In part 1, I described my involvement in the MARVELS project and the discovery of a brown-dwarf-mass object orbiting the star now known as MARVELS-1. I had been concerned about very large radial velocity residuals to our orbital fit, and was stunned to discover they were consistent with an inner planet orbiting the star in a 3:1 commensurability with the BD.

In part 2, I explained our attempt to characterize the system, and our general unease with the system:  the resonance appeared to be perfect, there were not many stable dynamical solutions, the star had two AO companions, and I kept getting lots of hints that this sort of thing might come from contamination.  But the spectrum was clean of contaminants, and the photometry was rock-steady.  We finally decided to get some Keck data to settle the issue.

When the Keck data came back in, it was consistent with HET:  both signals showed up clearly.  This ruled out a lot of my concerns about contamination from the AO companions:  if those companions were, against all odds, contributing flux to the HET spectra, the narrow slit at Keck should have filtered them out, or at least produced highly variable contribution.  Instead, the signal was exactly the same, no matter what angle the slit was positioned in.  This convinced me the AO companions were not a problem.  (In fact, Justin Crepp found that the distant one was, in all likelihood, a foreground M dwarf, further explaining why the star contributed no optical flux).

Still we worried.  To illustrate the level of our concern, here are some of the scenarios we seriously considered:

– A pulsating star, with slightly non-sinusoidal radial velocity signatures.  We looked at the known classes of variables, and concluded that Cepheid variables were our main confounders, given the 6-day period of the signal.  This is actually a surprisingly plausible explanation.  A survey like MARVELS might include a giant star by accident, since it does not have trigonometric distance measurements to most of its targets.  The North Star, Polaris, is (despite Shakespeare’s famous “I am constant as the Morning Star”) a Cepheid variable.  That this fact was not known for a long time is a testament to the low photometric amplitude and subtlety of a low-amplitude Cepheid.  In fact, Polaris shows 1 km/s amplitude RV variations that look for all the world like a giant planet in a short period orbit.  It also shows no spectral changes in temperature as a function of phase, so there is not much to tip you off that it is a pulsator:

From Hatzes and Cochran (2000).  This perfectly sinusoidal RV signal with a 3.94 day period around a star photometrically stable at the level 150 mmag level is not from a planet.  the star is Polaris, and the variations are from stellar pulsations.

But MARVELS-1 is decidedly not a giant, and the KELT photometry rules out variability at a much lower level than 150 mmag, and Cepheids to NOT have overtones with 3:1 period ration, so this is not what’s going on.

But still, this is something broad RV planet searches need to watch out for.

– Two objects orbiting two stars?  Could the two signals we see be from different stars?  The AO companions would be the candidates, but they are too faint.  Also, the 3:1 commensurability strongly implicates a single system, since it is so perfect.

– Could it be a binary brown dwarf?  If MARVELS-1 b were a equal-mass binary brown dwarf, we would see exactly the perturbations we see.  The idea here is two 14-Jupiter-mass BDs in mutual, 4-day orbit, together orbiting MARVELS-1 in a 6-day orbit.  Twice per 4-day orbit, the BDs would switch from being aligned with MARVELS-1 to being in quadrature, and the variable quadrupole moment would induce a weak 2-day signal on MARVELS-1.     

This possibility is actually plausible in an order of magnitude calculation, but the dynamical stability of the system was so manifestly impossible that I couldn’t get Eric Ford to stop rolling his eyes long enough to even decline to run the simulations.  

I thought it was pretty clever, though.

I called Debra Fischer for a consult.  Her immediate reaction was the same as many others’:  it’s contamination.  There has to be spectral contamination.  I explained why it couldn’t be:

She stuck to her guns:  it reeks of spectral contamination.

I was at the Jackson Hole Extreme Solar Systems II meeting (which served as a sort of festschrift for Geoff Marcy) and I spent a lot of time talking with Suvrath Mahadevan and Andrew Howard about the system.  The system kept passing every test, but we couldn’t shake the feeling something was wrong.  What if it was contamination (even thought it couldn’t be) what would that look like?

