Broad-Band X-Ray Study of a Transient Pulsar RX J0059.2-7138
Abstract
We report on the results of the ASCA and ROSAT observations on RX J0059.2-7138, a transient X-ray pulsar in the Small Magellanic Cloud. The barycentric pulse period has been precisely determined to be 2.763221 +/- 0.000004 s. The pulse shape is almost identical in all of the energy bands. The pulse fraction increases with the photon energy below ~ 2 keV, while it is nearly constant at ~ 37% above ~ 2 keV. The X-ray spectrum has been found to consist of two components. One is dominant above 2 keV, and exhibits sinusoidal pulsations. This component is well described by a typical model found in many X-ray binary pulsars, a power-law of photon index 0.4 with an exponential cut-off at 6.5 keV. The other is dominant below 1 keV and shows no significant pulsation. This component is represented by either a broken power-law with photon indices of 2.6 and 5.1 below and above a break energy of 0.9 keV, or a metal-poor thin-thermal plasma with a temperature of 0.37 keV. The phase-averaged luminosity is ~ 1038 erg s-1 (0.1-10.0 keV) for both components. A hint of oxygen over-abundance is found in the absorbing column, possibly due to circumstellar gas ejected from an evolved companion.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- April 2000
- DOI:
- 10.1093/pasj/52.2.299
- arXiv:
- arXiv:astro-ph/0003126
- Bibcode:
- 2000PASJ...52..299K
- Keywords:
-
- CIRCUMSTELLAR MATTER;
- PULSARS: INDIVIDUAL (RX J00592-7138);
- STARS: BE;
- STARS: NEUTRON;
- X-RAYS: BINARIES;
- Astrophysics
- E-Print:
- 6 pages, 4 postscript figures, to be published in PASJ, uses PASJ95.sty and PASJadd.sty