Fermi/GBM hard X-ray observations of pulsation from RX J0520.5-6932
ATel #5719; Mark H. Finger (USRA) and Peter A. Jenke (UAH)
on 3 Jan 2014; 22:41 UT
Credential Certification: Peter Jenke (peter.a.jenke@nasa.gov)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
Referred to by ATel #: 5856
Fermi/GBM is observing the recent outburst of the Be/X-ray pulsar RX J0520.5-6932 (ATels #4748, #5675). Pulsations from RX J0520.5-6932 have been detected since 2013 December 21 in the 12 - 25 keV band with the Fermi/GBM NaI detectors. The pulsations show rapid changes of barycentric frequency, likely due to a combination of accretion torques and Doppler shifts induced by binary motion. The pulse profile in the 12 -25 keV band is single peaked.
XMM observations in 2013 January 22 found a pulse period of 8.03533(3)s (ATel #5673). In the Fermi/GBM observations, we find that the barycentric pulse frequency varied from 124.4399(2) mHz (p=8.03601(2)s) on Dec 23.99 to 124.3918(9) mHz (p=8.03911(5)s) on 2014 January 2.50.
For the initial interval of December 21.0 to 23.0, the barycentric frequency rate was (3.4+/-2.2)x1E-11 Hz/s. This steadily decreased to (-8.0+/-1.0)x1E-11 Hz/s in the interval of 2013 Dec 27.0 to 29.0, and then increased to (-1.0+/-1.1)x1E-11 Hz/s in the interval of 2013 Dec 31.0 to 2014 to January 2.0. The changes in frequency rate found in the Fermi/GBM data over nearly half of the 24.45 day orbital period (Coe et al. 2001) suggest an orbital signature.
GBM Pulsar Project
