A detailed study of the 5-Hz quasi-periodic oscillations in the bright X-ray transient and black hole candidate GRS 1739-278

Rudy Adam Dirk Wijnands, M Méndez, JM Miller, J Homan

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12 Citations (Scopus)

Abstract

We present a detailed study of the 5-Hz quasi-periodic oscillation (QPO) recently discovered in the bright X-ray transient and black hole candidate (BHC) GRS 1739-278 (Borozdin & Trudolyubov) during a Rossi X-ray Timing Explorer observation taken on 1996 March 31. In total 6.6 ksec of on-source data were obtained, divided in two data sets of 3.4 and 3.2 ksec which were separated by similar to2.6 ksec. The 5-Hz QPO was only present during the second data set. The QPO increased in strength from below 2 per cent rms amplitude for photon energies below 4 keV to similar to5 per cent rms amplitude for energies above 10 keV. The soft QPO photons (below 5 keV) lagged the hard ones (above 10 keV) by almost 1.5 rad. Besides the QPO fundamental, its first overtone was detected. The strength of the overtone increased with photon energy (from <2 per cent rms below 5 keV to <similar to>8 per cent rms above 10 keV). Although limited statistics did not allow for an accurate determination of the lags of the first overtone, indications are that also for this QPO the soft photons lagged the hard ones. When the 5-Hz QPO was not detected (i.e., during the first part of the observation), a broad noise component was found for photon energies below 10 keV but it became almost a true QPO (with a Q value of similar to1.9) above that energy, with a frequency of similar to3 Hz. Its hard photons preceded the soft ones in a way reminiscent of the 5-Hz QPO, strongly suggesting that both features are physically related. We discuss our finding in the framework of low-frequency QPOs and their properties in BHCs.

Original languageEnglish
Pages (from-to)pp.451-460.
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume328
Issue number2
Publication statusPublished - 1 Dec 2001

Keywords

  • accretion, accretion discs
  • stars : individual : GRS 1739-278
  • X-rays : stars
  • PHASE-LAG VARIABILITY
  • NOVA GRS-1739-278
  • GRS-1915+105
  • DISCOVERY

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