Chandra discovery of activity in the quiescent nuclear black hole of NGC821

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dc.creatorBaldi, A.
dc.creatorFabbiano, G.
dc.creatorPellegrini, S.
dc.creatorSiemiginowska, A.
dc.creatorElvis, M.
dc.creatorZezas, A.
dc.creatorMcDowell, J. C.
dc.date2004-10-06
dc.date.accessioned2026-07-07T02:14:56Z
dc.date.available2026-07-07T02:14:56Z
dc.descriptionWe report the results of the Chandra ACIS-S observations of the elliptical galaxy NGC 821, which harbors a supermassive nuclear black hole (of 3.5x10^7 solar masses), but does not show sign of AGN activity. A small, 8.5" long (~1 kpc at the galaxy's distance of 23 Mpc), S-shaped, jet-like feature centered on the nucleus is detected in the 38 ksec ACIS-S integrated exposure of this region. The luminosity of this feature is L_X ~ 2.6 x 10^39 erg/s (0.3-10 keV), and its spectrum is hard (described by a power-law of Gamma = 1.8^{+0.7}_{-0.6}; or by thermal emission with kT > 2 keV). We discuss two possibilities for the origin of this feature: (1) a low-luminosity X-ray jet, or (2) a hot shocked gas. In either case, it is a clear indication of nuclear activity, detectable only in the X-ray band. Steady spherical accretion of the mass losses from the central stellar cusp within the accretion radius, when coupled to a high radiative efficiency, already provides a power source exceeding the observed radiative losses from the nuclear region.
dc.description8 pages, 3 figures, proceedings of the "6th Italian Conference on Active Galactic Nuclei", Volterra, 25-28 May 2004
dc.identifierhttps://arxiv.org/abs/astro-ph/0410169
dc.identifierhttp://arxiv.org/abs/astro-ph/0410169
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/8324
dc.subjectAstrophysics
dc.titleChandra discovery of activity in the quiescent nuclear black hole of NGC821
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