Astronomers Discover Most Scattered Pulsar Known To Date (Cosmology)

Using the Green Bank Telescope, a team of international astronomers detected radio pulsations from PSR J1813-1749 at 4.4–10.2 GHz. They found that, it is the most scattered pulsar known to date. Their study recently appeared in Arxiv.

PSR J1813-1749, is a 44.7 ms X-ray pulsar in the supernova remnant G12.82−0.02/HESS J1813−178 with characteristic age of 5600 yr and has the second highest spin-down luminosity of known pulsars in the Galaxy, with E˙ = 5.6 × 1037 erg s¯1.

Astronomers found that the pulse is highly scattered, with an exponential decay timescale τ longer than that of any other pulsar at these frequencies.

They also found that, it has large dispersion measure, DM = 1087 pc cm¯3, which provided additional evidence that the object is located at a large distance of either 6.2 or 12 kpc. The high X-ray measured column density of ≈ 1023 cm¯2 also supports a large distance.

© Camilo et al.

In addition, a proper motion of 0.0655 arcsec yr¯1 and its close presence to the center of the radio shell of G12.82–0.02 make PSR J1813-1749, the youngest known neutron star in the galaxy.

“If so, it would also be interesting if such a young supernova remnant (SNR) is accompanied by dense plasma that could cause the extreme scattering of the radio pulses.”

Finally, in concluding remarks, the astronomers underlined that, future Chandra observations are needed to confirm or disprove the reported high proper motion of PSR J1813−1749, which would imply a very young age for the system, and possibly be related to the extreme pulse scattering timescale. VLBI at 5 GHz could also measure proper motion, as well as image broadening that could be used to deduce the location of the scattering medium.

Featured image: Scattering timescale at 1 GHz versus dispersion measure for pulsars with the highest DM. Open circles are from the ATNF Pulsar Catalog, supplemented with recent measurements from MeerKAT © Camilo et al.

Reference: F. Camilo, S. M. Ransom, J. P. Halpern, D. A. Rosh, “Radio Detection of PSR J1813-1749 in HESS J1813-178: The Most Scattered Pulsar Known”, pp. 1-8, 2021.

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