On the Curious Pulsation Properties of the Accreting Millisecond Pulsar IGR J17379–3747
Author(s)
Bult, Peter; Markwardt, Craig B; Altamirano, Diego; Arzoumanian, Zaven; Chakrabarty, Deepto; Gendreau, Keith C; Guillot, Sebastien; Jaisawal, Gaurava K; Ray, Paul S; Strohmayer, Tod E; ... Show more Show less
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© 2019. The American Astronomical Society. All rights reserved.. We report on the Neutron Star Interior Composition Explorer (NICER) monitoring campaign of the 468 Hz accreting millisecond X-ray pulsar IGR J17379-3747. From a detailed spectral and timing analysis of the coherent pulsations we find that they show a strong energy dependence, with soft thermal emission lagging about 640 μs behind the hard, Comptonized emission. Additionally, we observe uncommonly large pulse fractions, with measured amplitudes in excess of 20% sinusoidal fractional amplitude across the NICER passband and fluctuations of up to ∼70%. Based on a phase-resolved spectral analysis, we suggest that these extreme properties might be explained if the source has an unusually favorable viewing geometry with a large magnetic misalignment angle. Due to these large pulse fractions, we were able to detect pulsations down to quiescent luminosities ( erg ). We discuss these low-luminosity pulsations in the context of transitional millisecond pulsars.
Date issued
2019Department
MIT Kavli Institute for Astrophysics and Space ResearchJournal
Astrophysical Journal
Publisher
American Astronomical Society