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MPINP:
Hochenergie-Astrophysik Theorie - Abteilung Hinton
Abstract:
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.