Relativistic Iron Line Emission from the Neutron Star Low‐Mass X‐Ray Binary 4U 1636‐536

Pandel, D.; Kaaret, Philip; Corbel, S.

doi:10.1086/592429

Cited by 65 publications

(109 citation statements)

References 28 publications

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“…Sometimes, in highly inclined sources, broad iron emission lines were found together with highly ionized iron lines in absorption, clearly indicating the presence of an out-flowing disk wind (see, e.g., the case of the bright atoll source GX 13+1; Pintore et al 2014, and references therein). In the case of 4U 1636-536, Pandel et al (2008) tentatively fitted the very broad emission feature present in the range 4 − 9 keV with a combination of several Kα lines from iron in different ionization states. In particular they fitted the iron complex with two broad emission lines with centroid energies fixed at 6.4 and 7 keV, respectively.…”

Section: The Combined Xmm-newton and Integral Spectrummentioning

confidence: 95%

XMM-Newtonand INTEGRAL view of the hard state of EXO 1745−248 during its 2015 outburst

Matranga

Papitto

Salvo

et al. 2017

A&A

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Context. Transient low-mass X-ray binaries (LMXBs) often show outbursts lasting typically a few-weeks and characterized by a high X-ray luminosity (L x ≈ 10 36 − 10 38 erg s −1 ), while for most of the time they are found in X-ray quiescence (L X ≈ 10 31 − 10 33 erg s −1 ). EXO 1745-248 is one of them. Aims. The broad-band coverage, and the sensitivity of instrumet on board of XMM-Newton and INTEGRAL, offers the opportunity to characterize the hard X-ray spectrum during EXO 1745-248 outburst. Methods. In this paper we report on quasi-simultaneous XMM-Newton and INTEGRAL observations of the X-ray transient EXO 1745-248 located in the globular cluster Terzan 5, performed ten days after the beginning of the outburst (on 2015 March 16th) shown by the source between March and June 2015. The source was caught in a hard state, emitting a 0.8-100 keV luminosity of ≃ 10 37 erg s −1 . Results. The spectral continuum was dominated by thermal Comptonization of seed photons with temperature kT in ≃ 1.3 keV, by a cloud with moderate optical depth τ ≃ 2 and electron temperature kT e ≃ 40 keV. A weaker soft thermal component at temperature kT th ≃ 0.6-0.7 keV and compatible with a fraction of the neutron star radius was also detected. A rich emission line spectrum was observed by the EPIC-pn on-board XMM-Newton; features at energies compatible with K-α transitions of ionized sulfur, argon, calcium and iron were detected, with a broadness compatible with either thermal Compton broadening or Doppler broadening in the inner parts of an accretion disk truncated at 20 ± 6 gravitational radii from the neutron star. Strikingly, at least one narrow emission line ascribed to neutral or mildly ionized iron is needed to model the prominent emission complex detected between 5.5 and 7.5 keV. The different ionization state and broadness suggest an origin in a region located farther from the neutron star than where the other emission lines are produced. Seven consecutive type-I bursts were detected during the XMM-Newton observation, none of which showed hints of photospheric radius expansion. A thorough search for coherent pulsations from the EPIC-pn light curve did not result in any significant detection. Upper limits ranging from a few to 15% on the signal amplitude were set, depending on the unknown spin and orbital parameters of the system.

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Section: The Combined Xmm-newton and Integral Spectrummentioning

confidence: 95%

XMM-Newtonand INTEGRAL view of the hard state of EXO 1745−248 during its 2015 outburst

Matranga

Papitto

Salvo

et al. 2017

A&A

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“…This finding is partly contested by Cackett et al (2010) who fit the same spectra with a blurred reflection model that includes effects like Compton broadening and line emission from relevant elements. Cackett et al (2010) showed that fitting the spectrum with a self-consistent reflection model resulted in slightly larger values for the inner disc radius than when the spectrum was fit with the phenomenological diskline model (Fabian et al 1989) used by Pandel et al (2008). Nonetheless, both the results of Pandel et al (2008) and Cackett et al (2010) are based on data which were not corrected for pileup effects.…”

