The Physics of the “Heartbeat” State of GRS 1915+105

Abstract

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 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 5 -10 6 R 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.

A model for the energy-dependent time-lag and rms of the heartbeat oscillations in GRS 1915+105

“…The four predicted curves are determined by only four free parameters resolved spectroscopy done earlier by Neilsen et al (2011Neilsen et al ( , 2012. Indeed as expected both analysis find that the basic feature of the oscillation is that the inner disk radius oscillates.…”

“…Nayakshin, Rappaport, & Melia 2000;Janiuk, Czerny, & Siemiginowska 2000;Janiuk & Czerny 2005). Phase resolved spectroscopy of the variability reveals a consistent picture where the instability causes the inner disk radius to vary with the luminosity variation, which may be due to mass ejection from the system (Neilsen et al 2011(Neilsen et al , 2012. The spectral modeling at different phases show complex components consisting of disk emission and a power-law with a high energy cutoff.…”

“…We note that the qualitative behaviour of the energy dependence is fairly generic. Indeed, the detailed phase resolved spectroscopy of different observations also show that the energy dependence is similar despite changes in the frequency of the oscillations (Neilsen et al 2011(Neilsen et al , 2012 3 DISCUSSION AND CONCLUSION GRS 1915+105 shows a fascinating clockwork in its ρ-class, reflected in the highly periodic light curves which resemble closely to the human cardiogram, thus is also called as heartbeat state. We have studied the energy-dependent frequency resolved lags and fractional rms of this variability and they show a unique behaviour.…”

Detection of Very Low-Frequency, Quasi-Periodic Oscillations in the 2015 Outburst of V404 Cygni

“…All sources share similar QPO properties: a relatively large fractional rms amplitude of up to 10%, a short QPO lifetime of at most a few days and occurrence during the LHS. This distinguishes them from the "heart beat" QPOs observed in GRS 1915+105 (Belloni et al 2000) and IGR J17091-3624 (Altamirano et al 2011), which show largeamplitude oscillations during the high soft state generally attributed to a limit cycle behavior of a radiation pressure instability that causes quasi-periodic evaporation of the inner parts of the accretion disk followed by a refilling of the same (Lightman & Eardley 1974;Belloni et al 1997b;Neilsen et al 2011). Most of the QPO variability is concentrated in the first 400 s of the light curve.…”

Stabilization of radiation pressure dominated accretion disks through viscous fluctuations

“…A combination of this viscous prescription and the assumption that a fraction of the power is transferred to a corona may explain the variability of the micro-quasar GRS 1915+105, in certain spectral states (Janiuk & Czerny 2011). GRS 1915+105 is not typical, and the apparent stability of other bright X-ray binaries and even for GRS 1915+105 in its stable states remains a puzzle (see e.g., Neilsen et al 2011).…”