A Search for Late M Supergiant Stars in the Direction of Galactic Latitude −2° < b < 2° and Galactic Longitude 351° < l < 1°

Abstract

AbstractOptical late M stars (spectral type later than M4) with IRAS colours of 0.7 < m12 − m25 < 1.6 belong to two possible luminosity classes; giants or supergiants (Raharto 1994). We have searched for supergiant candidates among the late M stars at low galactic latitude, between galactic longitude 351° < l < 1° and galactic latitude −2° < b < +2°, using data from the M star Catalogue (Raharto et al. 1984) and the IRAS Point Source Catalogue (Beichman et al. 1987). The search area is located in the direction of the galactic centre. M supergiants found in this survey will be necessarily a mixture of M supergiants in star forming regions in the interarm and galactic centre regions and M supergiants in the inner galactic arms.We found 154 of 1146 late M stars with unique IRAS point source counterparts within 15 arcsec. 122 of the 154 stars have good flux qualities in the 12 and 25 μm bands. 112 of these, or 73 per cent of the late M stars (later than M4), have IRAS infrared colours in the range 0.7 < m12 − m25 < 1.6. Only two stars out of 122 have infrared colours redder than 1.7.