Disk–Wind Connection during the Heartbeats of GRS 1915+105

Abstract

Disk and wind signatures are seen in the soft state of Galactic black holes, while the jet is seen in the hard state. Here we study the disk–wind connection in the ρ class of variability in GRS 1915+105 using a joint NuSTAR–Chandra observation. The source shows 50 s limit cycle oscillations. By including new information provided by the reflection spectrum and using phase-resolved spectroscopy, we find that the change in the inner disk inferred from the blackbody emission is not matched by reflection measurements. The latter is almost constant, independent of the continuum model. The two radii are comparable only if the disk temperature color correction factor changes, an effect that could be due to the changing opacity of the disk caused by changes in metal abundances. The disk inclination is similar to that inferred from the jet axis, and oscillates by ~10°. The simultaneous Chandra data show the presence of two wind components with velocities between 500 and 5000 km s^(−1), and possibly two more with velocities reaching 20,000 km s^(−1) (~0.06 c). The column densities are ~5 × 10^(22) cm^(−2). An upper limit to the wind response time of 2 s is measured, implying a launch radius of <6 × 10^(10) cm. The changes in wind velocity and absorbed flux require the geometry of the wind to change during the oscillations, constraining the wind to be launched from a distance of 290–1300 r_g from the black hole. Both data sets support fundamental model predictions in which a bulge originates in the inner disk and moves outward as the instability progresses.