Time variability of X-ray sources in the M 31 centre field

Abstract

We present an extension to our XMM-Newton X-ray source catalogue of M 31, containing 39 newly found sources. In order to classify and identify more of the sources we search for X-ray time variability in XMM-Newton archival data of the M 31 centre field. As a source list we used our extended catalogue based on observations covering the time span from June 2000 to July 2004. We then determined the flux or at least an upper limit at the source positions for each observation. Deriving the flux ratios for the different observations and searching for the maximum flux difference we determined variability factors. We also calculated the significance of the flux ratios. Using hardness ratios, X-ray variability and cross correlations with catalogues in the X-ray, optical, infrared and radio regimes, we detected three super soft source candidates, one supernova remnant and six supernova remnant candidates, one globular cluster candidate, three X-ray binaries and four X-ray binary candidates. Additionally we identified one foreground star candidate and classified fifteen sources with hard spectra, which may either be X-ray binaries or Crab-like supernova remnants in M 31 or background active galactic nuclei. The remaining five sources stay unidentified or without classification. Based on the time variability results we suggest six sources, which were formerly classified as "hard", to be X-ray binary candidates. The classification of one other source (XMMM31 J004236.7+411349) as a supernova remnant, has to be rejected due to the distinct time variability we found. We now classify this source as a foreground star.

13 pages, 6 figures, accepted for publication in A&A

References in corpus (38)

• The Properties of X-Ray and Optical Light Curves of X-Ray Novae
• A Survey of Local Group Galaxies Currently Forming Stars. I. UBVRI Photometry of Stars in M31 and M33
• X-ray source populations in galaxies
• Distance to M31 With the HST and Hipparcos Red Clump Stars
• 2MASS NIR photometry for 693 candidate globular clusters in M31 and the Revised Bologna Catalogue
• X-ray Point Sources in The Central Region of M31 as seen by Chandra
• The Distance to the M31 Globular Cluster System
• Catalog of supersoft X-ray sources
• X-ray monitoring of optical novae in M31 from July 2004 to February 2005
• Optical novae: the major class of supersoft X-ray sources in M 31
• The second ROSAT PSPC survey of M31 and the complete ROSAT PSPC source list
• The central region of M31 observed with XMM-Newton. II. Variability of the individual sources
• A Chandra High-Resolution Camera Observation of X-Ray Point Sources in M31
• XMM-Newton survey of the Local Group galaxy M 33
• A study of the population of LMXBs in the bulge of M31
• XMM-Newton survey of M 31
• Supersoft X-ray Sources in M31: I. A Chandra Survey and an Extension to Quasisoft Sources
• A First Look at the Nuclear Region of M31 with Chandra
• Bright X-Ray Sources in M31 Globular Clusters
• A Synoptic X-ray Study of M31 with the Chandra-HRC
• M31 Globular Cluster X-ray Sources: XMM-Newton and Chandra results
• The POINT-AGAPE Survey I: The Variable Stars in M31
• Wide-Field Survey of Globular Clusters in M31. I. A Catalog of New Clusters
• Chandra Studies of the X-ray Point Source Luminosity Functions of M31
• A Catalog of Transient X-ray Sources in M31
• A Close Look at the Population of Supersoft and Quasi-Soft X-Ray Sources Observed in M31 with XMM-Newton
• Discovery of Radio/X-ray/Optical Resolved Supernova Remnants in the Center of the Andromeda Galaxy
• Supersoft X-ray sources in M31: II. ROSAT-detected supersoft sources in the ROSAT, Chandra and XMM eras
• Tracing a Z-track in the M31 X-ray Binary RX J0042.6+4115
• XMM-Newton detection of type I X-ray bursts in M 31
• On the artificial nature of aperiodic variability in XMM-Newton observations of M31 X-ray sources and the ultraluminous X-ray source NGC 4559 ULX-7
• RX J0042.3+4115: a stellar mass black hole binary identified in M31
• Bright X-ray Transients in M31: 2004 July XMM-Newton Observations
• Discovery of an X-ray Nova in M31
• Identification of X-ray Point Sources and Study on the Nature of 62 X-ray Globular Cluster Candidates in M31
• Chandra and Hubble Study of a New Transient X-ray Source in M31
• Identifying a black hole X-ray transient in M31 with XMM-Newton and Chandra
• A Soft X-ray Transient in the M31 Bulge

Cited by in corpus (17)

• The XMM-Newton survey of the Small Magellanic Cloud: The X-ray point-source catalogue
• The deep XMM-Newton Survey of M 31
• X-ray monitoring of classical novae in the central region of M31. III. Autumn and winter 2009/10, 2010/11 and 2011/12
• X-ray monitoring of classical novae in the central region of M 31. II. Autumn and winter 2007/2008 and 2008/2009
• Methods for Estimating Fluxes and Absorptions of Faint X-ray Sources
• X-ray monitoring of classical novae in the central region of M 31. I. June 2006 - March 2007
• Supernova remnants and candidates detected in the XMM-Newton M31 large survey
• The first two transient supersoft X-ray sources in M 31 globular clusters and the connection to classical novae
• X-ray source variability study of the M 31 central field using Chandra HRC-I
• New XMM-Newton analysis of three bright X-ray sources in M31 globular clusters, including a new black hole candidate
• Deep XMM-Newton observations of the northern disc of M31. I. Source catalogue
• Around 200 new X-ray binary IDs from 13 years of Chandra observations of the M31 center
• The very short supersoft X-ray state of the classical nova M31N 2007-11a
• Supersoft sources in M 31: Comparing the XMM-Newton Deep Survey, ROSAT and Chandra catalogues
• Broadband study and the discovery of pulsations from the Be/X-ray binary eRASSU J052914.9-662446 in the Large Magellanic Cloud
• NuSTAR view of the central region of M 31
• SSS in young stellar populations and the "prompt" component of Type Ia supernovae