THE PHYSICS OF THE “HEARTBEAT” STATE OF GRS 1915+105
Author(s)
Neilsen, Joseph M. G.; Lee, Julia C.; Remillard, Ronald A
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We present the first detailed phase-resolved spectral analysis of a joint Chandra High-Energy Transmission Grating Spectrometer and Rossi X-ray Timing Explorer observation of the ρ variability class in the microquasar GRS 1915+105. The ρ cycle displays a high-amplitude, double-peaked flare that recurs roughly every 50 s and is sometimes referred to as the "heartbeat" oscillation. The spectral and timing properties of the oscillation are consistent with the radiation pressure instability and the evolution of a local Eddington limit in the inner disk. We exploit strong variations in the X-ray continuum, iron emission lines, and the accretion disk wind to probe the accretion geometry over nearly six orders of magnitude in distance from the black hole. At small scales (1-10 R [subscript g]), we detect a burst of bremsstrahlung emission that appears to occur when a portion of the inner accretion disk evaporates due to radiation pressure. Jet activity, as inferred from the appearance of a short X-ray hard state, seems to be limited to times near minimum luminosity, with a duty cycle of ~10%. On larger scales (10[superscript 5]-10[superscript 6] R [subscript g]), we use detailed photoionization arguments to track the relationship between the fast X-ray variability and the accretion disk wind. For the first time, we are able to show that changes in the broadband X-ray spectrum produce changes in the structure and density of the accretion disk wind on timescales as short as 5 s. These results clearly establish a causal link between the X-ray oscillations and the disk wind and therefore support the existence of a disk-jet-wind connection. Furthermore, our analysis shows that the mass-loss rate in the wind may be sufficient to cause long-term oscillations in the accretion rate, leading to state transitions in GRS 1915+105.
Date issued
2011-08Department
MIT Kavli Institute for Astrophysics and Space ResearchJournal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Neilsen, Joseph, Ronald A. Remillard, and Julia C. Lee. “THE PHYSICS OF THE ‘HEARTBEAT’ STATE OF GRS 1915+105.” The Astrophysical Journal 737, no. 2 (August 4, 2011): 69. © 2011 The American Astronomical Society
Version: Final published version
ISSN
0004-637X
1538-4357