Recent timing studies on RXTE observations of 4U 1538-52

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Baykal A., Inam S. C., Beklen E.

ASTRONOMY & ASTROPHYSICS, vol.453, no.3, pp.1037-1040, 2006 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 453 Issue: 3
  • Publication Date: 2006
  • Doi Number: 10.1051/0004-6361:20054616
  • Journal Name: ASTRONOMY & ASTROPHYSICS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1037-1040
  • Keywords: X-rays : binaries, stars : neutron, pulsars : individual : 4U 1538-52, accretion, accretion disks, ORBITAL PERIOD CHANGES, GINGA OBSERVATIONS, PULSE PERIOD, 4U 1538-52, HERCULES-X-1, DECAY
  • Middle East Technical University Affiliated: Yes

Abstract

The high mass X-ray binary pulsar 4U 1538-52 was observed between July 31 and August 7, 2003. Using these observations, we determined new orbital epochs for both circular and elliptical orbit models. The orbital epochs for both orbit solutions agreed with each other and yielded an orbital period derivative. P/P = (0.4 +/- 1.8) x 10(-6) yr(-1). This value is consistent with the earlier measurement P/P = (2.9 +/- 2.1) x 10(-6) yr(-1) at the 1 sigma level and gives only an upper limit to the orbital period decay. Our determination of the pulse frequency showed that the source spun up at an average rate of 2.76 x 10(-1)4 Hz s(-1) between 1991 and 2003.