A Comprehensive Library of X-ray Pulsars in the Small Magellanic Cloud: Time Evolution of their Luminosities and Spin Periods

• Main Authors: Yang, J, Laycock, S. G. T, Christodoulou, D. M, Fingerman, S, Coe, M. J, Drake, J. J
• Format: Journal Article
• Language: English
• Published: 15-03-2017
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.1703.05196

We have collected and analyzed the complete archive of {\itshape XMM-Newton\}
(116), {\itshape Chandra\} (151), and {\itshape RXTE\} (952) observations of
the Small Magellanic Cloud (SMC), spanning 1997-2014. The resulting
observational library provides a comprehensive view of the physical, temporal
and statistical properties of the SMC pulsar population across the luminosity
range of $L_X= 10^{31.2}$--$10^{38}$~erg~s$^{-1}$. From a sample of 67 pulsars
we report $\sim$1654 individual pulsar detections, yielding $\sim$1260 pulse
period measurements. Our pipeline generates a suite of products for each pulsar
detection: spin period, flux, event list, high time-resolution light-curve,
pulse-profile, periodogram, and spectrum. Combining all three satellites, we
generated complete histories of the spin periods, pulse amplitudes, pulsed
fractions and X-ray luminosities. Some pulsars show variations in pulse period
due to the combination of orbital motion and accretion torques. Long-term
spin-up/down trends are seen in 12/11 pulsars respectively, pointing to
sustained transfer of mass and angular momentum to the neutron star on decadal
timescales. Of the sample 30 pulsars have relatively very small spin period
derivative and may be close to equilibrium spin. The distributions of
pulse-detection and flux as functions of spin-period provide interesting
findings: mapping boundaries of accretion-driven X-ray luminosity, and showing
that fast pulsars ($P<$10 s) are rarely detected, which yet are more prone to
giant outbursts. Accompanying this paper is an initial public release of the
library so that it can be used by other researchers. We intend the library to
be useful in driving improved models of neutron star magnetospheres and
accretion physics.