Benjamin Montet

Presenting my work at Cool Stars 19, Uppsala, Sweden. Image Dave Charbonneau.

Long-Term Photometric Variations of Kepler Stars

Kepler has measured short-term variations in the observed flux of hundreds of thousands of stars as a part of its search for exoplanets. During this search, signs of long-term variability in the stars are intentionally destroyed. Full-frame image (FFI) data from Kepler provide an opportunity to recover this variability to better measure long-term photometric variations. In a recent paper, we applied this idea to KIC 8462852, finding it faded by more than 3 percent over the four years of the Kepler mission. We have since released this code as the f3 software package and applied this method to thousands of Sun-like stars, which you can read about in this preprint. The data behind this work can be found here.

Transit Timing Variations in Kepler

If a planet's inclination relative to our line of sight is just right it will transit its host star, causing a small dip in the amount of light received from the star once per orbit. A single planet orbiting a star will cause these transit events to occur exactly periodically. If there are multiple planets orbiting the same star, these planets can gravitationally perturb each other, causing the observed transit events to occur earlier or later than expected in a way that depends on the perturbing planet's mass, eccentricity, and inclination. Previously, other collaborations have built catalogs of the times of transit of planet candidates in the Kepler field. I am building on these catalogs by developing a database of posterior distributions for the time of each transit, incorporating the effects of correlated noise in Kepler and missing data. I'm working on this project with Juliette Becker (Michigan).

Young M Dwarf Binaries

Over the past decade, loose associations of young stars in the solar neighborhood with common ages, kinematics, and origins have been a subject of increasing interest. These young moving groups enable us to test theories of stellar evolution over the first 100 million years of stars' lifetimes. These theories have led to models of young stars, but these models are highly uncertain: different models can predict individual stellar masses that differ by a factor of two or more. To better constrain the low-mass end of these models, we are observing young M dwarf binaries. We have a sample of 60 stars in young, low-mass binary systems for which dynamical masses can be measured on short timescales. By combining astrometric imaging data throughout the orbits of these binary stars with radial velocities, we hope to measure the individual mass of many of these stars to a precision of about 15 percent. I'm working on this project with Brendan Bowler (Caltech).