NICER Discovery of the Accreting Millisecond X-ray Pulsar SRGA J144459.2-604207
Mason Ng, Paul S. Ray, Andrea Sanna, Tod E. Strohmayer, Alessandro Papitto, Giulia Illiano, Arianna C. Albayati, Diego Altamirano, Tuu{g}ba Boztepe, Tolga G"uver, Deepto Chakrabarty, Zaven Arzoumanian, D. J. K. Buisson, Elizabeth C. Ferrara, Keith C. Gendreau, Sebastien Guillot, Jeremy Hare, Gaurava K. Jaisawal, Christian Malacaria, Michael T. Wolff
arXiv:2405.00087v1 Announce Type: new
Abstract: We present the discovery, with the Neutron Star Interior Composition Explorer (NICER), of the 447.9 Hz accreting millisecond X-ray pulsar (AMXP) SRGA J144459.2-604207, which underwent a four-week long outburst starting on 2024 February 15. The AMXP resides in a 5.22 hr binary, orbiting a low-mass companion donor with $M_d>0.1M_odot$. We report on the temporal and spectral properties from NICER observations during the early days of the outburst, from 2024 February 21 through 2024 February 23, during which NICER also detected a type-I X-ray burst that exhibited a plateau lasting ~6 s. The spectra of the persistent emission were well described by an absorbed thermal blackbody and power-law model, with blackbody temperature $kTapprox0.9{rm,keV}$ and power-law photon index $Gammaapprox1.9$. Time-resolved burst spectroscopy confirmed the thermonuclear nature of the burst, where an additional blackbody component reached a maximum temperature of nearly $kTapprox3{rm,keV}$ at the peak of the burst. We discuss the nature of the companion as well as the type-I X-ray burst.arXiv:2405.00087v1 Announce Type: new
Abstract: We present the discovery, with the Neutron Star Interior Composition Explorer (NICER), of the 447.9 Hz accreting millisecond X-ray pulsar (AMXP) SRGA J144459.2-604207, which underwent a four-week long outburst starting on 2024 February 15. The AMXP resides in a 5.22 hr binary, orbiting a low-mass companion donor with $M_d>0.1M_odot$. We report on the temporal and spectral properties from NICER observations during the early days of the outburst, from 2024 February 21 through 2024 February 23, during which NICER also detected a type-I X-ray burst that exhibited a plateau lasting ~6 s. The spectra of the persistent emission were well described by an absorbed thermal blackbody and power-law model, with blackbody temperature $kTapprox0.9{rm,keV}$ and power-law photon index $Gammaapprox1.9$. Time-resolved burst spectroscopy confirmed the thermonuclear nature of the burst, where an additional blackbody component reached a maximum temperature of nearly $kTapprox3{rm,keV}$ at the peak of the burst. We discuss the nature of the companion as well as the type-I X-ray burst.