Transcript An unusually solar-like twin, and the virtue of

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
Pasquini et al. (2008)
Solar-twin candidates in M67
M67-1194
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!