Galactic component membership (i.e. bulge versus disk).
Bridging The Disconnect between UV and White-Light Flares in Low-Mass M Stars – James Jackman
Stellar flares are explosive phenomena that release radiation across the entire electromagnetic spectrum. The far-UV emission from flares can dissociate atmospheric species and exacerbate atmospheric erosion. Yet, the near-UV flux may be necessary for the emergence of life on rocky planets around low-mass stars such as Proxima Centauri, LHS 3384 and TRAPPIST-1. A detailed knowledge of the UV energies and rates of flares is therefore essential for our understanding of the habitability of M dwarf systems. However, measurements of UV flare rates can require expensive campaigns with space-based instruments, limiting such measurements to individual active stars. To get around this, habitability studies instead often use UV rates based on extrapolations from white-light studies with TESS. Despite their use in contemporary habitability studies, such extrapolations are untested and as such their accuracy remains unconstrained. To this end, we have combined TESS optical and archival GALEX UV photometry for main sequence M dwarfs from TESS cycles 1 to 3 to test the UV predictions of habitability studies. We will show how white-light flare and habitability studies underestimate the UV rates of flares and what this tells us about the UV properties of flares from low-mass stars. We will discuss how we can use our results to correct the UV predictions of flare models, and the impact these corrections have on our current understanding of the UV environments and habitability of terrestrial exoplanets around low-mass stars.
An observational test to planet formation theories around low-mass stars – Rafa Luque
Planets smaller than Neptune are ubiquitous in the Galaxy and those around M stars constitute the bulk of warm and temperate worlds amenable for detailed atmospheric characterization. In this talk, I will present a re-analysis of all the available data on small transiting planets around M dwarfs, refining their masses and radii (Luque & Pallé 2022, Science in press). Our precisely characterized sample reveals that this population is well described by only three discrete planet density populations, with bulk densities centered at 1.0, 0.5 and 0.24 relative to Earth’s. The first are rocky planets, the second are water worlds, and the third are puffy planets with Neptune-like densities. This density classification offers a much better insight to disentangle planet formation and evolution mechanisms, which are degenerate when using a radius-based classification. Our results are at odds with atmospheric mass-loss models aiming to explain the bimodal radius distribution and suggest that the gap separates dry from water worlds rather than rocky planets with or without H/He envelopes. Formation models including type I migration explain naturally the observations independently of the accretion mechanism: rocky planets form within the snow line, water worlds form beyond and later migrate inwards.
TOI 4600 b and c: Two long-period gas-giant planets orbiting an early K dwarf – Ismael Mireles
We report the discovery and validation of two long-period gas giants orbiting the early K dwarf TOI 4600 (V=12.6, T=11.9), first detected by the Transiting Exoplanet Survey Satellite (TESS). The inner planet, TOI 4600 b, is 6.88+/-0.59 R_e and has an orbital period of 82.69 d. The outer planet, TOI 4600 c, is 9.42+/-0.71 R_e and has a period range of 226-378 d, having transited only once during TESS observations. We combine TESS photometry and additional ground based spectroscopy, photometry, and high-resolution imaging to validate the two planets. With equilibrium temperatures of 343 K and <270 K, respectively, TOI 4600 b and c add to the small but growing population of temperate gas giants that bridge the gap between hot/warm Jupiters and the solar system gas giants. TOI 4600 is a promising target for further transit and precise RV observations to measure masses and orbits for the planets as well as search for additional non-transiting planets. Together, this system will lend insight into the formation and evolution of planet systems with multiple gas giants.
The Impact of Bayesian Hyperpriors on the Population-Level Eccentricity Distribution of Imaged Planets – Vighnesh Nagpal
Orbital eccentricities of directly imaged substellar companions such as giant planets and brown dwarfs are a powerful probe of these objects’ formational and dynamical histories. Recently, hierarchical Bayesian modeling (HBM) was used to find evidence that imaged giant planets and brown dwarfs have different population eccentricity distributions, pointing to distinct formation mechanisms for these objects. Here, we study the effect of hyperpriors on the population-level eccentricity distributions inferred from HBM, and find that the choice of hyperpriors can impact the recovered population-level eccentricity distributions, an effect that grows stronger for decreasing sample size and orbital coverage. We conduct forward modeling experiments to establish constraints on the family of minimally biased hyperprior distributions, sample size, and orbital coverage required to accurately recover an observational sample’s underlying eccentricity distribution using HBM. Applying our method to an observational sample of imaged giant planets at 5-100 AU, we find that the population eccentricity distribution is broadly consistent with those of radial velocity ‘Warm Jupiters’, similar to previous results. We package our HBM and forward modeling code into a Python package, ePop!, and make it freely available for the community to use.
Introducing Nomads, an observing program uncovering the origin of remnant planets in the hot Neptunian Desert: survey strategy and early results – Ares Osborn
A key signature in the planet population is the hot Neptunian desert, a dearth of Neptune mass planets close to their host stars. The desert has been the subject of intense study as to its origin, and is thought to arise due to a combination of tidal disruption and photoevaporation. TESS has significantly increased the population of planets inside the desert (“nomads”), making a systematic study of the population of planets in the desert possible for the first time. One example of such a planet is TOI-849b, the remnant core of a giant planet. The new discoveries pose a key question: what formation and evolution pathways can leave a planet inside the desert, when such pathways are clearly not the norm? “Nomads” is a new program studying the nature and origin of the Neptunian Desert, aiming to double the current number of nomad planets in the desert that have precisely measured masses and radii, constraining their planetary densities and hence compositions. The resulting sample of characterised planets will provide the basis for theoretical studies of the processes that place planets inside the desert. In this talk, we will present an overview of the Nomads program, including the survey strategy and preliminary results. We will present new measurements of the planetary masses of several nomad planets, including an exciting new heavy Neptune, likely to be another remnant core akin to TOI-849b.
TOI-544b: a newly-discovered small planet inside the radius valley – Hannah Osborne
TOI544b is a newly-characterised small planet (mass < 4 Earth masses) recently detected with TESS and followed-up by the KESPRINT consortium. High-precision RV observations have allowed the mass of the planet to be constrained within 15% uncertainty and detect a previously-unknown longer-period companion with a mass precision of 10%, meaning these are some of the most precisely known exoplanet masses found using the RV method. The relatively low density of the inner planet puts it within a small subset of exoplanets which could be composed of mainly rocky silicates or water ices with or without layers of atmospheric hydrogen. However, the short orbital period means the effective temperature of this planet is above what would be expected for a rocky core to be able to sustain a hydrogen layer. We discuss the possibility of this planet joining the small group of ‘ocean worlds’ containing a significant fraction of water. As well as this, the planet sits firmly within the radius valley, a region where very few exoplanets are expected to be found. This, coupled with the high Transmission Spectroscopy Metric (TSM) and Emission Spectroscopy Metric (ESM) values make TOI-544b an excellent target for future atmospheric characterisation with the recently-launched James Webb Space Telescope and future Ariel mission. Finally, the importance of the TOI-544 system in relation to the wider population of small exoplanets and our understanding of planetary compositions will be presented.
Toward Mitigating Granulation RV Noise with GRASS: the GRanulation And Spectrum Simulator – Michael Palumbo
Despite recent advances in extremely-precise radial velocity (EPRV) spectrographs, intrinsic stellar variability still poses a significant obstacle to the detection and characterization of Earth-mass exoplanets in their stars’ habitable zones. In addition to pulsations and magnetic activity, granulation in the atmospheres of Sun-like stars skews the shape of absorption lines, creating a persistent RV noise source on the order of a few tens of centimeters per second. To complement previous studies of granulation that have used computationally expensive magnetohydrodynamic (MHD) simulations, we have developed a synthetic spectrum generator that uses time- and disk-resolved observations of the Sun to efficiently generate synthetic time series of spectra. We present this tool, the GRanulation And Spectrum Simulator (GRASS; Palumbo et al. 2022; https://github.com/palumbom/GRASS), and use its output spectra to explore how granulation differentially affects lines with differing depth, excitation potential, and magnetic sensitivity. We use these results to assess which strategies for mitigating stellar variability are sensitive to granulation-driven variability. We additionally discuss other use-cases of GRASS as a testing ground for methods designed to mitigate RV noise arising from granulation.
Extremely Precise Radial Velocity Measurements with Lasers – Winter Parts
In the search for potentially habitable exoplanets, a major goal is to achieve the 10 cm/s radial velocity precision that would be necessary to detect an Earth-like planet in the habitable zone of a Sun-like star. Over the past decade, improvements in spectrograph technology have greatly improved instrumental systematic noise, pushing RV precision below 1 m/s and leaving stellar activity as the dominant source of RV noise. In this work, we will use a new technology–laser heterodyne spectroscopy coupled with frequency combs–to study select magnetically sensitive and insensitive Solar lines in the near infrared H band at resolutions exceeding 10^6, in an effort to measure the magnetic field variability that contributes to RV noise. These very high-resolution observations are directly pinned to the exquisite frequency stability enabled by laser combs, and enable observations whose systematic measurement errors are completely independent from those of current extreme precision RV spectrometers. With these observations, we hope to determine whether measurement of the magnetic field variability at the level needed to correct RV to sub-10cm/s precision is possible in a spatially unresolved star. We also hope to constrain the amplitude and signature of granulation and oscillation RV noise in the Sun at near-infrared wavelengths, and to prove the limits of RV precision on the Sun on timescales of days, weeks, and months, using this novel technique.
