Spectral and timing properties of the accreting millisecond X-ray pulsar IGR J17498−2921 during its 2023 outburst

We present a comprehensive study of the spectral properties of the accreting millisecond X-ray pulsar IGR J17498−2921 during its 2023 outburst. Similar to other accreting millisecond X-ray pulsars, the broadband spectral emission observed quasi-simultaneously by NICER and NuSTAR is well described by...

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Bibliographic Details
Authors: Illiano, Giulia, Papitto, Alessandro, Marino, Alessio, Strohmayer, T. E., Sanna, Andrea, Salvo, Tiziana di, La Placa, Riccardo, Ambrosino, Filippo, Miraval Zanon, Arianna, Coti Zelati, Francesco, Ballocco, Caterina, Malacaria, C., Ghedina, A., Cecconi, M., Gonzales, M., Leone, Francesco
Format: article
Status:Published version
Publication Date:2024
Country:España
Institution:Consejo Superior de Investigaciones Científicas (CSIC)
Repository:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/382765
Online Access:http://hdl.handle.net/10261/382765
http://arxiv.org/abs/2408.06895v1
Access Level:Open access
Keyword:Accretion, accretion disks
Pulsars: individual: IGR J17498-2921
Stars: neutron
X-rays: binaries
Description
Summary:We present a comprehensive study of the spectral properties of the accreting millisecond X-ray pulsar IGR J17498−2921 during its 2023 outburst. Similar to other accreting millisecond X-ray pulsars, the broadband spectral emission observed quasi-simultaneously by NICER and NuSTAR is well described by an absorbed Comptonized emission with an electron temperature of ∼17 keV plus a disk reflection component. The broadening of the disk reflection spectral features, such as a prominent iron emission line at 6.4–6.7 keV, is consistent with the relativistic motion of matter in a disk truncated at ∼21 Rg from the source, near the Keplerian corotation radius. From the high-cadence monitoring data obtained with NICER, we observed that the evolution of the photon index and the temperature of seed photons tracks variations in the X-ray flux. This is particularly evident close to a sudden ∼–0.25 cycle jump in the pulse phase, which occurs immediately following an X-ray flux flare and a drop in the pulse amplitude below the 3σ detection threshold. We also report on the non-detection of optical pulsations with TNG/SiFAP2 from the highly absorbed optical counterpart.

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