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On the Geometry of Broad-Line Regions in BL Lac Objects 被引量:1
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作者 Yun Xu Xin-Wu Cao 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2006年第6期649-654,共6页
The geometry of broad-line regions (BLRs) in active galactic nuclei (AGNs) is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolut... The geometry of broad-line regions (BLRs) in active galactic nuclei (AGNs) is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolute magnitude at R-band, MR, by using the empirical relation between MR and black hole mass Mbh. The sizes of the broad-line regions for MglI are derived from the widths of MglI lines and the black hole masses. Compared with the empirical relation between BLR size RBLR and MgII line luminosity LMglI, it is found the BLR sizes in the BL Lac objects derived in this paper are 2-3 orders of magnitude higher. If the BLR geometry of these sources is disklike, then the viewing angle between the axis and the line of sight is in the range of - 2° - 15°, which is consistent with the unification scheme. 展开更多
关键词 GALAXIES active BL Lacertae objects general-accretion accretion disks- black hole physics
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Dynamics of magnetic flux tubes and IR-variability of young stellar objects
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作者 Sergey Khaibrakhmanov Alexander Dudorov Andrey Sobolev 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2018年第8期13-20,共8页
We simulate the dynamics of slender magnetic flux tubes (MFTs) in the accretion disks of T Tauri stars. The dynamical equations of our model take into account aerodynamic and turbulent drag forces, and the radiative... We simulate the dynamics of slender magnetic flux tubes (MFTs) in the accretion disks of T Tauri stars. The dynamical equations of our model take into account aerodynamic and turbulent drag forces, and the radiative heat exchange between the MFT and ambient gas. The structure of the disk is calculated with the help of our MHD model of the accretion disks. We consider the MFTs formed at distances of 0.027 - 0.8 au from the star with various initial radii and plasma betas β0. The simulations show that MFTs with a weak magnetic field (β0 = 10) rise slowly with speeds less than the speed of sound. MFTs withβ0 = 1 form an outflowing magnetized corona above the disk. Strongly magnetized MFTs (β0 = 0.1) can cause outflows with velocities 20 - 50 km s-1. The tubes rise periodically over times from several days to several months according to our simulations. We propose that periodically rising MFTs can absorb stellar radiation and contribute to the IR-variability of young stellar objects. 展开更多
关键词 ACCRETION disks- instabilities- magnetohydrodynamics (MHD) - protoplanetary DISKS
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