Disc reflection and a possible disc wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9–342058

Degenaar, N.; Altamirano, D.; Parker, M. L.; Miller-Jones, J. C. A.; Miller, J. M.; Heinke, C. O.; Wijnands, Rudy; Ludlam, R. M.; Parikh, A. S.; Hessels, J. W. T.; Gusinskaia, N. V.; Deller, Adam T.; Fabian, A. C.

doi:10.1093/mnras/stw1593

Cited by 40 publications

(51 citation statements)

References 99 publications

(163 reference statements)

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“…Therefore, we have not determined a best-fit NH for SAX J1808.4−3658. Our values for the other sources are consistent with those reported in the literature Papitto et al 2013;Linares et al 2014;Del Santo et al 2014;Bozzo et al 2015;Ludlam et al 2016;Pintore et al 2016;Tetarenko et al 2016;Degenaar et al 2016).…”

Section: Resultssupporting

confidence: 92%

“…We only consider the hard state data for the best-fit N H determination. A hard to soft transition has been reported in literature only for 1RXS J180408.9−342058 (Degenaar et al 2016) and EXO 1745−248 (Tetarenko et al 2016 Figure C1. The photon index versus luminosity (0.5 -10 keV) for our six sources plotted for the N H left free, the Galactic N H , and the best-fit N H value.…”

Section: Appendix A: Best-fit N H As Determined From the Individual Fitsmentioning

confidence: 80%

“…To determine the different source states, we compared the MAXI data 4 of each of the sources with that obtained using Swift/BAT 5 . Unfortunately, only 1RXS J180408.9−342058 and EXO 1745−248 showed clearly different spectral states in those light curves (see also Degenaar et al 2016;Tetarenko et al 2016). For 1RXS J180408.9−342058, the state transition was also accompanied by a change in the NH trend (see Figure A1).…”

Section: Appendix A: Best-fit N H As Determined From the Individual Fitsmentioning

confidence: 96%

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Very hard states in neutron star low-mass X-ray binaries

Parikh

Wijnands

Degenaar

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report on unusually very hard spectral states in three confirmed neutron-star low-mass X-ray binaries (1RXS J180408.9−342058, EXO 1745−248, and IGR J18245−2452) at a luminosity between ∼ 10 36−37 erg s −1. When fitting the Swift X-ray spectra (0.5 -10 keV) in those states with an absorbed power-law model, we found photon indices of Γ ∼ 1, significantly lower than the Γ = 1.5 -2.0 typically seen when such systems are in their so called hard state. For individual sources very hard spectra were already previously identified but here we show for the first time that likely our sources were in a distinct spectral state (i.e., different from the hard state) when they exhibited such very hard spectra. It is unclear how such very hard spectra can be formed; if the emission mechanism is similar to that operating in their hard states (i.e., up-scattering of soft photons due to hot electrons) then the electrons should have higher temperatures or a higher optical depth in the very hard state compared to those observed in the hard state. By using our obtained Γ as a tracer for the spectral evolution with luminosity, we have compared our results with those obtained by Wijnands et al. (2015). We confirm their general results in that also our sample of sources follow the same track as the other neutron star systems, although we do not find that the accreting millisecond pulsars are systematically harder than the non-pulsating systems.

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Section: Resultssupporting

confidence: 92%

Section: Appendix A: Best-fit N H As Determined From the Individual Fitsmentioning

confidence: 80%

Section: Appendix A: Best-fit N H As Determined From the Individual Fitsmentioning

confidence: 96%

See 1 more Smart Citation

Very hard states in neutron star low-mass X-ray binaries

Parikh

Wijnands

Degenaar

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…These species are generally observed in LMXB outbursts (e.g., van Paradijs & McClintock 1995), and may be expected to be present if the donor star in J1957 were a late-K/early-M dwarf as assumed above (although not necessarily for short-period binaries; Degenaar et al 2016). The outburst characteristics of J1957 are in fact quite similar to those of the transient ultracompact LMXB candidate 1RXS J180408.9−34205 (Baglio et al 2016;Degenaar et al 2016). Indeed, the INTEGRAL hard X-ray detection of J1957 during the MJD 57153 outburst that possibly preceded the MAXI detection at softer energies may have represented a hard state of the system that transitioned to a soft state around the epoch of the MAXI observations, in analogy with the outburst of 1RXS J180408.9−34205.…”