I knew very well that in addition to the great planets — such as the Earth, Jupiter, Mars, Venus — to which we have given names, there are also hundreds of others, some of which are so small that one has a hard time seeing them through a telescope. When an astronomer discovers one of these he does not give it a name, but only a number. He might call it, for example, “Asteroid 325.”…

…[Asteroid B-612] has only once been seen through a telescope. That was by a Turkish astronomer, in 1909.

On making his discovery, the astronomer had presented it to the International Astronomical Congress, in a great demonstration. But he was in Turkish costume, and so nobody would believe what he said.

Grown-ups are like that…

Fortunately, however, for the reputation of Asteroid B-612, a Turkish dictator made a law that his subjects, under pain of death, should change to European costume. So in 1920 the astronomer gave his demonstration all over again, dressed with impressive style and elegance. And this time everybody accepted his report.

I had a pretty strong reaction to the IAU’s recent press release regarding exoplanet nomenclature.  The proximate cause of the IAU’s action was the Uwingu planet naming contests, but what got me riled up was what I felt was an imprecise (or, frankly, inaccurate) description of the IAU’s role in naming planets and how the databases like exoplanets.org get their designations.

I also made a second post clarifying my objections and offering suggestions of how I would have edited the IAU press release to make it accurate.

In the meantime, Rachel Akeson of the NExScI Exoplanet Archive contacted me to see if I would like to make a formal comment to Commission 53 regarding the role of our websites.  I agreed, and we enlisted both Jean Schneider (architect and maintainer of the Exoplanet Encyclopedia exoplanet.eu) and Alan Boss (former chair of the Working Group on Extrasolar Planets for the IAU; this group later became Commission 53) to join our effort.

The four of us put together a statement that you can find here.  It summarizes the history of the IAU’s role in the nomenclature of exoplanets.

The IAU has now responded to our letter. In particular, they agree that “[T]here have never been formal or official recommendations from the IAU about the nomenclature scheme” for exoplanets. 

I want to point out that the fact that Alan Boss, Jean Schneider, and Rachel Akeson signed on to this letter should not be read as implying that all of us endorse any opinions the others have expressed on the subject of the wisdom or propriety of the IAU, Uwingu, or any other organization giving names or formalizing designation schemes for exoplanets.  In fact, I am pretty sure that we do not agree on these topics, so please consider anything that I have written on the topic represent no one’s position but my own.  

My personal interest in getting this letter out was to clarify that the IAU does not bless or maintain any exoplanet list or database, and that the IAU does not name and has not named exoplanets, or granted any “official” designations to them.  I am pleased that the IAU has agreed with these points, as laid out in our letter.  I am also pleased to see that the full commission will be convening to address the issue of popular names, presumably including the efforts of Uwingu.

As Jean Schneider points out, this is all rather petty in the grand scheme of things.  But to any readers that think there is nothing to see here, and this is much ado about nothing, please contrast the original statement by the IAU with its response to our letter; contrast its implicit characterization of Uwingu with Uwingu’s actual actions; and consider my markup of their original press release.  Consider that an IAU press release outside of a General Assembly is a rare event and therefore a big deal, as it represents the official position of the global astronomical community.  I think it’s important that when this happens, it gets it right.

On April 29, Alan Boss, former chair of the Working Group on Extrasolar Planets of the IAU (now Commission 53), and the maintainers of three of the exoplanet databases, including me, sent the IAU a formal letter requesting that they join us in clarifying how exoplanets get their names and designations.  Here is the response from the Alain Leavelier des Etangs, President of Commission 53: 

On April 29, Rachel Akeson, Alan Boss, Jean Schneider, and I sent the following letter to the IAU [slightly edited for this forum].  The formal response from the IAU is here.

Alessandro Sozetti chairs the day’s final session, on “The Small Star Opportunity.”

Says “If you are a current or former student of Dave Latham, please raise your hands.”  A very good showing.  “If you are a long or short term collaborator, raise your hands” (most of the room has their hands up now).  

“The few who have not raised hands, please pay your registration fee.”

Now, the first speaker is (close AstroWright friend) John Johnson. 

He says that his experiences with Dave, mostly after having given a talk, is that Dave has been “extraordinarily kind to other scientist”  Dave looks incredulous until John continues  “…especially to younger scientists.  I’ve seen him be cranky with older scientists.”  Thanks Dave for that and says being kind to younger scientists really sets a good tone for science.  This gets applause.

