Spectral Properties of the Soft X-Ray Transient MAXI J0637−430 Using AstroSat

Thomas, Neal Titus; Gudennavar, S. B.; Misra, Ranjeev; Bubbly, S. G.

doi:10.3847/1538-4357/ac425e

Cited by 4 publications

(3 citation statements)

References 20 publications

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“…MAXI J0637−430 is a transient low-mass X-ray binary, discovered by the Monitor of All-sky X-ray Image (MAXI) when it went into outburst on 2019 November 2 (Negoro et al 2019). Its outburst evolution over the following weeks was monitored by several teams with a variety of X-ray and multiband facilities: the Neil Gehrels Swift Observatory (Swift) X-ray Telescope (XRT) and UltraViolet and Optical Telescope (UVOT) (Kennea et al 2019), the Insight-HXMT X-ray observatory (Ma et al 2022), the Nuclear Spectroscopic Telescope Array (NuSTAR) (Tomsick et al 2019), the Neutron star Interior Composition Explorer (NICER) (Remillard et al 2020), Astrosat (Thomas et al 2019), the Southern Astrophysical Research (SOAR) telescope (Strader et al 2019), the Australia Telescope Compact Array (ATCA) (Russell et al 2019). Based on this rich set of multiband data, several studies (Tetarenko et al 2021;Lazar et al 2021;Jana et al 2021;Ma et al 2022) have presented detailed analyses of the properties of this Galactic black hole (BH) candidate.…”

Section: Introductionmentioning

confidence: 99%

A 2-hr binary period for the black hole transient MAXI J0637-430

Soria

Tao

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We revisit various sets of published results from X-ray and optical studies of the Galactic black hole (BH) candidate MAXI J0637−430, which went into outburst in 2019. Combining the previously reported values of peak outburst luminosity, best-fitting radii of inner and outer accretion disk, viewing angle, exponential decay timescale and peak-to-peak separation of the He II λ4686 disk emission line, we improve the constraints on the system parameters. We estimate a heliocentric distance d ≈ (8.7 ± 2.3) kpc, a projected Galactocentric distance R ≈ (13.2 ± 1.8) kpc and a height |z| ≈ (3.1 ± 0.8) kpc from the Galactic plane. It is the currently known Milky Way BH candidate located farthest from the Galactic Centre. We infer a BH mass M1 ≈ (5.1 ± 1.6)M⊙, a spin parameter a* ≲ 0.25, a donor star mass M2 ≈ (0.25 ± 0.07)M⊙, a peak Eddington ratio λ ≈ 0.17 ± 0.11 and a binary period $P_{\rm orb} \approx 2.2^{+0.8}_{-0.6}$ hr. This is the shortest period measured or estimated so far for any Galactic BH X-ray binary. If the donor star is a main-sequence dwarf, such a period corresponds to the evolutionary stage where orbital shrinking is driven by gravitational radiation and the star has regained contact with its Roche lobe (low end of the period gap). The three Galactic BHs with the shortest period (≲3 hr) are also those with the highest vertical distance from the Galactic plane (≳2 kpc). This is probably because binaries with higher binding energies can survive faster natal kicks.

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Section: Introductionmentioning

confidence: 99%

A 2-hr binary period for the black hole transient MAXI J0637-430

Soria

Tao

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…MAXI J0637 430 was discovered by the Monitor of All-sky X-ray Image Gas Slit Camera (MAXI/GSC; Matsuoka et al 2009) on 2019 November 2 = MJD 58789 (Negoro et al 2019). Its X-ray outburst was then promptly monitored by the Neil Gehrels Swift Observatory X-ray Telescope (Swift/XRT; Burrows et al 2005) from November 3 (Kennea et al 2019), by the Neutron star Interior Composition ExploreR (NICER; Gendreau, Arzoumanian, & Okajima 2012)) also from November 3 (Remillard et al 2020), by Insight-HXMT (Zhang et al 2020) from November 4, by the Nuclear Spectroscopic Telescope Array (NuSTAR; Harrison et al 2013) from November 5 (Tomsick et al 2019), and by Astrosat (Singh et al 2014) from November 8 (Thomas et al 2019(Thomas et al , 2022.…”

Section: Introductionmentioning

confidence: 99%

The peculiar spectral evolution of the new X-ray transient MAXI J0637–430

Soria

Tao

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We studied the transient Galactic black hole candidate MAXI J0637−430 with data from Insight-HXMT, Swift and XMM-Newton. The broad-band X-ray observations from Insight-HXMT help us constrain the power-law component. MAXI J0637−430 is located at unusually high Galactic latitude; if it belongs to the Galactic thick disk, we suggest a most likely distance ≲7 kpc. Compared with other black hole transients, MAXI J0637−430 is also unusual for other reasons: a fast transition to the thermal dominant state at the start of the outburst; a low peak temperature and luminosity (we estimate them at ≈0.7 keV and ≲0.1 times Eddington, respectively); a short decline timescale; a low soft-to-hard transition luminosity (≲0.01 times Eddington). We argue that such properties are consistent with a small binary separation, short binary period (P ∼ 2 hr), and low-mass donor star (M2 ∼ 0.2 M⊙). Moreover, spectral modelling shows that a single disk-blackbody component is not a good fit to the thermal emission. Soft spectral residuals, and deviations from the standard $L_{\rm disk} \propto T_{\rm in}^4$ relation, suggest the need for a second thermal component. We propose and discuss various scenarios for such component, in addition to those presented in previous studies of this source. For example, a gap in the accretion disk between a hotter inner ring near the innermost stable orbit, and a cooler outer disk. Another possibility is that the second thermal component is the thermal plasma emission from an ionized outflow.

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“…The details of SXT and LAXPC instruments are given elsewhere (see for e.g. Thomas et al 2022Thomas et al , 2023. The details of data reduction are given in the next subsections.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

NuSTAR and AstroSat observations of GX 9+1: spectral and temporal studies

Thomas

Gudennavar

Bubbly

2023

Monthly Notices of the Royal Astronomical Society

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We have studied the spectro-temporal properties of the neutron star low mass X-ray binary GX 9+1 using data from NuSTAR/FPM and AstroSat/SXT and LAXPC. The hardness-intensity diagram of the source showed it to be in the soft spectral state during both observations. NuSTAR spectral analysis yielded an inclination angle (θ) = 29${^{+3}_{-4}}^{\circ }$ and inner disk radius (Rin) ≤ 19.01 km. Assuming that the accretion disk was truncated at the Alfvén radius during the observation, the upper limit of the magnetic dipole moment (μ) and the magnetic field strength (B) at the poles of the neutron star in GX 9+1 were calculated to be 1.45×1026 G cm3 and 2.08×108 G, respectively (for kA = 1). Flux resolved spectral analysis with AstroSat data showed the source to be in the soft spectral state (Fdisk/Ftotal ∼0.9) with a monotonic increase in mass accretion rate ($\dot{m}$) along the banana branch. The analysis also showed the presence of absorption edges at ∼1.9 and ∼2.4 keV, likely due to Si XIII and S XV, respectively. Temporal analysis with LAXPC-20 data in the 0.02 − 100 Hz range revealed the presence of noise components, which could be characterized with broad Lorentzian components.

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Spectral Properties of the Soft X-Ray Transient MAXI J0637−430 Using AstroSat

Cited by 4 publications

References 20 publications

A 2-hr binary period for the black hole transient MAXI J0637-430

A 2-hr binary period for the black hole transient MAXI J0637-430

The peculiar spectral evolution of the new X-ray transient MAXI J0637–430

NuSTAR and AstroSat observations of GX 9+1: spectral and temporal studies

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