AstroSat timing and spectral analysis of the accretion-powered millisecond X-ray pulsar IGR J17591--2342

Abstract

IGR J17591--2342, a transient accretion-powered millisecond X-ray pulsar, was discovered during its 2018 outburst. Here, we present a timing and spectral analysis of the source using {\it AstroSat} data of the same outburst. From the timing analysis, we obtain updated values of binary orbital parameters, which reveal an average pulsar spin frequency of 527.4256984(8) Hz. The pulse profiles can be fit well with four harmonically related sinusoidal components with fractional amplitudes of fundamental and second, third, and fourth harmonics as $\sim 13$\%, $\sim$6\%, $\sim$0.9\%, $\sim$0.2\%, respectively. The energy-dependent study of pulse profiles in the range of $3-20$ keV shows that the fractional amplitude of both the fundamental and first overtone is consistent with being constant across the considered energy band. Besides, a decaying trend has been observed for both the fundamental and first overtone in the phase-delay versus energy relation resulting in soft X-ray (2.8-3.3 keV) phase lags of $\sim$0.05 and $\sim$0.13 with respect to $\le 15$ keV photons, for the fundamental and first overtone, respectively. The combined spectra from the Large Area X-ray Proportional Counters and the Soft X-ray Telescope aboard {\it AstroSat} in the $1-18$ keV range can be fit well with an absorbed model consisting of a Comptonization, a blackbody and a Gaussian emission line component yielding as best-fit parameters a blackbody seed photon temperature $k{T}_{\mathrm{bb}}$ $\sim 0.95\pm 0.03$ keV, and an electron temperature $k{T}_{\mathrm{e}}$ $\sim 1.54\pm 0.03$ keV. The spectral aspects suggest the scattering of photons from the accretion disc or the neutron star's surface.

arXiv commentAccepted in MNRAS on November 14, 2024

References in corpus (17)

• On the Absorption of X-rays in the Interstellar Medium
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• On the Nature of the X-ray Emission from the Accreting Millisecond Pulsar SAX J1808.4-3658
• Calibration of the Large Area X-ray Proportional Counter (LAXPC) instrument on-board AstroSat
• The magnetic field strengths of accreting millisecond pulsars
• Accreting Millisecond X-Ray Pulsars
• AstroSat/LAXPC observation of Cygnus X-1 in the hard state
• Timing of the accreting millisecond pulsar SAX J1748.9-2021 during its 2015 outburst
• Accretion torques and motion of the hot spot on the accreting millisecond pulsar XTE J1807-294
• NuSTAR and NICER reveal IGR J17591-2342 as a new accreting millisecond X-ray pulsar
• The radio-bright accreting millisecond X-ray pulsar IGR J17591-2342
• Energy dependent ~100 μs time lags as observational evidence of Comptonization effects in the neutron star plasma environment
• Radio and X-ray monitoring of the accreting millisecond X-ray pulsar IGR J17591-2342 in outburst
• High-energy characteristics of the accretion-powered millisecond pulsar IGR J17591-2342 during its 2018 outburst
• Timing of the accreting millisecond pulsar IGR J17591-2342: evidence of spin-down during accretion
• Spectral analysis of the AMXP IGR J17591-2342 during its 2018 outburst
• Updated Spin and Orbital Parameters and Energy Dependent Pulse Behaviors of the Accreting Millisecond X-ray Pulsar IGR J17591$-$2342

Cited by in corpus (2)

• Observing Rayleigh-Taylor stable and unstable accretion through a Kalman filter analysis of X-ray pulsars in the Small Magellanic Cloud
• An unusual type-I X-ray burst from the neutron star X-ray binary IGR J17591-2342: a double-photospheric-radius-expansion burst?