Photometric variations from stellar activity as an age indicator for solar-twins

Stellar ages are elusive to measure, albeit being very important for understanding stellar evolution. We investigate the impact of photospheric activity on 2-min cadence light curves from the TESS/NASA mission of a selected sample of 30 solar-twins with well-determined ages. The photometric variability, A(T ESS), of the light curves due to rotational modulations by the presence of activ e re gions was estimated and correlated with chromospheric activity (Ca II H&K lines from an e xtensiv e High Accurac y Radial velocity Planet Searcher (HARPS) at the European Southern Observ atory (ESO) HARPS/ESO acti vity time series) and ages. Moreo v er, these results were compared with the total solar irradiance amplitude behaviour during the solar magnetic cycles 23 and 24, validating our findings for solar-twins. Our results show the photometric amplitude to be strongly correlated to the av erage lev el of chromospheric activity for the star sample. Also, we found a good correlation of A(T ESS) with stellar age (in Gyr) described by log t = + 12 . 239 - 0 . 894 log A(T ESS). In conclusion, stellar photometric variability A(T ESS )may be used as a simple age diagnostic for solar-twins.