Observations of X-ray sources in M31

Speybroeck, L. van; Epstein, A.; Forman, W.; Giacconi, R.; Jones, C.; Liller, W.; Smarr, Larry

doi:10.1086/183106

Cited by 100 publications

(31 citation statements)

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“…Combined with the high fraction of sources that are variable, this leads to the conclusion that the X-ray point-source population of the core of M31 is dominated by LMXBs, as previously suggested by other authors (e.g., van Speybroeck et al 1979). …”

Section: Pulsationssupporting

confidence: 71%

AChandraHigh Resolution Camera Observation of X‐Ray Point Sources in M31

Kaaret

2002

ApJ

161

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We present results from a 47 ks observation of the Andromeda galaxy, M31, using the High Resolution Camera of the Chandra X-Ray Observatory. We detect 142 point sources spanning 3 orders of magnitude in luminosity, from L X ¼ 2 Â 10 35 to 2 Â 10 38 ergs s À1 in the 0.1-10 keV band. The X-ray source location accuracy is better than 1 00 in the central regions of the galaxy. One source lies within 1>3 of SN 1885 but does not coincide with the UV absorption feature identified as the supernova remnant. However, there is an optical transient, which is likely an optical nova, at the location of the X-ray source. There is a weak source, L X $ 4 Â 10 36 ergs cm 2 s À1 , coincident with the nucleus of M31 and 14 sources coincident with globular clusters. Our observation has very high efficiency down to luminosities of 1:5 Â 10 36 ergs s À1 for sources within 5 0 of the nucleus. Comparing with a ROSAT observation made 11 yr earlier, we find that 0:46 AE 0:26 of the sources with L X > 5 Â 10 36 ergs s À1 are variable. We find no evidence for X-ray pulsars in this region, indicating that the population is likely dominated by low-mass X-ray binaries. The source density radial profile follows a power-law distribution with an exponent of 1:25 AE 0:10 and is inconsistent with the optical surface brightness profile. The X-ray point-source luminosity function is well fitted by a differential broken power law with a break at a luminosity of ð4:5 þ1:1 À2:2 Þ Â 10 37 ergs s À1 . The luminosity function is consistent with a model of an aging population of X-ray binaries.

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Section: Pulsationssupporting

confidence: 71%

AChandraHigh Resolution Camera Observation of X‐Ray Point Sources in M31

Kaaret

2002

ApJ

161

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“…Interestingly, S184 is one of the brighter point sources (>10 37 erg s −1 ) in the M31 bulge and has been detected with various X-ray telescopes (e.g., Einstein, van Speybroeck et al 1979;Trinchieri & Fabbiano 1991;ROSAT, Primini et al 1993;Supper et al 2001;Chandra, Kong et al 2002;Kaaret 2002;Hofmann et al 2013;Barnard et al 2014; XMM-Newton, Pietsch et al 2005;Stiele et al 2011). Its flux and spectral variabilities have been reported (e.g., Kong et al 2002).…”

Section: Source Identificationmentioning

confidence: 99%

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Yukita

Ptak

Hornschemeier

et al. 2017

ApJ

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We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E<10 keV observations did not generate much attention. This source has a spectrum with a soft X-ray excess (kT ∼ 0.2 keV) plus a hard spectrum with a power law of 1 G~and a cutoff around 15-20 keV, typical of the spectral characteristics of accreting pulsars. Unfortunately, any potential pulsation was undetected in the NuSTAR data, possibly due to insufficient photon statistics. The existing deep HST images exclude high-mass (>3 M  ) donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass (<3 M  ) companion or a symbiotic X-ray binary. We discuss other possibilities in more detail.

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“…Bowyer et al 1974) and the Uhuru satellite (Giacconi et al 1974), the imaging X-ray optics flown on the Einstein X-ray observatory permitted resolution of individual Xray sources in M 31 for the first time. In the entire set of Einstein imaging observations of M 31, Trinchieri & Fabbiano (1991, hereafter TF91) found 108 individual X-ray sources brighter than ∼6.4 × 10 36 erg s −1 , of which 16 sources showed variability (van Speybroeck et al 1979;Collura et al 1990). …”

Section: Introductionmentioning

confidence: 99%

The deepXMM-NewtonSurvey of M 31

Stiele

Pietsch

Haberl

et al. 2011

A&A

150

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Aims. The largest Local Group spiral galaxy, M 31, has been completely imaged for the first time, obtaining a luminosity lower limit ∼10 35 erg s −1 in the 0.2-4.5 keV band. Our XMM-Newton EPIC survey combines archival observations along the major axis, from The main goal of the paper is to study the X-ray source population of M 31.Methods. An X-ray catalogue of 1897 sources was created, with 914 detected for the first time. Source classification and identification were based on X-ray hardness ratios, spatial extent of the sources, and cross correlation with catalogues in the X-ray, optical, infrared, and radio wavelengths. We also analysed the long-term variability of the X-ray sources and this variability allows us to distinguish between X-ray binaries and active galactic nuclei (AGN). Furthermore, supernova remnant classifications of previous studies that did not use long-term variability as a classification criterion could be validated. Including previous Chandra and ROSAT observations in the long-term variability study allowed us to detect additional transient or at least highly variable sources, which are good candidate X-ray binaries. Results. Fourteen of the 30 supersoft source (SSS) candidates represent supersoft emission of optical novae. Many of the 25 supernova remnants (SNRs) and 31 SNR candidates lie within the 10 kpc dust ring and other star-forming regions in M 31. This connection between SNRs and star-forming regions implies that most of the remnants originate in type II supernovae. The brightest sources in X-rays in M 31 belong to the class of X-ray binaries (XRBs). Ten low-mass XRBs (LMXBs) and 26 LMXB candidates were identified based on their temporal variability. In addition, 36 LMXBs and 17 LMXB candidates were identified owing to correlations with globular clusters and globular cluster candidates. From optical and X-ray colour-colour diagrams, possible high-mass XRB (HMXB) candidates were selected. Two of these candidates have an X-ray spectrum as is expected for an HMXB containing a neutron star primary. Conclusions. While our survey has greatly improved our understanding of the X-ray source populations in M 31, at this point 65% of the sources can still only be classified as "hard" sources; i.e. it is not possible to decide whether these sources are X-ray binaries or Crab-like supernova remnants in M 31 or X-ray sources in the background. Deeper observations in X-ray and at other wavelengths would help classify these sources.

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Observations of X-ray sources in M31

Cited by 100 publications

References 0 publications

AChandraHigh Resolution Camera Observation of X‐Ray Point Sources in M31

AChandraHigh Resolution Camera Observation of X‐Ray Point Sources in M31

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

The deepXMM-NewtonSurvey of M 31

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