Problem: it’s difficult to characterize M dwarfs.  John is describing the work of several Jamie Lloyd students and postdocs, Barbara Rojas-Ayala, Phil Muirhead, and Kevin Covey.   This gives radii of the M dwarfs, lets us get good radii for the planets.

KOI 961 is a near twin of Barnard’s Star, which is very well characterized, which really helped.  The KOI 961 triple system has all 3 planets smaller than the Earth, and the best figure “for scale” is not 51 Peg, but Jupiter and the Galilean Satellites.  

“I love that I can say that and nobody gasps.  It’s just ‘yeah, we’ve seen that.’ What a great era this is.”

Two undergraduate students found a strange M dwarf transit around KOI 256 — the flat bottomed, very sharp ingress/egress.  RV work at Palomar revealed that the “transit” was at the wrong phase, is actually the secondary eclipse.  The true transit is at the wrong depth because of lensing effects.   Kepler does general relativity!

Next up, John Swift’s work on Kepler-32, a 5 planet system with the innermost planet in a 0.01 AU, 0.7 day orbit, and the next two out participate in a 3:2:1 period commensurability.    Might be very typical of M dwarf systems, which dominate planets in the Galaxy.

Next, Morton & Swift’s work on a period-normalized non-parametric radius function with a modified kernel density estimator.  Most common size planet around M dwarfs so far: 1 Earth radius.  Statistically significant bump near 2.2 Earth radius, maybe.  See a real deficit in distribution at less than 1 Earth radius.  Shows that MEarth will have great success with just a bit more precision (distribution falls off above 3 Earth radii = GJ 1214).

Cites Dressing’s work that there are 0.15 Habitable Zone planets per star.  Nearest Earth-size planet in the HZ is 21 pc away.

Next up Suvrath Mahadevan about the “challenges and opportunities” of near infrared precise radial velocities (“another tool in our toolbox in finding planets around M stars”).  

Starts with a detour about APOGEE: 300 fibers on the Sloan telescope doing H band velocities.  

At one point, the APOGEE team said “we think we’ve found a planet” and sent him an RV curve that got sent to him; APOGEE was very excited because they saw a 80-day period signal around a 7th magnitude star.  This sounded very familiar.  [At this point Dave Latham is looking at the 2MASS ID, which has the coordinates, and says “hey, wait a minute” and the audience starts to catch on].  Suvrath^* looked the star up in the literature, and it turned out to be HD 114762!  They were using this as a telluric standard, and the RV pipeline had seen variation.  This is the first NIR exoplanet detection!  Suvrath declares that NIR can now clearly detect exoplanets.

NIR information content isn’t as high as optical, but more flux means you win in Z, Y, J.  Habitable Zone Planet Finder (HPF) has R~50,000, with requirement of < 3 m/s precision and goal of 1 m/s on best stars.  Heritage comes from Larry Ramsey’s Pathfinder tested at Hobby-Eberly Telescope.  Pathfinder retired a lot of risk and concern about NIR spectrographs, including detector issues (persistence, inter-pixel capacitance) and calibration sources.  

Shows actual on-sky laser fiber comb velocities, showing stability of carbon dioxide telluric lines (only stable to 5-10 m/s) and stars.  Also shows Fabry-P�rot interferometer comb tested at APOGEE, which looks great.

Hand agitation of fibers seems to reduce modal noise, but this is “not practical for a five-year survey.”  Commercial device solves the problem: “OptoTune laser speckle remover” which does exactly what it sounds like, and combines with an integrating sphere to solve modal noise of bright calibration sources.  

Octagonal fibers + double scramblers give sufficient scrambling to get sub-m/s precision.

Last speaker is Jonathan Irwin, talking about MEarth.  We would like to be able to do the sorts of science we do on GJ 1214 to Earth-sized HZ planets.  This makes mid- to late M dwarfs the most important targets.  

MEarth has been running since 2008, original survey sensitive to 2 Earth radii.

The original MEarth building was Cold War era laser ranging station.  It is bomb-proof, roof has never failed.  Also housed Fairborn Observatory before MEarth.

