학술논문
NICER Discovery that SRGA J144459.2–604207 Is an Accreting Millisecond X-Ray Pulsar
Document Type
article
Author
Mason Ng; Paul S. Ray; Andrea Sanna; Tod E. Strohmayer; Alessandro Papitto; Giulia Illiano; Arianna C. Albayati; Diego Altamirano; Tuğba Boztepe; Tolga Güver; 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
Source
The Astrophysical Journal Letters, Vol 968, Iss 1, p L7 (2024)
Subject
Language
English
ISSN
2041-8213
2041-8205
2041-8205
Abstract
We present the discovery, with the Neutron Star Interior Composition Explorer (NICER), that SRGA J144459.2−604207 is a 447.9 Hz accreting millisecond X-ray pulsar (AMXP), which underwent a 4 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 > 0.1 M _⊙ . 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 kT ≈ 0.9 keV and power-law photon index Γ ≈ 1.9. Time-resolved burst spectroscopy confirmed the thermonuclear nature of the burst, where an additional blackbody component reached a maximum temperature of nearly kT ≈ 3 keV at the peak of the burst. We discuss the nature of the companion as well as the type I X-ray burst.