Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622+3749 Observed by LHAASO-KM2A

We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622 + 3749 with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of 8.2 sigma for E > 25 TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) = (95.47 degrees +/- 0.11 degrees, 37.92 degrees +/- 0.09 degrees), and the extension is 0.40 degrees +/- 0.07 degrees. The energy spectrum can be described by a power-law spectrum with an index of -2.92 +/- 0.17(st)(at) +/- 0.02(sys). No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations arc consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of similar to 160 TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.

Automated summary

A study reported the discovery of an extended very-high-energy gamma-ray source around the middle-aged pulsar PSR J0622 + 3749 with the LHAASO. The energy spectrum follows a power-law distribution, and the source is consistent with a scenario where VHE electrons escape from the pulsar, diffuse in the interstellar medium, and scatter the interstellar radiation field.