Determining the Mass of Kepler-78b with Nonparametric Gaussian Process Estimation

Presented in a press release session at the American Astronomical Society Meeting in Seattle, WA in January 2015.

Transcript

1. Determining the Mass of Kepler-78b with Nonparametric Gaussian Process Estimation Samuel K. Grunblatt, University of Hawaii SKGrunblatt@gmail.com (845) 430-4603 www.ifa.hawaii.edu/users/skg Key Collaborators: Andrew Howard, Raphaëlle Haywood
2. A New Method to Measure Small Planet Masses Around Active Stars Samuel K. Grunblatt, University of Hawaii SKGrunblatt@gmail.com (845) 430-4603 www.ifa.hawaii.edu/users/skg Key Collaborators: Andrew Howard, Raphaëlle Haywood
3. Context - Radial Velocity (RV): motion toward or away from us, measured as redshift (or blueshift) of spectral lines. Can come from stellar proper motion, stellar activity, or reflex motion due to a planet. - First known extrasolar planet detected in RV signal. - First signal: ~70 m/s - Current detection limit: ~1 m/s - RV signal from Sun’s activity: ~1-10 m/s - RV signal of Earth: 9 cm/s Need to account for stellar activity to detect Earth in RV.
4. Kepler-78b: Detection Sanchis-Ojeda et al. (2013) Porb = 8.55hr Rpl = 1.16 ± 0.19R
5. Kepler-78b: Confirmation Howard et al. (2013) M HIRES = 1.69 ± 0.41M M HARPS N = 1.86+0.38 0.25 M
6. Nonparametric vs. parametric RV models HARPS-N data HIRES data Howard et al. (2013) vspot(t, ) = 3 X i=1 ai sin[ i + i2⇡t/Prot] + ⌃ij = k(ti, tj) = h2exp  ⇣ti tj ⌘2 Grunblatt et al. (2015)
7. Nonparametric vs. parametric RV models HARPS-N data HIRES data Howard et al. (2013) vspot(t, ) = 3 X i=1 ai sin[ i + i2⇡t/Prot] + ⌃ij = k(ti, tj) = h2exp  ⇣ti tj ⌘2 Grunblatt et al. (2015)
8. Using lightcurves and RVs together Kepler lightcurve of Kepler-78 HARPS-N data HIRES data
9. Using lightcurves and velocities together Kepler lightcurve of Kepler-78 HARPS-N data HIRES data
10. Results M HIRES = 1.69 ± 0.41M M HARPS N = 1.86+0.38 0.25 M Kepler-78b Mpl = 1.87+0.27 0.26 M K = 1.86 ± 0.25 m s 1 (KEarth = 0.09 m s-1)
11. Finding new planets around active stars Barclay et al. (2015) Kepler-91b: Giant planet around active, red giant star
12. Finding Earth 2.0 - Better instruments needed: Stellar activity is 10x weaker, but planetary signal is 20x smaller, so similar analysis necessary - Longer time baseline needed: nonparametric method necessary after a few stellar rotations to describe appearance and disappearance of starspots, but Porb ~ 15 stellar rotations. - First test case: Kepler-10?
13. Summary Contact: SKGrunblatt@gmail.com (845) 430-4603 www.ifa.hawaii.edu/users/skg - Developed new, more robust method to measure the mass of a planet - Reproduced results of previous studies. - An important step toward measuring the mass of Earth 2.0! M HIRES = 1.69 ± 0.41M M HARPS N = 1.86+0.38 0.25 M Kepler-78b Mpl = 1.87+0.27 0.26 M
14. Thanks for listening! Contact: SKGrunblatt@gmail.com (845) 430-4603 www.ifa.hawaii.edu/users/skg