English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We study the spectral and temporal properties of MAXI J0637-430 during its2019-2020 outburst using \textit{NICER}, \textit{AstroSat} and\textit{Swift-XRT} data. The source was in a disc dominant state within a dayof 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 obtainedin 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 amulticolour disc emission (\textit{diskbb}) convolved with a thermalComptonisation component (\textit{thcomp}). The disc temperature decreases from0.6 keV to 0.1 keV during the decay with a corresponding decrease in photonindex ($\Gamma$) from 4.6 to 1.8. The fraction of Compton scattered photons($f_{cov}$) remains $<$ 0.3 during the decay upto mid-January 2020 andgradually increases to 1 as the source reaches hard state. Power DensitySpectra (PDS) generated in the 0.01-100 Hz range display no Quasi-periodicOscillations (QPOs) although band-limited noise (BLN) is seen towards the endof January 2020. During \textit{AstroSat} observations, $\Gamma$ lies in therange $2.3-2.6$ and rms increases from 11 to 20\%, suggesting that the sourcewas in an intermediate state till 21 November 2019. Spectral fitting with therelativistic disc model (\textit{kerrbb}), in conjunction with the soft-hardtransition luminosity, favour a black hole with mass $3-19$ $M_{\odot}$ withretrograde spin at a distance $<15$ kpc. Finally, we discuss the possibleimplications of our findings.

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