Is LTT 1445 Ab a Cold Haber World or Hycean World?: An Exploration with Twinkle – Caprice Phillips
We present work on studying the atmospheric composition and detecting a potential biosignature, ammonia (NH3), in the nearby terrestrial-like planet LTT 1445 Ab. At a distance of 6.9 pc, this system is the second closest known transiting system and will be observed for transmission spectroscopy with the upcoming Twinkle mission. Twinkle is equipped with a 0.45m telescope, covers a spectral wavelength range of 0.5 – 4.5 um simultaneously with a resolution between 50 – 70, and is designed to study exoplanet, bright stars, along with solar system objects. Twinkle is scheduled to launch in 2024, and will have a 7 year mission lifetime. We use petitRADTRANS and a Twinkle simulator to simulate observed transmission spectra for a Cold Haber World with a N2-H2-dominated atmosphere, for which NH3is thought to be a biosignature. We study the detectability under different scenarios: varying hydrogen fraction, concentration of ammonia, and cloud coverage. Given the error across the Twinkle wavelength range for 25 transits, and 4.0 ppm of NH3 we find that transmission spectroscopy with Twinkle, would detect ammonia at a ~3sigma level, given non-cloudy optimal conditions. We also investigate and conclude that Twinkle data can distinguish between a Cold Haber World and a Hycean World with a a H2O-H2-dominated atmosphere.
The Hubble Space Telescope PanCET Program: An Extended Transmission Spectrum of the Warm Neptune HAT-P-26b – Lakeisha Ramos-Rosado
We present a new and extended transmission spectrum of the warm Neptune HAT-P-26b obtained with the Hubble Space Telescope (HST) Space Telescope Imagining Spectrograph (STIS) as part of the Panchromatic Comparative Exoplanet Treasury (PanCET) program. Our spectra cover a range of 0.2-0.5 microns, and we are combining it with previously published data from the 0.5-1.6 micron region taken with HST STIS and HST Wide Field Camera 3 (WFC3), as well as with data at 3.6 and 4.5 microns from Spitzer Infrared Array Camera (IRAC). With our new wavelength coverage, we are able to better constrain the clouds in the atmosphere of the planet and similarly the metallicity. From (Wakeford et al, 2017) we know that HAT-P-26b has a lower bulk density compared to other Neptune-sized planets and by using water abundance, they measured a metallicity value that is below what is expected from the mass-metallicity relationship observed in the Solar System giant planets. This planet is one of the few Neptune-mass planets to have a precise metallicity measured. This makes HAT-P-26b an important target because the atmospheric composition of close-in Neptune-sized planets opens a window to distinguish planet formation theories and evolution such as core-accretion, planetesimal accretion or other planet formation scenarios, as there are still unknowns regarding the formation of this class of planets.
Performing Phase-Resolved Spectroscopy on Hot Jupiters with The Exoplanet Climate Infrared Telescope – Tim Rehm
The EXoplanet Climate Infrared TElescope (EXCITE) is a purpose-designed instrument dedicated to performing phase-resolved spectroscopy on the atmospheres of extrasolar giant planets (EGPs), also known as ‘hot Jupiters’. Transiting EGPs orbit their host star closely (< 0.1 AU) and are suitable candidates for atmospheric studies since spectra can be taken during transit through secondary eclipse. EXCITE will carry a moderate resolution (Rayleigh criterion R ~ 50) near-infrared (NIR) spectrograph and will fly a long duration balloon (LDB) mission in Antarctica. By targeting bright, short period EGPs over a wide range of equilibrium temperatures, EXCITE will obtain spectra during entire orbital periods and define the first spectral classification of hot Jupiters. Observing over a range of wavelengths probes different pressures (or altitudes) inside the planet’s atmosphere and allows one to constrain 1D pressure-temperature profiles and 3D general circulation models. EXCITE will fly at stratospheric altitudes (~ 38 km) above 99% of Earth’s atmosphere to reduce optical and NIR variations. The 1– 4 micron spectral range of EXCITE will probe a wider range of wavelengths than the Hubble Space Telescope Wide Field Camera 3 and overlaps with the James Webb Space Telescope passband to maximize the possible science results. Here, we give an overview of the science motivation, mechanical design, and development status of the experiment. We discuss the thermal goals of the EXCITE cryogenic receiver which will house the readout electronics, focal plane array (an H2RG infrared detector) and a high-throughput spectrometer. We review the telescope design and integration with the gondola. We also introduce the correlated systematics that EXCITE will experience during LDB flight and detrending techniques to eliminate these effects from the signal.
Precise Dynamical Masses of New Directly Imaged Companions from Combining Relative Astrometry, Radial Velocities, and Hipparcos-Gaia eDR3 Accelerations – Emily Rickman
Very little is known about giant planets and brown dwarfs at an orbital separation great than 5 AU. And yet, these are important puzzle pieces needed for constraining the uncertainties that exist in giant planet formation and evolutionary models that are plagued by a lack of observational constraints. In order to observationally probe this mass-separation parameter space, direct imaging is necessary but faces the difficulty of low detection efficiency. To utilize the power of direct imaging, pre-selecting companion candidates with long-period radial velocities, coupled with proper anomalies from Hipparcos and Gaia, provide a powerful tool to hunt for the most promising candidates for direct imaging. Not only does this increase the detection efficiency, but this wealth of information removes the degeneracy of unknown orbital parameters, like the orbital inclination, leading to derived dynamical masses which can serve as benchmark objects to test models of formation and evolution. With upcoming missions like JWST and Roman, as well as ground-based facilities like the ELT, observing time is valuable and the strategy of direct imaging needs to be re-defined to pre-select targets. Looking further ahead, perfecting these strategies will be necessary as we look towards a large IR/O/UV mission, as recommended by the Astro 2020 decadal survey report, to pinpoint the location of terrestrial planets amenable to direct imaging. I present the detection of new directly imaged companions from VLT/SPHERE with derived model-independent precise dynamical masses from combining relative astrometry, radial velocities, and astrometry from Hippacros-Gaia eDR3 accelerations. I also present the ongoing work towards hunting for the most amenable targets for direct imaging with upcoming and future instruments. Ultimately this will lead us to a catalog of precisely characterized benchmark objects that can be used to test models of planet formation and evolution.
Staring at the Sun to Better See Exoplanets: A Solar Calibrator for the Keck Planet Finder – Ryan Rubenzahl
Standing between astronomers and the “holy grail” of 10 cm/s radial velocity (RV) precision needed to discover Earth-Sun analogs is stellar activity – RV noise caused by processes on the stellar surface which can be as large as several m/s. The upcoming Keck Planet Finder (KPF) will have an instrumental stability of 30 cm/s, and thus will have its planet-detecting capabilities limited by stellar noise on most stars. In this talk/poster I will present the Solar Calibrator (SoCal for short), an instrument that will feed stable disc-integrated sunlight to KPF via a pair of optical fibers, allowing Sun-as-a-calibration or Sun-as-a-star observing. I will present the instrument development, ongoing integration and testing with KPF, how we aim to use SoCal to calibrate and optimize KPF’s performance, and first science results. Long term monitoring of solar activity cycles will yielding bountiful and rich datasets for probing stellar activity. When combined with contemporaneous resolved ground and space-based solar observatories (e.g. NASA SDO), we will study in unmatched detail how activity influences RVs so that we may apply such knowledge to our nighttime observations of exoplanet host stars.
Constraints on low-mass planets in the WASP-62 system from TESS transit timing variations – Brianna Ryan
The formation of hot Jupiters remains an interesting enigma in the field of exoplanetary science. The three main proposals are in-situ formation, disk migration, and high-eccentricity migration, all of which may play some part in sculpting the hot Jupiter population. The existence of co-planar planetary companions to hot Jupiters offers a valuable constraint on formation scenarios, though very few hot Jupiters have known planetary companions. Here we use transit timing variations (TTVs) of the hot Jupiter WASP-62b to determine the likelihood of a companion planet in the system, particularly one in a period resonance. WASP-62b is an optimal target for TTV studies as the Transiting Exoplanet Survey Satellite (TESS) has observed more than 100 of its transits. Using the updated ephemeris from Ivishina & Winn (2022), we calculated the TTVs for all of these transits. From these measurements, we present the upper mass limits of a companion planet at a wide range of periods, including many key resonances that can be populated in disk-migration scenarios. These upper mass limits were obtained by comparing the TTVs of WASP-62b to those derived from a suite of dynamical simulations of WASP-62b and a possible companion planet. Based upon these simulations, we rule out an Earth-mass planet in the 2:1 and the 3:2 resonances, and a Neptune-mass planet up to a 5:3 resonance. Comparing these results to hot Jupiter systems with known companions, as well as discussing other features of the WASP-62 system, we find that disk migration is unlikely for this system. We discuss how applying this analysis to many hot Jupiter systems can provide us with better insight into the formation mechanism, or combination of mechanisms, that lead to these unique planets.
Temperature of Starspots from Multifilter Photometry – Maria Schutte
Starspots are a major source of stellar contamination in transmission spectroscopy of exoplanet atmospheres, and the correction for exoplanet analyses depends on the temperature of the starspots and the covering fraction. Using simultaneous multi-filter observations of a primary transit, we can determine the temperature of a starspot by modeling the radius and position of the spots. We model the spot using the starspot modeling program STarSPot (STSP) which uses the transiting companion as a knife-edge probe of the stellar surface. With known spot position and radius, the simultaneous multi-filter transits show different spot signatures that can only be attributed to differences in the contrast (or temperature) of the spot. Then, we compare the contrast found using the multi-filter transits to theoretically determined contrast curves, which are determined by interpolating synthetic spectra over multiple filters for both the stellar photosphere and a range of spot temperatures. The contrast of the spot, which is the integrated flux of the spot over the integrated flux of the star’s photosphere, is calculated for a range of filters and spot temperatures. From these calculated contrasts, we find that comparing the SDSS g’ and i’ filters maximizes the signal difference caused by the spot in the transit for a range of spot and photosphere temperatures. We introduce this technique and preliminary results for HAT-P-1, a K dwarf with known spot properties and simultaneous multi-filter transits we obtained using LCO’s MuSCAT3 instrument which allows for simultaneous multi-filter diffuser assisted high-precision photometry on the 2-meter telescope at Haleakala Observatory.
