Discovery of Radio Pulsation from the Radio-quiet Gamma-ray Pulsar PSR J2238+5903 with Deep FAST Observations

ATel #17756; Jianli Zhang(NAOC, CAS), Hui Zhu(NAOC, CAS), Guanhong Lin(NAOC, CAS), DeJia Zhou(NAOC, CAS), Songzhan Chen(IHEP, CAS), Wen-Jun Huang(GZU), Zi-Wei Ou(SYSU), P. H. Thomas Tam(SYSU), Sha Wu(IHEP, CAS), Qiang Yuan(PMO, CAS), Yi Zhang(PMO, CAS)
on 17 Apr 2026; 04:13 UT
Credential Certification: Jianli Zhang (jlzhang@bao.ac.cn)

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We report the detection of radio pulsations from the radio-quiet gamma-ray pulsar PSR J2238+5903 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST; [1]). This is the first radio detection of this source, establishing a critical multi-wavelength connection between its gamma-ray and very-high-energy (VHE) gamma-ray emission.
PSR J2238+5903 is spatially associated with 1LHAASO J2238+5900 [2], a VHE gamma-ray source in the first LHAASO catalog. This source is located at RA = 22:38:28.15, Dec = +59:03:44.8 (J2000), with a spin period of P = 0.16274 s derived from gamma-ray observations [3].
The FAST observations were carried out on 2021 August 14 in the L-band (1.0-1.5 GHz) with the 19-beam receiver, with a total on-source integration time of 3000 s. Data were processed using the PRESTO pipeline [4]. A significant periodic signal was detected, fully consistent with the gamma-ray ephemeris, at an optimal dispersion measure of DM = 248.0 pc cm⁻³. The distance to the source is estimated to be ∼7 kpc from the YMW16 Galactic electron density model.
This detection confirms that PSR J2238+5903 is a faint but detectable radio pulsar despite being classified as radio-quiet in gamma-ray studies. Its coincidence with a VHE source provides a unique key to understanding particle acceleration, pulsar wind nebulae, and the origin of VHE gamma-rays associated with pulsars.
References
1. Nan, R., et al. 2011, Int. J. Mod. Phys. D, 20, 989
2. Cao, Z., et al. 2024, ApJS, 271, 25
3. Smith, D. A., et al. 2023, ApJ, 958, 191
4. Ransom, S. M. 2001, ASP Conf. Ser. 245, 551