High proper motion of M dwarfs very useful, and MEarth data can generate parallaxes.  MEarth also 

People are always asking “has MEarth found another planet?”  Says answer is “no, and we’d like to understand why.” To do this “I have to do something naughty” — he is extrapolating from early M’s in Kepler to the late M’s from MEarth.  GJ 1214 looks like an oddball if you do this extrapolation, but if you compare by equilibrium temperature it’s not too bad.  Kepler shows the planet frequencies goes up in the same dimensions that MEarth’s sensitivities go down, so a bit more precision will yield a lot of new planets.

MEarth South is coming along soon!  

That’s a wrap for day 1.  Hopefully blogging will commence for tomorrow’s session, but perhaps not by me.  

[^* Update:  Suvrath points out that it was David Nidever and Scott Fleming were the ones that made the identification.  The full story is here.]

Post-lunch session:

[I’m indenting Latham-specific stuff to separate it from the science content here.  Dave has clearly made this a prospective conference, but many participants cannot resist anecdotes and comments about his prolific career.]

First up is Lars Burchave talking about deriving metallicities of the Kepler stars.   Two ingredients needed to extend known relations to lower-mass planets:  huge sample, and metallicities for the stars in it.  Kepler gives us the first; lots of work into getting the second.  Simple cross-correlation of synthetic library spectra to high resolution spectra of KIC stars yields good effective temperatures and metallicities; does not require high SNR.   Yields a homogeneous sample of parameters for 152 host stars.

Average metallicity correlates with detected planet radius with high statistical significance; below 2 Earth radius average metallicity is sub-solar.

Finishes with images from Google searches on “David Latham,” including those of a band called “David Latham and the Strangers,” and as an actor in “Jesus Christ Superstar”.  

More seriously, he showed images of Dave on a bike at Loveland Pass (way up at the Continental Divide) and other places, and closes with “congratulations on being one of the pioneers in the exoplanets field, so all of the rest of us can do such great work.”

Now we move on to TESS, from the PI himself, George Ricker.  Chair Josh Winn points out that George was “converted” by David Latham from an X-ray astronomer to “one of us.”  George starts with 7 years of “TESS-related proposal covers”: HETE-2 (High Energy Transient Explorer-2) turning into “Hot Exoplanet Transit Experiment-Survey by using the star tracker.  In 2008, TESS was proposed from scratch as a SMEX2 and finally a full explorer TESS to launch in 2017.  Will discover the “best” 1,000 small exoplanets.  Whole sky survey from magnitudes 4-12; 500,000 stars.  TESS will find planets around brighter stars than Kepler, although the planets will be bigger on average.   

Shows prototype TESS cameras and a full-scale mockup, and a movie illustrating the 4 camera FOV, (23 degrees square, each), which have 27 day-long stares.  The movie is very slick, and features a nifty lunar gravity assist into a transfer orbit, followed by a burn to go into a 2:1 orbital resonance with the moon, an orbit that is stable over decades (the orbit exploits the Kozai mechanism!).  

http://www.youtube.com/watch?v=mpViVEO-ymc

Josh assures the audience that the repetitive movie music will eventually get out of our heads with time (it is called “Night City” George tells us, comes free with Apple movie software).

George and Dave apparently competed over getting better deals for things when traveling;  George found the cheapest rental cars, but Dave consistently found the cheapest hotel rooms.  In this, “Dave’s tolerance for bedbugs beat mine.”

In the Q&A, we learn that TESS will point with reaction wheels (like Kepler) but George assures us that it will have 4 of them, and there is a mission that had one last for 6 whole years (the audience is both very amused and very concerned).  

Finally, Josh Winn introduces David Latham to talk about TESS.  

Josh tells us that 7 years ago he started as an exoplanet researcher, and Dave invited him into his office to discuss being part of the the Kepler followup mission.  Josh was surprised because at this point he had only 3 exoplanet papers, one of which nobody cites (“I don’t even cite it,” he says) and another that was wrong (“but does get cited!” Geoff interjects, to much amusement).  Josh concludes: “I am not the only one in this room that has benefitted from Dave’s generosity” and his “childlike enthusiasm” when he has every right to be an old grump.

At this point, Dave approaches the podium to a lengthy standing ovation.  He says that people do occasionally call him “crusty.”