TESS Spots a Mini-Neptune Interior to a Hot Saturn in the TOI-2000 System – Lizhou Sha
Hot gas giants (P < 10 days) are almost always found alone around their stars, but a small number (< 5) have close-by companions. These rare cases constrain formation history by ruling out dynamical migration. We report the discovery and mass measurements of two planets in the TOI-2000 system, which hosts the first known inner companion to a hot Saturn-mass planet. The mini-neptune TOI-2000 b (2.64±0.12 R_E, 10.3±2.2 M_E) is in a 3.09833±0.00002 day orbit, and the hot saturn TOI-2000 c (0.711±0.011 R_J, 0.238±0.012 M_J) is in a 9.1270553±0.0000073 day orbit. Both planets transit their host star TOI-2000 (TIC 371188886, V = 10.98, TESS = 10.36), a metal-rich ([Fe/H] = 0.44±0.4) G dwarf 173 pc away. TESS observed the two planets in sectors 9–11 and 36–38, and we followed up with ground-based photometry, spectroscopy, and speckle imaging. Radial velocities from HARPS allowed us to confirm both planets through direct mass measurement. Because the mass and radius of TOI-2000 b suggest a volatile-rich atmosphere, it must have formed before its protoplanetary disk fully dissipated, thereby strongly constraining its possible formation pathways. Among all the inner companions to hot gas giants, TOI-2000 b is a prime candidate for atmospheric characterization by the JWST.
K2 & TESS Synergy: Combining NASA’s Planet Hunters – Erica Thygesen
In the era of JWST, we are poised to observe the atmospheres of transiting exoplanets with unprecedented detail – but only if we know when to look. The legacies of Kepler and K2 have provided us with thousands of planets to study with ongoing and future missions like JWST and ARIEL. However, the majority of K2-discovered exoplanets have typical uncertainties on future times of transit within the next decade of greater than four hours, making observations impractical for many upcoming facilities. Fortunately, NASA’s TESS mission has recently re-observed most of the known K2 planets during its first extended mission, providing the valuable opportunity to significantly improve the ephemerides of these systems. The K2 and TESS Synergy project is a dedicated effort to provide the community with a catalog of updated K2 planet ephemerides and self-consistent parameters for future studies. By combining observations from K2 and TESS with archival radial velocities, we reduce the uncertainties on future transit times from hours to minutes. I will present our results for the TESS prime mission sample and discuss our plans to reanalyze the sample of ~300 K2 systems observed by TESS during its first extended mission.
First Results from the Distant Giants Survey: 3 New Gas Giants around Sun-like Stars – Judah Van Zandt
We report the status of Distant Giants, a 3-year radial velocity (RV) survey designed to estimate the conditional occurrence of long-period Jupiter analogs in systems hosting small transiting planets. NASA’s Kepler Space Telescope taught us that small planets close to their host star occur at a rate of ~1 per Sun-like star. Meanwhile, ground-based RV surveys have shown that long-period gas giants are relatively rare, with an occurrence rate of ~0.1 per Sun-like star. Because there is so little overlap between these two stellar samples, the connection between inner small planets and distant giants is poorly understood. The Distant Giants survey is observing 47 stars with small transiting planets discovered by NASA’s TESS mission, searching for RV signatures of large outer planets. Thus far, we have detected evidence of distant companions in 10 of these systems, including 2 Jupiter analogs with orbits of ~1 year. Many candidate detections have orbital periods much longer than the current observing baseline. We introduce a forward modeling technique to constrain the properties of longer-period companions by combining RVs, astrometry, and direct imaging, and apply it to the Distant Giants target HD 191939. We find that the outer companion in this system has a mass of 2-16 Jupiter masses and a period of 4-30 years at 95% confidence. After examining this method’s performance in individual systems, we discuss its extension to the completed Distant Giants survey. The measured occurrence of Jupiter analogs in our sample will let us determine whether they are correlated, anti-correlated, or decoupled from small inner planets. This will refine exoplanet formation models and help us determine whether the solar system’s architecture is a common outcome of system evolution.
Mapping Starspots on AU Mic to Complement Hubble Transmission Spectroscopy of its Young Planet – Will Waalkes
AU Mic is a 30 Myr pre-main sequence M dwarf in the stellar neighborhood (10pc) which is very active and has a rotation period of 4.65 days. There are at least two known planets orbiting AU Mic, AU Mic b and c are both warm Neptunes (R_b = 4.1 Re and R_c = 3.2 Re) on 8.5 and 18.9-day periods, respectively [see Plavchan+ 2020 and Martioli+ 2021]. AU Mic has a heavily spotted surface as evidenced in its strong photometric rotational modulations. The transmission spectrum of AU Mic b is being observed with Hubble, and we aim to better understand unocculted starspots using ground-based photometry and spectra in order to complement those observations and better constrain the planetary transmission spectrum. Unocculted spots can introduce spurious transit depth variations seen in transmission spectra, known as the Transit Light Source Effect (TLSE) (Rackham+ 2018). Unocculted spots affect not only the in-transit interpretation of transmission spectra, but also the out-of-transit temporal and wavelength variations in the stellar flux. By studying the stellar spectrum out of transit, we may be able to independently constrain the spectral signatures of AU Mic’s starspots so we can correct their effect in the atmospheric observations of the planet. We gathered LCO 0.4m SBIG photometry in broad bandpasses to study the star’s rotational modulations and LCO NRES high-resolution spectra to model the effect of multiple spectral components on the integrated spectrum of the star. Our expanded use of various techniques to study starspots will help us better understand this system and may have applications for interpreting the transmission spectra for exoplanets transiting stars of a wide range of activity levels.
The Aligned Orbit of WASP-148b and the statistic implications from the distribution of stellar sky-projected obliquities – Xian-Yu Wang
High-eccentricity migration, which strips a hot Jupiter of primordial neighboring planets and leaves the system misaligned, naturally leads to the loneliness of hot Jupiters and the spin-orbit misalignments of their systems. In this light, the WASP-148 system has a special importance as a systems containing a hot Jupiter that is also part of a compact multi-planet system. We present spectroscopic measurements of the Rossiter-McLaughlin effect for WASP-148b, the only known hot Jupiter with a nearby warm-Jupiter companion, from the WIYN/NEID and Keck/HIRES instruments. WASP-148b is consistent with being in alignment with the sky-projected spin axis of the host star, with λ= {8.2}_{-9.7}^{+8.7} degrees. The low obliquity observed in the WASP-148 system is consistent with the orderly-alignment configuration of most compact multi-planet systems around cool stars with obliquity constraints, including our solar system, and may point to an early history for these well-organized systems in which migration and accretion occurred in isolation, with relatively little disturbance. By contrast, previous results have indicated that high-mass and hot stars appear to more commonly host a wide range of misaligned planets: not only single hot Jupiters, but also compact systems with multiple super-Earths. We suggest that, to account for the high rate of spin-orbit misalignments in both compact multi-planet and isolated-hot-Jupiter systems orbiting high-mass and hot stars, spin-orbit misalignments may be caused by distant giant planet perturbers, which are most common around these stellar types.
Kepler-80 Revisited: How a Newly Discovered Planet Changes the Dynamical Character of the System – Drew Weisserman
Looking at particularly stable systems with tightly-packed inner planets (STIPs) can help us better understand the outcomes of planet formation. One particular planetary system, Kepler-80, contains five short-period planets locked in a chain of resonances that keeps them stable and hints at their migration history. However, drawing insights from systems like Kepler-80 can be complicated by the fact that systems may host undiscovered planets, which can mean a solution derived from a partial system could be incorrect. In this presentation, we consider the chain of resonances in the Kepler-80 system and evaluate the impact that the additional member of the resonant chain discovered in Shallue & Vanderburg (2018) has on the dynamics of the system and on the physical parameters (including planetary mass) that can be recovered by a transit timing variation fit. In addition, we assess the current state of two-body and three-body resonances in the system and discuss whether or not the planets appear to be in any resonances or resonant chains given the measured orbital parameters.
The TESS Grand Unified Hot Jupiter Survey – Samuel Yee
Although Hot Jupiters (HJs) were the first exoplanets to be discovered, and hundreds are now known, the current sample is drawn mainly from a heterogeneous collection of ground-based transit surveys with poorly quantified selection functions, making it difficult to draw statistical inferences. The TESS mission will be essentially complete to detecting transiting HJs around relatively bright stars across the entire sky, presenting an opportunity to unify and expand upon previous transit searches, leading to a large and statistically useful sample of hot Jupiters. We estimate that a magnitude-limited sample of transiting HJs orbiting stars brighter than G < 12.5 will comprise approximately 400 planets, an order-of-magnitude increase over the best statistical sample currently available (from Kepler). Of these, roughly 40% are already known, with the remainder being new detections from TESS. Our survey seeks to confirm many of these planet candidates with ground-based follow-up observations. We present an update on the design and progress of our survey, which has confirmed 10 new planets and is making headway toward confirming another ≈30 planets.
Posters
ACCESS: Tentative detection of H2O in the ground-based optical transmission spectrum of the low density hot-Saturn HATS-5b – Natalie Allen (#13)
One of the most important questions to answer in the field of exoplanet atmospheres is to know which parameters shape their cloudiness levels. These not only define the general feedback mechanisms, but also their observational prospects: cloudy worlds typically have muted atmospheric features in transmission, making them observationally challenging to study. Recent works have predicted a window of “clearer” atmospheres for exoplanets at an equilibrium temperature around 1000 K, which is in between the regimes where silicate clouds and hydrocarbon hazes are believed to dominate. With an estimated T~1025 K, HATS-5b is in this “clear” regime, which also sits at the interesting dividing temperature between “warm” and “hot” giant planets. In this contribution, we present a new, precise ground-based optical transmission spectrum of the hot-Saturn HATS-5b, obtained as part of the ACCESS survey with the IMACS multi-object spectrograph mounted on the Magellan/Baade Telescope. Our spectra cover the 0.5 to 0.9 micron region, and are the product of 5 individual transits observed between 2014 and 2018. We introduce, for the first time in our collaboration, the usage of additional second order light in our analyses. This allows us to extract an “extra” transit lightcurve from our data, improving the overall precision of our combined transit spectrum. In addition, we also highlight how optimal spectral extraction can be much more effective than simple extraction, even in the case of high signal-to-noise ratios, as they can naturally compensate for bad pixels and cosmic rays. We find that the favored atmospheric model for this transmission spectrum is a solar-metallicity atmosphere with C/O = 0.39 +- 0.18, whose features are dominated by H2O, and so we report a tentative detection of H2O in the atmosphere of HATS-5b. If confirmed, this does indeed point to a “clearer” atmosphere at the pressure levels probed by transmission spectroscopy.
