Monitoring the X-ray Sources in the Bulge of M31
Session 102 -- X-Ray Variables, Binaries and Transients
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

## [102.10] Monitoring the X-ray Sources in the Bulge of M31

F.A. Primini (SAO), E. Alfaro (IAA,Granada), J. Cowan (U. Oklahoma), P. Crane (Interferometrics), J. Dickel (U. Illinois), G. Hasinger (AIP,Potsdam), W.H.G. Lewin (MIT), E. Magnier (U. Amsterdam), W. Pietsch (MPE), D. Roberts (U. Illinois), J. van Paradijs (U. Ala.,Huntsville)

We present the first results of our program to monitor the x-ray sources in the bulge of M31. The program includes observations made with the ROSAT HRI, together with nearly simultaneous radio and optical observations. Results from two $\sim$25 ksec HRI observations, taken in July 1994, will be discussed here. We present new x-ray source lists and updated globular cluster identifications. Comparison of x-ray intensities from the current epoch with those obtained from similar observations taken in 1990 indicates that a number of x-ray sources varied significantly in the interim. We use current results and those from the earlier ROSAT and Einstein HRI observations to estimate the rate of x-ray transients in M31. Among the sources observed to vary is the x-ray source associated with the nucleus of M31. This source is of particular interest because of the discovery of an unresolved nuclear radio source (Crane, Dickel \& Cowan 1992, ApJ Letters, 390, L9), and we discuss the status of our VLA observational program on the nuclear x-ray source, as well as on other x-ray sources within $\sim$3$^{\prime}$ of the nucleus. Finally, we briefly discuss our H$_{\alpha}$ observations of the M31 bulge.