Multiwavelength observation of a candidate pulsar halo LHAASO J0621+3755 and the first X-ray detection of PSR J0622+3749

Adams, C. B.; Rabinowitz, P. L.; Quinn, J.; Donato, F.; Chen, Y.; Kieda, D.; Holder, J.; Kertzman, M.; Kaaret, P.; Tak, D.; Kleiner, T. K.; Woo, J.; Lang, M. J.; VERITAS Collaboration; Jin, W.; Millis, J.; Mooney, C. L.; Kumar, S.; Mukherjee, R.; Pandey, A.; Lundy, M.; Valverde, J.; Ribeiro, D.; Mori, K.; Hanlon, W.; Saha, L.; Ragan, K.; Godoy, M. Escobar; Fortson, L.; Sembroski, G. H.; Sadeh, I.; Furniss, A.; Kherlakian, M.; Rizk, L.; Archer, A.; Feng, Q.; Millard, M. J.; Duerr, A.; Hervet, O.; Chromey, A. J.; Williams, D. A.; Feldman, S.; Christiansen, J. L.; Roache, E.; Talluri, A. K.; Falcone, A.; Benbow, W.; Errando, M.; Tsuji, N.; Safi-Harb, S.; Maier, G.; XMM-Newton Collaboration; Hailey, C. J.; Tucci, J. V.; Zhang, S.; Kundu, S.; Di Mauro, M.; Reynolds, P. T.; Manconi, S.; Humensky, T. B.; Kwong, J.; Moriarty, P.; Krennrich, F.; Splettstoesser, M.; Buckley, J. H.; Ning, W.; Shang, R.; Bangale, P.; Bartkoske, J. T.; Pohl, M.; Wong, S. L.; Hinrichs, C. E.; Johnson, M. N.; Ong, R. A.; Pueschel, E.; Korzoun, N.

Preprint

PUBDB-2025-04856

Multiwavelength observation of a candidate pulsar halo LHAASO J0621+3755 and the first X-ray detection of PSR J0622+3749

Adams, C. B. ; Archer, A. ; Bangale, P. ; Bartkoske, J. T. ; Benbow, W. ; Buckley, J. H. ; Chen, Y. ; Christiansen, J. L. ; Chromey, A. J. ; Duerr, A. ; Errando, M. ; Godoy, M. E. ; Falcone, A. ; Feldman, S. ; Feng, Q. ; Fortson, L. ; Furniss, A. ; Hanlon, W. ; Hervet, O. ; Hinrichs, C. E. ; Holder, J. ; Humensky, T. B. ; Jin, W. ; Johnson, M. N. ; Kaaret, P. ; Kertzman, M. ; Kherlakian, M. ; Kieda, D. ; Kleiner, T. K. ; Korzoun, N. ; Krennrich, F. ; Kumar, S. ; Kundu, S. ; Lang, M. J. ; Lundy, M. ; Maier, G. ; Millard, M. J. ; Millis, J. ; Mooney, C. L. ; Moriarty, P. ; Mukherjee, R. ; Ning, W. ; Ong, R. A. ; Pandey, A. ; Pohl, M. ; Pueschel, E. ; Quinn, J. ; Rabinowitz, P. L. ; Ragan, K. ; Reynolds, P. T. ; Ribeiro, D. ; Rizk, L. ; Roache, E. ; Sadeh, I. ; Saha, L. ; Sembroski, G. H. ; Shang, R. ; Splettstoesser, M. ; Tak, D. ; Talluri, A. K. ; Tucci, J. V. ; Valverde, J. ; Williams, D. A. ; Wong, S. L. ; Woo, J. ; Kwong, J. ; Mori, K. ; Hailey, C. J. ; Safi-Harb, S. ; Zhang, S. ; Tsuji, N. ; Manconi, S. ; Donato, F. ; Di Mauro, M. ; VERITAS Collaboration (Collaboration author) ; XMM-Newton Collaboration (Collaboration author)

2025

[10.3204/PUBDB-2025-04856]

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Please use a persistent id in citations: doi:10.3204/PUBDB-2025-04856

Report No.: arXiv:2504.02185

Abstract: 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

Keyword(s): High Energy Astrophysical Phenomena (astro-ph.HE) ; Instrumentation and Methods for Astrophysics (astro-ph.IM) ; FOS: Physical sciences

Note: Accepted for publication in ApJ. 28 pages, 19 figures

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