Robust exoplanet masses from transit timing variations

I’m going to try to post on a semi-regular basis about whatever astronomy thing has interested me on a given day. it’s probably be a bit random and not well explained.

Today I was chatting with some by Kepler buddies about a paper by Ofir where they measure the mass of two planets orbiting KOI-1574 using transit timing variations. The part I find interesting is that Ofir finds one of the planets has a density of 0.1 g/cc – much lower than any planet in our own Solar System. We were concerned with the uniqueness of the solution given there are only 4 transits of the planets of each planet in the Kepler data.

Dan Foreman-Mackey has been developing an n-body/transit model code that can be used to used to model systems like KOI-1574. I hope/plan to run an MCMC simulation that should reveal whether the ultra-low density found by Ofir is significant and robust. Not that I’m trying to pick on Ofir, his analysis seems perfectly reasonable to me. It does however provide a convenient example to test the code upon.


We’re back!

We’re back, and by that I mean the US government is back. For the last 16 days I’ve been locked out of my office at NASA Ames. As a contractor I’ve been allowed to work, indeed I’ve had quite a productive few weeks.

The first week of the shutdown the SETI Institute in Mountain View kindly hosted me and provided free coffee! With all the Kepler science office in the same room we were able to chat about a few projects we were all working on and it looks like a few papers that have been a long time coming are nearly finished (Kepler planet catalog papers).

Last week I took the opportunity to visit New York University as a guest of David Hogg. We have a few projects together that have been left on the backburner. Hopefully we/I will get these going this time. One of the more straight forward ideas we have is to measure limb darkening using transit of multi-planet systems.

Anyway, I’m going to try and use this blog as a bit of a research/work journal. It may not work, let’s see.