Transit Hunt for Young and Maturing Exoplanets (THYME) VIII: a Pleiades-age association harboring two transiting planetary systems from Kepler – Madyson Barber (#42)
We describe a young association (MELANGE-3) in the Kepler field harboring two transiting planetary systems (KOI-3876 and Kepler-970). We initially identified MELANGE-3 by searching for kinematic and spatial overdensities around stars with high levels of lithium (in this case, KOI-3876). To better determine the age and membership of MELANGE-3, we combine archival light curves, velocities, and astrometry, with new high-resolution spectra of stars nearest KOI-3876 spatially and kinematically. The resulting rotation sequence, lithium levels, and color-magnitude diagram of members are all consistent with the Pleiades, confirming the population is co-eval and providing an age estimate of 105±10 Myr. MELANGE-3 may be one edge of the recently identified Theia 316 stream, also estimated to be ~108 Myr. For the two exoplanet systems, we revise the stellar and planetary parameters, taking into account the newly-determined age. We fit the 4.5 yr Kepler light curves and find that KOI-3876.01 is a 2.0 ±0.1R⊕ planet that orbits its star every 19.58 days, while Kepler-970 is a 2.8±0.2R⊕ planet that orbits its star every 16.73 days. KOI-3876 was previously flagged as an eclipsing binary, but we rule this out using radial velocities from APOGEE and statistically validate the signal as planetary in origin. Given its overlap with the Kepler field, MELANGE-3 is valuable for studies of spot evolution on timescales of years, and both planets contribute to the growing work on transiting planets in young stellar associations.
The Youngest Planets from the Prime Kepler Mission – Luke Bouma (#9)
Many processes in planet evolution happen during the first few million years after disk dispersal. However, nearly all known exoplanets are billions of years old. I will discuss how new data from Gaia and TESS are helping to rectify this situation, by enabling the discoveries of the youngest planets from the prime Kepler mission. These planets come from a dispersed group of 38 ± 6 million year old stars spanning Cepheus (l=100°) to Hercules (l=45°), hereafter the Cep-Her complex. This group includes four previously known Kepler Objects of Interest: Kepler-1627 Ab (3.8 ± 0.1 Earth radii; 7.2 day orbital period), Kepler-1643 b (2.3 ± 0.2 Earth radii; 5.3 days), KOI-7368 b (2.2 ± 0.1 Earth radii, 6.8 days), and KOI-7913 Ab (2.3 ± 0.2 Earth radii, 24.2 days). The color-absolute magnitude diagrams from Gaia, all-sky stellar rotation periods from TESS, and spectroscopy show that these systems are all between 35 and 50 million years old. Based on the transit shapes and high resolution imaging, we also statistically validate them as planets (FPP < 1%). With help from Gaia and TESS, the main Kepler mission is at last expanding the census of young close-in planets, and is yielding the first empirical demonstration that mini-Neptunes with sizes of ≈2 Earth radii exist at ages of ≈40 million years.
MIRAC-5: A Ground-Based Mid-IR Instrument with the Potential to Detect Ammonia in Gas Giants – Rory Bowens (#40)
We present the Mid-Infrared Array Camera (MIRAC-5) instrument which will use a new Geosnap mid-infrared (3 – 13 microns) detector as part of the Mid-InfraRed Adaptive-optics(AO)-assisted Instrument Development (MIRAID) Project. Advances in AO systems and mid-infrared detectors are enabling ground-based mid-infrared systems to complement space-based missions, particularly in areas requiring high spatial resolution and deep contrast. As one of the only 3-13 micron cameras used in tandem with AO, MIRAC-5 will be complementary to the James Webb Space Telescope and capable of characterizing gas giant planets and imaging forming protoplanets (and characterizing their circumplanetary disks). We describe key features of Geosnap, a long-wave Mercury-Cadmium-Telluride (MCT) array produced by Teledyne Imaging Sensors (TIS), including its high quantum efficiency (> 65%), large well-depth, linear output, and low noise. We summarize MIRAC-5’s important capabilities, including prospects for obtaining the first continuum mid-IR measurements for several gas giants and the first 10.2-10.8 micron NH3 detection in the atmosphere of a warm planetary mass companion such as GJ 504b (Teff ~ 550 K). Finally, we describe plans for future upgrades to MIRAC-5 via improvements such as adding a coronagraph. MIRAC-5 will be commissioned on the MMT utilizing the new MAPS AO system in later-2022 with plans to move to Magellan with the MagAO system in 2023.
Prograde spin-up via gravitational collapse – Marc Brouwers (#2)
Asteroids, planets, stars in some open clusters, as well as molecular clouds appear to possess a preferential spin-orbit alignment, pointing to shared processes that tie their rotation at birth to larger parent structures. We present a new mechanism that describes how collections of particles or ‘clouds’ gain a prograde rotational component when they collapse or contract while subject to an external, central force. The effect is geometric in origin, as relative shear on curved orbits moves the cloud’s center-of-mass slightly inward and toward the external potential during a collapse. The orbital angular momentum that is thus liberated, adds a prograde component to the spin of the object that forms. The total rotational gain increases with the size of the cloud prior to its collapse. Clouds that are similar in size to their Hill radius form at the interface of shear and self-gravity. For these clouds, even setups with large initial retrograde rotation collapse to form prograde-spinning objects. When applied to the Solar System, we suggest that this mechanism of prograde spin-up provides an explanation for the observed spin-orbit alignment of trans-Neptunian binaries.
Small Changes with Big Consequences: Solar System Stability – Garett Brown (#23)
Much of the long-term architecture and evolution of planetary systems are shaped by planet-planet interactions. For many configurations, the system’s stochastic walk through phase space may eventually lead to collisions between planets. For systems with dynamics dominated by secular interactions, like the Solar System, characterizing relevant changes and understanding their consequences improves our understanding of system stability. For the Solar System, the stability of Mercury is sensitive to its rate of perihelion precession. Small perturbations to this precession rate can increase the likelihood of a secular resonance between Mercury and Jupiter, which can drive Mercury to collide with Venus. We explore two scenarios that look at small perturbations from the outside-in and the inside-out. We look at flyby encounters which are too weak to immediately destabilize the Solar System but are nevertheless strong enough to measurably perturb its dynamical state. And separately, we also explore the sensitivity of Solar System stability by linearly varying the strength of general relativistic corrections to perihelion precession over the lifetime of the Solar System using N-body simulations. We estimate the strength of such perturbations on a secularly evolving system using a simple analytic model and confirm those estimates with direct N-body simulations. Our ensembles of long-term integrations of the Solar System show that even small perturbations from stellar flybys or changes in general relativity can significantly affect the stability of planetary systems over stellar lifetimes. Due to the coupled nature of the Solar System, we find that small perturbations to Neptune’s orbit cascade inward, increasing the likelihood that the inner Solar System will destabilize. We also find that the stability of the Solar System can be used as a test of general relativity.
Training Machine Learning models for exoplanet searching in radial velocity data – Felipe Burgos (#41)
“Training Machine Learning models for exoplanetary detection in HARPS data The detection and characterization of extrasolar planets (exoplanets) represent one of the main challenges in modern astrophysics and astronomical data analysis. The High Accuracy Radial velocity Planet Searcher (HARPS) has been collecting data since 2003, and one of the most interesting results it has shown has been on M-stars. In particular, M-Dwarfs are prime targets to find rocky planets orbiting their habitable zone. Using HARPS radial velocity data of M-dwarfs with confirmed planetary detections, we have trained two machine learning models in order to create an automatic tool to detect planetary candidates with high confidence. These models are Random Forest and Support Vector Machines. We trained these models on periodograms derived from the radial velocities of several low-mass stars, achieving F-number ~ 0.95 with both algorithms and thus demonstrating that machine learning can be effectively used in planet detection from radial velocity time series. In this talk, I will discuss the results of this work in the context of the applications of machine learning to planet search, together with their implications for the general field of exoplanets.”
Stellar Surface Escape Velocities and Stellar Wind — Implications for Exoplanet Habitability – Craig Corbin (#15)
Winds from stars can be related to the escape velocity at the stellar surface, which is determined by the mass and radius of the star. These winds determine the radius of the heliosphere by interacting with the interstellar medium, so they also determine the size of the stellar heliosphere equivalent. Thus, determining the escape velocity for stars represents an important step to discovering the radius of the equivalent heliosphere in a planetary system, which are referred to as the astrosphere and astropause for the boundary. For several reasons, this is an important parameter for exoplanet habitability, as the stellar wind’s effect on a planet plays an important role in atmosphere retention. The escape velocities at the surface of each star with confirmed exoplanets in the Kepler Objects of Interest(KOI) database will be calculated using their mass and radius. Although the surface gravity is calculated for each star in the database, the escape velocity at the stellar surface has not been determined. Thus, this is a novel piece of information derived from the existing data. Also, the asymmetric uncertainty of the stellar mass and radius given by the KOI Database will be propagated through to calculate the uncertainty of the escape velocity. To start, the stellar surface’s escape velocity will be compared to the solar surface’s escape velocity. Properties of the stellar wind as a function of distance can be approximated by scaling the escape velocity to that of the sun. Since the heliosphere depends on wind speed, the size of the astrosphere can be scaled to the sun as well. As the project evolves, additional parameters may be used in the calculations. As telescopes are utilized to further study the properties of known exoplanets, approximating the size of the astrosphere and where exoplanets are with respect to the astropause, and the ability to estimate the stellar wind properties at the planet’s location, are likely to be important parameters for habitability.
