TY  - JOUR
AU  - Archer, A.
AU  - Bangale, P.
AU  - Bartkoske, J. T.
AU  - Benbow, W.
AU  - Buckley, J. H.
AU  - Chen, Y.
AU  - Christiansen, J. L.
AU  - Chromey, A. J.
AU  - Duerr, A.
AU  - Errando, M.
AU  - Godoy, M. Escobar
AU  - Feldman, S.
AU  - Feng, Q.
AU  - Foote, J.
AU  - Fortson, L.
AU  - Furniss, A.
AU  - Hanlon, W.
AU  - Hervet, O.
AU  - Hinrichs, C. E.
AU  - Holder, J.
AU  - Humensky, T. B.
AU  - Jin, W.
AU  - Johnson, M. N.
AU  - Kaaret, P.
AU  - Kertzman, M.
AU  - Kherlakian, M.
AU  - Kieda, D.
AU  - Kleiner, T. K.
AU  - Korzoun, N.
AU  - Kumar, S.
AU  - Kundu, S.
AU  - Lang, M. J.
AU  - Maier, G.
AU  - Lundy, M.
AU  - Millard, M. J.
AU  - Mooney, C. L.
AU  - Moriarty, P.
AU  - Mukherjee, R.
AU  - Ning, W.
AU  - Ong, R. A.
AU  - Pohl, M.
AU  - Pueschel, E.
AU  - Quinn, J.
AU  - Rabinowitz, P. L.
AU  - Ragan, K.
AU  - Reynolds, P. T.
AU  - Ribeiro, D.
AU  - Roache, E.
AU  - Saha, L.
AU  - Santander, M.
AU  - Sembroski, G. H.
AU  - Shang, R.
AU  - Tak, D.
AU  - Talluri, A. K.
AU  - Tucci, J. V.
AU  - Williams, D. A.
AU  - Wong, S. L.
AU  - Woo, J.
TI  - Constraints on the X-Ray and Very-high-energy Gamma-Ray Flux from Supernova Remnant W44
JO  - The astrophysical journal / Part 1
VL  - 983
IS  - 1
SN  - 0004-637X
CY  - London
PB  - Institute of Physics Publ.
M1  - PUBDB-2025-04855
M1  - arXiv:2503.09778
SP  - 73
PY  - 2025
N1  - 9 pages, 3 figures, 1 table, accepted for publication in ApJ
AB  - 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<sup>−13</sup> erg cm<sup>−2</sup> s<sup>−1</sup> 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<sup>−12</sup> erg s<sup>−1</sup> cm<sup>−2</sup> 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.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.3847/1538-4357/adc07d
UR  - https://bib-pubdb1.desy.de/record/640716
ER  -