Artificial variability in XMM‐Newton observations of X‐ray sources: M31 as a case study

Barnard, R.; Trudolyubov, S.; Haswell, C. A.; Kolb, U.; Osborne, J. P.; Priedhorsky, W. C.

doi:10.1063/1.2774929

Cited by 12 publications

(15 citation statements)

References 17 publications

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“…No variability was detected by Feng & Kaaret (2005) in the observations of NGC 4395 X‐1, NGC 3628 X‐1, M83 ULX and NGC 2403 X‐1. Barnard et al (2007) detected no variability in NGC 4559 X‐1 (revising the previous report by Cropper et al 2004). Only the remaining five observations have detailed power spectral analyses published to date.…”

Section: Sample Selectionsupporting

confidence: 45%

“…In fact, six sources (eight observations) showed significant variability: Ho IX X‐1, NGC 5408 X‐1, NGC 1313 X‐1, NGC 1313 X‐2, NGC 55 ULX and M82 X‐1. Investigation of the PSD from NGC 4559 X‐1 revealed it to be flat with no indication of the variability features analysed in Cropper et al (2004), this is believed to be due to artificial variability caused by the analysis method as discussed in Barnard et al (2007).…”

Section: Resultsmentioning

confidence: 95%

“…Footnotes indicate references as follows: columns 1–2 footnotes indicate the identification of sources with the given name(s); column 3 footnotes refer to previous power spectral analyses of the observations; column 5 footnotes provide references to source positions. a Guainazzi et al (2000); b Roberts & Warwick (2000); c Stobbart et al (2006); d Humphrey et al (2003); e Soria et al (2006); f Colbert et al (1995); g Miller et al (2004); h Dewangan et al (2004); i Strohmayer & Mushotzky (2003); j Liu & Bregman (2005); k Colbert & Ptak (2002); l Winter, Mushotzky & Reynolds (2006); m Matsumoto et al (2001); n Fabbiano (1989); o Kaaret et al (2003); p Cropper et al (2004) q Goad et al (2006) r Feng & Kaaret (2005) s Barnard et al (2007) t Dewangan et al (2006a) u Dewangan et al (2006b) v Strohmayer et al (2007).…”

Section: Sample Selectionmentioning

confidence: 99%

See 2 more Smart Citations

A systematic study of variability in a sample of ultraluminous X-ray sources

Heil

Vaughan

Roberts

2009

Monthly Notices of the Royal Astronomical Society

101

136

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We present results from a study of short‐term variability in 19 archival observations by XMM–Newton of 16 ultraluminous X‐ray sources (ULXs). Eight observations (six sources) showed intrinsic variability with power spectra in the form of either a power‐law or broken power‐law‐like continuum and in some cases quasi‐periodic oscillations (QPOs). The remaining observations were used to place upper limits on the strength of possible variability hidden within. Seven observations (seven sources) yielded upper limits comparable to, or higher than, the values measured from those observations with detectable variations. These represented the seven faintest sources, all with fx < 3 × 10−12 erg cm−2 s−1. In contrast, there are four observations (three sources) that gave upper limits significantly lower than both the values measured from the ULX observations with detectable variations, and the values expected by comparison with luminous Galactic black hole X‐ray binaries (BHBs) and active galactic nuclei (AGN) in the observed frequency bandpass (10−3–1 Hz). This is the case irrespective of whether one assumes characteristic frequencies appropriate for a stellar mass (10 M⊙) or an intermediate mass (1000 M⊙) black hole, and means that in some ULXs the variability is significantly suppressed compared to bright BHBs and AGN. We discuss ways to account for this unusual suppression in terms of both observational and intrinsic effects and whether these solutions are supported by our results.

