Timing and spectral studies of SRGA J144459.2$-$604207 with NICER, Einstein Probe, IXPE, NuSTAR, Insight-HXMT and INTEGRAL during its 2024 outburst

Abstract

SRGA J144459.2$-$604207 is a newly confirmed accreting millisecond X-ray pulsar and type I X-ray burster. We present the broadband X-ray timing and spectral behaviors of SRGA J144459.2$-$604207 during its 2024 outburst. The data were collected from NICER, Einstein Probe, IXPE, Insight-HXMT, NuSTAR and INTEGRAL observations. X-ray pulsations have been detected for the 1.5--90 keV energy range throughout the `ON' phase of the outburst from MJD $\sim 60355-60385$. We refined the orbital and spin ephemerides assuming a circular orbit, and found that the pulsar was in a spin-up state during MJD $\sim$ 60361--60377 showing a significant spin-up rate $\dot{\nu }$ of $(3.15\pm 0.36)\times 10^{-13}\mathrm{Hz}{\mathrm{s}}^{-1}$. Around MJD $\sim 60377$ a swing was detected in the spin evolution accompanied by significantly enhanced pulsed emission. We studied the pulse profile morphology during the X-ray bursts as observed by Insight-HXMT, IXPE and NuSTAR. During the bursts, pulsations were detected across the 2--60 keV with shapes broadly consistent with those observed for the persistent emission. We found, however, that the `burst' pulse profiles exhibit significant phase offsets relative to the pre- and post-burst profiles. These offsets systematically decrease with increasing energy, $\Delta \varphi \approx 0.15$, 0.11 and 0.02 for IXPE, Insight-HXMT ME and HE in 2--8, 5--30 and 20--60 keV, respectively, and $\Delta \varphi \approx 0.21$, 0.10 and 0.07 for NuSTAR in 3--10, 20--35 and 35--60 keV, respectively, compared to the pre- and post-burst profiles. We performed a joint spectral analysis of quasi-simultaneous NICER, NuSTAR, and Insight-HXMT data for two epochs. The resulting spectra from both observations were consistent and well-described by an absorbed thermal Comptonization model, nthcomp, plus relativistic reflection, relxillCp.

13 pages. Submitted to ApJ on 2025 May 13, accepted on 2025 July 1, published on 2025 August 22

References in corpus (22)

• The role of the reflection fraction in constraining black hole spin
• A Massive Neutron Star in the Globular Cluster M5
• Science objectives of the Einstein Probe mission
• Intermediate long X-ray bursts from the ultra-compact binary source SLX 1737-282
• Spectral and timing properties of the accreting X-ray millisecond pulsar IGR J17511-3057
• The 2015 outburst of the accretion-powered pulsar IGR J00291+5934: INTEGRAL and Swift observations
• An accreting low magnetic field magnetar for the ultraluminous X-ray source in M82
• Spectral and timing properties of the accreting X-ray millisecond pulsar IGR J17498-2921
• NICER-NuSTAR Observations of the Neutron Star Low-Mass X-ray Binary 4U 1735-44
• In-orbit timing calibration of the Insight-Hard X-ray Modulation Telescope
• High-energy characteristics of the accretion-powered millisecond pulsar IGR J17591-2342 during its 2018 outburst
• Outflows and spectral evolution in the eclipsing AMXP SWIFT J1749.4-2807 with NICER, XMM-Newton and NuSTAR
• Timing analysis of the 2022 outburst of the accreting millisecond X-ray pulsar SAX J1808.4$-$3658: hints of an orbital shrinking
• SRG/ART-XC discovery of SRGAJ144459.2-604207: a well-tempered bursting accreting millisecond X-ray pulsar
• Discovery of Polarized X-Ray Emission from the Accreting Millisecond Pulsar SRGA J144459.2-604207
• Study on the magnetic field strength of NGC 300 ULX1
• Broadband X-ray timing and spectral characteristics of the accretion-powered millisecond X-ray pulsar MAXI J1816$-$195
• Broad-band X-ray spectra and timing of the accretion-powered millisecond pulsar Swift J1756.9$-$2508 during its 2018 and 2019 outbursts
• Accreting neutron star spins and the equation of state
• A comprehensive study of type I (thermonuclear) bursts in the new transient SRGA J144459.2$-$604207
• Disk reflection and energetics from the accreting millisecond pulsar SRGA J144459.2-604207
• Broad-band X-ray spectral and timing properties of the accreting millisecond X-ray pulsar IGR J17498$-$2921 during the 2023 outburst

Cited by in corpus (1)

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