Red supergiants in the inner Galaxy: stellar properties.
MESSINEO M., ZHU Q., MENTEN K.M., IVANOV V.D., FIGER D.F., KUDRITZKI R.-P. and CHEN C.-H.R.
Abstract (from CDS):
Red supergiants (RSGs) are luminous cool stars detectable in disks of distant spirals. About a thousand are known in the Galaxy. Here, we analyze a sample of late-type stars recently observed by Messineo et al. in the inner Galaxy (10○l60○). A total of 58 targets (25% of previously known RSGs) were reported as supergiants based on their large equivalent widths of the CO band-head at 2.293 µm (EWs > 45 A, >=M0I). In this work, luminosities are estimated with infrared measurements and distance moduli for 47 spectroscopically classified RSGs; they range from 3.2×104 to 1.3×105L☉. Six other RSGs with smaller EW(CO)s are classified according to their luminosities. Using a prescription based on Ks–[W4], moderate mass-loss rates from 10–8 to 10–6.5M☉ yr–1 are inferred. In addition, we report on H and K spectra of 26 stars at R = 1500-2200. EWs of the CO at 2.293 and 1.620 µm, and of atomic lines, are consistent with those of nearby RSGs, within uncertainties. Mg I appears to be a useful diagnostic to confirm RSGs at R = 1500-2200. RSG #66 is a member of the cluster Alicante 7. Star #92 is projected onto the overdensity #495 of Camargo et al., but our analysis suggests they are unrelated. Remaining targets are isolated from other known RSGs within ≃3'.