N-body Interactions will be Detectable in the HR-8799 System within 5 years with VLTI-GRAVITY – Sofia Covarrubias (#6)
While Keplerian orbits account for the majority of the astrometric motion of directly-imaged planets, perturbations due to N-body interactions allow us to directly constrain exoplanet masses in multiplanet systems. This has the potential to improve our understanding of massive directly-imaged planets, which nearly all currently have only model-dependent masses. The VLTI-GRAVITY instrument has demon- strated that interferometry can achieve 100x better astrometric precision than existing methods, a level of precision that makes detection of planet-planet interactions possible. In this study, we show that in the HR-8799 system, planet-planet deviations from currently used Keplerian approximations are expected to be up to one-quarter of a milliarc- second within five years, which will make them detectable with VLTI-GRAVITY. Modeling of this system to directly constrain exoplanet masses will be crucial in order to make precise predictions.
Contemporaneous Observations of Hα Luminosities and Photometric Amplitudes for M dwarfs – Aylin Garcia Soto (#28)
M dwarfs are smaller, cooler and redder than G dwarfs and result in deeper exoplanet transits. Thus, it is easier to find planets around these stars than larger stars like the Sun. M dwarfs also pose a problem because they are magnetically active stars, which effects transmission spectroscopy. It is generally assumed that the surface of the host star is homogeneous and so the region of the star blocked by a transiting planet is the same as the unocculted surface. However, stars are not homogeneous, starspots and faculae can create differences in the transmission spectra. Currently, we are still unsure about the properties of their starspots and the origin of their magnetic dynamos. Both starspots and magnetic activity are related to the surface magnetic field, so one means of examining magnetic phenomena is to connect photometric variability (driven by starspots) and magnetic activity. We studied 56 M dwarfs with periods of 0.1 to 27 days. We present time-series optical photometry from the Transiting Exoplanet Survey Satellite (TESS) and contemporaneous optical spectra obtained using the Ohio State Multi-Object Spectrograph (OSMOS) on the MDM 2.4m telescope in Arizona. Using the TESS light curves, we measure rotation periods and photometric amplitudes. From the OSMOS spectra, we calculate the equivalent width of Hα. We find a loose positive correlation between Hα luminosity and photometric amplitudes for stars in the saturated regime of the rotation-activity relation (Pearson correlation coefficient 0.664_{-0.026}^{+0.023}). We additionally see short term variability in Hα equivalent widths and enhancement from flares.
TOI 904: A multiplanet system around an M dwarf with a cold sub-Neptune – Mallory Harris (#38)
We report the discovery of two sub-Neptunes transiting the early M dwarf star, TOI 904 (TIC 261257684). Both planets were first detected in observations from the Transiting Exoplanet Survey Satellite (TESS). Reconnaissance radial velocity measurements (taken with SMARTS/CHIRON and EULER/CORALIE) and high resolution speckle imaging with adaptive optics (obtained from SOAR/HRCAM and Gemini South/ZORRO) show no evidence of an eclipsing binary or a nearby companion, validating the planetary nature of these candidates. We measure the orbital period and radius of the known TOI-904.01 to be 10.9 days and 2.62REarth, respectively. We also find a colder outer planet, TIC 261257684.02, with a similar radius (~2.6REarth) and a period of 84 days. This outer planet is the longest-period M dwarf exoplanet found by TESS, with an estimated equilibrium temperature ~219K. As the three other validated planets with comparable host stars and orbital periods were observed around dim stars (Jmag>12) by Kepler, this planet, orbiting a brighter star (Jmag =9.6), could be the coldest M dwarf planet accessible for atmospheric follow-up.
De-biasing the Minimum-Mass Extrasolar Nebula: On the Diversity of Solid Disk Profiles – Matthias Yang He (#14)
A foundational idea in the theory of in situ planet formation is the “minimum mass extrasolar nebula” (MMEN), a power-law profile for the surface density of disk solids that is necessary to form the planets we see in their present locations. While the MMEN framework is intuitively simple, it continues to be debated whether most exoplanetary systems fit a universal disk template. Previous studies have relied on simplistic treatments for detection biases and the exoplanet mass-radius relationship to construct the MMEN from the Kepler planet catalog. The recent development of detailed forward models for the Kepler mission has enabled unprecedented inferences on the intrinsic population of inner planetary systems from the observed population, leading to advanced statistical models, such as the “maximum AMD model” that captures the underlying architectures and correlations in multi-planet systems. Here, we use simulated catalogs from this model to reconstruct the MMEN. Fitting a power-law relation for the solid surface density as a function of semi-major axis to each individual multi-planet system results in a diverse distribution of disk profiles. Our approach allows us to account for the role of non-transiting and undetected planets in altering the MMEN; we find that while transit observations do not tend to bias the inferred median power-law slope, they can lead to both over- and under-estimated normalizations for the disk density and thus significantly broaden the inferred distribution for MMEN mass. We discuss the implications for planet formation.
TOI 4189 b: A long period sub-Neptune planet around a Sun-like star – Katharine Hesse (#24)
We report the discovery and validation of TOI-4189 b, a temperate sub-Neptune transiting planet orbiting a Sun-like star at a period of 46.9 days with a radius of 2.47 Earth radii. We use data from the SPOC Data Analysis Pipeline to analyze the transit and derive orbital and planetary parameters. We combine data from TESS and follow-up observations to rule out false-positive scenarios and validate the planet. With an equilibrium temperature of ~470 K, TOI-4189 b is among the coolest ~5% of planets discovered by TESS. Combined with the host star’s relative brightness (V= 9.4), TOI-4189b is a very promising target for follow-up mass measurements and atmospheric characterization that will probe this sparsely populated temperate sub-Neptune regime.
Doppler Shadow of Nodal Precessed XO-3b – Kyle Hixenbaugh (#31)
The hot jupiter X0-3b is a well studied planet with an interesting configuration, having a mass on the limit between giant planets and low mass stars, an eccentric orbit, and a short period. Previous works have presented Rossiter-McLaughlin measurements to constrain the obliquity that have been in tension with each other (70.0 degrees with error of 15.0 degrees, Hébrard et al. 2008; 37.3 degrees with error of 3.7 degrees, Winn et al. 2009; 37.3 degrees with error of 3.0 degrees, Hirano et al. 2011). In this work we use Doppler tomography measurements, recently obtained from the NEID spectrograph at WIYN, combined with previous data to present a more accurate measure of the obliquity of X0-3b. The obliquity of X0-3b in combination with it orbiting around a massive rapidly rotating star means X0-3b nodally precesses around its host star.
Do short-period gas giants predominantly form around metal-rich early M dwarfs? – Shubham Kanodia (#18)
M dwarfs are the most common type of stars in the Galaxy, and seem to host a higher number of planets on average, compared to FGK stars. Yet, due to their lower stellar (and disk) masses — and associated slower formation time scales — gas giants are expected to be infrequent around M dwarfs. In this presentation, we discuss the trends seen in a transiting sample of gas giants (Rp > 4 Re), with respect to the dependence on host stellar metallicity and mass. While more detailed high resolution spectral synthesis routines are required to robustly determine abundances; using both empirical and photometric metallicities we note an emerging trend which suggests that the transiting planets (closer-in; warmer) typically orbit more metal-rich and massive M dwarfs compared to the RV sample (further-out; colder). We also compare the M dwarf giant planet sample (transiting + RV) with planets around FGK stars, and find statistically significant evidence that the metallicity distributions for the two differ. We contextualize these trends with planetary formation theories, and discuss future prospects for improving the robustness of studies such as this, with upcoming samples from TESS, and GAIA. We also note the potential of this sample for population level comparative studies using transmission spectroscopy due to the narrow range of stellar and planetary parameters it spans. Finally, we present a new planet discovered using a combination of TESS photometry and radial velocities (RV) from the precision RV spectrographs – HPF and NEID. This low-density (rho ~ 0.3 g/cm3) Jovian sized planet around an early M dwarf presents a corner-case thereby testing the hypotheses of planet formation presented earlier. Furthermore, its large scale height (~ 400 km) makes it an excellent target for studies of atmospheric escape as well as transmission spectroscopy to determine atmospheric composition.
The Exoplanet Modeling and Analysis Center: An Online Repository for Exoplanet Related Tools – Cameron Kelahan (#19)
The intersection of the open-source coding revolution and the golden age of exoplanet discovery has led to an explosion in software-based resources developed by the exoplanet research community. The Exoplanet Modeling and Analysis Center (EMAC) is a website which serves as a catalog, repository and integration platform for the aforementioned resources focused on the study of exoplanet characteristics and environments. EMAC hosts user-submitted software ranging in categories from planetary interior models to data visualization tools. In the past several months, EMAC has received a number of substantial updates to better assist with our goal of serving as a comprehensive repository for researchers to access a variety of exoplanet resources that can assist them in their work. These updates include improvements to the visual appeal and ease-of-use of the website, additional features to specific hosted tools and the website as a whole, and a new subscription service that notifies users when new tools become published of specific categories they are interested in. A number of exciting changes are being developed for release in the near future and we are constantly adding new tools from the astronomy community.
A photoevaporative investigation of planets either side of the radius-period valley – George King (#1)
A dearth of planets around 2 Earth radii uncovered in the exoplanet population, dubbed the “radius gap” or “radius-period valley”, has been the subject of much study over the past few years. There are currently two leading mechanisms proposed to explain the observed valley: X-ray and EUV-driven photoevaporation, and core-powered mass loss. We present XMM-Newton observations and evolution simulations of two systems containing planets residing either side of the valley, TOI-431 and HD 136352, in order to explore their compatibility with the photoevaporation mechanism. With our measured X-ray fluxes, we estimate the current ongoing high-energy-driven mass loss from the planets. In the evolution simulations, we investigate the past history of the planets and their atmospheres resulting from XUV-driven escape, constraining possible early life properties.
