Observations inspect X-ray radiation from Vela X-1

Utilizing the Imaging X-ray Polarimetry Explorer (IXPE), a global crew of astronomers has carried out X-ray polarimetric observations of an accreting X-ray pulsar often known as Vela X-1. Outcomes of the observational marketing campaign, introduced March 3 on the arXiv pre-print server, ship necessary insights into the properties of X-ray radiation from this pulsar.

X-ray binaries are composed of a traditional star or a white dwarf transferring mass onto a compact neutron star or a black hole. 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).

At a distance of some 6,500 light years away from the Earth, Vela X-1 is a runaway high-mass X-ray binary (HMXB) system, consisting of an accreting neutron star and the supergiant donor HD 77581 in a decent 9-day orbit. HD 77581 launches a powerful stellar wind that causes a bow shock because it interacts with the interstellar medium. This makes Vela X-1 considered one of solely two HMXBs recognized to expertise a bow shock.

Lately, a bunch of astronomers led by Sofia Forsblom of the College of Turku in Finland, has investigated Vela X-1 with IXPE, hoping to shed extra mild on the character of this pulsar.

“On this paper, we current the primary outcomes of X-ray polarimetric observations of Vela X-1 by IXPE carried out on two separate events throughout 2022,” the researchers wrote.

Initially, the crew measured the spin interval of Vela X-1 utilizing the phase connection approach, which was discovered to be roughly 283.4 seconds. The pulsed fraction within the 2–8 keV power band was decided to be 53.3% for the primary remark and 48.1% for the second remark.

Afterward, it was discovered that In your complete IXPE power band (2–8 keV), the common polarization diploma (PD) and polarization angle (PA) are at a degree of about 3.9% and −51.5 levels, respectively, for the primary remark. For the second remark, the common PD and PA have been measured to be 3.7% and −48.9 levels, respectively. Furthermore, a spectro-polarimetric evaluation of the phase-averaged information for Vela X-1 discovered a PD of two.3% and PA of −47.3 levels.

The astronomers concluded that such a low polarization diploma is in step with the outcomes obtained for different recognized X-ray pulsars. They suppose that the obtained worth of PD could also be because of the inverse temperature construction of the neutron star ambiance. Nevertheless, they added that the low PD can also be a results of the sturdy variations of the PD and PA with power, or sturdy variations of the PA with the pulsar phase.

The authors of the research famous that additional research of Vela X-1 are required so as to draw last conclusions.

“A whole and detailed evaluation of the difficult power dependence of the polarization properties of Vela X-1 is out of the scope of this paper and is topic to future, extra intensive work,” the scientists wrote.

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