Utilizing the Arduous X-ray Modulation Telescope (HXMT), astronomers from Shanghai Astronomical Observatory in China have detected a low frequency, quasi-periodic oscillation in a black gap excessive mass X-ray binary often called Cygnus X-1. The discovering is reported in a paper revealed April 29 on arXiv.org.
X-ray binaries encompass a traditional star or a white dwarf transferring mass onto a compact neutron star or a black gap. Primarily based on the mass of the companion star, astronomers divide them into low-mass X-ray binaries (LMXBs) and high-mass X-ray binaries (HMXBs).
X-ray binaries might exhibit X-ray variability within the type of comparatively sharp quasi-periodic oscillations (QPOs) with millihertz (mHz) to kilohertz (kHz) frequencies. Researchers consider that QPOs happen when X-rays are emitted close to the inside fringe of an accretion disk wherein gasoline swirls onto a compact object like a neutron star or a black gap. Usually, QPOs are divided into type-A, -B, and -C, in response to their frequency, amplitude and coherence.
Positioned some 6,100 mild years away from the Earth within the constellation Cygnus, Cygnus X-1 is a vivid, persistent HMXB consisting of a black gap accreting matter from an OB star. Earlier observations of this supply have proven that its X-ray emission undergoes dramatic adjustments in spectral distribution and brightness.
Now, a crew of astronomers led by Zhen Yan studies the detection of a short-lived, low frequency QPO in Cygnus X-1. The discovering was made utilizing HXMT (often known as Perception), China’s first X-ray astronomy satellite tv for pc.
“On this paper, we report the detection of a mHz QPO in one of many Perception-HXMT observations of Cygnus X-1 through the gentle state,” the researchers wrote within the examine.
The QPO was detected at 88 mHz, through the first 200 minutes of the longest HXMT statement of Cygnus X-1 that came about in August 2017. The fractional root-mean-square (RMS) amplitude of this QPO seems to be power impartial because it decreases at decrease power.
HXMT information recommend that the mHz QPO recognized in Cygnus X-1 is completely different from the type-A, -B, and -C QPOs normally noticed in black gap X-ray binaries (BH XRBs). For example, it has a big high quality issue, which is analogous to the type-C QPOs, nonetheless, its frequency and RMS are smaller than most type-C QPOs noticed in different BH XRBs.
The outcomes additionally allowed the astronomers to shed extra mild into the parameters of Cygnus X-1. The information point out that the system has an orbital interval of about 5.6 days, the black gap mass is roughly 21.2 photo voltaic lots, and its distance is larger than beforehand thought—some 7,200 mild years.
In concluding remarks, the researchers supplied a proof to the origin of QPOs present in related methods.
“We evaluate QPOs at related frequencies which were beforehand detected in one other persistent excessive mass X-ray binaries within the gentle state, we speculate that such QPOs may relate to some native inhomogeneity hardly ever fashioned within the accretion circulation of wind-fed accretion methods,” the authors of the paper wrote.
Millihertz quasi-periodic oscillations detected in an X-ray binary
Detection of a low frequency quasi-periodic oscillation within the gentle state of Cygnus X-1 with Perception-HXMT, arXiv:2104.14307 [astro-ph.HE] arxiv.org/abs/2104.14307
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Quasi-periodic oscillation detected in Cygnus X-1 (2021, Might 5)
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