Broadband spectral analysis of MXB 1659−298 in its soft and hard state

Iaria, R.; Mazzola, S. M.; Bassi, Tiziana; Gambino, A. F.; Marino, A.; Salvo, T. Di; Sanna, A.; Riggio, A.; Burderi, L.; D’Amico, N.

doi:10.1051/0004-6361/201833982

Cited by 12 publications

(9 citation statements)

References 63 publications

(75 reference statements)

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“…The emissivity parameter is −2.14 +0.08 −0.13 for NB spectrum, and Betor= −2.5 +0.5 −1.0 in FB, accordingly with the value expected for a LMXB to be between -2 (in the case of a dominating central illuminating flux) and -3, which describes approximately the intrinsic emissivity of a disc (see e.g. Dauser et al 2013;Ponti et al 2018;Di Salvo et al 2019;Mazzola et al 2019;Marino et al 2019;Iaria et al 2019Iaria et al , 2020. Slightly large residuals are observed around 7.8 keV, especially for the NB spectrum (see central panels in Figure 7).…”

Section: Modelmentioning

confidence: 57%

“…The strength of the reflection is mainly indicated by the presence of a strong broad (FWHM up to 1 keV) emission line from Fe atoms between 6.4 and 6.97 keV (Fe-K region), identified with the Kα radiative transition of iron at different ionisation states (e.g. Iaria et al 2019Iaria et al , 2016Papitto et al 2013;Sanna et al 2013;Miller et al 2013;Di Salvo et al 2009;Iaria et al 2009Iaria et al , 2007. These features most likely originate in the region of the accretion disc closer to the compact object, where matter is rapidly rotating and reaches velocities up to a few tenths of the speed of light (see e.g.…”

Section: Introductionmentioning

confidence: 99%

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Fe K$α$ and Fe K$β$ line detection in the NuSTAR spectrum of the ultra-bright Z-source Scorpius X-1

Mazzola,

Iaria,

Di Salvo

et al. 2021

Preprint

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Context. Low-mass X-ray binaries hosting a low-magnetised neutron star, which accretes matter via Roche-lobe overflow, are generally grouped in two classes, named Atoll and Z sources after the path described in their X-ray colour-colour diagrams. Scorpius X-1 is the brightest persistent low-mass X-ray binary known so far, and it is the prototype of the Z sources.Aims. We analysed the first NuSTAR observation of this source to study its spectral emission exploiting the high statistics data collected by this satellite. Examining the colour-colour diagram, the source was probably observed during the lower normal and flaring branches of its Z-track. We separated the data from the two branches in order to investigate the evolution of the source along the track. Methods. We fitted the 3-60 keV NuSTAR spectra using the same models for both the branches. We adopted two description for the continuum: in the first case we used a blackbody and a thermal Comptonisation with seed photons originating in the accretion disc; in the second one, we adopted a disc-blackbody and a Comptonisation with a blackbodyshaped spectrum of the incoming seed photons. A power-law fitting the high energy emission above 20 keV was also required in both cases.Results. The two models provide the same physical scenario for the source in both the branches: a blackbody temperature between 0.8 and 1.5 keV, a disc-blackbody with temperature between 0.4 and 0.6 keV, and an optically thick Comptonising corona with optical depth between 6 and 10 and temperature about 3 keV. Furthermore, two lines related to the Kα and Kβ transitions of the He-like Fe xxv ions were detected at 6.6 keV and 7.8 keV, respectively. A hard tail modelled by a power law with a photon index between 2 and 3 was also required for both the models.

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Section: Modelmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Fe K$α$ and Fe K$β$ line detection in the NuSTAR spectrum of the ultra-bright Z-source Scorpius X-1

Mazzola,

Iaria,

Di Salvo

et al. 2021

Preprint

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“…MXB 1659-298 (Iaria et al 2019). The parameters of this component are N H ξ , log(ξ), f , and z: N H ξ describes the equivalent hydrogen column density associated with the ionized absorber, log(ξ) describes the ionization degree of the absorbing material, f is a dimensionless covering fraction of the emitting region, and z is the redshift associated with the absorption features.…”

Section: Spectral Analysismentioning

confidence: 99%

Evidence of a non-conservative mass transfer in the ultra-compact X-ray source XB 1916-053

