A large high-energy gamma-ray flare from the blazar 3C 273

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dc.creatorCollmar, W.
dc.creatorReimer, O.
dc.creatorBennett, K.
dc.creatorBloemen, H.
dc.creatorHermsen, W.
dc.creatorLichti, G. G.
dc.creatorRyan, J.
dc.creatorSchoenfelder, V.
dc.creatorSteinle, H.
dc.creatorWilliams, O. R.
dc.creatorBoettcher, M.
dc.date2000-01-12
dc.date.accessioned2026-07-07T01:51:41Z
dc.date.available2026-07-07T01:51:41Z
dc.descriptionThe Compton Gamma-Ray Observatory (CGRO) experiments EGRET and COMPTEL observed the Virgo sky region continuously for 7 weeks between December 10, 1996 and January 28, 1997. The prominent quasar 3C~273 was found to be the brightest source in gamma-rays and was significantly detected by EGRET and COMPTEL. The EGRET experiment observed a time-variable flux at energies above 100 MeV, which reached in a 2-week flaring period (December 30, 1996 to January 14, 1997) its highest flux level observed during the CGRO-era. COMPTEL, however, does not observe obvious time variability at energies below ~30 MeV contemporaneous to EGRET. In particular, no flare was observed, indicating that this outburst is solely a high-energy (>100 MeV) phenomenon. The energy spectrum between 3 MeV and 10 GeV is well represented by a simple power-law model. Below 3 MeV a spectral turnover is indicated. Performing spectral analysis for different time periods, we found evidence for a spectral hardening during the flaring period, which is consistent with the flare occurring mainly at the higher energies and with its absence at COMPTEL energies of a few MeV. This may be interpreted as an indication that the emission in the EGRET energy range is dominated by a different radiation mechanism than the MeV emission. We argue that the most likely mechanism for the high-energy flare is inverse-Compton scattering of reprocessed accretion-disk radiation.
dc.description9 pages including 7 figures, accepted for publication in A&A
dc.identifierhttps://arxiv.org/abs/astro-ph/0001204
dc.identifierhttp://arxiv.org/abs/astro-ph/0001204
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/377
dc.subjectAstrophysics
dc.titleA large high-energy gamma-ray flare from the blazar 3C 273
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