My student Sharon Wang (王雪凇) has recently finished a big paper with lots of goodies in it.
First of all, there is the announcement of a new Jupiter analog. It’s a bit on the massive side (at least 3.4 times the mass of Jupiter) but it’s on a circular orbit with a 7.5 year period around a star a bit cooler than the sun, HD 37605. There are not very many of these in the literature, but they’re starting to pop out now that Doppler searchers have gotten old.
We actually co-discovered this planet with the Texas group, led by Bill Cochran, Mike Endl, and Phillip MacQueen. This star was already known to host a 55-day period super-Jupiter; in fact that planet was the first planet discovered with the Hobby-Eberly Telescope. The Texas team had already discovered the second planet almost three years ago, and we noticed it soon thereafter.
We were trying to firm up the orbit with Stephen Kane as part of the TERMS project to detect the transits of long-period planets. We were using Keck and HET velocities together, and noticed that there must be a long-period planet because there were large residuals to the published solution.
Stephen announced this at a AAS meeting where Bill was in the audience, and a collaboration was born. The Texas team very graciously sent us all of their raw data so that we could do a robust joint analysis, and now it’s finally here.
Sharon worked very hard on formalizing our procedure for calculating robust uncertainties for orbital parameters, especially the transit time parameter. Uncertainties for transit times cannot be accurately calculated from published orbital solutions (a point we describe in detail in this paper), and Sharon’s new code, called “BOOTTRAN” uses a statistical bootstrapping technique to determine orbital parameters and their uncertainties, including transit times. BOOTTRAN is available for download along with RVLIN, our IDL code for fitting radial velocities. Sharon also provides a thorough statistical description of how our bootstrapping works in an appendix.
Also in the paper is a thorough transit search by Gregory Henry’s APT array and Stephen’s team using the MOST satellite. We were looking to see if our new solution for the inner planet allowed us to determine if the planet transits. We find that the solution is good enough, and that the planet does not transit.
But we can’t just say we “failed to detect a transit”, because we didn’t fail: we succeeded, at more than the 100-sigma level, in showing that there is no transit. That’s the power of BOOTTRAN’s uncertainty estimates and MOST’s photometric precision.
So we have a “dispositive null” of non-grazing transits, and we said so in the paper, both in the title and in a footnote where we define the term.
Sharon also did a thorough comparison of BOOTTRAN’s uncertainties vs. the output of an MCMC dynamical model by Matthew Payne, which produced parameter uncertainties as well. There are a lot of details and caveats, but the bottom line is that BOOTTRAN gives the right answers.
So fellow scientists: you can now use the term “dispositive null” and cite its definition in the refereed literature. You can now get accurate parameter uncertainties with all-in-one IDL code that uses and plays nice with RVLIN. And there is a new multiplanet system on the block, one that contains a good Jupiter analog.