Dave says it’s in retrospect a good thing that the SMEX version of TESS did not get selected, because lessons learned from Kepler have shown how hard it would have been to have a low duty cycle and low Earth orbit.  Once Kepler launched Dave “got distracted by other things,” but eventually got back to TESS.  His admonishment “sleep is for sissies” to the TESS gang made it into the glossary.   

Lessons from Kepler that informs TESS: 

• Small planets are common, so TESS will find hundreds of planets. 
• Multiples are common (and coplanar), so gravitational interactions would be important and measurable.  This also makes continuous coverage very important.  
• Photodynamical analysis is powerful and multitransiting systems are “information rich”
• Followup with HARPS-N will be essential.  
• The pipeline is challenging and critical.  Dave quotes Andrew Howard from earlier, calling the Kepler pipeline one of the great achievements in scientific computing; agrees that “that’s not far off.”

Dave’s talk is gracious and full of praise for his collaborators, especially Jon Jenkins’ team.

Josh asks for questions for “the discoverer of Latham’s planet.”

Session 2

Geoff Marcy is next talking about radial velocity measurements of 52 planets orbiting 22 stars from Kepler, half of which have asteroseismology measurements. The revealed masses and densities of some of these planets appear to be negative, because the team declined to enforce positivity in the MCMC posteriors in order to avoid biasing the overall statistics of the sample.  That is, many of the planets have not been detected in radial velocities.  

Some of the detections are consistent with rocky planets, densities of a few g/cc, others are clearly gaseous (about 1.5 g/cc).  The bigger planets are lower density, consistent with earlier transiting work and the smaller (below 2 Earth radii) planets are “mostly rocky planets” (where the “mostly” is deliberately ambiguously modifying “rocky” and “planets”, or possibly both).  Above 100 Earth masses, the trend reverses, as we transition from planets to brown dwarfs.

Geoff says 21 years ago Dave summoned the nascent radial velocity community here, and Geoff has his transparencies for his talk at that meeting with him!  Back in 1992, there were no BDs and no exoplanets.  Shows a an image of the 429 RVs for HD 114762 presented there.  Dave’s introductory remarks state that the “conventional wisdom” is that giant planets will only be found in decade-long orbits, so this will be a long-term project.  

Geoff cites, still from that conference, Bill Cochran’s First Commandment of Planet Detection: Thou shalt not embarrass thyself and they colleagues by claiming false planets.

  

The following events occurred amid a jocular mood:  “And now a controversial topic”: “Who may name a planet?”  Marcy says that anyone may suggest a planet name, and so he solicits nominations from the gallery for names for HD 114762b.  “Latham’s planet” is loudly and prominently shouted from many points of the room (and may or may not have come from plants who were sitting next to me prior to the talk).  Marcy quickly closes the nomination and holds a lightning-fast vote (“all in favor” gets hands; a vote for “all opposed” is not taken).  Marcy’s next slide:

 “HD 114762b is hereafter known as: Latham’s planet*” (“*=pending IAU approval, of course”).  

Next up is Leslie Rogers showing how Kepler has filled out the mass-radius diagram below 10 Earth radii and 50 Earth masses, including adding a new dimension of incident flux, allowing us to study retention and survival of atmospheres.  Describes the problem of inverting mass and radius measurements with uncertainties into a probability of being “rocky”.  Finds a dividing line around 1.5-2 Earth radii between rocky vs. non-rocky planets, consistent with Geoff’s talk.

Leslie finds that the boundary between “rocky” and “non-rocky” can be tightly constrained between 1.7-1.8 Earth radii in a simple, one-parameter model where “rockiness” is a simple function of radius.  In a two-parameter model with a transition region, values up to 2 Earth radii are allowed.

Finishes with a Latham memory, despite not having ever worked with him.  Dave gave many conference highlight talks at many of her first conferences, and she saw him as a “a kind senior authority figure”.  It became her aspiration to “make it into one of your summary highlight reels”. :)

Next up is Ruth Murray-Clay giving an overview of the physical processes that we have to worry about for these lower mass planet atmospheres. Shows fraction of mass lost over 10 Gyr at 0.05 AU.  HD 209458 loses 1% of its mass, which is not a big deal because it is made entirely of gas.  For a super-Earth, this is a substantial fraction of its atmosphere.

