A possible disk mechanism for the 23d QPO in Mkn~501

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dc.creatorFan, J. H.
dc.creatorRieger, F. M.
dc.creatorHua, T. X.
dc.creatorJoshi, U. C.
dc.creatorLi, J.
dc.creatorWang, Y. X.
dc.creatorZhou, J. L.
dc.creatorYuan, Y. H.
dc.creatorSu, J. B.
dc.creatorZhang, Y. W.
dc.date2007-10-06
dc.date.accessioned2026-07-07T11:19:48Z
dc.date.available2026-07-07T11:19:48Z
dc.descriptionOptically thin two-temperature accretion flows may be thermally and viscously stable, but acoustically unstable. Here we propose that the O-mode instability of a cooling-dominated optically thin two-temperature inner disk may explain the 23-day quasi-periodic oscillation (QPO) period observed in the TeV and X-ray light curves of Mkn~501 during its 1997 high state. In our model the relativistic jet electrons Compton upscatter the disk soft X-ray photons to TeV energies, so that the instability-driven X-ray periodicity will lead to a corresponding quasi-periodicity in the TeV light curve and produce correlated variability. We analyse the dependence of the instability-driven quasi-periodicity on the mass (M) of the central black hole, the accretion rate ($\rm{\dot{M}}$) and the viscous parameter ($α$) of the inner disk. We show that in the case of Mkn~501 the first two parameters are constrained by various observational results, so that for the instability occurring within a two-temperature disk where $α=0.05-1.0$, the quasi-period is expected to lie within the range of 8 to 100 days, as indeed the case. In particular, for the observed 23-day QPO period our model implies a viscosity coefficient $α\leq 0.28$, a sub-Eddington accretion rate $\dot{M} \simeq 0.02 \dot{M}_{\rm Edd}$ and a transition radius to the outer standard disk of $r_0 \sim 60 r_g$, and predicts a period variation $δP/P \sim 0.23$ due to the motion of the instability region.
dc.description18 pages, 1 figure, accepted by APh
dc.identifierhttps://arxiv.org/abs/0710.1340
dc.identifierhttp://arxiv.org/abs/0710.1340
dc.identifierAstropart.Phys.28:508-515,2008
dc.identifierdoi:10.1016/j.astropartphys.2007.08.011
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/193812
dc.subjectAstrophysics
dc.titleA possible disk mechanism for the 23d QPO in Mkn~501
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