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

Abstract

ABSTRACT 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, $\mathcal {A}_{ {{TESS}}}$, of the light curves due to rotational modulations by the presence of active regions was estimated and correlated with chromospheric activity (Ca ii H&K lines from an extensive High Accuracy Radial velocity Planet Searcher (HARPS) at the European Southern Observatory (ESO) HARPS/ESO activity time series) and ages. Moreover, 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 average level of chromospheric activity for the star sample. Also, we found a good correlation of $\mathcal {A}_{ {{TESS}}}$ with stellar age (in Gyr) described by $\log t = +12.239-0.894 \log \mathcal {A}_{ {{TESS}}}$. In conclusion, stellar photometric variability $\mathcal {A}_{ {{TESS}}}$ may be used as a simple age diagnostic for solar-twins.