Journal Article

PUBDB-2025-04855

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Constraints on the X-Ray and Very-high-energy Gamma-Ray Flux from Supernova Remnant W44

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. ; Feldman, S. ; Feng, Q. ; Foote, J. ; 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.DESY* ; Korzoun, N. ; Kumar, S. ; Kundu, S. ; Lang, M. J. ; Maier, G.DESY* ; Lundy, M. ; Millard, M. J. (Corresponding author) ; Mooney, C. L. ; Moriarty, P. ; Mukherjee, R. ; Ning, W. ; Ong, R. A. ; Pohl, M.DESY* ; Pueschel, E.DESY* ; Quinn, J. ; Rabinowitz, P. L. ; Ragan, K. ; Reynolds, P. T. ; Ribeiro, D. ; Roache, E. ; Saha, L. ; Santander, M. ; Sembroski, G. H. ; Shang, R. ; Tak, D. ; Talluri, A. K. ; Tucci, J. V. ; Williams, D. A. ; Wong, S. L. ; Woo, J.

2025
Institute of Physics Publ. London

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Please use a persistent id in citations: doi:10.3847/1538-4357/adc07d  doi:10.3204/PUBDB-2025-04855

Report No.: arXiv:2503.09778

Abstract: Observations of GeV gamma-ray emission from the well-studied mixed-morphology supernova remnant (SNR) W44 by Fermi-Large Area Telescope and AGILE imply that it is a site of significant cosmic-ray acceleration. The spectral energy distribution (SED) derived from the GeV data suggests that the gamma-ray emission likely originates from the decay of neutral pions generated by cosmic-ray interactions. It is essential to measure the SED of W44 in the X-ray and very-high-energy (VHE) gamma-ray bands to verify the hadronic origin of the emission and to gauge the potential contributions from leptonic emission. We report an upper limit of the nonthermal X-ray flux from W44 of 5 × 10$^{−13}$ erg cm$^{−2}$ s$^{−1}$ in the 0.5–8.0 keV band based on ∼300 ks of XMM-Newton observations. The X-ray upper limit is consistent with previously estimated hadronic models, but in tension with the leptonic models. We estimate the VHE flux upper limit of ∼1.2 × 10$^{−12}$ erg s$^{−1}$ cm$^{−2}$ in the 0.5–5.0 TeV range from W44 using data from the Very Energetic Radiation Imaging Telescope Array System. Our nondetection of W44 at VHE wavelengths is in agreement with observations from other imaging atmospheric Cherenkov telescopes and is perhaps consistent with the evolutionary stage of the SNR.

Note: 9 pages, 3 figures, 1 table, accepted for publication in ApJ

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Contributing Institute(s):

1. VERITAS (Z_VER)

Research Program(s):

1. 613 - Matter and Radiation from the Universe (POF4-613) (POF4-613)

Experiment(s):

1. Very Energetic Radiation Imaging Telescope Array System

Appears in the scientific report 2025

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Linked articles:

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Preprint Archer, A. ; Bangale, P. ; Bartkoske, J. T. ; et al
Constraints on the X-Ray and Very-high-energy Gamma-Ray Flux from Supernova Remnant W44
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