MHD SIMULATIONS OF ACCRETION ONTO Sgr A*: QUIESCENT FLUCTUATIONS, OUTBURSTS, AND QUASIPERIODICITY

被引:51
作者
Chan, Chi-Kwan [1 ,2 ]
Liu, Siming [3 ]
Fryer, Christopher L. [2 ,4 ]
Psaltis, Dimitrios [2 ,5 ]
Oezel, Feryal [2 ,5 ]
Rockefeller, Gabriel [4 ]
Melia, Fulvio [2 ,5 ]
机构
[1] Harvard Smithsonian Ctr Astrophys, Inst Theory & Computat, Cambridge, MA 02138 USA
[2] Univ Arizona, Dept Phys, Tucson, AZ 85721 USA
[3] Univ Glasgow, Dept Phys & Astron, Glasgow G12 8QQ, Lanark, Scotland
[4] Los Alamos Natl Lab, Computat Comp Sci Div, Los Alamos, NM 87545 USA
[5] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
基金
美国国家科学基金会;
关键词
accretion; accretion disks; black hole physics; Galaxy: center; instabilities; MHD; relativity; 3-DIMENSIONAL MAGNETOHYDRODYNAMIC SIMULATIONS; SUPERMASSIVE BLACK-HOLE; X-RAY FLARE; ROSSBY-WAVE INSTABILITY; SAGITTARIUS-A; GALACTIC-CENTER; SPECTRAL METHODS; ELECTRON ACCELERATION; HYDRODYNAMIC DISKS; ANGULAR-MOMENTUM;
D O I
10.1088/0004-637X/701/1/521
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
High-resolution observations of Sgr A* have revealed a wide variety of phenomena, ranging from intense rapid flares to quasi-periodic oscillations (QPOs), making this object an ideal system to study the properties of low luminosity accreting black holes. In this paper, we use a pseudospectral algorithm to construct and evolve a three-dimensional magnetohydrodynamic (MHD) model of the accretion disk in Sgr A*. Assuming a hybrid thermal nonthermal emission scheme and calibrating the parameters by observations, we show that the MHD turbulence in the environment of Sgr A* can by itself only produce factor two fluctuations in luminosity. These fluctuations cannot explain the magnitude of flares observed in this system. However, we also demonstrate that external forcing of the accretion disk, which may be generated by the "clumpy material" raining down onto the disk from the large-scale flow, do produce outbursts qualitatively similar to those observed by XMM-Newton in X-rays and by ground- based facilities in the near infrared. Strong, but short-term QPOs emerge naturally in the simulated light curves. We attribute these to nonaxisymmetric density perturbations that emerge as the disk evolves back toward its quiescent state.
引用
收藏
页码:521 / 534
页数:14
相关论文
共 74 条
[1]  
Abramowicz MA, 1996, ASTRON ASTROPHYS, V313, P334
[2]   The variability of accretion on to Schwarzschild black holes from turbulent magnetized discs [J].
Armitage, PJ ;
Reynolds, CS .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2003, 341 (03) :1041-1050
[3]   Quasi-periodic oscillations from magnetorotational turbulence [J].
Arras, Phil ;
Blaes, Omer ;
Turner, Neal J. .
ASTROPHYSICAL JOURNAL, 2006, 645 (01) :L65-L68
[4]   X-ray flares reveal mass and angular momentum of the Galactic Center black hole [J].
Aschenbach, B ;
Grosso, N ;
Porquet, D ;
Predehl, P .
ASTRONOMY & ASTROPHYSICS, 2004, 417 (01) :71-78
[5]   Chandra X-ray spectroscopic imaging of Sagittarius A* and the central parsec of the Galaxy [J].
Baganoff, FK ;
Maeda, Y ;
Morris, M ;
Bautz, MW ;
Brandt, WN ;
Cui, W ;
Doty, JP ;
Feigelson, ED ;
Garmire, GP ;
Pravdo, SH ;
Ricker, GR ;
Townsley, LK .
ASTROPHYSICAL JOURNAL, 2003, 591 (02) :891-915
[6]   Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre [J].
Baganoff, FK ;
Bautz, MW ;
Brandt, WN ;
Chartas, G ;
Feigelson, ED ;
Garmire, GP ;
Maeda, Y ;
Morris, M ;
Ricker, GR ;
Townsley, LK ;
Walter, F .
NATURE, 2001, 413 (6851) :45-48
[7]   A POWERFUL LOCAL SHEAR INSTABILITY IN WEAKLY MAGNETIZED DISKS .1. LINEAR-ANALYSIS [J].
BALBUS, SA ;
HAWLEY, JF .
ASTROPHYSICAL JOURNAL, 1991, 376 (01) :214-222
[8]  
BALLANTYNE DR, 2007, APJ, V663, P17
[9]   Periodic modulations in an X-ray flare from Sagittarius A* [J].
Belanger, G. ;
Terrier, R. ;
de Jager, O. C. ;
Goldwurm, A. ;
Melia, F. .
GALACTIC CENTER WORKSHOP 2006: FROM THE CENTER OF THE MILKY WAY TO NEARBY LOW-LUMINOSITY GALACTIC NUCLEI, 2006, 54 :420-+
[10]   Correlation between flux and spectral index during flares in Sagittarius A [J].
Bittner, Jonathan M. ;
Liu, Siming ;
Fryer, Christopher L. ;
Petrosian, Vahe .
ASTROPHYSICAL JOURNAL, 2007, 661 (02) :863-874