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arXiv · 1904.11311

On the curious pulsation properties of the accreting millisecond pulsar IGR J17379-3747

Peter Bult·Craig B. Markwardt·Diego Altamirano·Zaven Arzoumanian·Deepto Chakrabarty·Keith C. Gendreau·Sebastien Guillot·Gaurava K. Jaisawal·Paul. S. Ray·Tod E. Strohmayer
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Abstract

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 microseconds 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 (~5 x 10^33 erg s^-1). We discuss these low-luminosity pulsations in the context of transitional millisecond pulsars.

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Peter Bult, Craig B. Markwardt, Diego Altamirano, Zaven Arzoumanian, Deepto Chakrabarty, Keith C. Gendreau, Sebastien Guillot, Gaurava K. Jaisawal, Paul. S. Ray, Tod E. Strohmayer. 2019-04-25. On the curious pulsation properties of the accreting millisecond pulsar IGR J17379-3747. https://doi.org/10.3847/1538-4357%2Fab1b26

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