Discovery of a 115 Day Orbital Period in the Ultraluminous X-Ray Source NGC 5408 X-1

. (2015) 'X-ray spectral residuals in NGC 5408 X-1 : diuse emission from star formation, or the signature of a super-Eddington wind?', Astrophysical journal., 814 (1). p. 73.Further information on publisher's website: Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTIf ultraluminous X-ray sources (ULXs) are powered by accretion onto stellar remnant black holes, then many must be accreting at super-Eddington rates. It is predicted that such high accretion rates should give rise to massive, radiatively driven winds. However, observational evidence of a wind, in the form of absorption or emission features, has remained elusive. As such, the reported detection of X-ray spectral residuals in XMM-Newton spectra of NGC 5408 X-1, which could be related to absorption in a wind is potentially very exciting. However, it has previously been assumed by several authors that these features simply originate from background diffuse plasma emission related to star formation in the ULX's host galaxy. In this work we utilize the spatial resolving power of Chandra to test whether we can rule out this latter interpretation. We demonstrate that the majority of the luminosity in these spectral features is emitted from a highly localized region close to the ULX, and appears pointlike even with Chandra. It is therefore highly likely that the spectral features are associated with the ULX itself, and little of the flux in this spectral component originates from spatially extended emission in the host galaxy. This may be consistent with the suggestion of absorption in an optically thin phase of a super-Eddington wind. Alternatively, we could be seeing emission from collisionally ionized material close to the black hole, but critically this would be difficult to reconcile with models where the source inclination largely determines the observed X-ray spectral and timing properties.

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“…- (Strohmayer 2009). Details of the observations included in this work are given in Table 1, and a combined exposure map is shown in Figure 2.…”

Section: Analysis and Resultsmentioning

confidence: 99%

X-Ray Spectral Residuals in NGC 5408 X-1: Diffuse Emission From Star Formation, or the Signature of a Super-Eddington Wind?

Sutton

Roberts

Middleton

2015

ApJ

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“…Most of these monitoring programs are dedicated for the study of long-term variability of ULXs including the search of periodic or quasi-periodic signals (e.g., Kaaret & Feng 2009;Strohmayer 2009;Grisé et al 2013;Lin et al 2015;Walton et al 2016a;Hu et al 2017). For a single observation, the typical exposure time is 1-3 ks, and the typical recurrent time between observations is 2-6 days.…”

Section: Data and Resultsmentioning

confidence: 99%

Evidence for Precession due to Supercritical Accretion in Ultraluminous X-Ray Sources

Weng

Feng

2018

ApJ

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Most ultraluminous X-ray sources (ULXs) are thought to be supercritical accreting compact objects, where massive outflows are inevitable. Using the long-term monitoring data with the Swift X-ray Telescope, we identified a common feature in bright, hard ULXs: they display a quasi-periodic modulation in their hard X-ray band but not in their soft band. As a result, some sources show a bimodal distribution on the hardness intensity map. We argue that these model-independent results can be well interpreted in a picture that involves supercritical accretion with precession, where the hard X-ray emission from the central funnel is more or less beamed, while the soft X-rays may arise from the photosphere of the massive outflow and be nearly isotropic. It implies that precession may be ubiquitous in supercritical systems, such as the Galactic microquasar SS 433. How the hard X-rays are modulated can be used to constrain the angular distribution of the hard X-ray emission and the geometry of the accretion flow. We also find that two ULX pulsars (NGC 5907 ULX-1 and NGC 7793 P13) show similar behaviors but no bimodal distribution, which may imply that they have a different beaming shape or mechanism.

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“…Another intriguing property is that its X-ray intensity varies regularly with a period of 62 days (Kaaret et al 2006;Kaaret & Feng 2007, KF07 hereafter). Such long periodic X-ray modulations have been seen from two other ULXs, NGC 5408 X-1 (115 days and 243 days ;Strohmayer 2009;Han et al 2012;Pasham & Strohmayer 2013a) and HLX ESO 243-39 (375 days; e.g., Servillat et al 2011). The 62 day period of M82 X-1 has been claimed to be the orbital period of the black hole binary system (KF07).…”

Section: Introductionmentioning

confidence: 87%

Can the 62 Day X-Ray Period of Ulx M82 X-1 Be Due to a Precessing Accretion Disk?

Pasham

Strohmayer

2013

ApJ

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We have analyzed all archival Rossi X-Ray Timing Explorer/Proportional Counter Array monitoring observations of the ultraluminous X-ray source M82 X-1 in order to study the properties of its 62 day X-ray period, which was found by Kaaret and Feng in 2007. Based on its high coherence, it has been argued that the observed period is the orbital period of the binary. Utilizing a much longer data set than in previous studies, we find the following. (1) The phase-resolved X-ray (3-15 keV) spectra-modeled with a thermal accretion disk and a power law-suggest that the accretion disk's contribution to the total flux is strongly modulated with phase. (2) Suggestive evidence for a sudden phase shift of approximately 0.4 in phase (25 days) between the first and the second halves of the light curve separated by roughly 1000 days. If confirmed, the implied timescale to change the period is ∼10 yr, which is exceptionally fast for an orbital phenomenon. These two independent pieces of evidence are consistent with the periodicity being due to a precessing accretion disk, similar to the super-orbital periods observed in systems like Her X-1, LMC X-4, and SS433. However, the timing evidence for a change in the period needs to be confirmed with additional observations. This should be possible with further monitoring of M82 with instruments such as the Swift X-Ray Telescope.

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Discovery of a 115 Day Orbital Period in the Ultraluminous X-Ray Source NGC 5408 X-1

Cited by 48 publications

References 35 publications

X-Ray Spectral Residuals in NGC 5408 X-1: Diffuse Emission From Star Formation, or the Signature of a Super-Eddington Wind?

X-Ray Spectral Residuals in NGC 5408 X-1: Diffuse Emission From Star Formation, or the Signature of a Super-Eddington Wind?

Evidence for Precession due to Supercritical Accretion in Ultraluminous X-Ray Sources

Can the 62 Day X-Ray Period of Ulx M82 X-1 Be Due to a Precessing Accretion Disk?

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