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

Alston, W. N.; Pinto, C.; Barret, D.; D’Aí, A.; Santo, M. Del; Earnshaw, Hannah P.; Fabian, A. C.; Kara, Erin; Kosec, P.; Middleton, Matthew; Parker, M. L.; Pintore, Fabio; Robba, A.; Roberts, T. P.; Sathyaprakash, R.; Walton, D. J.; Ambrosi, E.

doi:10.1093/mnras/stab1473

Cited by 24 publications

(22 citation statements)

References 58 publications

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“…In case of the ULX NGC 5408 X-1, it could be interpreted that the observed reverberation could be mainly from the single scattering (or few scatterings) of hard photons with the extended wind that is much further away from the BH, ∼ 10 4 -10 6 𝑟 g (e.g. Middleton et al 2014;Sutton et al 2014;Alston et al 2021). Also, this reverberation region is in agreement with that is expected by Hernández-García et al (2015).…”

Section: The Disc Wind Geometry and Its Evolutionsupporting

confidence: 75%

X-ray reverberation models of the disc wind in ultraluminous X-ray source NGC 5408 X-1

Luangtip,

Chainakun,

Loekkesee

et al. 2021

Preprint

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Majority of ultraluminous X-ray sources (ULXs) are believed to be super-Eddington objects, providing a nearby prototype for studying an accretion in super-critical regime. In this work, we present the study of time-lag spectra of the ULX NGC 5408 X-1 using a reverberation mapping technique. The time-lag data were binned using two different methods: time averaged-based and luminosity-based spectral bins. These spectra were fitted using two proposed geometric models: single and multiple photon scattering models. While both models similarly assume that a fraction of hard photons emitted from inner accretion disc could be down-scattered with the super-Eddington outflowing wind becoming lagged, soft photons, they are different by the number that the hard photons scattering with the wind: i.e. single vs multiple times. In case of averaged spectrum, both models consistently constrained the mass of ULX in the range of ∼80-500 M . However, for the modelling results from the luminosity based spectra, the confidence interval of the BH mass is significantly improved and is constrained to the range of ∼75-90 M . In addition, the models suggest that the wind geometry is extended in which the photons could down-scatter with the wind at the distance of ∼10 4 -10 6 𝑟 g . The results also suggest the variability of the lag spectra as a function of ULX luminosity, but the clear trend of changing accretion disc geometry with the spectral variability is not observed.

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Section: The Disc Wind Geometry and Its Evolutionsupporting

confidence: 75%

X-ray reverberation models of the disc wind in ultraluminous X-ray source NGC 5408 X-1

Luangtip,

Chainakun,

Loekkesee

et al. 2021

Preprint

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“…Assuming the numbers derived in Paper I, we would obtain a wind photosphere R = 10 12 cm, from which together with the measured 0.17c wind velocity provides a traveltime t = R/v = 200 s. This is short enough to produce the dips by obscuring the innermost regions. We note that the wind photosphere is comparable to size of the region producing the peaks in the PDS, if we assume Keplerian motion (Alston et al 2021). A similar value is obtained if we calculate the maximum distance of the wind by assuming that the cloud size does not exceed its distance, i.e.…”

Section: The Occultation Scenariosupporting

confidence: 73%

The Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1

D’Aí

Pinto

Santo

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Soft Ultra-Luminous X-ray (ULXs) sources are a sub-class of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems, dips have been observed. The mechanism behind this state transition and the dips nature are still debated. To investigate these issues, we obtained a long XMM-Newton monitoring campaign of a member of this class, NGC 247 ULX-1. We computed the hardness-intensity diagram for the whole data-set and identified two different branches: the normal branch and the dipping branch, which we study with four and three hardness-intensity resolved spectra, respectively. All seven spectra are well described by two thermal components: a colder (kTbb ∼ 0.1-0.2 keV) black-body, interpreted as emission from the photo-sphere of a radiatively-driven wind, and a hotter (kTdisk ∼ 0.6 keV) multi-colour disk black-body, likely due to reprocessing of radiation emitted from the innermost regions. In addition, a complex pattern of emission and absorption lines has been taken into account based on previous high-resolution spectroscopic results. We studied the evolution of spectral parameters and flux of the two thermal components along the two branches and discuss two scenarios possibly connecting the state transition and the dipping phenomenon. One is based on geometrical occultation of the emitting regions, the other invokes the onset of a propeller effect.

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“…This is short enough to produce the dips by obscuring the innermost regions. We note that the wind photosphere is comparable to size of the region producing the peaks in the PDS, if we assume Keplerian motion (Alston et al 2021). A similar value is obtained if we calculate the maximum distance of the wind by assuming that the cloud size does not exceed its distance, i.e.…”

Section: The Occultation Scenariosupporting

confidence: 73%

The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1

D'Aì,

Pinto,

Del Santo

et al. 2021

Preprint

View full text Add to dashboard Cite

Soft Ultra-Luminous X-ray (ULXs) sources are a sub-class of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems, dips have been observed. The mechanism behind this state transition and the dips nature are still debated. To investigate these issues, we obtained a long XMM-Newton monitoring campaign of a member of this class, NGC 247 ULX-1. We computed the hardness-intensity diagram for the whole data-set and identified two different branches: the normal branch and the dipping branch, which we study with four and three hardness-intensity resolved spectra, respectively. All seven spectra are well described by two thermal components: a colder (kT bb ∼ 0.1-0.2 keV) black-body, interpreted as emission from the photo-sphere of a radiatively-driven wind, and a hotter (kT disk ∼ 0.6 keV) multi-colour disk black-body, likely due to reprocessing of radiation emitted from the innermost regions. In addition, a complex pattern of emission and absorption lines has been taken into account based on previous high-resolution spectroscopic results. We studied the evolution of spectral parameters and flux of the two thermal components along the two branches and discuss two scenarios possibly connecting the state transition and the dipping phenomenon. One is based on geometrical occultation of the emitting regions, the other invokes the onset of a propeller effect.

show abstract

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

Cited by 24 publications

References 58 publications

X-ray reverberation models of the disc wind in ultraluminous X-ray source NGC 5408 X-1

X-ray reverberation models of the disc wind in ultraluminous X-ray source NGC 5408 X-1

The Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1

The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1

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