Two kinds of escape: kinetic, and hydrodynamic, regulated by the Jeans escape limit and hydrodynamic escape limits, respectively.  UV photons heat atmospheres through ionization.

3 fates for this energy: radiated away in place, conducted lower in the atmosphere, then radiated, or it could drive an outflow; all of these could be observable.  Ly-α and H₃⁺.  Low-T planets will have molecules that are good radiators, so the energy will come out as radiation.  For hot Jupiters, the result could be an energy-limited outflow.

Festschrift — A publication or conference honoring a respected academic during their lifetime, typically published on the occasion of the honoree’s retirement, sixtieth or sixty-fifth birthday, or other notable career anniversary. 

But he starts with a description of his first night on a telescope with David Latham on the 61″ Wyeth Telescope, which retired in 2005 after a 72 year lifespan.  He describes Oak Ridge Observatory and its various components.  He recognizes Robert Stefanik and Joe Zajac as the workhorses of the observatory that kept it going.

Dave’s farm is across the street from the observatory, and Dave observed every Sunday night.  He has pictures of Dave with a chainsaw taking care of the trees that have grown up around the observatory over the decades.  Andrew points out that the 61″ discovered the first exoplanet.  Andrew describes his optical SETI detector (searching for optical nanosecond laser pulses) and working with Dave on that.

Holy ****! Yes we need more precision. We are planning on asking for DDT time anyways early next week…

What if its an SB2? Could that cause aliasing of some sort to create this signal?

• Juggling the HET queue, we slowly started knocking down the sidelobes of the power spectrum with “adaptive scheduling” to only observe on nights (and tracks) that would rule out competing aliases of the period consistent with a 3:1 resonance.  Sure enough, every shot we got strengthened our conviction that the 3:1 resonance was the correct solution.  But the resonance was perfect.  Most resonances show period ratios near an integer ratio, but rarely exact, because of dynamical interactions.  This ratio was perfect to within one part in ten thousand.
• Matt Payne’s analysis struggled with the sparse data, but we finally got enough points for his code to settle into a favored overall solution, and the stable solutions were very dynamically active (which means, very exciting for a dynamicist to study!)  They also predicted HUGE transit timing variations, if the system was transiting (10 hours!), an order of magnitude larger than anything seen before (this was pre-Kepler).
• The KELT photometry came back totally stable:  this was not some sort of variable star or eclipsing binary.  It was tricky to look for transits, given the large variations expected, but Scott and the others were able to rule out most transiting scenarios, which was disappointing to some extent, but the stable photometry ruled out most false positive scenarios, too.
• The spectral analysis came back clean, with no hint of contamination, again.  But the gravity of the star changed with the new data:  we now had a regular main sequence F star, not a subgiant.  This wasn’t a big deal, but it was strange that we couldn’t pin it down better.
• Then Justin Crepp found a couple of AO companions, just to make our lives interesting:

On his blog, Preposterous Universe, Caltech Physicist Sean Carroll explains why he will not take money from the John Templeton Foundation (I saw the article reprinted at Slate).  This gave me pause: did I make a mistake when I applied for a grant through their New Horizons program, and an even bigger mistake when I accepted grant money to work on the research I proposed?

I encourage you to read his post, because he makes a cogent argument, and I don’t want to address all of the points he makes (because it would take me longer than I want to spend on the topic).

Dr. Carroll’s main point follows from his naturalism and atheism.  He believes that religion and science are fundamentally irreconcilable, and he believes that the John Templeton Foundation is dedicated to contradicting that belief.  He writes:

Justin Crepp has been getting AO imaging of our planet-search targets, helping us to figure out what the causes of our “trendy” stars are.  I’ve written about his work discovering benchmark M dwarfs orbiting nearby stars before here and here.

¹ It’s true, look it up in the Oxford English Dictionary or Encyclopaedia Britannica.

My first experience using the HET spectrograph for precise radial velocities was as soon as I arrived here at Penn State 3.5 years ago.  Suvrath Mahadevan had asked me to get some RVs for some candidates from MARVELS, the multiplexed Doppler instrument on the Sloan telescope, and part of SDSS-III. 

Figure 2 from Lee et al., announcing MARVELS-1 b, the brown dwarf companion to MARVELS-1.