Constraints on the Occurrence of `Oumuamua-like Objects – Garrett Levine (#21)
1I/2017 U1 (`Oumuamua), the first-detected macroscopic interstellar interloper near the Earth, provided an unprecedented view of a small body that originated outside of the Solar nebula. Surprisingly, `Oumuamua’s unique attributes do not fit within the current categorization of small bodies and are dissimilar to those of 2I/Borisov. Currently, there exists no consensus in the astronomical community regarding either the bulk composition or the formation mechanism for `Oumuamua. In this presentation, we assess the merits of the various interpretations that have been suggested to explain `Oumuamua’s observed non-Keplerian trajectory with the non-detection of typical cometary volatiles. Specifically, we attempt to reconcile the leading hypotheses on the nature of `Oumuamua with the implied reservoir of similar objects from its detection by Pan-STARRS. By developing a general framework to quantify the population of interstellar objects from a given interpretation, we can directly compare the various proposed formation histories. We consider two exotic ices, hydrogen and nitrogen, as well as compositions attributing `Oumuamua’s non-gravitational acceleration to solar radiation pressure. While we conclude that none of these interpretations are perfectly satisfactory, we make predictions that will be testable by the Vera Rubin Observatory to resolve the tension introduced by `Oumuamua.
Investigations of Non-equal Mass and Non-equal Spacing Packing of Planetary Bodies – Zhixing Liu (#20)
The optimal packing of non-equally massed and non-equally spaced multi-planet systems through numerical N-body simulations are studied and the recent results will be presented. Previous studies have generally assumed that a system of equal mass planets will be optimally packed if they are also equally spaced, i.e., if the semi-major axis ratios between planet pairs is a constant. We explicitly test this assumption by obtaining the stability timescales of 5-planet systems around a Sun-like star (with masses varying from 3 Earth masses to 3 Jupiter masses) with increasing degrees of non-uniform-spacing represented by the parameter 0 < k < 1. For planets with equal masses, a value of k = 1 corresponds to equal spacing, whereas a value of k < 1 leads to the inner planets being more widely spaced than outer planets. We study the optimal value of k for optimal planet packing (i.e., longest stability time) under both equal mass and non-equal mass scenarios and find evidence that k = 1 may not be optimal under all scenarios and. We also find system stability will decrease with the increase of mass variation. The role that distance to mean-motion resonances (MMRs) play in determining the configurations of optimal planet packing will also be demonstrated. The distinction of different exponents and different mass variation in system stability is potentially explained by their MMR distributions, and graph illustration will also be presented.
Impact of Correlated Noise on the Mass Precision of Earth-analog Planets in Radial Velocity Surveys – Jacob Luhn (#29)
Characterizing the masses and orbits of near-Earth-mass planets is crucial for interpreting observations from future direct imaging missions (e.g., HabEx, LUVOIR). Newman et al. (2022) simulated several 10-year extreme-precision radial velocity (RV) surveys with differing telescope architectures, demonstrating that they can precisely measure the masses of potentially habitable Earth-mass planets in the absence of stellar variability. Here, we introduce Gaussian process kernels for active regions, granulation, and oscillations to investigate the effect of stellar variability on the signal-to-noise ratio (SNR) of the planet mass measurements in these simulated surveys. We present the impact of these components of stellar variability by exploring both their combined and individual effect on each survey architecture, in addition to modified architectures where we vary the survey duration and instrumental precision. We find that correlated noise due to active regions has the largest effect on the observed mass SNR, followed by granulation, with p-mode oscillations having little impact on the proposed survey strategies. In the presence of correlated noise, 5-cm s−1 instrumental precision offers little improvement over 10-cm s−1 precision, highlighting the need to mitigate astrophysical variability. Finally, with our noise models, reaching 10% mass precision on Earth-analogs in the simulated 10-year surveys is only possible for planets orbiting stars < 0.76 M⊙ (< 0.86 M⊙ for a 15-year survey); reaching this precision threshold for planets orbiting solar mass stars will require additional observations per target than simulated or improved mitigation of astrophysical variability.
Characterizing the planets of K2-138 through resonances – Mariah MacDonald (#4)
The study of orbital resonances allows for the constraint of planetary properties of compact systems. Five of the six planets orbiting K2-138 have been proposed to be in the longest chain of 3:2 mean motion resonances. To characterize the dynamics of the system, we run thousands of N-body simulations of these five planets and their host, integrating for 8Myr to ensure stability. We are able to confirm a chain of 3:2 resonances, as 99.2% of our simulations result in such a chain, although only 11% result in a five-planet resonance chain. We use these resonances to further constrain the orbital periods and masses of the planets and investigate the potential compositions of each planet with these updated values. Planets c and d likely have similar composition with more than 0.01% of their mass as atmospheres or 80% of their mass as hydrospheres, while planet b does not require an atmosphere to satisfy its density and planet e requires a more substantial atmosphere with a mass of ~0.065M_E, 800 times more massive than Venus’ atmosphere. We find, then, that K2-138 does not showcase the inter-planetary uniformity that we see in other resonant or compact systems.
From Directly Imaged Planets to Directly Characterized Planets: A Multi-pronged Approach to Understand Planet Formation Processes in Preparation for Next Generation Facilities – Raquel Martinez (#11)
In this presentation, I will discuss three on-going projects that are investigating various planet formation processes and preparing for the future of exoplanet observations with JWST and planned ground-based 30 m telescopes. I will first report on my latest efforts to build and characterize the population of planetary-mass and substellar companions, an enigmatic class of astrophysical objects whose origins are not well understood. I will describe the infrastructure I have developed to perform PSF-subtraction on archival Spitzer/Infrared Array Camera images to reveal low-mass companions, whether they have disks, and the properties of those disks. Then I will discuss preliminary results from a Keck pilot study to measure the accretion rates of known young exoplanets, calibrating and extending empirical relationships between hydrogen recombination line fluxes and accretion luminosity down to planetary masses. These observations could place the first constraints on Br alpha emission in accreting substellar objects, enabling the exploration of using it and Pa alpha as a potential protoplanet search strategy in the JWST era. Finally, I will discuss my work to carry out future exoplanet science with SCALES, an under-development mid-infrared high-contrast integral-field spectrograph that will detect and characterize exoplanets that have never been accessible to detailed study before. I will briefly describe SCALES’ instrument design and science goals, ending with discussion of my plans to create and execute science verification observations following instrument commissioning.
Next Generation of Noise Correction Techniques to Improve Transit Light Curve Modelling – Mario Morvan (#43)
Although planets are being discovered at an exponential rate, we are still struggling to detect small exoplanets and measure their radii, show evidence of exomoons and rings, or study exoplanets in challenging stellar environments. This is due in part to the particular faintness of the signal itself, yet another part of the problem resides in our difficulty to properly account for the complex time-correlated noise and trends in our observations, coming from both the instrument and the host star(s). On the bright side, we now have millions of stellar light curves coming from transit surveys and are stepping into an era of population-scale characterisation missions. After presenting the limitations of current denoising techniques in the context of high precision photometry, we present novel deep learning approaches to model and remove the noise in datasets of light curves. In particular, we present 1) a recurrent neural network model trained to correct systematics applied to individual Spitzer light curves, 2) A transformer encoder-based self-supervised model applied to the first sector of TESS observations, 3) a hybrid framework to combine explicit transit model with deep learning models. Finally, we advise more generally on the useful advances, possible benefits and challenges of deep learning to make the most of our datasets of stellar and transit light curves and prepare for the next generation of processing pipelines to undertake the challenges currently faced by our field.
TOI-1994b: A Transiting Brown Dwarf Near the Planet Mass Regime – Emma Page (#22)
We present the discovery of TOI-1994b, an eccentric brown dwarf transiting a hot star. TOI-1994 has an effective temperature of 7550 K and V magnitude of 10.51 mag. We find that the brown dwarf is close to the planet and brown dwarf mass transition with a low mass of 22 M_Jup, a period of 4.03 d, an eccentricity of .3, and a radius of 1.28 R_Jup. TOI-1994b was detected by the Transiting Exoplanet Survey Satellite (TESS) and followed up with radial velocity measurements from MINERVA-Australis. The global analysis and characterization of TOI-1994b will augment the small number of transiting brown dwarfs and allow further study of objects near the planet and brown dwarf mass transition.
Observational constraints on the atmospheric dynamics of the inspiraling ultra-hot Jupiter WASP-12 b – Anusha Pai Asnodkar (#27)
Atmospheric escape of highly irradiated planets is a relevant phenomenon that shapes entire populations of exoplanets and poses direct consequences for the habitability of terrestrial planets. WASP-12 b is an ultra-hot Jupiter of particular interest for studies of atmospheric escape since it is on an observably inspiraling orbit which may enhance mass outflow from the planet as it heats up in closer proximity to its host star. Previous works have identified tentative evidence both for and against the detection of active mass loss from the atmosphere of this planet. To address this controversy, we analyze two new transits of WASP-12 b with the optical high-resolution PEPSI spectrograph on the Large Binocular Telescope and one publicly available archival data set from HARPS-N. From these data, we place constraints on atmospheric escape from upper limits on planetary Balmer line absorption. We also conduct a spectral survey of atomic species present in WASP-12 b’s atmosphere to trace atmospheric circulation and conduct comparative planetology by evaluating the composition of WASP-12 b’s atmosphere in the broader context of the overall ultra-hot Jupiter population observed thus far.