Iaria

Sanna

Salvo

et al. 2021

A&A

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Context. The dipping source XB 1916-053 is a compact binary system with an orbital period of 50 min harboring a neutron star. It shows a positive and a negative superhump, which suggests the presence of a precessing elliptic accretion disk tilted with respect to the equatorial plane of the system. The orbital ephemeris indicates a large orbital period derivative, Ṗ/P = 1.53 × 10−7 yr−1, that can be explained assuming a high non-conservative mass transfer rate. Finally, the spectrum shows prominent absorption lines indicating the presence of an ionized absorber along the line of sight. Aims. Using ten new Chandra observations and one Swift/XRT observation, we are able to extend the baseline of the orbital ephemeris; this allows us to exclude some models that explain the dip arrival times. The Chandra observations provide a good plasma diagnostic of the ionized absorber and allow us to determine whether it is placed at the outer rim of the accretion disk or closer to the compact object. Methods. From the available observations we are able to obtain three new dip arrival times extending the baseline of the orbital ephemeris from 37 to 40 years. The Chandra spectra are fitted adopting a Comptonized continuum. To fit the absorption lines we adopt the ZXIPCF component obtaining information on the ionization parameter and the equivalent hydrogen column density of the ionized absorber. Results. From the analysis of the dip arrival times we confirm an orbital period derivative of Ṗ = 1.46(3) × 10−11 s s−1. Furthermore, the unabsorbed 0.1–100 keV luminosity observed from the Chandra spectra show a variation between 3 × 1036 and 1.4 × 1037 erg s−1. We show that the Ṗ value and the luminosity values are compatible with neutron star masses higher than 1.4 M⊙ with a mass accretion rate lower than 10% of the mass transfer rate. We show that the mass ratio q = m2/m1 of 0.048 explains the apsidal precession period of 3.9 d and the nodal precession period of 4.86 d deduced from the superhump and infrahump detected period. The observed absorption lines are associated with the presence of Ne X, Mg XII, Si XIV, SXVI, and Fe XXVI ions. We observe a redshift in the absorption lines between 1.1 × 10−3 and 1.3 × 10−3. By interpreting it as gravitational redshift, as recently discussed in the literature, we find that the ionized absorber is placed at a distance of 108 cm from the neutron star with a mass of 1.4 M⊙ and has a hydrogen atom density greater than 1015 cm−3. Instead, the absorber is more distant and could be placed at the outer rim of the accretion disk (1.7 × 1010 cm) during the dip activity. Conclusions. We show that the mass ratio of the source is 0.048; this value is obtained from the nodal precession period of the disk and from the apsidal precession period taking into account the pressure term due to the spiral wave present in the disk. From our analysis we estimate a pitch angle of the spiral wave smaller than 30°, in agreement with the values observed in several cataclysmic variables. We show that the outer radius of the disk is truncated at the radius in which a 3:1 resonance occurs, which is 1.7 × 1010 cm for a neutron star mass of 1.4 M⊙. The large orbital period derivative is likely due to a high non-conservative mass transfer with a mass transfer rate of 10−8 M⊙ yr−1. The variation in observed luminosity could be explained assuming that the ejection point from which the matter leaves the system moves close to the inner Lagrangian point.

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“…XTE J1710-281 exhibits intensity dips. Therefore, zxipcf will account for the presence of local ionized absorber around the NS which is an ubiquitous feature of LMXBs primarily detected in high-inclination sources (Díaz Trigo et al 2006;Díaz Trigo & Boirin 2016;Sharma et al 2018;Iaria et al 2019). The ionized absorber column density N ion H , ionization parameter log(ξ) and covered source fraction Cvr.…”

Section: Spectral Analysismentioning

confidence: 99%

“…Mitsuda et al (1984), White & Mason (1985), and Mitsuda et al (1989) evinced the bimodality in the X-ray spectral states of LMXBs, namely the high/soft state and the low/hard state. The canonical model, describing the X-ray spectra of LMXBs (e.g., Sco X-1, 4U 1608-522, GX 5-1 and GX 349+2) in soft state, consists of a multi-colour blackbody component attributed to the emission from accretion disc near the NS and a blackbody component to account for E-mail: princerajsharma31@gmail.com the emission from NS surface/boundary layer (kT ∼ 0.5-2 keV) with a weak (∼ 3-5 keV) Comptonization (Mitsuda et al 1984(Mitsuda et al , 1989Iaria et al 2019). This emission model has been strengthened by many studies (Zhang et al 2014(Zhang et al , 2016Gambino et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Broad-band spectral analysis of LMXB XTE J1710-281 with Suzaku

Sharma,

Jain

et al. 2020

Preprint

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This work presents the broad-band time-averaged spectral analysis of neutron star low-mass X-ray binary, XTE J1710-281 by using the Suzaku archival data. The source was in a hard or an intermediate spectral state during this observation. This is the first time that a detailed spectral analysis of the persistent emission spectra of XTE J1710-281 has been done up to 30 keV with improved constraints on its spectral parameters. By simultaneously fitting the XIS (0.6-9.0 keV) and the HXD-PIN (15.0-30.0 keV) data, we have modelled the persistent spectrum of the source with models comprising a soft component from accretion disc and/or neutron star surface/boundary layer and a hard Comptonizing component. The 0.6-30 keV continuum with neutral absorber can be described by a multi-colour disc blackbody with an inner disc temperature of kT disc = 0.28 keV, which is significantly Comptonized by the hot electron cloud with electron temperature of kT e ≈ 5 keV and described by photon index Γ = 1.86. A more complex three-component model comprising a multi-colour disc blackbody ≈ 0.30 keV, single temperature blackbody ≈ 0.65 keV and Comptonization from the disc, partially absorbed (about 38 per cent) by an ionized absorber (log(ξ) ≈ 4) describes the broadband spectrum equally well.

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Broadband spectral analysis of MXB 1659−298 in its soft and hard state

Cited by 12 publications

References 63 publications

Fe K$α$ and Fe K$β$ line detection in the NuSTAR spectrum of the ultra-bright Z-source Scorpius X-1

Fe K$α$ and Fe K$β$ line detection in the NuSTAR spectrum of the ultra-bright Z-source Scorpius X-1

Evidence of a non-conservative mass transfer in the ultra-compact X-ray source XB 1916-053

Broad-band spectral analysis of LMXB XTE J1710-281 with Suzaku

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