Section: An Unidentified Mass Donor?mentioning

confidence: 82%

MAXI J1957+032: An Accreting Neutron Star Possibly in a Triple System

Ravi

2017

ApJ

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I present an optical characterization of the Galactic X-ray transient source MAXI J1957+032. This system flares by a factor of 10 4 every few hundred days, with each flare lasting ∼5days. I identify its quiescent counterpart to be a late-K/early-M dwarf star at a distance of 5±2 kpc. This implies that the peak 0.5 10 keV -luminosity of the system is 10 36.4 0.4  erg s −1 . As found by Mata Sanchez et al. the outburst properties of MAXI J1957+032 are most consistent with the sample of accreting millisecond pulsars. However, the low inferred accretion rate, and the lack of evidence for a hydrogen-rich accretion flow, are difficult to reconcile with the late-K/early-M dwarf counterpart being the mass donor. Instead, the observations are best described by a low-mass hydrogen-and possibly heliumpoor mass donor, such as a carbon-oxygen white dwarf, forming a tight interacting binary with a neutron star. The observed main-sequence counterpart would then likely be in a wide orbit around the inner binary.

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“…Thus the inner disc radius sets an upper limit to the radius of the NS and hence can constrain the NS equation of state (Piraino et al 2000;Cackett et al 2008;Bhattacharyya 2011). Fe K line profile can also be used to obtain an upper limit on the strength of the magnetic field associated with the NS (Ludlam et al 2019;Degenaar et al 2016a;King et al 2016).…”

Section: Introductionmentioning

confidence: 99%

On the disc reflection spectroscopy of NS LMXB Serpens X-1: analysis of a recent NuSTAR observation

Mondal

Dewangan

Raychaudhuri

2020

Monthly Notices of the Royal Astronomical Society

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We present NuSTAR observation of the atoll type neutron star (NS) low-mass X-ray binary (LMXB) Serpens X-1 (Ser X-1) performed on 17 February 2018. We observed Ser X-1 in a soft X-ray spectral state with 3 − 79 keV luminosity of L X ∼ 0.4 × 10 38 erg s −1 (∼ 23% of the Eddington luminosity), assuming a distance of 7.7 kpc. A positive correlation between intensity and hardness ratio suggests that the source was in the banana branch during this observation. The broadband 3 − 30 keV NuSTAR energy spectrum can be well described by a three-component continuum model consisting of a disk blackbody, a single temperature blackbody and a power-law. A broad iron line ∼ 5−8 keV and the Compton back-scattering hump peaking at ∼ 10−20 keV band are clearly detected in the X-ray spectrum. These features are best interpreted by a self-consistent relativistic reflection model. Fits with relativistically blurred disc reflection model suggests that the inner disc R in is truncated prior to the ISCO at (1.7 − 2.3) R ISCO (≃ 10.2 − 13.8 R g or 23 − 31 km) and the accretion disc is viewed at an low inclination of i ≃ 18 • − 21 • . The disc is likely to be truncated either by a boundary layer or by the magnetosphere. Based on the measured flux and the mass accretion rate, the maximum radial extension for the boundary layer is estimated to be ∼ 6.4 R g from the NS surface. The truncated inner disc in association with pressure from a magnetic field sets an upper limit of B 1.6 × 10 9 G.

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Disc reflection and a possible disc wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9–342058

Cited by 40 publications

References 99 publications

Very hard states in neutron star low-mass X-ray binaries

Very hard states in neutron star low-mass X-ray binaries

MAXI J1957+032: An Accreting Neutron Star Possibly in a Triple System

On the disc reflection spectroscopy of NS LMXB Serpens X-1: analysis of a recent NuSTAR observation

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