The 2021 outburst of 2S 1417-624 revisited with AstroSat

TL;DR

This study presents the first broadband timing and spectral analysis of the 2021 outburst of Be-HMXB 2S 1417-624 using AstroSat, revealing pulsation characteristics, spectral features, and comparisons with previous outbursts.

Contribution

First broadband timing and spectral analysis of 2S 1417-624 during its 2021 outburst using AstroSat data, including detailed pulse profile and spectral modeling.

Findings

Detected coherent pulsations at ~17.36633 s across energy bands

Pulse profile was dual peaked with energy-dependent features

Spectrum well described by absorbed power-law with cut-off and additional components

Abstract

This work presents the first ever broadband (0.7-25.0 keV) timing and spectral analysis of Be-HMXB 2S 1417-624 during its 2021 outburst. Using AstroSat observations, coherent pulsations at ~17.36633 s (MJD 59239.082) were detected in 0.7-7.0 keV SXT and 3.0-25.0 keV LAXPC data. The pulse profile was dual peaked at all energies, with the relative intensity of main peak increasing with energy. The peaks in the SXT profiles were broad and comprised of several mini-structures. The LAXPC profiles were relatively smooth and had higher pulsed fraction which increased with energy. The SXT+LAXPC simultaneous energy spectrum is well described by an absorbed power-law with exponential cut-off, along with ~1.6 keV black body component and 6.47 keV emission line. A model comprising of an absorbed power law with high energy cutoff plus a partial covering absorber and Gaussian emission line also fits the spectrum quite well. These results have been compared with timing and spectral features during the previous outbursts of this transient pulsar.