X-ray studies of the black widow pulsar PSR B1957+20

Huang, R. H. H.; Kong, Albert; Takata, J.; Hui, C. Y.; Lin, L.; Cheng, K. S.

doi:10.1017/s1743921312024295

Cited by 1 publication

(1 citation statement)

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“…[8,9,10]. Moreover, radio eclipses of the MSP, likely due to absorption, are observed centered around superior conjunction when the companion is between the pulsar and the observer.…”

Section: Introductionmentioning

confidence: 99%

The Aid of Optical Studies in Understanding Millisecond Pulsar Binaries

Wadiasingh¹,

Harding²,

Venter³

et al. 2016

Proceedings of SALT Science Conference 2015 — PoS(SSC2015)

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A large number of new "black widow" and "redback" energetic millisecond pulsars with irradiated stellar companions have been discovered through radio and optical searches of unidentified Fermi sources. Synchrotron emission, from particles accelerated up to several TeV in the intrabinary shock, exhibits modulation at the binary orbital period. Our simulated double-peaked X-ray light curves modulated at the orbital period, produced by relativistic Doppler-boosting along the intrabinary shock, are found to qualitatively match those observed in many sources. In this model, redbacks and transitional pulsar systems where the double-peaked X-ray light curve is observed at inferior conjunction have intrinsically different shock geometry than other millisecond pulsar binaries where the light curve is centered at superior conjunction. We discuss, and advocate, how current and future optical observations may aid in constraining the emission geometry, intrabinary shock and the unknown physics of pulsar winds. BackgroundThe Fermi Large Area Telescope (LAT) has been prolific at discovering γ-ray pulsars, with millisecond pulsars (MSPs) representing a disproportionately high share of these detections. Followup studies in the optical and radio of unassociated Fermi-LAT sources and γ-ray MSPs have increased the number of known Galactic black widows (BWs) and redbacks (RBs) from four to almost 30, principally through precision radio timing of the MSPs revealing the existence of a companion by Doppler wobbling. These MSP binaries, first established with the discovery of B1957+20 [1], are old Gyr recycled systems with orbital periods < 1 day in tight circular orbits. The pulsars are spun-up from their past accretion history and are now slowly ablating their companions by an energetic pulsar wind.The systems can be loosely grouped into two classes [2] based on the stellar companion's estimated mass M c : BWs (M c 0.05M ) and RBs M c 0.1M . The RBs unusual companions are typically closer spectroscopically to the main sequence than those of BWs. In most of these systems, the energetics of emission in various wavebands are expected to be underpinned by the properties of the energetic pulsar wind, powered by electromagnetic rotational spin-down of the MSP. Crucially, relevant in the IR/optical context here, the secondary's luminosity may exceed, by several orders of magnitude, what one would naively expect from mass-luminosity relations for red dwarfs because of the irradiation and anisotropic heating of the photosphere by the 10 34−35 erg s −1 pulsar wind. Moreover, some BW companions may be white dwarfs. Recently, there has been some excitement over the discovery of transitional RB systems, e.g., J1023+0038 [3] or J1824-2452I [4], that switch between low-mass X-ray binary accretion-powered and radio pulsar rotation-powered states confirming the evolutionary link between these classes, with the accretion flow in the former state shrouding or switching off the pulsed radio emission from the pulsar.Our focus is on the rotation-powered s...

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“…[8,9,10]. Moreover, radio eclipses of the MSP, likely due to absorption, are observed centered around superior conjunction when the companion is between the pulsar and the observer.…”

Section: Introductionmentioning

confidence: 99%