A new millisecond pulsar discovered by astronomers

Discovery plot of PSR J1835−3259B folded with a prefold showing time versus phase and frequency versus phase intensity in grayscale. Credit: Gautam et al., 2022.

An international team of astronomers reports the discovery of a new millisecond pulsar in the globular cluster NGC 6652. The newly discovered pulsar has been given the designation PSR J1835−3259B. The study detailing the basic parameters of discovery and disclosure of this object was published on May 30 on the arXiv prepublication server.

Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The fastest rotating pulsars, with rotation periods of less than 30 milliseconds, are called millisecond pulsars (MSP). Astronomers speculate that they form in binary systems when the initially most massive component transforms into a neutron star which is then rotated due to accretion of material from the secondary star.

Now, a group of astronomers led by Tasha Gautam of the Max Planck Institute for Radio Astronomy in Bonn, Germany, has detected another MSP as part of the Enhanced Giant VHF Radio Telescope (uGMRT) survey. During radio observations of eight GCs at 400 MHz and 650 MHz with uGMRT’s new Wideband Backend (GWB) GMRT system, they discovered that NGC 6652 harbors a rapidly rotating pulsar.

“In this paper, we have presented the results of a GC pulsar survey that we performed with the new broadband receivers at uGMRT to search for steep-spectrum pulsars at 400 MHz and 650 MHz. We observed eight GCs and searched each group for isolated and binary pulsar systems with segmented and full-length acceleration and jerk search techniques. We discovered a new MSP binary, J1835−3259B in NGC 6652,” the researchers explained.

PSR J1835−3259B is the first pulsar discovered by uGMRT. It has a rotation period of about 1.83 milliseconds, an orbital period of nearly 1.2 days, and a dispersion measurement of about 63.5 pc/cm3.

The results show that PSR J1835−3259B is a wide-orbiting binary system with relatively low eccentricity. Astronomers estimate that the characteristic age of this MSP is at least 430 million years old and that its surface magnetic field strength is no more than 350 million Gauss.

The study found that the median mass of the companion object in PSR J1835−3259B is most likely 0.21 solar masses, assuming the mass of the pulsar is at a level of 1.4 solar masses. The researchers assume that the companion is a helium white dwarf because the results obtained are consistent with those of MSP systems containing such objects.

Besides the detection of PSR J1835−3259B, the research also estimated the flux density and spectral indices of all pulsars in the eight GCs studied by Gautam’s team. It turned out that the PSR J1835−3259B is the brightest of all the pulsars among all the others in these clusters. Additionally, astronomers have identified three radio sources not associated with known pulsars in NGC 6652. Further observations are needed to unravel their nature.

Two millisecond pulsars detected in globular cluster NGC 6440

More information:

Improved GMRT reading for pulsars in globular clusters. I: Discovery of a millisecond binary pulsar in NGC 6652, arXiv:2205.15274 [astro-ph.HE] arxiv.org/abs/2205.15274

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New millisecond pulsar discovered by astronomers (2022, June 7)
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