Can an exo-Oort cloud pollute white dwarfs? – Dang Pham (#35)
Strong metal absorption lines are found in the spectra of 25-50% of white dwarfs atmospheres. These elements are expected to sink quickly, pointing to a scenario of materials accretion delivered from elsewhere in these evolved exoplanetary systems. In addition, the inferred accretion rate is found to be roughly constant, decreasing by only about one order of magnitude, over the course of 8 Gigayears. A potential reservoir for these materials would be an Oort cloud analog. Here, we are contributing to prior work on white dwarf pollution via an Oort cloud by finding the flux rate of comets experiencing the following perturbations: galactic tides, stellar flyby, white dwarf natal kick and an interior planet. We use lessons from studying our own Solar System’s Oort cloud perturbations via galactic tides and stellar perturbations, approximating the white dwarf kick as impulsive and using N-body simulations to account for scattering by a planet.
Planetary target TOI-3785b: M-Dwarf Harboring Jovian-Sized Candidate – Luke Powers (#8)
Planetary target TOI-3785b is a Neptune-sized planet (~5 Earth Radii) harbored around an M-Dwarf star. First discovered by use of TESS photometry, this target has been followed up by a multitude of ground based instruments such as the 0.6 meter telescope at the Red Buttes Observatory (RBO) as well as the instrument ARCTIC (3.5 m) at the Apache Point Observatory. Both have been successful in collecting ground based transits of this target progressing the path towards conformation. Radial velocity data has also been collected from both HPF and NEID in order to come closer to a conclusion on a mass constraint. In a broader sense, this target is of particular interest due to its moderate rarity in it being a Neptune around an M-Dwarf as well as it possessing ideal characteristics for transmission spectroscopy since it is a relatively cool (T~517K) and low density planet (p~0.6 g/cm^3). With continued investigation into this target’s planetary and stellar motions as well as an analysis of its atmosphere, there is a clear path towards increased parameter accuracy that could lead towards final conformation.
In-situ Formation Can Naturally Explain Why Hot Jupiters are Observationally Isolated – Brandon Radzom (#30)
An outstanding issue with the formation of short-period gas giants is that a substantially lower fraction of hot Jupiters are observed to have nearby planetary companions than their more distant analogs, warm Jupiters. We demonstrate through numerical simulations and analytic considerations that this is a natural dynamical consequence of an in situ formation process where planets in compact, multiple super-Earth systems are mass-boosted to gas giant status. We find that these in-situ-formed hot Jupiters achieve on average larger period ratios with their nearest companions than warm Jupiters. Additionally, our results predict there is a “sweet spot” for hot Jupiters (around periods of 5-7 days) wherein nearby inner companions are likely to stabilize, which is in good agreement with current observations.
AU Mic b, or not AU Mic b: the question of the young planet’s escaping atmosphere – Keighley Rockliffe (#39)
AU Mic is an M1Ve star in the β Pic moving group and therefore has an age of 23 +/- 3 Myr. At 9.79 +/- 0.04 pc, it is one of the closest pre-main sequence stars to Earth. Two exoplanets transiting AU Mic have been discovered using data from TESS. AU Mic b orbits closer to its host, with a period of 8.46 days. It has a radius measurement of 4.20 Earth radii, placing it on the edge of the hot Neptune desert. We expect planets at this size (indicating a large gaseous envelope) and orbital period (highly irradiated) to be experiencing significant photoevaporation. This and its youth prompt the detailed study of AU Mic b’s potentially escaping atmosphere. We obtained Lyman-alpha transits of AU Mic b with HST/STIS. We present a detailed analysis of the flares within these observations. The flare-removed Lyman-alpha light curves do not exhibit any evidence of escaping neutral hydrogen. This supports theoretical work done by Owen & Murray-Clay (2021) showing that some hot Neptunes and sub-Saturns will have their escaping envelopes photoionized too quickly to be observable in Lyman-alpha.
A reanalysis of the composition of K2-106b, an ultra-short period super-Mercury candidate – Romy Rodríguez (#5)
Super-Mercuries are a class of exoplanets with radii less than ~1.5 Re, high bulk densities and relatively large core-mass fractions (CMFs). The study of super-Mercuries will shed light on the composition of low-mass, terrestrial exoplanets as well as on the mechanisms that lead to the formation of iron-rich planets. However, only a few exoplanets have been confirmed as super-Mercuries, in part because of the challenges of obtaining the precise stellar and planetary parameters required to confirm them. We perform a reanalysis of the K2-106 system, which contains an ultra-short period, super-Mercury candidate with a density from the literature of 13.1 (+5.4 -3.6) g/cc, approximately twice the density of Earth. We globally model extant photometry and radial velocity of the system and derive a planetary mass and radius that leads to a considerably lower density than previously reported. We derive the host star’s Fe, Mg and Si abundances and combine them with planet interior models to infer the CMF and interior composition of K2-106b. Using a statistical framework, we compared the planet’s CMF as expected from the planet’s density and the CMF as expected from the host star. Our analysis suggests that, although K2-106b has a high density and CMF, it is statistically unlikely to be a super-Mercury.
Gravitational Instabilities in Protoplanetary Discs: A Vanishing Act – Sahl Rowther (#16)
In their youth, protoplanetary discs are expected to be massive and self-gravitating, which results in non-axisymmetric spiral structures. However recent observations of young protoplanetary discs with ALMA have revealed that discs with large-scale spiral structure are rarely observed in the midplane. Instead, axisymmetric discs with some also having ring & gap structures are more commonly observed. To investigate this discrepancy between theoretical expectations and observation, we use 3D SPH simulations to separately consider two processes that are expected to commonly occur in these discs. The first is planet-disc interactions which is commonly used to explain the origin of the rings & gaps. The second is warps which can be caused by discs interacting in their chaotic star forming environment. Both of these processes are likely to occur when the disc is young, and potentially massive enough to be gravitationally unstable. Our simulations show how the evolution of gravitationally unstable discs can be altered, potentially resolving this discrepancy by showing that massive discs that would be expected to be gravitationally unstable can appear axisymmetric when complex processes such as planet-disc interactions or warps are considered. Thus, the absence of observed large-scale spiral structures alone is not enough to place upper limits on the disc’s mass.
Mapping the Limbs and Constraining the Rock-to-Ice Ratio of an Ultrahot Jupiter – Zafar Rustamkulov (#3)
The rock-to-ice ratio of a gas giant can give important clues to its formation location. Gas giants accreting at or just outside the water ice line of their protoplanetary disk, for instance, are likely to show a relatively low rock-to-ice ratio due to the large abundance of water ice there. We present our observations of WASP-178 b, an ultrahot Jupiter, whose high temperature enables unique constraints of its rock-to-ice ratio with atmospheric spectroscopy. In particular, we show precise NUV-to-NIR transmission spectroscopy obtained with HST, with abundance measurements of information-rich species such as SiO, Fe, Mg, and H2O. We show preliminary results of our atmospheric retrievals, and share our constraints on the planet’s rock-to-ice ratio. We also show independent spectral measurements of WASP-178 b’s leading and trailing terminators gleaned from asymmetries in the transit light curve at ingress and egress.
Efficiently Imaging Accreting Protoplanets from Space: Reference Star Differential Imaging of the PDS 70 Planetary System with the HST/WFC3 PSF Library – Aniket Sanghi (#17)
Accreting protoplanets provide key insights into how planets form within their natal protoplanetary disks. The direct detections of Hα emission from newly formed planets have constrained planetary-mass accretion rates and enabled quantitative studies of accretion physics, planet-disk interactions, and planetary luminosity evolution. Recently, Zhou et al. 2021 used angular differential imaging (ADI) with Hubble Space Telescope’s Wide Field Camera 3 (HST/WFC3) to recover the young accreting planet PDS 70 b in F656N (Hα) at a S/N of 7.9. Here we demonstrate the applicability of reference star differential (RDI) with the same dataset. We compile a reference library from the database of WFC3 point-spread functions (PSFs) provided by Space Telescope Science Institute and develop a set of morphology-significance criteria for pre-selection of reference frames to improve RDI subtraction. We explore different implementations of RDI by varying the library size, reference star subsets, and subtraction regions to find the optimal setups for planet detections with HST/WFC3. RDI with this PSF library results in a detection of PDS 70 b at a S/N of 5.3, opening up the possibility of imaging accreting planets more efficiently than with ADI. The lower detection significance with RDI can be attributed to the ~100 times lower S/N of the reference PSFs compared to the ADI PSFs. Building a high-quality reference library with WFC3 will enable unique opportunities to monitor planetary accretion variability and efficiently search for actively accreting protoplanets in Hα around targets inaccessible to current ground-based adaptive optics systems, such as faint transition disk hosts.
Eight New TESS Hot Jupiters and the Search for Migration Pathways – Jack Schulte (#34)
We present the discovery and characterization of TOI-1855b (TIC 81247740.01), TOI-2107b (TIC 446549906.01), TOI-2368b (TIC 401125028.01), TOI-3129b (TIC 4711.01), TOI-3321b (TIC 306648160.01), TOI-3894b (TIC 165464482.01), TOI-3919b (TIC 23769326.01), and TOI-4153b (TIC 470171739.01) from NASA’s Transiting Exoplanet Survey Satellite (TESS). These are all short-period giant planets with periods between 1.4 days and 7.4 days, radii between 0.9 RJ and 2.1 RJ, and masses between 0.57 MJ and 4 MJ. The host stars of these systems have V-band magnitudes between 11 and 12.9. We have obtained radial velocity measurements from CHIRON and TRES, and are continuing to collect follow-up photometry of each planet to confirm these systems as bonafide exoplanets. In our poster, we will present preliminary model fits and place these systems in the context of the larger population of short-period giant planets. These planets are important new additions in a larger effort within TESS to construct a magnitude-limited sample of Hot Jupiters that will be used to better understand the eccentricity distribution and migration histories of giant planets.