Section: U 1636-53mentioning

confidence: 99%

“…As demonstrated by Ng et al (2010), re-analyses of the same XMM-Newton data considering pileup and background effects, suggested a different iron line profile. Ng et al (2010) found that the Fe lines in the three spectra of 4U 1636-53 used by Pandel et al (2008) appeared to be symmetric and could be well fit with a Gaussian profile, although, due to the statistics, a relativistic origin of the line could not be excluded. However, Ng et al (2010) did not include the simultaneous RXTE data in their fits, which can affect the Fe emission line profile that strongly depends on the underlying continuum.…”

Section: U 1636-53mentioning

confidence: 99%

“…Broad Fe lines are also detected in NS systems although they are weaker than in BH systems. With instruments like Chandra, XMM-Newton and Suzaku, relativistically broadened Fe emission lines have been observed in many NS LMXBs (e.g., Piraino et al 2007;Cackett et al 2008;Pandel et al 2008;di Salvo et al 2009;Cackett et al 2010; see also Ng et al 2010 for an almost complete list of NS LMXBs with Fe lines detected with XMM-Newton).…”

Section: Introductionmentioning

confidence: 99%

“…Bhattacharyya & Strohmayer 2007;Lin et al 2007;Pandel et al 2008;Cackett et al 2008). However, as the Fe emission line is a reflection signature, it should be accompanied with a reflection continuum extending over a wide bandpass; at the same time, the line and its reflection continuum should self-consistently determine the ionisation balance of the disc and include Compton scattering (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Broad iron line in the fast spinning neutron-star system 4U 1636−53

Sanna

Hiemstra

Méndez

et al. 2013

Monthly Notices of the Royal Astronomical Society

111

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We analysed the X-ray spectra of six observations, simultaneously taken with XMMNewton and Rossi X-ray Timing Explorer (RXTE), of the neutron star low-mass X-ray binary 4U 1636-53. The observations cover several states of the source, and therefore a large range of inferred mass accretion rate. These six observations show a broad emission line in the spectrum at around 6.5 keV, likely due to iron. We fitted this line with a set of phenomenological models of a relativistically broadened line, plus a model that accounts for relativistically smeared and ionised reflection from the accretion disc. The latter model includes the incident emission from both the neutronstar surface or boundary layer and the corona that is responsible for the high-energy emission in these systems. From the fits with the reflection model we found that in four out of the six observations the main contribution to the reflected spectrum comes from the neutron-star surface or boundary layer, whereas in the other two observations the main contribution to the reflected spectrum comes from the corona. We found that the relative contribution of these two components is not correlated to the state of the source. From the phenomenological models we found that the iron line profile is better described by a symmetric, albeit broad, profile. The width of the line cannot be explained only by Compton broadening, and we therefore explored the case of relativistic broadening. We further found that the direct emission from the disc, boundary layer, and corona generally evolved in a manner consistent with the standard accretion disc model, with the disc and boundary layer becoming hotter and the disc moving inwards as the source changed from the hard in to the soft state. The iron line, however, did not appear to follow the same trend.

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High-Frequency Variability in Neutron-Star Low-Mass X-ray Binaries

Méndez

Belloni

2020

Astrophysics and Space Science Library

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Binary systems with a neutron-star primary accreting from a companion star display variability in the X-ray band on time scales ranging from years to milliseconds. With frequencies of up to ∼1300 Hz, the kilohertz quasi-periodic oscillations (kHz QPOs) represent the fastest variability observed from any astronomical object. The sub-millisecond time scale of this variability implies that the kHz QPOs are produced in the accretion flow very close to the surface of the neutron star, providing a unique view of the dynamics of matter under the influence of some of the strongest gravitational fields in the Universe. This offers

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Relativistic Iron Line Emission from the Neutron Star Low‐Mass X‐Ray Binary 4U 1636‐536

Cited by 65 publications

References 28 publications

XMM-Newtonand INTEGRAL view of the hard state of EXO 1745−248 during its 2015 outburst

XMM-Newtonand INTEGRAL view of the hard state of EXO 1745−248 during its 2015 outburst

Broad iron line in the fast spinning neutron-star system 4U 1636−53

High-Frequency Variability in Neutron-Star Low-Mass X-ray Binaries

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