Discovery of an obscured globular cluster associated with GX 354+0 (=4U/MXB 1728-34).
Abstract
A diffuse infrared source identified as the most heavily obscured globular cluster yet found, was observed using the NASA 3m infrared telescope facility and Einstein positions for the X-ray source GX 354+0 (=4U/MXB 1728-34). Color excesses were measured to 1.4 + or - 0.3 for E(J-H) and 0.63 + or - 0.07 for E(H-K), and the visual extinction was determined at 10.6 + or - 1.3. The magnitude of several giant branch stars imply the cluster to be at a distance of 10.0 + or - 3.9 kpc, if metal rich, or 5.2 + or - 1.4 kpc, if metal poor. A single burst from MXB 1728-34 was observed with a blackbody temperature and cluster distance that indicated the luminosity to be not less than 10 times the Eddington limit for a neutron star model. This identification brings to 11 the number of compact X-ray sources in globular clusters, and reinforces the connection between GX sources, bursters, and globular clusters.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1981
- DOI:
- 10.1086/183580
- Bibcode:
- 1981ApJ...247L..17G
- Keywords:
-
- Globular Clusters;
- Heao 2;
- Infrared Astronomy;
- Signal To Noise Ratios;
- Stellar Spectrophotometry;
- X Ray Sources;
- Flare Stars;
- Interstellar Extinction;
- Metallic Stars;
- Star Distribution;
- Stellar Luminosity;
- Astronomy