Abstract Details
| Name: Varghese Reji Affiliation: Tata Institute of Fundamental Research Mumbai Conference ID: ASI2025_456 Title : Modelling the vertical velocity gradient to disentangle stellar activity from exoplanet signal Authors and Co-Authors : Varghese Reji 1, Joe Ninan 1, Asha Lakshmi K V, NEID team Abstract Type : Poster Abstract Category : Sun, Solar System, Exoplanets, and Astrobiology Abstract : Extreme precision radial velocity (EPRV) measurements are critical for discovering habitable planets and estimating planet mass. Modern EPRV instruments are intrinsically stable at a few cm/s, 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. Stellar activity signals are spurious Doppler shifts measured in the spectrum of a star due to any changes in the fluid flows of the photosphere. The formation of active regions and star spots, or the suppression of the convection flow, causes spurious disc-averaged radial velocity shifts in the order of m/sec. Disentangling this signal from Doppler shifts due to a planet is the central problem in the planet discovery field. Since the spurious radial velocity shifts are driven by the changes in the average flow velocities in the stellar photosphere, we expect to see signatures of this in the radial velocity measured at different heights of the stellar atmosphere. 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 atmosphere. Based on this idea, we are developing a method to disentangle stellar activity signals and planetary signals in radial velocity data. We first model the spectra generated from various depths of the photosphere, then calculate the radial velocity associated with that. We will use the NEID solar data to fit our models and test the ability of the algorithm to disentangle the photospheric velocities from the planetary signal. Here I shall present our model and the progress so far. |