Diagnosing the accretion flow in ultraluminous X-ray sources using soft X-ray atomic features

Middleton, Matthew; Walton, D. J.; Fabian, A. C.; Roberts, T. P.; Heil, L.; Pinto, C.; Anderson, G.; Sutton, Andrew D.

doi:10.1093/mnras/stv2214

Cited by 119 publications

(158 citation statements)

References 60 publications

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“…It was suggested (Sutton et al 2013) that ULXs seen at lower inclination (down the polar funnel) have harder X-ray spectra, while those seen at higher inclination (through the disk wind) have softer spectra with a lower-energy downturn, due to a higher degree of Compton scattering in the wind. This interpretation is consistent with the presence of absorption and emission features (interpreted as signatures of the outflow) in the X-ray spectra of ULXs with softer spectra (Middleton et al 2014(Middleton et al , 2015b. It is also in agreement with a higher degree of short-term variability (interpreted as the imprint of a clumpy wind) in sources with softer spectra (Middleton et al 2015a).…”

Section: Introductionsupporting

confidence: 86%

“…Even if we allow for the possibility of < p 0.6 in a sub-Eddington disk, the presence of strong line residuals in the soft X-ray band is another, stronger piece of evidence against the standard disk model. It is instead indicative of Eddington accretion and associated outflows (Middleton et al 2015b;Pinto et al 2016a). For these reasons, we disfavor the sub-Eddington standard disk model for ULX-1.…”

Section: Spectral Models For Ulx-1mentioning

confidence: 84%

“…An extended hot halo is a characteristic feature of the best-studied eclipsing X-ray binary, the low-mass Galactic system EXO 0748−676 (Bonnet-Bidaud et al 2001). Soft X-ray residuals consistent with thermal-plasma emission (and/or absorption) have been reported in several other (non-eclipsing) ULXs such as NGC 5408 X-1 (Middleton et al 2014(Middleton et al , 2015bSutton et al 2015;Pinto et al 2016b), NGC 6946 X-1 (Middleton et al 2014), Ho II X-1 (Miyaji et al 2001;Dewangan et al 2004), NGC 4395 X-1 (Stobbart et al 2006), NGC 4559 X-1 ), NGC 7424 ULX-2 (Soria et al 2006), NGC 1313 X-1 (Bachetti et al 2013;Pinto et al 2016b), and Ho IX X-1 . The last two of those ULXs are hard ultraluminous sources, while all the others are classified as soft ultraluminous.…”

Section: Spectral Properties: Broadened Disks Comptonization and Thementioning

confidence: 97%

“…Finally, we tested whether the addition of a thermal-plasma emission component improves the fit. The justification for this component is that some ULXs (especially those seen at high viewing angles) may show emission features in the ∼1 keV region (Middleton et al 2014(Middleton et al , 2015b. 2) hardness ratio vs. 0.3-7.0 keV count rate for ULX-1 and ULX-2 in eclipse and non-eclipse intervals during the Chandra observations.…”

Section: Spectral Models For Ulx-1mentioning

confidence: 99%

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Two Eclipsing Ultraluminous X-Ray Sources in M51

Urquhart

Soria

2016

ApJ

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We present the discovery, from archival Chandra and XMM-Newton data, of X-ray eclipses in two ultraluminous X-ray sources (ULXs), located in the same region of the galaxy M51: CXOM51 J132940.0+471237 (ULX-1, for simplicity) and CXOM51 J132939.5+471244 (ULX-2). Three eclipses were detected for ULX-1 and two for ULX-2. The presence of eclipses puts strong constraints on the viewing angle, suggesting that both ULXs are seen almost edge-on and are certainly not beamed toward us. Despite the similar viewing angles and luminosities ( »Ĺ 2 10 X 39 erg s −1 in the 0.3-8 keV band for both sources), their X-ray properties are different. ULX-1 has a soft spectrum, well fitted by Comptonization emission from a medium with electron temperature » kT 1 keV e . ULX-2 is harder, well fitted by a slim disk with » kT 1.5 in -1.8 keV and normalization consistent with a ∼10 M e black hole. ULX-1 has a significant contribution from multi-temperature thermal-plasma emission ( »Ĺ 2 10 X,mekal 38 erg s −1 ). About 10% of this emission remains visible during the eclipses, proving that the emitting gas comes from a region slightly more extended than the size of the donor star. From the sequence and duration of the Chandra observations in and out of eclipse, we constrain the binary period of ULX-1 to be either »6.3 days, or ≈12.5-13 days. If the donor star fills its Roche lobe (a plausible assumption for ULXs), both cases require an evolved donor, most likely a blue supergiant, given the young age of the stellar population in that Galactic environment.

