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arXiv 0908.2094astro-ph.SRastro-ph.HE
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哈勃空间望远镜对BK Lyn、V751 Cygni和V380 Oph三个特殊类新星变星的STIS光谱研究

Hubble Space Telescope STIS Spectroscopy of Three Peculiar Nova-Like Variables: BK Lyn, V751 Cygni and V380 Oph

Robert Zellem, Nicholas Hollon, Ronald-Louis Ballouz, Edward M. Sion, Patrick Godon, Boris T. Gänsicke, Knox Long

摘要:

我们获得了三个类新星变星的哈勃STIS光谱:V751 Cygni,V380 Oph,以及-唯一被证实的类新星变星已知低于周期间隙- BK Lyn。在所有三个系统中,光谱都是在高光学亮度状态下拍摄的,并且发光的吸积盘主导了它们的远紫外(FUV)光。我们通过应用\citet{Knigge2006}的红外光度法评估了距离的下限。在所施加的限制,由鲜为人知的系统参数(如倾角,白矮星的质量,和稳态吸积盘的适用性),我们得到了满意的适合BK林恩使用光学厚吸积盘模型与吸积率$\dot{M} = 1\times10^{-9} M_{\odot}$年$^{-1}$的$M_{wd} = 1.2 M_{\odot}$和$\dot{M} = 1 \times 10^{-8} M_{\odot}$年$^{-1}$为$M_{wd} = 0.4 M_{\odot}$的白矮星质量。然而,对于VY Scl型新星类变量V751天鹅座和SW性星V380 Oph,我们无法获得令人满意的合成光谱拟合的高状态FUV光谱使用光学厚稳态吸积盘模型。FUV光谱信息的缺乏到莱曼极限阻碍了在这些类新星系统的高状态期间关于吸积白矮星的信息的提取。

英文摘要:

We obtained Hubble STIS spectra of three nova-like variables: V751 Cygni, V380 Oph, and - the only confirmed nova-like variable known to be below the period gap - BK Lyn. In all three systems, the spectra were taken during high optical brightness state, and a luminous accretion disk dominates their far ultraviolet (FUV) light. We assessed a lower limit of the distances by applying the infrared photometric method of \citet{Knigge2006}. Within the limitations imposed by the poorly known system parameters (such as the inclination, white dwarf mass, and the applicability of steady state accretion disks) we obtained satisfactory fits to BK Lyn using optically thick accretion disk models with an accretion rate of $\dot{M} = 1\times10^{-9} M_{\odot}$ yr$^{-1}$ for a white dwarf mass of $M_{wd} = 1.2 M_{\odot}$ and $\dot{M} = 1 \times 10^{-8} M_{\odot}$ yr$^{-1}$ for $M_{wd} = 0.4 M_{\odot}$. However, for the VY Scl-type nova-like variable V751 Cygni and for the SW Sex star V380 Oph, we are unable to obtain satisfactory synthetic spectral fits to the high state FUV spectra using optically thick steady state accretion disk models. The lack of FUV spectra information down to the Lyman limit hinders the extraction of information about the accreting white dwarf during the high states of these nova-like systems.

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