@misc{8be164a418d742029924117ca5995ff3,
title = "NICER Discovers Millisecond Pulsations and a Type I X-ray Burst from SRGA J144459.2-604207",
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 Md > 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.",
keywords = "X-ray, Neutron Star, Transient, Pulsar",
author = "M. Ng and A. Sanna and Strohmayer, {T. E.} and Z. Arzoumanian and Gendreau, {K. C.} and Ray, {P. S.} and Coley, {J. B.} and D. Chakrabarty and S. Guillot and S. Bogdanov and D. Altamirano and J. Chenevez and J. Hare and Wolff, {M. T.} and T. G{\"u}ver and Jaisawal, {G. K.} and Z. Wadiasingh and Ferrara, {E. C.}",
year = "2024",
month = feb,
day = "23",
language = "English",
series = "The Astronomer's telegram",
publisher = "R. Rutledge",
number = "ATel #16474",
type = "Other",
}