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Section: Introductionsupporting

confidence: 86%

Section: Spectral Models For Ulx-1mentioning

confidence: 84%

Section: Spectral Properties: Broadened Disks Comptonization and Thementioning

confidence: 97%

Section: Spectral Models For Ulx-1mentioning

confidence: 99%

See 2 more Smart Citations

Two Eclipsing Ultraluminous X-Ray Sources in M51

Urquhart

Soria

2016

ApJ

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“…It was claimed that the Doppler-shifted X-ray lines had been detected in the X-ray binary 4U1630−47 (Cui et al 2000;Díaz Trigo et al 2013), though it was not confirmed (Neilsen et al 2014). The X-ray observation of the ULX NGC 1313 X-1 provides evidence of soft X-ray atomic features associated with the winds or outflows (Middleton et al 2015;Pinto et al 2016). The thermal X-ray line emission from the outflows may provide useful clues on the nature of ULXs.…”

Section: Introductionmentioning

confidence: 99%

On the Thermal Line Emission From the Outflows in Ultraluminous X-Ray Sources

Cao

2016

ApJ

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The atomic features in the X-ray spectra ofultraluminous X-ray sources (ULXs) may be associated with the outflow, which may provide a way to explore the physics of the ULXs. We construct a conical outflow modeland calculate the thermal X-ray Fe emission lines from the outflows. Our results show that thermal line luminosity decreases with increasing outflow velocity and/or opening angle of the outflow for a fixed kinetic power of the outflows. Assuming the kinetic power of the outflows to be comparable with the accretion power in the ULXs, we find that the equivalent width can be several eV for the thermal X-ray Fe emission line from the outflows in the ULXs with stellar-mass black holes. The thermal line luminosity is proportional to 1/M bh (M bh is the black hole mass of the ULX). The equivalent width decreases with the black hole mass, which implies that the Fe line emission from the outflows can hardly be detected if the ULXs contain intermediate-mass black holes. Our results suggest that the thermal X-ray Fe line emission should be preferentially be detected in the ULXs with high kinetic power slowly moving outflows from the accretion disks surrounding stellar-mass black holes/neutron stars. The recently observed X-ray atomic features of the outflows in aULX may imply that it contains a stellar-mass black hole.

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A new characterization of the Compton process in the ULX spectra

2016

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Attempts were made to construct a unified description of the spectra of ULX (Ultra Luminous X-ray source) objects, including their Power-Law (PL) state and Disk-like state. Among spectral models proposed to explain either state, the present work adopts the one which combines multi-color disk (MCD) emission and its thermal Comptonization (THC). This model was applied to several datasets of ULXs obtained by Suzaku, XMM-Newton, and Nustar. The model well explains all the spectra, regardless of the spectral states, in terms of a cool disk (Tin = 0.2 − 0.5 keV) and a cool thick (Te = 1 − 3 keV, τ ∼ 10) corona. The fit results can be characterized by two new parameters. One is Q ≡ Te/Tin which describes balance between the Compton cooling and gravitational heating of the coronal electrons, while the other is F ≡ 1−F direct /F total , namely, the covering fraction of the MCD by the corona. Here, F direct and F total are luminosity in the directly-visible disk emission and the total radiation, respectively. Then, the PL-state spectra have been found to show Q ∼ 10 and F ∼ 0.5, while those of the Disk-like state Q ∼ 3 and F ∼ 1. Thus, the two states are clearly separated in terms of Q and F . The obtained results are employed to argue for their interpretation in terms of high-mass (several tens to several hundreds M⊙) black holes.

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Diagnosing the accretion flow in ultraluminous X-ray sources using soft X-ray atomic features

Cited by 119 publications

References 60 publications

Two Eclipsing Ultraluminous X-Ray Sources in M51

Two Eclipsing Ultraluminous X-Ray Sources in M51

On the Thermal Line Emission From the Outflows in Ultraluminous X-Ray Sources

A new characterization of the Compton process in the ULX spectra

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