A Hard X-Ray Power-Law Spectral Cutoff in Centaurus X-4

Chakrabarty, Deepto; Tomsick, John A.; Grefenstette, Brian W.; Psaltis, Dimitrios; Bachetti, Matteo; Barret, D.; Boggs, Steven E.; Christensen, Finn Erland; Craig, William W.; Fürst, Felix; Hailey, Charles J.; Harrison, Fiona A.; Kaspi, V. M.; Miller, J. M.; Nowak, Michael A.; Rana, V.; Stern, Daniel; Wik, Daniel R.; Wilms, J.; Zhang, William W.

doi:10.1088/0004-637x/797/2/92

Cited by 61 publications

(104 citation statements)

References 100 publications

(147 reference statements)

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“…The origin of the power-law spectral component is less well understood, but it may be related to the presence of a residual accretion flow and/or the magnetic field of the neutron star (e.g., Campana et al 1998a;Rutledge et al 2001;Chakrabarty et al 2014;Wijnands et al 2015). Typically, this hard spectral component contributes ≃50% or less to the total unabsorbed 0.5-10 keV flux (e.g., Jonker 2008;Fridriksson et al 2011;Lowell et al 2012;Degenaar et al 2013bDegenaar et al , 2014Homan et al 2014).…”

Section: Aql X-1mentioning

confidence: 99%

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Waterhouse

Degenaar

Wijnands

et al. 2016

Mon. Not. R. Astron. Soc.

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Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as well as the short and faint 2015 outburst, to investigate the hypothesis that cooling of the accretion-heated neutron star crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that the X-ray light curves and measured neutron star surface temperatures are consistent with the expectations of the crust cooling paradigm. By using a thermal evolution code, we find that ≃1.2 − 3.2 MeV nucleon −1 of shallow heat release describes the observational data well, depending on the assumed mass-accretion rate and temperature of the stellar core. We find no evidence for varying strengths of this shallow heating after different outbursts, but this could be due to limitations of the data. We argue that monitoring Aql X-1 for up to ≃1 year after future outbursts can be a powerful tool to break model degeneracies and solve open questions about the magnitude, depth and origin of shallow heating in neutron star crusts.

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Section: Aql X-1mentioning

confidence: 99%

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Waterhouse

Degenaar

Wijnands

et al. 2016

Mon. Not. R. Astron. Soc.

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“…40 A typical EW of the iron lines from MCVs ranges from ∼150 to 300 eV (Ezuka & Ishida 1999). On the other hands, quiescent XBs (10 33 erg s -1 ) do not appear to exhibit detectable Fe line emission (50-120 eV) although their sample size is small (e.g., Bradley et al 2007;Chakrabarty et al 2014;Rana et al 2016). …”

Section: ) (A-mentioning

confidence: 99%

NuSTAR HARD X-RAY SURVEY OF THE GALACTIC CENTER REGION. II. X-RAY POINT SOURCES

Hong

Mori

Hailey

et al. 2016

ApJ

Self Cite

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We present the first survey results of hard X-ray point sources in the Galactic Center (GC) region by NuSTAR. We have discovered 70 hard (3-79 keV) X-ray point sources in a 0.6 deg 2 region around SgrA * with a total exposure of 1.7 Ms, and 7 sources in the SgrB2 field with 300 ks. We identify clear Chandra counterparts for 58 NuSTAR sources and assign candidate counterparts for the remaining 19. The NuSTAR survey reaches X-ray luminosities of ∼4× and ∼8×10 32 erg s -1 at the GC (8 kpc) in the 3-10 and 10-40 keV bands, respectively. The source list includes three persistent luminous X-ray binaries (XBs) and the likely run-away pulsar called the Cannonball. New source-detection significance maps reveal a cluster of hard (>10 keV) X-ray sources near the SgrA diffuse complex with no clear soft X-ray counterparts. The severe extinction observed in the Chandra spectra indicates that all the NuSTAR sources are in the central bulge or are of extragalactic origin. Spectral analysis of relatively bright NuSTAR sources suggests that magnetic cataclysmic variables constitute a large fraction (>40%-60%). Both spectral analysis and logN-logS distributions of the NuSTAR sources indicate that the X-ray spectra of the NuSTAR sources should have kT>20 keV on average for a single temperature thermal plasma model or an average photon index of Γ=1.5-2 for a power-law model. These findings suggest that the GC X-ray source population may contain a larger fraction of XBs with high plasma temperatures than the field population.

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“…Centaurus X-4 Chakrabarty et al (2014) conducted joint NuSTAR and XMM-Newton observations of the long-known, nearby LMXB Cen X-4. Although at a comparable luminosity level, unlike PSR J1023+0038, the non-thermal component of Cen X-4 in quiescence shows a spectral cutoff at ∼10 keV.…”

Section: Sax J18084-3658mentioning

confidence: 99%

Coordinated X-Ray, Ultraviolet, Optical, and Radio Observations of the PSR J1023+0038 System in a Low-Mass X-Ray Binary State

Bogdanov

Archibald

Bassa

et al. 2015

ApJ

103

112

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The PSR J1023+0038 binary system hosts a neutron star and a low-mass, main-sequence-like star. It switches on year timescales between states as an eclipsing radio millisecond pulsar and a low-mass X-ray binary (LMXB). We present a multi-wavelength observational campaign of PSR J1023+0038 in its most recent LMXB state. Two long XMM-Newton observations reveal that the system spends ∼70% of the time in a ≈3 × 10 33 erg s −1 X-ray luminosity mode, which, as shown in Archibald et al., exhibits coherent X-ray pulsations. This emission is interspersed with frequent lower flux mode intervals with 5 10 32 ≈ × erg s −1 and sporadic flares reaching up to ≈10 34 erg s −1 , with neither mode showing significant X-ray pulsations. The switches between the three flux modes occur on timescales of order 10 s. In the UV and optical, we observe occasional intense flares coincident with those observed in X-rays. Our radio timing observations reveal no pulsations at the pulsar period during any of the three X-ray modes, presumably due to complete quenching of the radio emission mechanism by the accretion flow. Radio imaging detects highly variable, flat-spectrum continuum radiation from PSR J1023+0038, consistent with an origin in a weak jet-like outflow. Our concurrent X-ray and radio continuum data sets do not exhibit any correlated behavior. The observational evidence we present bears qualitative resemblance to the behavior predicted by some existing "propeller" and "trapped" disk accretion models although none can account for key aspects of the rich phenomenology of this system.

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A Hard X-Ray Power-Law Spectral Cutoff in Centaurus X-4

Cited by 61 publications

References 100 publications

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

NuSTAR HARD X-RAY SURVEY OF THE GALACTIC CENTER REGION. II. X-RAY POINT SOURCES

Coordinated X-Ray, Ultraviolet, Optical, and Radio Observations of the PSR J1023+0038 System in a Low-Mass X-Ray Binary State

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