Study of the reflection spectrum of the accreting neutron star GX 3+1 using XMM–Newton and INTEGRAL

Pintore, Fabio; Salvo, T. Di; Bozzo, E.; Sanna, A.; Burderi, L.; D’Aí, A.; Riggio, A.; Scarano, F.; Iaria, R.

doi:10.1093/mnras/stv758

Cited by 36 publications

(35 citation statements)

References 66 publications

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“…Di Salvo et al 2000Salvo et al , 2001D'Amico et al 2001;Iaria et al 2004;Di Salvo et al 2006;Paizis et al 2006;D'Aí et al 2007;Tarana et al 2007;Piraino et al 2007). During this state, the hard tails do not present high energy cut-off and they provide a small percentage of the total flux emission (a few percent), although in the case of the accreting NS GX 3+1 such a component was found to carry up to ∼20% of the total emission (Pintore et al 2015). Several scenarios were proposed in order to explain hard tails: in particular, they can be either by non-thermal Comptonization of non thermal, relativistic, electrons in a local outflow (e.g.…”

Section: Discussionmentioning

confidence: 91%

Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9−2021

Pintore

Sanna

Salvo

et al. 2016

Mon. Not. R. Astron. Soc.

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We analyzed a 115 ks XMM-Newton observation and the stacking of 8 days of INTE-GRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (∼2 keV) and an additional hard X-ray emission described by a power-law (Γ ∼ 2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high energy tail is still under debate. In addition, a number of broad (σ = 0.1-0.4 keV) emission features likely associated to reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity of the source is ∼5×10 37 erg s −1 , about 25% of the Eddington limit assuming a 1.4 M NS. We suggest that the spectral properties of SAX J1748.9-2021 are consistent with a soft state, differently from many other accreting X-ray millisecond pulsars which are usually found in the hard state. Moreover, none of the observed type-I burst reached the Eddington luminosity. Assuming that the burst ignition and emission are produced above the whole NS surface, we estimate a neutron star radius of ∼ 7 − 8 km, consistent with previous results.

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Section: Discussionmentioning

confidence: 91%

Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9−2021

Pintore

Sanna

Salvo

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The presence of a hard power-law component is often found in the spectra of bright LMXBs in the soft state (see e.g. Piraino et al 2007;Pintore et al 2015, and has been interpreted as comptonization of soft photons off a non-thermal population of electrons (see e.g. Di Salvo et al 2000).…”

Section: Discussionmentioning

confidence: 99%

A re-analysis of theNuSTARandXMM-Newtonbroad-band spectrum of Serpens X-1

Matranga

Salvo

Iaria

et al. 2017

A&A

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Context. High resolution X-ray spectra of neutron star Low Mass X-ray Binaries (LMXBs) in the energy range 6.4-6.97 keV, are often characterized by the presence of Kα transition features of iron at different ionization stages. Since these lines are thought to originate by reflection of the primary Comptonization spectrum over the accretion disk, the study of these features allows us to investigate the structure of the accretion flow close to the central source. Thus, the study of these features gives us important physical information on the system parameters and geometry. Ser X-1 is a well studied LMXB which clearly shows a broad iron line. Several attempts to fit this feature as a smeared reflection feature have been performed on XMM-Newton, Suzaku, NuSTAR, and, more recently, on Chandra data, finding different results for the inner radius of the disk and other reflection or smearing parameters. For instance, Miller et al. (2013) have presented broad-band, high quality NuSTAR data of Ser X-1. Using relativistically smeared self-consistent reflection models, they find a value of R in close to 1.0 R IS CO (corresponding to 6 R g , where R g is the Gravitational radius, defined as usual2 ), and a low inclination angle of less than ∼ 10• . Aims. The aim of this paper is to probe to what extent the choice of reflection and continuum models (and uncertainties therein) can affect the conclusions about the disk parameters inferred from the reflection component. To this aim we re-analyze all the available public NuSTAR and XMM-Newton which have the best sensitivity at the iron line energy observations of Ser X-1. Ser X-1 is a well studied source, its spectrum has been observed by several instruments, and is therefore one of the best sources for this study. Methods. We use slightly different continuum and reflection models with respect to those adopted in literature for this source. In particular we fit the iron line and other reflection features with self-consistent reflection models as reflionx (with a power-law illuminating continuum modified with a high energy cutoff to mimic the shape of the incident Comptonization spectrum) and rfxconv. With these models we fit NuSTAR and XMM-Newton spectra yielding consistent spectral results. Results. Our results are in line with those already found by Miller et al. (2013) but less extreme. In particular, we find the inner disk radius at ∼ 13 R g and an inclination angle with respect to the line of sight of ∼ 27• . We conclude that, while the choice of the reflection model has little impact on the disk parameters, as soon as a self-consistent model is used, the choice of the continuum model can be important in the precise determination of the disk parameters from the reflection component. Hence broad-band X-ray spectra are highly preferable to constrain the continuum and disk parameters.

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“…We note that, if we eliminate the powerlaw component from this continuum model, we get a worse fit, corresponding to a decrease of ∆χ 2 = 191 for the addition of two parameters when the powerlaw component is included in this fit. So, powerlaw component remains signifant as it required to fit high-energy residuals of the atoll sources in the soft state (Pintore et al 2015;Iaria et al 2001). This combination of continuum model has been frequently used for the soft state spectra of many atoll type NS LMXBs (Lin et al 2007;Cackett et al 2010;Miller et al 2013).…”

Section: Continuum Modelingmentioning

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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Study of the reflection spectrum of the accreting neutron star GX 3+1 using XMM–Newton and INTEGRAL

Cited by 36 publications

References 66 publications

Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9−2021

Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9−2021

A re-analysis of theNuSTARandXMM-Newtonbroad-band spectrum of Serpens X-1

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

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