Black hole X-ray binary GRS 1915+105 has a variable magnetic disc wind, study suggests

Using NASA’s Chandra spacecraft, astronomers have performed high-resolution X-ray spectroscopic observations of a transient black hole X-ray binary known as GRS 1915+105. They report that the source exhibits a variable magnetic accretion disc wind.

The team found a series of wind absorption lines in the soft state of GRS 1915+105. These lines appear to follow a nonlinear dependence of velocity width, velocity shift and equivalent width with respect to ionization. This, according to the study, points out to a multiple component or stratified outflow. When it comes to the object’s hard state, the astronomers found only a faint absorption line of Fe XXVI.

In general, the researchers say that the results are indicative of a persistent presence of disc winds even during the hard state, although their spectroscopic appearance appears to be much weaker. Moreover, the intrinsic wind condition seems to change internally in different states of GRS 1915+105. Therefore, the results suggest that the disc wind in this binary has a magnetic origin.

“We note that the broad ionization range seen in the absorption lines, interpreted as a multiple component outflow by many authors (Miller et al. 2015, 2016), supports a magnetic origin,” the astronomers concluded.

The authors of the paper added that the mass outflow rate of the wind in GRS 1915+105 is comparable to the accretion rate. This finding suggests an intimate link between accretion and ejection processes that lead to state changes in black hole binaries.

Source: “Black hole X-ray binary GRS 1915+105 has a variable magnetic disc wind, study suggests” PhysOrg, 23 December 2020

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