Day ‘N’ Nite: Habitability of Tidally-Locked Planets with Sporadic Rotation – Cody Shakespeare (#36)
TRAPPIST-1 has 7 Earth-size exoplanets in close proximity that are in resonance. N-body simulations show that these planets can experience relatively large eccentricity and mean motion variations. Most studies and discussions of these planets’ climates assume these planets are always tidally locked, as are many other M-dwarf, habitable-zone planets with short orbital periods. However, large eccentricity and mean motion variations in TRAPPIST-1 can lead to sporadic rotation of the planets with synodic rotation periods on the order of years. I conduct N-body simulations using REBOUND to retrieve the evolution of orbital parameters in the TRAPPIST-1 system. The orbital parameters are used to produce a continuous equation of motion which describes the evolution of the substellar longitude and, thus, the hemisphere illuminated by the star. I will discuss the nature of these planets that transition between tidally-locked and slow rotation states, the origin of these transitions in TRAPPIST-1’s unique orbital dynamics, and the impact on climate using EBM models.
Revised Demographics of Earth-like Planets in Binary Star Systems – Kendall Sullivan (#7)
To infer intrinsic planet formation properties it is vital to fully leverage the statistical strength of all known planets in a population, especially when measuring important features like the average number of Earth-like planets around each star or planets near the radius gap. One reason for excluding systems from consideration in occurrence rate calculations is stellar multiplicity, which can bias observed stellar and planetary properties. However, binaries are common, so although planet occurrence is suppressed in binaries, neglecting potential Earth analogs and other interesting systems because of stellar multiplicity reduces the statistical robustness of occurrence rates. Planets in close binary systems (separation < 50 AU) are rare, meaning that planets in multiples are also interesting in their own right as outliers in the planet formation process. To explore the population of planets in binary stars, we are retrieving the properties of spectroscopically unresolved binary stars, which will allow us to explore the properties of binary-star planet-hosts and revise the properties of planets in binary star systems. We will present initial results from this work and discuss ongoing efforts to expand our study to interesting new subsamples, such as planets around the radius gap.
Detecting Planet-planet Occultations in Multi-planet Systems – Nick Tusay (#37)
Transit timing variations (TTVs) have proven useful in accurately predicting transit events for planets in multi-planet systems. This can be extended to determine the position of planets in well characterized systems at any point in their orbit. When the orbital plane of a given system is edge on, planets can be observed to pass in front of each other as well as their host star in a scenario called planet-planet occultation (PPO). These points in the orbits of such systems may present unique observational opportunities. Analogous to the way the Deep Space Network operates, radio signal spillover may be optimally detectable during these PPO windows. This applies directly to time-domain technosignature detection. Determining PPOs can identify particularly interesting times to conduct a Search for Extraterrestrial Intelligence (SETI) both in archival data and for future observations. The work presented here describes the progress of this project, including identifying ideal exoplanetary systems, demonstrating PPO determination, conducting a search on archival Breakthrough Listen data for Technosignatures, and future observations and applications.
The role of planet formation in protoplanetary disk chemistry – Eric Van Clepper (#12)
The carbon to oxygen (C/O) ratio of giant planets may be used to constrain formation location in the protoplanetary disk (PPD) based on predicted disk C/O ratios between the gas and dust which vary as volatiles freeze-out at snowlines (Oberg et al. 2011). However, disk observations have revealed much higher C/O ratios (>1; Bosman et al. 2021) in the gas phase, that cannot be explained by snowlines alone. Destruction of carbon monoxide (CO) vapor via UV photons, followed by reprocessing of O into water ice may be an effective way of removing O while leaving C in more volatile chemical species is one viable means of reaching these high ratios (Miotello et al. 2019). To date, consideration of these processes have yet to produce the high C/O ratios inferred in the disks. These previous studies, however, have relied on static disk models, where processing occurs in a range of fixed conditions. In reality, we know disks to be dynamic environments, with dust settling and growth occurring along side chemical processing in the first few million years of the disk lifetime. The removal of fine dust from the disk surface as pebbles form at the midplane decreases the UV opacity, allowing for increased rates of photochemistry deeper in the disk, while simultaneously depleting the available surface area for ice deposition. Additionally, many disks, even young ones, exhibit substructures potentially carved by forming planets; such planets would create complex gas flows within the gas and halt the radial transport of solid material. These dynamic effects can lead to local variations in chemistry, including the bulk C/O ratio as well as a range of carriers of varying volatilities for C and O (Van Clepper et al. 2022). Understanding the coupled chemical and physical effects, and their feedbacks, on the disk composition is key to connecting giant planet compositions to their formation history in the PPD.
Powerful flare phenomena in water vapor maser lines in IRAS 16293-2422 – Alexandr Volvach (#32)
IRAS 16293-2422 is a protostellar system of Class 0, as seen in surveys of young stellar objects. The paper presents new data on powerful long-term water maser phenomena in features with a radial velocities near -1.5, 6 and 8 km/s, occurred in the young binary system IRAS 16293 and provides an interpretation of the data obtained. The observations at a frequency 22.235 GHz of the 6_16 – 5_23 water-vapor maser transition have been made from 2019 January to 2020 February using the 22-meter telescope located in Simeiz. Unusual powerful flare phenomena at features near 6 and 8 km/s, consisting of individual water maser flares and emanating from maser spots located close to each other in maser clusters were discovered. Short power maser flares occurred on the top of a longer duration ones but less powerful flares, possibly initiating a powerful maser radiation of more short flares. In a separate case, additionally, such a powerful initiator of maser emission was an ultra-short flare of an unsaturated water maser. It was also established for the emergence of powerful water masers, a sufficiently high (more than 0.5 kJy) input flux into the maser formation is required. Important physical parameters of IRAS 16293-2422 water maser flares have been obtained: states of the water maser during flares their amplitudes, maser line widths and kinetic temperatures, the existence of a cascade amplification of the water maser in cases of powerful short flares.
TOI-588b an inflated brown dwarf around a young, rapidly rotating A-star – Noah Vowell (#33)
We present the discovery and characterization of TOI-588b from NASA’s Transiting Exoplanet Survey Satellite (TESS). TOI-588b is an inflated (1.6 RJ) brown dwarf on a highly eccentric (e = 0.54) 39 day period. The host star is a bright (V = 7.3) 10,500K A-star with a mass of 2.3M and radius of 1.8R making it the hottest brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion’s mass of 67 MJ as well as the host star’s rotation rate (vsini ~ 55km/s). We identify a comoving group of stars of which TOI-588 is a member, and estimate its age to be ~100 Myr. With a measured mass, radius, and age, TOI-588b becomes a benchmark for substellar evolutionary models.
High-contrast imaging with the JWST MIRI MRS – Kadin Worthen (#10)
The JWST Mid-Infrared Instrument (MIRI) Medium Resolution Spectrograph (MRS) will provide the first mid-infrared spectra of directly image exoplanets and revolutionize our understanding of giant exoplanet atmospheres. Only the MRS will be able to characterize the silicate cloud particles in directly imaged planet atmospheres. The MRS was not designed with coronagraphic capabilities in mind, so PSF subtraction is the only path to spatially resolved, high-contrast spectroscopy of giant exoplanets. The publicly available MIRI simulation tool is known to have unrealistic PSFs, so we generate our own simulated observations with realistic PSFs, detector effects, and pointing uncertainties. We develop a reference differential imaging (RDI) PSF subtraction technique to test contrast performance and determine optimal observing strategies. We achieve a 1σ contrast of approximately 1×10-4 at a separation of 1 arcsecond at 5 microns. We demonstrate that is method of RDI can recover a companion with a separation of 1.5 arcseconds and a contrast of 5×10-4 with a signal-to-noise ratio of ~10. We find that including target acquisition can improve contrast performance by up to a factor of 3 at small angular separations. We are currently determining the best observing strategies for high-contrast observations and investigating the contrast performance across all MRS wavelengths.
Mapping the Inner Edge and Interior Cavity of Circumbinary Protoplanetary Disk AK Sco – Brianna Zawadzki (#26)
With recent exoplanet-hunting missions like Kepler and TESS, over 5000 exoplanets have now been confirmed. However, fewer than two dozen are circumbinary (CB) planets. In order to contextualize this population of CB planets, it is necessary to better understand the CB disks from which they form. A strong source for a case study is the disk around AK Sco, an equal mass F5 binary with an orbital period of 13.6 days and eccentricity e=0.47. We are analyzing high resolution (0.02”, 2.8 au) ALMA continuum observations of AK Sco, which reveal a large (>20 au) cleared dust cavity and azimuthal asymmetries in the dust ring. We will use these observations to better constrain the morphology of the inner edge of the disk, as well as search for additional structure that may be present as a result of influences from the central binary, one or more giant planets, or the advanced age of the 11 Myr old system. We are also analyzing high spectral resolution (0.16 km/s) ALMA observations of the 12CO J=2-1 line, which will probe the gas kinematics in the inner disk. Mapping the dust distribution and gas velocity field of AK Sco will help constrain CB disk properties such as mass and lifetime, shedding light on processes that occur in CB disks and the formation of CB planets.
FIESTA II. Disentangling stellar and instrumental variability from exoplanetary Doppler shifts in Fourier domain – Jinglin Zhao (#25)
We present an improved FourIEr phase SpecTrum Analysis (FIESTA) to disentangle apparent velocity shifts due to a line deformation from a true Doppler shift. FIESTA projects stellar spectrum’s cross correlation function (CCF) onto a truncated set of Fourier basis functions. Using the amplitude and phase information from each Fourier mode, we can trace the line variability at different CCF width scales to robustly identify and mitigate multiple sources of RV contamination. For example, in our study of the 3 years of HARPS-N solar data, FIESTA reveals the solar rotational effect, the long-term trend due to solar magnetic cycle, instrumental instability and apparent solar rotation rate changes. Applying a multiple linear regression model on FIESTA metrics, we reduce the weighted root-mean-square noise from 1.89 m/s to 0.98 m/s. In addition, we observe a ~3 days lag in the FIESTA metrics, similar to the findings from previous studies on BIS and FWHM.