2017ApJ...835L...9H -
Astrophys. J., 835, L9-L9 (2017/January-3)
Swift detection of a 65 day X-ray period from the ultraluminous pulsar NGC 7793 P13.
HU C.-P., LI K.L., KONG A.K.H., NG C.-Y. and LIN L.C.-C.
Abstract (from CDS):
NGC 7793 P13 is an ultraluminous X-ray source harboring an accreting pulsar. We report on the detection of a ∼65 day period X-ray modulation with Swift observations in this system. The modulation period found in the X-ray band is P = 65.05 ± 0.10 days and the profile is asymmetric with a fast rise and a slower decay. On the other hand, the u-band light curve collected by Swift UVOT confirmed an optical modulation with a period of P = 64.24 ± 0.13 days. We explored the phase evolution of the X-ray and optical periodicities and propose two solutions. A superorbital modulation with a period of ∼2700-4700 days probably caused by the precession of a warped accretion disk is necessary to interpret the phase drift of the optical data. We further discuss the implication if this ∼65 day periodicity is caused by the superorbital modulation. Estimated from the relationship between the spin-orbital and orbital-superorbital periods of known disk-fed high-mass X-ray binaries, the orbital period of P13 is roughly estimated as 3-7 days. In this case, an unknown mechanism with a much longer timescale is needed to interpret the phase drift. Further studies on the stability of these two periodicities with a long-term monitoring could help us to probe their physical origins.
Abstract Copyright:
© 2017. The American Astronomical Society. All rights reserved.
Journal keyword(s):
accretion, accretion disks - galaxies: individual: NGC 7793 - stars: neutron - X-rays: binaries - X-rays: individual: (NGC 7793 P13, CXOU J235750.9-323726) - X-rays: individual: (NGC 7793 P13, CXOU J235750.9-323726)
Simbad objects:
8
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