J/A+A/706/A8ivo://CDS.VizieR/J/A+A/706/A8CDSAcharyya A.Aharonian F.Ashkar H.Backes M.Batzofin R.Berge D.,Bernloehr K.Boettcher M.Boisson C.Bolmont J.Brun F.Bruno B.,Burger-Scheidlin C.Bylund T.Casanova S.Celic J.Cerruti M.Chen A.,Chernyakova M.Chibueze J.O.Chibueze O.Cornejo B.Cotter G.,de Assis Scarpin J.de Bony de Lavergne M.de Naurois M.,de Ona Wilhelmi E.Delgado Giler A.G.Devin J.Djannati-Atai A.,Dmytriiev A.Egberts K.Egg K.Ernenwein J.-P.Escanuela Nieves C.,Fauverge P.Feijen K.Filipovic M.D.Fontaine G.Funk S.Gabici S.,Gallant Y.A.Glicenstein J.F.Glombitza J.Goswami P.Grondin M.-H.,Heckmann L.Hess B.Hinton J.A.Hofmann W.Holch T.L.Holler M.,Jamrozy M.Jankowsky F.Jardin-Blicq A.Jaroschewski I.Jimeno D.,Jung-Richardt I.Katarzynski K.Kerszberg D.Khelifi B.Komin N.,Kosack K.Kostunin D.Lang R.G.Lazarevic S.Lemiere A.,Lemoine-Goumard M.Lenain J.-P.Liniewicz P.Luashvili A.Mackey J.,Malyshev D.Marandon V.Mayer M.G.F.Mehta A.Mitchell A.M.W.,Moderski R.Mohrmann L.Montanari A.Moulin E.Niemiec J.,Olivera-Nieto L.Moghadam M.O.Panny S.Parsons R.D.Pensec U.,Pichard P.Preis T.Puehlhofer G.Punch M.Quirrenbach A.Reimer A.,Reimer O.Reis I.Remy Q.Ren H.X.Reville B.Rieger F.,Roellinghoff G.Rowell G.Rudak B.Sabri K.Safi-Harb S.Sahakian V.,Santangelo A.Sasaki M.Schuessler F.Shapopi J.N.S.Si Said W.Sol H.,Stawarz L.Steinmassl S.Tanaka T.Taylor A.M.Taylor G.L.Terrier R.,Tian Y.Timmermans A.Tsirou M.Tsuji N.Unbehaun T.van Eldik C.,Vecchi M.Venter C.Vink J.Voitsekhovskyi V.Wagner S.J.,Wierzcholska A.Zacharias M.Zdziarski A.A.Zech A.Zhong W.,H.E.S.S.CollaborationTakekawa S.2026-03-20T08:06:18Z2026-01-27T08:35:52ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frquasarsgamma-ray-astronomyMicroquasars have emerged as promising candidates to explain the cosmic-ray flux at PeV energies. LHAASO observations reveal V4641 Sgr as the most extreme example so far, with a gamma-ray spectrum extending up to 800~TeV, requiring multi-PeV energy particles. The TeV emission is highly extended, challenging expectations given the reported low-inclination angle of the V4641 Sgr jets. We aim to spatially and spectrally resolve the gamma-ray emission from V4641 Sgr and investigate particle acceleration in the system. Using ~100h of H.E.S.S. data we perform a spectro-morphological study of the gamma-ray emission around V4641 Sgr. We employ HI and dedicated CO observations of the region to infer the presence of target material for cosmic-ray interactions. Multi-TeV emission around V4641 Sgr is detected with high significance. The emission region is elongated with major and minor axes: 0.34{deg}+/-0.04_stat_+/-0.01_syst_ and 0.06{deg}+/-0.01_stat_+/-0.01_syst_, respectively. A power-law spectrum with index ~1.8 is found and, together with results by other gamma-ray instruments, reveals for the first time a spectral energy distribution (SED) peaking at energies of ~100TeV. We find indications (3{sigma}) of a two-component morphology, with indistinguishable spectral properties. The position of V4641 Sgr is inconsistent with both the best-fit position of the single-component model and the dip between the two components. We find no significant evidence of energy-dependent morphology. No dense gas is found at any distance towards V4641 Sgr, placing an upper limit of n_gas_<~0.2cm^-3^ within the gamma-ray emission region. The peak of the SED at ~100TeV identifies V4641 Sgr as a candidate cosmic-ray accelerator beyond the Knee. However, the absence of dense target gas places stringent energetic constraints on hadronic interpretations. The H.E.S.S. measurement requires an unusually hard (~1.5) spectral index for protons. A leptonic scenario faces fewer obstacles, provided particle transport is fast enough to avoid losses and reproduce the observed energy-independent morphology, though the absence of bright X-ray emission across the gamma-ray emission region requires a magnetic field strength <~3muG. Our findings favour a leptonic origin of the gamma-ray emission. This conclusion does not exclude hadron acceleration in the V4641 Sgr system.2026A&A...706A...8Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/706/A8CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/706/A8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/706/A8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/706/A8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/706/A8https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/706/A8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/706/A8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/706/A8/list (Information of fits map)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/706/A8/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/706/A8/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/706/A8/list?GETtext/xml+votable180.050000true274.8401406-25.40717930.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/706/A86/28798https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/706/A8?format=asciiGamma-raydefaultJ/A+A/706/A8/listInformation of fits maprecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGLONGalactic longitude of center (J2000)degpos.galactic.lonGLATGalactic latitude of center (J2000)degpos.galactic.latNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.raindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decindexed