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Astronomers report the discovery of two new highly scattered pulsars as part of the Australian SKA Pathfinder (ASKAP) Variables and Slow Transients (VAST) survey. The findings are detailed in a research paper September 24 on the arXiv preprint server.

In general, pulsars are rotating neutron stars with intense magnetic fields, observed to emit a beam of electromagnetic radiation. They are usually identified in the form of short bursts of radio emission; however, some of them are also detected with the help of optical, X-ray and gamma-ray telescopes.

There are also radio pulsars that are highly scattered as radio pulses from these objects traverse the turbulent interstellar medium and multi-path propagation causes temporal and spatial scattering. These highly scattered pulsars are hard to detect for the majority of astronomical surveys.

Now, a team of astronomers led by Rahul Sengar of the Max Planck Institute for Gravitational Â鶹ÒùÔºics in Germany has identified two new pulsars of this type as part of the VAST survey, which targets the southern galactic plane. Their pulsar nature was confirmed by follow-up observations using the Parkes radio telescope.

"In this paper, we present the discovery of two highly scattered pulsars—PSR J1646−4451 and PSR J1837−0616—which are among a sample of four circularly polarized sources detected in the ASKAP Variable and Slow Transients (VAST) survey and were subsequently confirmed as pulsars with the Parkes radio telescope," the researchers write.

The newfound pulsars PSR J1646−4451 and PSR J1837−0616 have scattering indices of 3.28 and 3.1, while their scattering timescales at 1 GHz were measured to be 2,479 and 2,154 milliseconds, respectively. These values place them among the five most heavily scattered pulsars known to date.

According to the study, PSR J1646−4451 has a spin period of approximately 217 milliseconds and a dispersion measure of 928 pc/cm³. The pulsar has a spin-down luminosity of 8.3 decillion erg/s, surface magnetic field strength of 694 billion Gauss, and its characteristic age is estimated to be about 1.6 million years. The distance to PSR J1646−4451 was measured to be some 31,000 light years.

PSR J1837−0616 spins about two times faster than PSR J1646−4451 as its spin period was measured to be 118 milliseconds. The pulsar, located 28,600 light years away, has a dispersion measure of 793.7 pc/cm³ and a spin-down luminosity at a level of 100 decillion erg/s. The collected data indicate that PSR J1837−0616 has a surface magnetic field strength of 712 billion Gauss and a characteristic age of around 447,300 years.

The authors of the paper noted that their discovery of PSR J1646−4451 and PSR J1837−0616 highlights the potential of using circular polarization in radio continuum images as a tool for identifying highly scattered pulsars. They added that future wide-field radio continuum surveys will be crucial for detecting pulsars obscured by scattering in the galactic plane, which remain challenging to traditional time-domain searches.