%0 Electronic Article
%A Adams, C. B.
%A Archer, A.
%A Bangale, P.
%A Bartkoske, J. T.
%A Benbow, W.
%A Buckley, J. H.
%A Chen, Y.
%A Christiansen, J. L.
%A Chromey, A. J.
%A Duerr, A.
%A Errando, M.
%A Godoy, M. Escobar
%A Falcone, A.
%A Feldman, S.
%A Feng, Q.
%A Fortson, L.
%A Furniss, A.
%A Hanlon, W.
%A Hervet, O.
%A Hinrichs, C. E.
%A Holder, J.
%A Humensky, T. B.
%A Jin, W.
%A Johnson, M. N.
%A Kaaret, P.
%A Kertzman, M.
%A Kherlakian, M.
%A Kieda, D.
%A Kleiner, T. K.
%A Korzoun, N.
%A Krennrich, F.
%A Kumar, S.
%A Kundu, S.
%A Lang, M. J.
%A Lundy, M.
%A Maier, G.
%A Millard, M. J.
%A Millis, J.
%A Mooney, C. L.
%A Moriarty, P.
%A Mukherjee, R.
%A Ning, W.
%A Ong, R. A.
%A Pandey, A.
%A Pohl, M.
%A Pueschel, E.
%A Quinn, J.
%A Rabinowitz, P. L.
%A Ragan, K.
%A Reynolds, P. T.
%A Ribeiro, D.
%A Rizk, L.
%A Roache, E.
%A Sadeh, I.
%A Saha, L.
%A Sembroski, G. H.
%A Shang, R.
%A Splettstoesser, M.
%A Tak, D.
%A Talluri, A. K.
%A Tucci, J. V.
%A Valverde, J.
%A Williams, D. A.
%A Wong, S. L.
%A Woo, J.
%A Kwong, J.
%A Mori, K.
%A Hailey, C. J.
%A Safi-Harb, S.
%A Zhang, S.
%A Tsuji, N.
%A Manconi, S.
%A Donato, F.
%A Di Mauro, M.
%T Multiwavelength observation of a candidate pulsar halo LHAASO J0621+3755 and the first X-ray detection of PSR J0622+3749
%N arXiv:2504.02185
%M PUBDB-2025-04856
%M arXiv:2504.02185
%D 2025
%Z Accepted for publication in ApJ. 28 pages, 19 figures
%X Pulsar halos are regions around middle-aged pulsars extending out to tens of parsecs. The large extent of the halos and well-defined central cosmic-ray accelerators make this new class of Galactic sources an ideal laboratory for studying cosmic-ray transport. LHAASO J0621+3755 is a candidate pulsar halo associated with the middle-aged gamma-ray pulsar PSR J0622+3749. We observed LHAASO J0621+3755 with VERITAS and XMM-Newton in the TeV and X-ray bands, respectively. For this work, we developed a novel background estimation technique for imaging atmospheric Cherenkov telescope observations of such extended sources. No halo emission was detected with VERITAS (0.3-10 TeV) or XMM-Newton (2-7 keV) within 1 degree and 10 arcmin around PSR J0622+3749, respectively. Combined with the LHAASO-KM2A and Fermi-LAT data, VERITAS flux upper limits establish a spectral break at  1-10 TeV, a unique feature compared with Geminga, the most studied pulsar halo. We model the gamma-ray spectrum and LHAASO-KM2A surface brightness as inverse Compton emission and find suppressed diffusion around the pulsar, similar to Geminga. A smaller diffusion suppression zone and harder electron injection spectrum than Geminga are necessary to reproduce the spectral cutoff. A magnetic field
%K High Energy Astrophysical Phenomena (astro-ph.HE) (Other)
%K Instrumentation and Methods for Astrophysics (astro-ph.IM) (Other)
%K FOS: Physical sciences (Other)
%F PUB:(DE-HGF)25
%9 Preprint
%R 10.3204/PUBDB-2025-04856
%U https://bib-pubdb1.desy.de/record/640717