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State Transition of Accretion-Disk Winds in BH XRBs

Published onJun 01, 2020
State Transition of Accretion-Disk Winds in BH XRBs

An apparent feature distinct to BH XRBs, discovered by our ability to follow them through entire cycles of flux change, is a hysteresis in their spectral/timing properties, which follow a well-known q-diagram. This trend outlines the great diversity of the spectral/timing properties, as well as the global evolution of accretion disk properties with their accretion rate. The diagram generally exhibits two phenomenological regions from spectroscopic observations; high/soft state where (blueshifted) ionized absorbers of v < 1,000 km/s are detected and low/hard state in the apparent absence of such absorbers, thus implying a wind dichotomy. Motivated with the state-of-the-art Chandra grating data from GRO J1655-40, H1743-322 and 4U 1630-47 as canonical sources, we present a disk-wind model in an effort to systematically understand the underlying X-ray wind condition in both states in the context of a magnetic driving scenario. By multi-ion spectral fitting for a broad-band spectrum (e.g. 1-10 keV) within the framework of 3D magnetized disk winds, we demonstrate a possibility of the physical presence of winds even during low/hard state with a special focus on wind density, inclination and density gradient of a global wind structure. In anticipation of the upcoming new X-ray observatories such as XRISM/Resolve and Athena/X-IFU, we also present a preliminary simulation of the expected absorption spectra in both states, which we believe can ultimately address whether ionized winds exist or not during low/hard state.

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