Adipol Phosrisom | Searcharxiv

arXiv2026

Pulsar Discoveries from the TRAPUM UHF Survey of Fermi-LAT Sources

The Fermi Large Area Telescope (LAT) provides advantages for radio pulsar searches by enabling efficient target selection. We can confidently point radio telescopes to the positions of Fermi unidentified gamma-ray sources that have a high probability of hosting a pulsar. As part of Transients and Pulsars with MeerKAT (TRAPUM), we conducted a survey of Fermi-LAT sources using the Ultra High Frequency (UHF; 544-1088 MHz) receiver of the MeerKAT radio telescope. We observed 79 sources that were identified as pulsar-like candidates using a random forest technique from the Fermi-LAT Fourth Source Catalogue. We observed each target for 10 minutes at two separate epochs. As a result, we discovered nine new millisecond pulsars (MSPs) and six slow pulsars. Based on the radio discoveries, we also searched for gamma-ray pulsations, confirming that seven of the newly discovered MSPs are associated with Fermi-LAT sources, and performed joint radio and gamma-ray pulsar timing. Companion mass estimates and evidence of radio eclipses indicate that among the nine MSPs there are three black widows and three redbacks. Lastly, we compared the discovered pulsars in the MeerKAT UHF survey against the previous Fermi sources TRAPUM survey at L band, concluding the superiority of UHF observations in sensitivity to fainter pulsars and in detection rate than L band for finding new gamma-ray MSPs.

astro-ph.HE↗

arXiv2025

Multiwavelength observations of a new black-widow millisecond pulsar PSR J1544-2555

We report the discovery of a new black-widow millisecond pulsar, PSR J1544-2555, associated with the Fermi-LAT source 4FGL J1544.2-2554. Optical, radio, and gamma-ray observations confirmed its nature as a compact spider binary system. Optical photometry from ULTRACAM revealed a \(\sim\)2.7-hour orbital period, guiding MeerKAT observations that detected \(\sim\)2.4-ms radio pulsations. Subsequent timing campaigns using the Murriyang Parkes Telescope, the Effelsberg 100-m Radio Telescope, and the Nançay Radio Telescope allowed us to obtain a preliminary timing solution, which enabled us to find gamma-ray pulsations. The final timing solution, spanning 16 years of Fermi-LAT gamma-ray data, also displays orbital period variations typical of spider pulsars. X-ray observations from eROSITA indicate non-thermal emission, but the relatively low count rate prohibits the search for X-ray pulsations. Optical light curve modelling using Icarus suggests the asymmetry is best explained by a spot model, where uneven heating creates localised temperature variations on the companion. While the optical spectra we obtained are compatible with the physical properties we infer for the companion star, they were not of sufficient signal-to-noise to allow for radial velocity measurements, thus limiting constraints on the neutron star's mass. The observed bluer colour near the light curve minimum suggests possible non-thermal emission from intra-binary shocks, supported by the presence of an X-ray source. This discovery exemplifies the proven capability of the Fermi-LAT catalogue in identifying millisecond pulsar candidates and highlights the role of optical surveys in detecting variable sources suitable for radio follow-up.

astro-ph.HE↗