| Name: Varghese Reji |
| Affiliation: Tata Institute of Fundamental Research Mumbai |
| Conference ID: ASI2026_273 |
| Title: Modeling the vertical velocity gradient to disentangle stellar activity from exoplanet signal |
| Abstract Type: Oral |
| Abstract Category: Sun, Solar System, Exoplanets, and Astrobiology |
| Author(s) and Co-Author(s) with Affiliation: Varghese Reji(Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai - 400005, India), Joe Philip Ninan(Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai - 400005, India), Asha Lakshmi K V(Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai - 400005, India) |
| Abstract: Extremely precise radial velocity (EPRV) measurements are critical for discovering
habitable planets and estimating their masses. Modern EPRV instruments have achieved cm/s stability, however, that hasn’t translated to the discovery of earth-like planets around sun-like stars. Below a few m/s, the Doppler shift of spectral lines due to stellar activity will start dominating planetary signals. A planetary radial velocity signal should be consistent across all the heights, while a stellar activity-induced photospheric velocity, could be different at different heights of the stellar atmosphere. Based on this idea, we developed a method to disentangle stellar activity signals and planetary signals in radial velocity data. In our model, we treat the rising and falling lanes of granulation separately. We first calculate the ‘granulation contrast’, and then determine the velocity profile of both raising and falling lanes. Using Korg, a julia package for spectral synthesis, we solve the radiative transfer equation with an atmospheric model after Doppler shifting each photospheric layer by a vertical velocity profile model. To test our model, we fit this synthetic spectrum with multi epochs of disk-averaged solar spectra observed with NEID. The stellar activity parameters of our model are the coefficients of the velocity gradient polynomial. In this talk, I will present our model and its effectiveness in disentanglling planetary signals from stellar activity signals.
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