Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Vasilopoulos, Georgios; Koliopanos, Filippos; Haberl, F.; Treiber, H.; Brightman, Murray; Earnshaw, Hannah P.; Gúrpide, A.

doi:10.3847/1538-4357/abda49

Cited by 19 publications

(11 citation statements)

References 65 publications

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“…Dipping behaviour in the X-ray light curve have also been observed in some ULXs, e.g. NGC 55 (Stobbart et al 2004), M 94 (Lin et al 2013), NGC 628 (Liu et al 2005), NGC 5408 X-1 (Pasham & Strohmayer 2013;Grisé et al 2013 andM 51 ULX-7 (Hu et al 2021;Vasilopoulos et al 2021). The number of dips observed in these sources has so far been limited, however they suggest we are viewing these sources at high inclination or could be evidence for a precessing disc.…”

Section: Introductionmentioning

confidence: 82%

Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1

Alston

Pinto

Barret

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Most ultraluminous X-ray sources (ULXs) are believed to be stellar mass black holes or neutron stars accreting beyond the Eddington limit. Determining the nature of the compact object and the accretion mode from broadband spectroscopy is currently a challenge, but the observed timing properties provide insight into the compact object and details of the geometry and accretion processes. Here we report a timing analysis for an 800 ks XMM-Newton campaign on the supersoft ultraluminous X-ray source, NGC 247 ULX-1. Deep and frequent dips occur in the X-ray light curve, with the amplitude increasing with increasing energy band. Power spectra and coherence analysis reveals the dipping preferentially occurs on ∼5 ks and ∼10 ks timescales. The dips can be caused by either the occultation of the central X-ray source by an optically thick structure, such as warping of the accretion disc, or from obscuration by a wind launched from the accretion disc, or both. This behaviour supports the idea that supersoft ULXs are viewed close to edge-on to the accretion disc.

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Section: Introductionmentioning

confidence: 82%

Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1

Alston

Pinto

Barret

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…The X-ray flux dipping episodes have been observed in many ULXs, for example NGC 55 ULX1 (Stobbart et al 2004;Pintore et al 2015), NGC 628 (Liu et al 2005), M94 (Lin et al 2013, NGC 5408 (Pasham & Strohmayer 2013;Grisé et al 2013), NGC 247 (Feng et al 2016;D'Aì et al 2021;Alston et al 2021;Pinto et al 2021), M 51 ULX-7 (Vasilopoulos et al 2021;Hu et al 2021), M51 and M81 (Urquhart & Soria 2016). Significant X-ray dipping behaviour has been reported in NGC 55 ULX1 using the XMM-Newton observations conducted in 2001 (Stobbart et al 2004).…”

Section: Discussionmentioning

confidence: 94%

Spectral and Temporal Properties of Ultra-luminous X-ray Source NGC 55 ULX1

Jithesh

2021

Preprint

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We investigate the spectral and temporal properties of ultra-luminous X-ray source (ULX) NGC 55 ULX1 using Swift, XMM-Newton and NuSTAR observations conducted during 2013-2021. In these observations, the source flux varies by a factor of ∼ 5 − 6, and we identify the source mainly in the sof t ultraluminous (SUL) state of ULXs. We fit the X-ray spectra with a two thermal component model consisting of a blackbody (for the soft component) and a disc (for the hard component), and the soft component dominates in these observations. The soft component in the SUL state shows properties similar to that of ultraluminous supersoft sources, for example, an anti-correlation between the characteristic radius and temperature of the blackbody component. In addition, we observe a positive correlation between the blackbody and inner disc temperatures when the X-ray spectra are fitted with the two-thermal component model. The source exhibits marginal evidence of X-ray flux dips in the Swift and XMM-Newton observations at different intensity levels. We explain the observed spectral and temporal properties of the source by invoking the supercritical radiatively driven outflow mechanism.

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“…4U 1700-37, Haberl et al 1989). In fact, the shadow wind model (Blondin 1994) has been offered as a possible mechanism to explain periodic dips (on orbital timescales) seen in the ULXP M51 ULX-7 (Vasilopoulos et al 2021) and in SMC X-2 during its 2015 super-Eddington outburst (Li et al 2016). Summarizing, Xray emission from the compact object can lead to anisotropic and inhomogeneous stellar winds.…”

Section: Interpretation Of Modelling Results Of Swift J02436+6124mentioning

confidence: 99%

Radio emission from colliding outflows in high-mass X-ray binaries with strongly magnetized neutron stars

Chatzis,

Petropoulou,

Vasilopoulos

2021

Preprint

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We present a toy model for radio emission in HMXBs with strongly magnetized NSs where a wind-collision region is formed by the NS outflow and the stellar wind of the massive companion. Radio emission is expected from the synchrotron radiation of shock-accelerated electrons and the free-free emission of the stellar wind. We found that the predicted relation between the GHz luminosity (L R ) and the accretion X-ray luminosity (L X ) can be written as L R ∝ L b X for most parameters. No correlation with X-rays is expected (b = 0) when the thermal emission of the stellar wind dominates in radio. We typically find a steep correlation (b = 12/7) for sub-Eddington X-ray luminosities and a more shallow one (b = 2(p−1)/7) for super-Eddington X-ray luminosities, where p is the power-law index of accelerated electrons. The maximum predicted radio luminosity is independent of the NS properties, while it depends on the stellar wind momentum, binary separation distance, and the minimum electron Lorentz factor. Using a Bayesian approach we modelled the radio observations of Swift J0243.6+6124 that cover a wide range of mass accretion rates. Our results support a shock origin for the radio detections at sub-Eddington X-ray luminosities. However, no physically meaningful parameters could be found for the super-Eddington phase of the outburst, suggesting a different origin. Future observations with more sensitive instruments might reveal a large number of HMXBs with strongly magnetized NSs in radio, allowing determination of the slope in the L R − L X relation, and putting the wind-collision scenario into test.

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Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Cited by 19 publications

References 65 publications

Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1

Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1

Spectral and Temporal Properties of Ultra-luminous X-ray Source NGC 55 ULX1

Radio emission from colliding outflows in high-mass X-ray binaries with strongly magnetized neutron stars

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