EMISSION-LINES FROM X-RAY-HEATED ACCRETION DISKS IN LOW-MASS X-RAY BINARIES

被引:72
作者
KO, YK [1 ]
KALLMAN, TR [1 ]
机构
[1] UNIV CALIF BERKELEY,CTR EUV ASTROPHYS,BERKELEY,CA 94720
关键词
ACCRETION; ACCRETION DISKS; BINARIES; CLOSE; STARS; CORONAE; X-RAYS;
D O I
10.1086/174485
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We investigate the structure of accretion disks illuminated by X-rays from a central compact object in a binary system. X-rays can photoionize the upper atmosphere of the disk and form an accretion disk corona (ADC) where emission lines can form. We construct a model to calculate the vertical structure and the emission spectrum of the ADC with parameters appropriate to low-mass X-ray binaries. These models are made by nonlocal thermodynamic equilibrium calculations of ion and level populations and include a large number of atomic processes for 10 cosmically abundant elements. Transfer of radiation is treated by using the escape probability formalism. The vertical temperature profile of the ADC consists of a Compton-heated region and a mid-T zone where the temperature is approximately 10(6) K. A thermal instability occurs close to the disk photosphere and causes the temperature of the ADC to drop abruptly from 10(6) K to several times 10(4) K. The emission spectrum in the optical, ultraviolet, extreme ultraviolet, and X-ray range is discussed and compared with the observations.
引用
收藏
页码:273 / 301
页数:29
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