On the origin of stars with and without planets Tc trends and clues to Galactic evolution

We explore a sample of 148 solar-like stars to search for a possible correlation between the slopes of the abundance trends versus condensation temperature (known as the T-c slope) with stellar parameters and Galactic orbital parameters in order to understand the nature of the peculiar chemical signatures of these stars and the possible connection with planet formation. We find that the T-c slope significantly correlates (at more than 4 sigma) with the stellar age and the stellar surface gravity. We also find tentative evidence that the T-c slope correlates with the mean galactocentric distance of the stars (R-mean), suggesting that those stars that originated in the inner Galaxy have fewer refractory elements relative to the volatiles. While the average T-c slope for planet-hosting solar analogs is steeper than that of their counterparts without planets, this difference probably reflects the difference in their age and R-mean. We conclude that the age and probably the Galactic birth place are determinant to establish the star's chemical properties. Old stars (and stars with inner disk origin) have a lower refractory-to-volatile ratio.