Observations explore the properties of X-ray binary LMC X–4

Utilizing the AstroSat spacecraft, Indian astronomers have investigated a excessive mass X-ray binary system often called LMC X–4. Outcomes of the research, introduced December 2 on arXiv.org, yield essential insights into the properties of this supply and shed extra gentle on the quasi-periodic oscillations that it experiences.

X-ray binaries are composed of a traditional star or a white dwarf transferring mass onto a compact neutron star or a black hole. Based mostly on the mass of the companion star, astronomers divide them into low-mass X-ray binaries (LMXBs) and high-mass X-ray binaries (HMXBs).

Positioned some 163,000 light years away, LMC X–4 is a extremely luminous, eclipsing HMXB within the Massive Magellanic Cloud (LMC). The system consists of a neutron star, about 25% extra large than the sun, spinning at a interval of 13.5 seconds and accreting matter from an OB star. The X-ray eclipse of LMC X–4 lasts about 5 hours and recurs each 33.6 hours.

The X-ray emission from LMC X–4 showcases depth variation as a result of a precessing tilted accretion disk that periodically obscures direct X-ray emission from the compact object. Furthermore, the supply experiences massive X-ray flares with quasi-periodic variability at frequencies of 0.65−1.35 and a couple of − 20 mHz. Current observations have discovered that LMC X–4 additionally reveals 27 mHz quasi-periodic oscillation (QPO) in its X-ray emission.

In an effort to be taught extra in regards to the properties of LMC X–4 and its QPO conduct, a gaggle of astronomers led by Rahul Sharma of the Raman Analysis Institute in Bangalore, India, inspected this binary with AstroSat’s Massive Space X-ray Proportional Counter (LAXPC) and Comfortable X-ray Telescope (SXT) devices.

“On this work, we now have introduced the outcomes of broadband timing and spectral evaluation of HMXB LMC X–4 by utilizing AstroSat knowledge from August 2016. The supply was in its excessive state of super-orbital movement throughout this commentary,” the researchers defined.

The research discovered that the heartbeat interval of LMC X–4 is 13.501606 seconds and recognized power dependent pulse profiles. Furthermore, the observations detected an power dependent 26 mHz QPO in a large power band of three–40 keV.

The heart beat profiles within the tender X-ray energies (3–6 keV and 6–12 keV) confirmed advanced dip-like options, presumably as a result of absorption from the accretion stream. It was added that at increased energies, these profiles are single-peaked, easy and present an virtually sinusoidal conduct.

Relating to the power spectrum of LMC X–4, the astronomers famous that it’s usually described by a mannequin comprising a power-law with high-energy cutoff. They modeled the 0.5–25 keV power spectrum with an influence regulation continuum (about 0.8) and a excessive power cutoff of about 16 keV.

The QPO root imply sq. (RMS) was discovered to be growing with power with a slope of about 0.06% per keV in a broad power band of three–40 keV. In line with the researchers, this outcome means that the aperiodic oscillations usually are not pushed by the chilly disk element.

The analysis additionally discovered that the 0.5–25 keV luminosity of LMC X–4 is at a stage of 200 undecillion erg/s and that the rate at its internal accretion disk is roughly 20,000 km/s.

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