These systems with a black hole and a huge star are called high-mass X-ray binaries and have actually been extremely useful in understanding the nature of black holes.
Lots of more of them were anticipated to exist, particularly offered that many binary black holes (the future states of high-mass X-ray binaries) have actually been discovered with gravitational waves in the previous few years. We find it is generally difficult to have sufficient angular momentum falling onto the black hole in high-mass X-ray binaries. As an outcome, the gas can fall into the black hole directly without producing an accretion disk, so the black hole is nearly unnoticeable.
If this is true, why do we see any X-ray binaries at all? In our paper, we solved the equations of movement for outstanding winds and we discovered that the wind does not blow symmetrically when the great void is close adequate to the star. The wind blows with a slower speed in the direction towards and far from the black hole, due to the tidal forces. Since of this break of symmetry in the wind, the gas can now have a large amount of angular momentum, enough to form an accretion disk around the great void and shine in X-rays. The needed conditions for this asymmetry are rather stringent, so only a little portion of black hole + enormous star binaries will have the ability to be observed.
The model in our research study discusses why there are only a little number of identified high-mass X-ray binaries, but this is just the initial step in comprehending uneven excellent winds. By examining this model even more, we may be able to resolve many other secrets of high-mass X-ray binaries. Written by OzGrav Postdoc Ryosuke Hirai, Monash University
Reference: “Conditions for accretion disc formation and observability of wind-accreting X-ray binaries” by Ryosuke Hirai and Ilya Mandel, 18 November 2021, Publications of the Astronomical Society of Australia.DOI: 10.1017/ pasa.2021.53.
Artists impression of CygnusX-1. Credit: Mark Myers, OzGrav-Swinburne University
The first proof of the existence of black holes was found in the 1960s, when strong X-rays were discovered from a system called Cygnus X-1. In this system, the black hole is orbited by an enormous star blowing a very strong wind, more than 10 million times more powerful than the wind blowing from the Sun. Part of the gas in this wind is gravitationally brought in towards the great void, developing an accretion disk, which releases the strong X-rays that we observe. These systems with a massive star and a black hole are called high-mass X-ray binaries and have actually been extremely handy in understanding the nature of great voids.
Lots of more of them were anticipated to exist, especially offered that lots of binary black holes (the future states of high-mass X-ray binaries) have actually been found with gravitational waves in the past couple of years. There are also lots of binaries discovered in our Galaxy that are expected to eventually become a high-mass X-ray binary.
One description states that even if a great void is orbited by a massive star blowing a strong wind, it does not always release X-rays. To release X-rays, the black hole requires to produce an accretion disk, where the gas swirls around and becomes hot prior to falling in. To create an accretion disk, the falling gas requires angular momentum, so that all the gas particles can rotate around the black hole in the exact same direction. We find it is generally challenging to have adequate angular momentum falling onto the black hole in high-mass X-ray binaries. This is since the wind is generally thought about to be blowing symmetrically, so there is nearly the same amount of gas flowing past the great void both clockwise and counter-clockwise. As an outcome, the gas can fall into the great void straight without producing an accretion disk, so the great void is almost invisible.
