Abstract Details
| Name: Gayathri Viswanath Affiliation: Christ (Deemed to be University), Bengaluru Conference ID: ASI2019_275 Title : Star-Planet Interactions: a study in UV using GALEX and GAIA Authors and Co-Authors : Gayathri Viswanath, Mayank Narang, Manoj Puravankara, Blesson Mathew Abstract Type : Oral Abstract Category : Stars, ISM and Galaxy Abstract : Most (>80%) of the ~3800 confirmed exoplanets known today orbit very close to their host stars, within 0.5 AU. Planets at such small orbital distances can result in significant interactions with their host stars. Through gravitational/tidal and/or magnetic interactions, planets can induce increased activity levels in host stars; host stars can also affect and shape planetary properties via stellar irradiation. Such interactions and their observable consequences are best studied in the ultraviolet regime. In this work, we study the star-planet interactions in the UV using a large sample of GALEX detected host stars with confirmed exoplanets and making use of the improved host star parameters from Gaia DR2. We find that the variation of planet radius with insolation flux from the host star shows a tuning fork trend: beyond a threshold flux, the planet radius increases with increasing insolation flux for giant planets (Rp > 8 R_Earth) and decreases with increasing insolation flux for small planets (Rp < 4 R_Earth). A clear dearth of planets between 4-8 R_Earth also shows up as a sub-Saturn desert. A similar trend is seen in a multi-wavelength analysis of the planet radius variation with FUV, NUV, Visual and NIR flux from the host star at the planet location. Our analysis indicate that either a wavelength independent inflation mechanism is operating or an even higher energy flux contributes more significantly to the planets' atmospheric heating. We further examined if the star-planet interactions enhance the UV activity of stars hosting massive close-in planets. We do not see any clear evidence for enhanced UV activity in stars with close-in planets compared to those with far-out planets, contrary to the claims made by previous studies. |