Revealing the nature of the transient source MAXI J0637-430 through spectro-temporal analysis

Abstract

We study the spectral and temporal properties of MAXI J0637-430 during its 2019-2020 outburst using \textit{NICER}, \textit{AstroSat} and \textit{Swift-XRT} data. The source was in a disc dominant state within a day of its detection and traces out a `c' shaped profile in the HID, similar to the `mini'-outbursts of the recurrent BHB 4U 1630-472. Energy spectrum is obtained in the $0.5-10$ keV band with \textit{NICER} and \textit{Swift-XRT}, and $0.5-25$ keV with \textit{AstroSat}. The spectra can be modelled using a multicolour disc emission (\textit{diskbb}) convolved with a thermal Comptonisation component (\textit{thcomp}). The disc temperature decreases from 0.6 keV to 0.1 keV during the decay with a corresponding decrease in photon index ($\Gamma$) from 4.6 to 1.8. The fraction of Compton scattered photons ($f_{cov}$) remains $<$ 0.3 during the decay upto mid-January 2020 and gradually increases to 1 as the source reaches hard state. Power Density Spectra (PDS) generated in the 0.01-100 Hz range display no Quasi-periodic Oscillations (QPOs) although band-limited noise (BLN) is seen towards the end of January 2020. During \textit{AstroSat} observations, $\Gamma$ lies in the range $2.3-2.6$ and rms increases from 11 to 20\%, suggesting that the source was in an intermediate state till 21 November 2019. Spectral fitting with the relativistic disc model (\textit{kerrbb}), in conjunction with the soft-hard transition luminosity, favour a black hole with mass $3-19$ $M_{\odot }$ with retrograde spin at a distance $<15$ kpc. Finally, we discuss the possible implications of our findings.

References updated, final version

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Cited by in corpus (10)

• Unraveling the foretime of GRS 1915+105 using AstroSat observations: Wide-band spectral and temporal characteristics
• Wideband Study of the Brightest Black Hole X-ray Binary 4U 1543-47 in the 2021 Outburst: Signature of Disk-Wind Regulated Accretion
• Study of general relativistic magnetohydrodynamic accretion flow around black holes
• The peculiar spectral evolution of the new X-ray transient MAXI J0637-430
• Spectral and Temporal Studies of Swift\,J1658.2--4242 using {\it AstroSat} Observations with {\tt JeTCAF} Model
• Broadband X-ray properties of black holes GRS 1758-258 and 1E 1740.7-2942: AstroSat and NuSTAR results
• Spectral properties of soft X-ray transient MAXI J0637$-$430 using AstroSat
• The spin measurement of MAXI J0637-430: a black hole candidate with high disk density
• Swift J1753.5-0127 : Understanding the accretion geometry through frequency resolved spectroscopy
• On the origin of core radio emissions from black hole sources in the realm of relativistic shocked accretion flow