X-Ray States of Redback Millisecond Pulsars

Linares, M.
Bibliographical reference

The Astrophysical Journal, Volume 795, Issue 1, article id. 72, 10 pp. (2014).

Advertised on:
11
2014
Number of authors
1
IAC number of authors
1
Citations
84
Refereed citations
75
Description
Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks," constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk, and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback that showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L X), between (6-9) × 1032 erg s–1 (disk-passive state) and (3-5) × 1033 erg s–1 (disk-active state). This strongly suggests that mode switching—which has not been observed in quiescent low-mass X-ray binaries—is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks that have developed accretion disks have relatively high L X in the pulsar state (>1032 erg s–1).
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