A transient low-frequency quasi-periodic oscillation from the black hole binary GRS 1915+105

• Published in: Monthly notices of the Royal Astronomical Society 2008-01, Vol.383 (3), p.1089-1102
• Main Authors: Soleri, P., Belloni, T., Casella, P.
• Format: Article
• Language: English
• Subjects: accretion; accretion discs; accretion, accretion discs; Astronomy; Black holes; Double stars; Earth, ocean, space; Exact sciences and technology; Spectrum analysis; X-ray astronomy; X-rays: binaries
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2007.12596.x

We present the results of the timing analysis of five Rossi X-ray Timing Explorer observations of the black hole candidate GRS 1915+105 between 1996 September and 1997 December. The aim was to investigate the possible presence of a type B quasi-periodic oscillation (QPO). Since in other systems this QPO is found to appear during spectral transitions from hard to soft states, we analysed observations characterized by a fast and strong variability, in order to have a large number of transitions. In GRS 1915+105, transitions occur on very short time-scales (∼s): to single them out we averaged power density spectra following the regular path covered by the source on a 3D hardness–hardness–intensity diagram. We identified both the type C and the type B QPOs: this is the first detection of a type B QPO in GRS 1915+105. As the spectral transitions have been associated to the emission and collimation of relativistic radio-jets, their presence in the prototypical Galactic jet source strengthens this connection.