The central region of M 31 observed with $\vec{XMM}$-$\vec{Newton}$

Abstract

Abstract. We present the results of a study of the variability of X-ray sources in the central 30 of the nearby Andromeda Galaxy (M 31) based on XMM-Newton Performance Verification observations. Two observations of this field, with a total exposure time of about 50 ks, were performed in June and December of 2000. We found 116 sources brighter than a limiting luminosity of 6×10 35 erg s −1 (0.3-12 keV, d = 760 kpc). For the ∼60 brightest sources, we searched for periodic and non-periodic variability; at least 15% of these sources appear to be variable on a time scale of several months. We discovered a new bright transient source ∼2.9 from the nucleus in the June observation; this source faded significantly and was no longer detected in December. The behaviour of the object is similar to a handful of Galactic LMXB transients, most of which are supposed to harbor black holes. We detected pulsations with a period of ∼865 s from a source with a supersoft spectrum. The flux of this source decreased significantly between the two XMM observations. The detected period is unusually short and points to a rapidly spinning magnetized white dwarf. The high luminosity and transient nature of the source suggest its possible identification with classical or symbiotic nova, some of which were observed earlier as supersoft sources.

The deepXMM-NewtonSurvey of M 31

“…These blocks will be found by the SAS detection tools and appear as sources with extremely soft spectrum (so called supersoft sources). To reduce the number of false detections in this source 2 See also http://xmm2.esac.esa.int/docs/documents/ CAL-TN-0050-1-0.ps.gz Primini et al (1993, PFJ93) R (HRI) 86 > ∼ 1.8 × 10 36 bulge region 18 sources variable; ∼3 transients (0.2-4 keV) Supper et al (1997Supper et al ( , 2001 R (PSPC) 560 5 × 10 35 -5 × 10 38 whole galaxy two deep surveys (SPH97, SHL2001) (0.1-2.4 keV) 491 sources not detected with Einstein 11 sources variable, 7 transients compared to Einstein 34 sources variable, 8 transients between ROSAT surveys Osborne et al (2001) X 116 > ∼ 6 × 10 35 centre examined the ∼60 brightest sources for variability (0.3-12 keV) Kong et al (2002b) C (ACIS-I) 204 > ∼ 2 × 10 35 central ∼17 × 17 observations between 1999 and 2001 (0.3-7 keV) ∼50% of the sources are variable, 13 transients Kaaret (2002) C (HRC) 142 2 × 10 35 -2 × 10 38 centre one 47 ks observation; 46 ± 26% of the sources (0.1-10 keV) with L X > 5 × 10 36 erg s −1 are variable Di Stefano et al (2002) C ( A C I S -I /S) 28 5 × 10 35 -3 × 10 38 3 disc fields bright X-ray binaries (0.3-7 keV) Di Stefano et al (2004) C (ACIS-S S3) 33 3 disc fields + centre supersoft sources and quasisoft sources Williams et al (2004) C (HRC) 166 1.4 × 10 36 -5 × 10 38 major axis + centre > ∼ 25% showed significant variability (0.1-10 keV) Trudolyubov & Priedhorsky (2004) C , X 4 3 ∼10 35 -∼10 39 major axis + centre globular cluster study (0.3-10 keV) Pietsch et al (2005b X 856 4.4 × 10 34 -2.8 × 10 38 major axis + centre source catalogue (0.2-4.5 keV) Pietsch et al (2005a C, R, X 21 ∼10 35 -∼10 38 centre correlations with optical novae (0.2-1 keV) Orio (2006) C , X 4 2 6 × 10 35 -∼10 39 major axis + centre supersoft sources and quasisoft sources (0.2-2 keV) (0.3-10 keV) Pietsch et al (2007 C, X 46 ∼10 35 -∼10 38 centre correlations with optical novae (0.2-1 keV) Voss & Gilfanov (2007) C 263 5 × 10 33 -1.5 × 10 38 bulge region low mass X-ray binary study (0.5-8 keV) Stiele et al (2008 X 39 7 × 10 34 -6 × 10 37 centre re-analysis of archival and new 2004 observations 300 4.4 × 10 34 -2.8 × 10 38 time variability analysis; 149 sources with a significance (0.2-4.5 keV)…”

“…Previous source lists based on archival XMM-Newton observations were presented in Osborne et al (2001), PFH2005, Orio (2006), SPH2008, and SBK2009. Of these four studies, PFH2005 covers the largest area of M 31.…”

“…They studied their spectral properties, time variability and log N-log S relations. Osborne et al (2001) used XMM-Newton Performance Verification observations to study the variability of X-ray sources in the central region of M 31. They found 116 sources brighter than a limiting luminosity of 6 × 10 35 erg s −1 and examined the ∼60 brightest sources for periodic and non-periodic variability.…”

Supernova remnants and candidates detected in theXMM-NewtonM 31 large survey

“…The next generation X-ray satellites Chandra X-ray Observatory (Weisskopf et al 2002) and X-ray Multi-Mirror Mission (XMM-Newton, Jansen et al 2001), which were both launched in 1999, have significantly improved on the spatial and spectral resolutions of the prior X-ray telescopes. They have also A&A 544, A144 (2012) performed several observations of M 31 and allowed us to obtain a comprehensive list of X-ray sources and study individual sources (e.g., Osborne et al 2001;Kong et al 2002b;Kaaret 2002;Pietsch et al 2005;Stiele et al 2008;Barnard et al 2008). The entire galaxy M 31 was observed by XMM-Newton in a large programme (LP) between June 2006 and February 2008 with the European Photon Imaging Cameras (EPICs, Strüder et al 2001;Turner et al 2001) as prime instruments.…”

Magnetic Field Evolution in Accreting White Dwarfs

“…Unfortunately, we know little about the magnetic fields of these white dwarfs. Pulsations are seen in the symbiotic Z And (Sokoloski & Bildsten 1999), and a supersoft source in M31 (Osborne et al 2001;King, Osborne, & Schenker 2002). If due to magnetic accretion, then a rough estimate gives B « 10 7 G in each case.…”