On the curious pulsation properties of the accreting millisecond pulsar IGR J17379-3747. (arXiv:1904.11311v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bult_P/0/1/0/all/0/1">Peter Bult</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Markwardt_C/0/1/0/all/0/1">Craig B. Markwardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Altamirano_D/0/1/0/all/0/1">Diego Altamirano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arzoumanian_Z/0/1/0/all/0/1">Zaven Arzoumanian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chakrabarty_D/0/1/0/all/0/1">Deepto Chakrabarty</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gendreau_K/0/1/0/all/0/1">Keith C. Gendreau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guillot_S/0/1/0/all/0/1">Sebastien Guillot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jaisawal_G/0/1/0/all/0/1">Gaurava K. Jaisawal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ray_P/0/1/0/all/0/1">Paul. S. Ray</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Strohmayer_T/0/1/0/all/0/1">Tod E. Strohmayer</a>
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.
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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