An unusually solar-like twin, and the virtue of differential spectroscopy in Galactic studies

Bengt Gustafsson

Dept of Astronomy and Astrophysics

Uppsala University

Solar Twins

M67

VandenBerg et al.

Weiss

M67-1194

M67-1194

Pasquini et al. (2008)Solar-twin candidates in M67

M67-1194 Sun diff

(Å)

• Excitation of Fe I + H => 5780 ± 20 K • Fe I/Fe II + MgIb => log g = 4.44 ± 0.05 (cgs) t = 0.95 km/s• [Fe/H] = 0.023 ± 0.015

Age• Isochrones (Teff vs log g) by VandenBerg (2010): 4.2 ± 0.3 Gyr

If Y is different by 0.01 => 0.2 Gyr

• C.f. photometry,Yadav et al. (2008):3.5 - 4.8 Gyr

+ Meléndez et al. (2009)

• M67-1194

+ Meléndez et al. (2009)

• M67-1194

< 6% chance!