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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/8267
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dc.contributor.authorMandal, Manoj-
dc.contributor.authorSharma, Rahul-
dc.contributor.authorPal, Sabyasachi-
dc.contributor.authorJaisawal, G. K.-
dc.contributor.authorGendreau, Keith C.-
dc.contributor.authorNg, Mason-
dc.contributor.authorSanna, Andrea-
dc.contributor.authorMalacaria, Christian-
dc.contributor.authorTombesi, Francesco-
dc.contributor.authorFerrara, E. C.-
dc.contributor.authorMarkwardt, Craig B.-
dc.contributor.authorWolff, Michael T.-
dc.contributor.authorColey, Joel B.-
dc.date.accessioned2024-06-06T09:11:29Z-
dc.date.available2024-06-06T09:11:29Z-
dc.date.issued2023-09-12-
dc.identifier.citationMonthly Notices of the Royal Astronomical Society, 2023, Vol.526, p771-781en_US
dc.identifier.urihttp://hdl.handle.net/2289/8267-
dc.descriptionOpen Accessen_US
dc.description.abstractThe X-ray pulsar RX J0440.9 + 4431 went through a giant outburst in 2022 and reached a record-high flux of 2.3 Crab, as observed by Swift /BAT. We study the evolution of different spectral and timing properties of the source using NICER observations. The pulse period is found to decrease from 208 s to 205 s, and the pulse profile evolves significantly with energy and luminosity. The hardness ratio and hardness intensity diagram (HID) show remarkable evolution during the outburst. The HID turns towards the diagonal branch from the horizontal branch abo v e a transition (critical) luminosity, suggesting the presence of two accretion modes. Each NICER spectrum can be described using a cutoff power law with a blackbody component and a Gaussian at 6.4 keV. At higher luminosities, an additional Gaussian at 6.67 keV is used. The observed photon index shows negative and positive correlations with X-ray flux below and abo v e the critical luminosity , respectively . The evolution of spectral and timing parameters suggests a possible change in the emission mechanism and beaming pattern of the pulsar depending on the spectral transition to sub- and supercritical accretion regimes. Based on the critical luminosity, the magnetic field of the neutron star can be estimated in the order of 10 12 or 10 13 G, assuming different theoretical models. Moreo v er, the observ ed iron emission line evolves from a narrow to a broad feature with luminosity. Two emission lines originating from neutral and highly ionized Fe atoms are evident in the spectra around 6.4 and 6.67 keV (later is seen only in higher luminosities).en_US
dc.language.isoenen_US
dc.publisherOxford University Press on behalf of Royal Astronomical Societyen_US
dc.relation.urihttps://ui.adsabs.harvard.edu/abs/2023MNRAS.526..771M/abstracten_US
dc.relation.urihttps://arxiv.org/abs/2306.08083en_US
dc.relation.urihttps://doi.org/10.1093/mnras/stad2767en_US
dc.rights2023, The Author(s)en_US
dc.subjectaccretion,accretion discs –starsen_US
dc.subjectmagnetic field –starsen_US
dc.subjectneutron –pulsarsen_US
dc.subjectindividualen_US
dc.subjectRX J0440.9 + 4431en_US
dc.titleProbing spectral and timing properties of the X-ray pulsar RX J0440.9 + 4431 in the giant outburst of 2022–2023en_US
dc.typeArticleen_US
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