Detection of Reflection Features in the Neutron Star Low-mass X-Ray Binary Serpens X-1 with NICER

Ludlam, R. M.; Miller, J. M.; Arzoumanian, Zaven; Bult, Peter; Cackett, E.; Chakrabarty, Deepto; Dauser, Robert C.; Enoto, Teruaki; Fabian, A. C.; García, Javier A.; Gendreau, Keith C.; Guillot, Sebastien; Homan, J.; Jaisawal, Gaurava K.; Keek, L.; Marr, B. La; Malacaria, C.; Markwardt, C. B.; Steiner, James F.; Strohmayer, Tod E.

doi:10.3847/2041-8213/aabee6

Cited by 73 publications

(62 citation statements)

References 36 publications

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“…The inclination angle is found to be i ∼ 19 • in agreement with the fact that neither dips nor eclipses have been observed in the light curve of Ser X-1. Additionally, this low inclination angle agrees with the previous NuSTAR results (Miller et al 2013), the Suzaku results (Cackett et al 2010), the NICER results (Ludlam et al 2018) and the results from optical spectroscopy (Cornelisse et al 2013). The reflection component has an intermediate disc ionization of ξ ≃ 160 − 232 erg s −1 cm which is consistent with logξ ∼ (2 − 3) seen in other NS LMXBs (Cackett et al 2010).…”

Section: Reflection Modelsupporting

confidence: 91%

“…This would correspond to Rin = (10.2 − 13.8) Rg or (23 − 31) km for a 1.5M⊙ NS. The inner disc radius of the source Ser X-1 has been measured by different authors (Ludlam et al 2018;Chiang et al 2016b,a;Bhattacharyya & Strohmayer 2007;Matranga et al 2017;Cackett et al 2010;Miller et al 2013) in different flux states using data taken from different satellite missions (see Table 2). The inner disc radius spans a range between ∼ 8 − 25 Rg and the flux between ∼ (3 − 11) × 10 37 erg s −1 (corresponding to L/L Edd ∼ 0.2 − 0.6).…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Reflection Modelsupporting

confidence: 91%

Section: Discussionmentioning

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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“…NuSTAR spectra have been reduced as described in Buisson et al 2019). The NICER spectrum has been analysed with response matrix version 1.02 corrected by application of a function derived from observations of the Crab nebula (Ludlam et al 2018). A radio flare occurred just before observation Nu23 (Bright et al 2018), which can be considered as in a short intermediate state.…”

Section: The X-ray Spectramentioning

confidence: 99%

The soft state of the black hole transient source MAXI J1820+070: emission from the edge of the plunge region?

Fabian

Buisson

Kosec

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The Galactic black hole X-ray binary MAXI J1820+070 had a bright outburst in 2018 when it became the second brightest X-ray source in the Sky. It was too bright for X-ray CCD instruments such as XMM-Newton and Chandra, but was well observed by photon-counting instruments such as NICER and NuSTAR. We report here on the discovery of an excess emission component during the soft state. It is best modelled with a blackbody spectrum in addition to the regular disk emission, modelled either as diskbb or kerrbb. Its temperature varies from about 0.9 to 1.1 keV which is about 30 to 80 per cent higher than the inner disc temperature of diskbb. Its flux varies between 4 and 12 percent of the disc flux. Simulations of magnetised accretion discs have predicted the possibility of excess emission associated with a non-zero torque at the Innermost Stable Circular Orbit (ISCO) about the black hole, which from other NuSTAR studies lies at about 5 gravitational radii or about 60 km (for a black hole mass is 8 M ). In this case the emitting region at the ISCO has a width varying between 1.3 and 4.6 km and would encompass the start of the plunge region where matter begins to fall freely into the black hole.

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“…We regrouped the spectra by combining every three successive, native energy (PI) channels, and we also applied a normalization factor derived from spectral fits to data from the Crab nebula. See Ludlam et al (2018) for a discussion of this procedure, which provides a way to reduce the influence of the strongest remaining unmodeled residuals in the NICER response function. We then fit each spectrum in the band 0.3 -7 keV with a two component model comprising a Comptonized component for the persistent emission and a black body for the thermal burst flux.…”

Section: Single Burst Spectramentioning

confidence: 99%

NICER Discovers Spectral Lines during Photospheric Radius Expansion Bursts from 4U 1820−30: Evidence for Burst-driven Winds

Strohmayer

Altamirano

Arzoumanian

et al. 2019

ApJL

Self Cite

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We report the discovery with the Neutron Star Interior Composition Explorer (NICER) of narrow emission and absorption lines during photospheric radius expansion (PRE) X-ray bursts from the ultracompact binary 4U 1820−30. NICER observed 4U 1820−30 in 2017 August during a low flux, hard spectral state, accumulating about 60 ks of exposure. Five thermonuclear X-ray bursts were detected of which four showed clear signs of PRE. We extracted spectra during the PRE phases and fit each to a model that includes a comptonized component to describe the accretion-driven emission, and a black body for the burst thermal radiation. The temperature and spherical emitting radius of the fitted black body are used to assess the strength of PRE in each burst. The two strongest PRE bursts (burst pair 1) had black body temperatures of ≈ 0.6 keV and emitting radii of ≈ 100 km (at a distance * NASA Postdoctoral Fellow Cottam,

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Detection of Reflection Features in the Neutron Star Low-mass X-Ray Binary Serpens X-1 with NICER

Cited by 73 publications

References 36 publications

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

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

The soft state of the black hole transient source MAXI J1820+070: emission from the edge of the plunge region?

NICER Discovers Spectral Lines during Photospheric Radius Expansion Bursts from 4U 1820−30: Evidence for Burst-driven Winds

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