NuSTAR Observations and Broadband Spectral Energy Distribution Modeling of the Millisecond Pulsar Binary PSR J1023+0038
Abstract
We report the first hard X-ray (3-79 keV) observations of the millisecond pulsar (MSP) binary PSR J1023+0038 using NuSTAR. This system has been shown transiting between a low-mass X-ray binary (LMXB) state and a rotation-powered MSP state. The NuSTAR observations were taken in both LMXB state and rotation-powered state. The source is clearly seen in both states up to ~79 keV. During the LMXB state, the 3-79 keV flux is about a factor of 10 higher than in the rotation-powered state. The hard X-rays show clear orbital modulation during the X-ray faint rotation-powered state but the X-ray orbital period is not detected in the X-ray bright LMXB state. In addition, the X-ray spectrum changes from a flat power-law spectrum during the rotation-powered state to a steeper power-law spectrum in the LMXB state. We suggest that the hard X-rays are due to the intrabinary shock from the interaction between the pulsar wind and the injected material from the low-mass companion star. During the rotation-powered MSP state, the X-ray orbital modulation is due to Doppler boosting of the shocked pulsar wind. At the LMXB state, the evaporating matter of the accretion disk due to the gamma-ray irradiation from the pulsar stops almost all the pulsar wind, resulting in the disappearance of the X-ray orbital modulation.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2014
- DOI:
- 10.1088/0004-637X/797/2/111
- arXiv:
- arXiv:1410.4563
- Bibcode:
- 2014ApJ...797..111L
- Keywords:
-
- accretion;
- accretion disks;
- binaries: close;
- pulsars: individual: PSR J1023+0038;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 8 pages, 6 figures