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Section: Sample Selectionsupporting

confidence: 45%

Section: Resultsmentioning

confidence: 95%

Section: Sample Selectionmentioning

confidence: 99%

See 1 more Smart Citation

A systematic study of variability in a sample of ultraluminous X-ray sources

Heil

Vaughan

Roberts

2009

Monthly Notices of the Royal Astronomical Society

101

136

View full text Add to dashboard Cite

show abstract

“…However, some measurements have been made. Cropper et al (2004) detected a putative break at 28 mHz in the PSD of NGC 4559 X7, which they suggest supports the case that it harbours a ∼ 1000M ⊙ black hole, although the presence of this spectral break is now disputed (Barnard et al 2007). Another detection of a break frequency was made by Soria et al (2004), who found a break at 2.5 mHz in the PSD of NGC 5408 X-1.…”

Section: Power Spectral Densities For Ulxsmentioning

confidence: 70%

X-ray observations of ultraluminous X-ray sources

Roberts

2007

Astrophys Space Sci

178

187

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Ultraluminous X-ray sources (ULXs) are amongst the most intriguing of X-ray source classes. Their extreme luminosities -greater than 10 39 erg s −1 in the 0.3 -10 keV band alone -suggest either the presence of black holes larger than those regularly encountered in our own Galaxy (the Galactic centre excepted), or sources apparently radiating well above the Eddington limit. We review the insights afforded us by studies of their X-ray emission, focussing on what this reveals about the underlying compact object. In particular, we discuss recent deep observations of ULXs by the XMMNewton observatory, and how the unprecedented data quality provided by this mission is starting to discriminate between the different physical models for these extraordinary X-ray emitters.

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“…For spectral analysis, we used data in the 0.3-10 keVenergy band. To synchronize source and background light curves from individual EPIC detectors, we used the identical time filtering criteria based on mission relative time (MRT), following the procedure described in Barnard et al (2007). The background light curves were not subtracted from the source light curves, but were used later to estimate the background contribution in the calculation of the source pulsed fractions.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

ChandraandXMM‐NewtonDiscovery of Transient X‐Ray Pulsar in the Nearby Spiral Galaxy NGC 2403

Trudolyubov

Priedhorsky

2007

ApJ

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We report on the discovery and analysis of the transient X-ray pulsar CXOU J073709.1+653544 detected in the 2004 August-October Chandra and XMM-Newton observations of the nearby spiral galaxy NGC 2403. The X-ray source exhibits X-ray pulsations with a period P $ 18 s and a nearly sinusoidal pulse shape and pulsed fraction 46%-70% during the first three observations. The observed pulsation period decreased rapidly from 18.25 s on August 9 to 17.93 s on September 12 and possibly 17.56 s on 2004 October 3. The X-ray spectra of CXOU J073709.1+653544 are hard and are well fitted with an absorbed simple power law of photon index À $ 0:9 1:2 in the 0.3-7 keV energy band. The X-ray properties of the source and the absence of an optical /UV counterpart brighter than 20 mag allow us to identify CXOU J073709.1+653544 as an accreting X-ray pulsar in NGC 2403. The maximum unabsorbed luminosity of the source in the 0.3-7 keV range, L X $ 2:6 ; 10 38 ergs s À1 at 3.2 Mpc, is at least 260 times higher than its quiescent luminosity. The estimated source luminosity in the 0.3-100 keV energy range could be as high as $1:2 ; 10 39 ergs s À1 . The rate of decrease of the pulsation period of the source (Ṗ $ À10 À7 s s À1 ) is one of the fastest observed among accreting pulsars. The evolution of the pulsation period suggests that it is dominated by the intrinsic spin-up of the compact object, which is almost certainly a neutron star. The X-ray luminosity of CXOU J073709.1+653544 is high enough to account for the observed spin-up rate, assuming that the X-ray source is powered by disk accretion onto a highly magnetized neutron star. Based on the transient behavior and overall X-ray properties of the source, it could be an X-ray pulsar belonging to either a Be binary system or a low-mass system similar to the transient Galactic bursting pulsar GRO J1744À28.

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Artificial variability in XMM‐Newton observations of X‐ray sources: M31 as a case study

Cited by 12 publications

References 17 publications

A systematic study of variability in a sample of ultraluminous X-ray sources

A systematic study of variability in a sample of ultraluminous X-ray sources

X-ray observations of ultraluminous X-ray sources

ChandraandXMM‐NewtonDiscovery of Transient X‐Ray Pulsar in the Nearby Spiral Galaxy NGC 2403

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