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 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 similar 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 (similar to 5 x 1033 erg s-1. We discuss these low-luminosity pulsations in the context of transitional millisecond pulsars.
Original language | English |
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Article number | 70 |
Journal | Astrophysical Journal |
Volume | 877 |
Issue number | 2 |
Number of pages | 12 |
ISSN | 0004-637X |
DOIs | |
Publication status | Published - 2019 |
Keywords
- Stars: neutron
- X-rays: binaries
- X-rays: individual (IGR J17379-3747)