Variability in Ultra-luminous X-ray Sources

Webb, N.; Cseh, D.; Kirsten, F.

doi:10.1017/pasa.2014.1

Cited by 9 publications

(7 citation statements)

References 105 publications

(154 reference statements)

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“…One scenario that can result in rapid rises in accretion rate is for the system to have a highly eccentric orbit, with large accretion bursts triggered close to periastron, broadly similar to Be/X-ray binaries (e.g., Reig 2011;Casares et al 2014). This scenario is currently the leading interpretation for the almost periodic outbursts exhibited by the most extreme ULX observed to date, ESO 243-49 HLX1 (L X,peak ∼ 10 42 erg s −1 ), which displays a repeated "fast-rise-exponential-decay" (FRED) outburst profile with similarly large and rapid flux increases to those seen in our observations of NGC 5907 ULX1 (e.g., Lasota et al 2011;Webb et al 2014, although see King & Lasota 2014). Given the poor sampling to date of the long-term behavior of NGC 5907 ULX1, it is possible that something similar could be occurring in this case, albeit at a lower absolute luminosity, and with the source rising into a potentially super-Eddington state (in contrast, HLX-1 seems to exhibit the standard evolution shown by sub-Eddington Galactic binaries during its outbursts; Servillat et al 2011;Godet et al 2012).…”

Section: Discussionsupporting

confidence: 67%

NUSTARANDXMM-NEWTONOBSERVATIONS OF THE EXTREME ULTRALUMINOUS X-RAY SOURCE NGC 5907 ULX1: A VANISHING ACT

Walton

Harrison

Bachetti

et al. 2015

ApJ

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Section: Discussionsupporting

confidence: 67%

NUSTARANDXMM-NEWTONOBSERVATIONS OF THE EXTREME ULTRALUMINOUS X-RAY SOURCE NGC 5907 ULX1: A VANISHING ACT

Walton

Harrison

Bachetti

et al. 2015

ApJ

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“…We looked more carefully for possible spectral changes in the 12 variable sources mentioned above, and found none. The lack of such changes is common when the flux variability is only a factor of a few (Fridriksson et al 2008;Soria et al 2009;Webb et al 2014).…”

Section: Ulx Variabilitymentioning

confidence: 99%

A Comprehensive X-Ray and Multiwavelength Study of the Colliding Galaxy Pair NGC 2207/Ic 2163

Mineo¹,

Rappaport²,

Levine³

et al. 2014

ApJ

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We present a comprehensive study of the total X-ray emission from the colliding galaxy pair NGC 2207/IC 2163, based on Chandra, Spitzer, and GALEX data. We detect 28 ultra-luminous X-ray sources ('ULXs'), 7 of which were not detected previously due to X-ray variability. Twelve sources show significant long-term variability, with no correlated spectral changes. Seven sources are transient candidates. One ULX coincides with an extremely blue star cluster (B-V = -0.7). We confirm that the global relation between the number and luminosity of ULXs and the integrated star formation rate ('SFR') of the host galaxy also holds on local scales. We investigate the effects of dust extinction and/or age on the X-ray binary ('XRB') population on sub-galactic scales. The distributions of N X and L X are peaked at L IR /L NUV ∼ 1, which may be associated with an age of ∼10 Myr for the underlying stellar population. We find that ∼1/3 of the XRBs are located in close proximity to young star complexes. The luminosity function of the X-ray binaries ('XRBs') is consistent with that typical for high-mass X-ray binaries, and appears unaffected by variability. We disentangle and compare the X-ray diffuse spectrum with that of the bright XRBs. The hot interstellar medium dominates the diffuse X-ray emission at E 1 keV, has a temperature kT = 0.28 +0.05 −0.04 keV and intrinsic 0.5-2 keV luminosity of 7.9 × 10 40 erg s −1 , a factor of ∼2.3 higher than the average thermal luminosity produced per unit SFR in local star-forming galaxies. The total X-ray output of NGC 2207/IC 2163 is 1.5 × 10 41 ergs s −1 , and the corresponding total integrated SFR is 23.7 M yr −1 .

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“…Fabbiano 2006;Feng and Soria 2011;Webb et al 2014;Bachetti et al 2015b in prep.). In this review, I will concentrate on the discoveries and progress in the understanding of these objects gained in recent times (three/four years).…”

Section: Introductionmentioning

confidence: 97%

Ultraluminous X‐ray sources: Three exciting years

Bachetti

2016

Astron Nachr

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The extreme extragalactic sources known as Ultraluminous X-ray Sources (ULX) represent a unique testing environment for compact objects population studies and the accretion process. Their nature has long been disputed. Their luminosity, well above the Eddington luminosity for a stellar-mass black hole, can imply the presence of an intermediate-mass black hole or a stellar black hole accreting above the Eddington limit. Both these interpretations are important to understand better the accretion process and the evolution of massive black holes. The last few years have seen a dramatic improvement of our knowledge of these sources. In particular, the super-Eddington interpretation for the bulk of the ULX population has gained a strong consensus. Nonetheless, exceptions to this general trend do exist, and in particular one ULX was shown to be a neutron star, and another was shown to be a very likely IMBH candidate. In this paper, I will review the progress done in the last few years.

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Variability in Ultra-luminous X-ray Sources

Cited by 9 publications

References 105 publications

NUSTARANDXMM-NEWTONOBSERVATIONS OF THE EXTREME ULTRALUMINOUS X-RAY SOURCE NGC 5907 ULX1: A VANISHING ACT

NUSTARANDXMM-NEWTONOBSERVATIONS OF THE EXTREME ULTRALUMINOUS X-RAY SOURCE NGC 5907 ULX1: A VANISHING ACT

A Comprehensive X-Ray and Multiwavelength Study of the Colliding Galaxy Pair NGC 2207/Ic 2163

Ultraluminous X‐ray sources: Three exciting years

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