Radio continuum observations of possible B-type stars in the halo of M 31
Abstract
We present Very Large Array (VLA) 5 GHz continuum observations of six point sources towards the halo of M 31, which have featureless optical spectra and magnitudes ranging from V=21.5-22.2, in order to determine whether these objects are BL Lacs. No radio emission coincident with the optical positions is detected to a 5sigma noise level of between 0.08 and 0.11 mJy. The resulting upper limits to the two-point radio-to-optical spectral indexes from 5 GHz to 2500 Å (alpha_RO ) are less than 0.30 for all of the sample. These observations make it highly likely that these objects are not BL Lacs, and hence strengthens the case that they are normal B-type stars in the halo of M 31. Based on observations taken at the National Radio Observatory which is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation, USA
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2000
- Bibcode:
- 2000A&A...361...60S
- Keywords:
-
- GALAXIES: BL LACERTAE OBJECTS: GENERAL;
- GALAXIES: HALOS;
- GALAXIES: INDIVIDUAL: M 31;
- RADIO CONTINUUM: GENERAL;
- STARS: EARLY-TYPE