The effect of stellar activity on the stellar parameters of a young solar twin
Most spectroscopic surveys of stellar chemical composition assume that spectroscopic equilibrium holds in solar-type stars, even for young spotted stars with high stellar activity. However, it is known that there are important abundance anomalies in young open clusters, which could be related to overexcitation and overionization effects, hence potentially affecting the assumption of spectroscopic equilibrium. Furthermore, it is known that magnetic activity causes radial velocity variability, hampering true detection of exoplanets.
In this work, we have tested for the first time variations in stellar parameters and chemical abundances for the young solar twin HIP36515 (~0.6 Gyr, Prot ~ 5 days). This object has stellar parameters well established and its activity cycle is estimated in ~7 years (from our previous observations with HARPS at LaSilla/ESO). The stellar parameters of three different epochs in the cycle (minimum, intermediate and maximum) were estimated using spectroscopic equilibrium, achieving an extremely high precision (~5 K in effective temperature, ~0.01 dex in surface gravity and metallicity). Surprisingly, we find a correlation between effective temperature (-0.85, p-value=0.18) and microturbulence (+0.98, p-value=0.02) with stellar activity.