Astronomers Discover Young and Energetic Pulsar In The Small Magellanic Cloud (Planetary Science)

Astronomers discover a 22 ms pulsar, “PSR J0058-7218”, in the Small Magellanic Cloud

A team of international astronomers using XMM-Newton, reported on the discovery of a young and energetic pulsar PSR J0058– 7218 inside the IKT 16, a supernova remnant in the Small Magellanic Cloud (SMC). Their study recently appeared in Arxiv.

The Large and the Small Magellanic Clouds (LMC and SMC) are gas-rich irregular galaxies orbiting the Milky Way. A large population of High Mass X-ray Binaries HMXBs (predominantly Be X-ray binaries) has been discovered and extensively studied in the SMC. However, just a handful number of ‘younger’ population of isolated neutron stars that constitute the rotation powered pulsars, are known. Only seven such systems have been discovered in the SMC until now.

Now, C. Maitra and colleagues, reported on the discovery of a young and energetic pulsar PSR J0058– 7218 inside the SNR IKT 16 in the SMC. They detected X-ray pulsations corresponding to a period of 21.7661076(2) ms. They also found that, the pulsar spins down at a rate of 2.9(3) × 10¯14 ss¯1 consistent with the scenario expected from a young rotation powered pulsar.

“To search for a periodic signal, we started with the barycentre-corrected XMM-Newton EPIC-pn data in the energy range of 0.4–10.0 keV by using a Lomb–Scargle periodogram analysis in the period range of 12 ms to 1 s. We detected a strong periodic signal around 22 ms. While, in order to determine the period more precisely, we employed the Bayesian periodic signal detection method.”

With this measured spin period and the spin period derivative they derived several other parameters of PSR J0058-7218 like spin down luminosity (𝐸¤), characteristic age (𝜏c), the equatorial surface magnetic field (𝐵surf) of the pulsar etc. They are given in Table 1 below.

Table 1. Spin ephemeris of PSR J0058–7218 © Maitra et al.

In addition, they suggested that, the spin down luminosity of 1.1 × 1038 erg s¯1 indicated that the pulsar is Crab-like. Moreover, the characteristic age of the pulsar is 12 kyr.

Finally, they searched for the signal in archival data collected in radio with the Parkes telescope and in 𝛾-rays with the Fermi/LAT, but no evidence for pulsation was found in these energy bands.

“PSR J0058–7218 provides a unique opportunity to probe the braking mechanisms and birth-spin models of rotation-powered pulsars. Future monitoring of PSR J0058–7218 is crucial to constrain the second derivative of the period in order to measure the braking-index of the pulsar and allow deeper searches in the radio and 𝛾- rays, and look for putative glitches that are fairly common in young rotation powered pulsars on timescales of a few years. A continuous monitoring of the spin evolution will also be very important because of its potential as a source of detectable gravitational waves. “

— concluded authors of the study

Featured image: P-Pdot diagram showing the position of PSR J0058–7218 (red dot), PSR J0537–6910 (cyan star), PSR J0540–6919 (orange triangle) and the Crab pulsar (blue cross) © Maitra et al.

Reference: C. Maitra, P. Esposito, A. Tiengo, J. Ballet, F. Haberl, S. Dai, M. D. Filipovic, M.Pilia, “IKT16: Discovery of a 22 ms energetic rotation-powered pulsar in the Small Magellanic Cloud”, Arxiv, pp. 1-5, 2021.

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