发射线AM CVn系统GP Com和V396 Hya的UVES和X射线光谱
UVES and X-Shooter spectroscopy of the emission line AM CVn systems GP Com and V396 Hya
摘要：
我们目前的时间分辨光谱的AM CVn型二进制GP Com和V396 Hya获得VLT/X-射手和VLT/UVES。我们完全解决了狭窄的中心组成部分的主导氦线，并确定径向速度半振幅的$K_{\rm spike} = 11.7\pm0.3$公里的$^{-1}$的GP Com和$K_{\rm spike} = 5.8\pm0.3$公里的V396 Hya的$^{-1}$。窄的中心分量的平均速度显示从线到线的变化。相比，包括斯塔克加宽的计算线的轮廓，我们能够解释的位移，和禁止氦线的外观，通过额外的斯塔克加宽的电子密度$n_e\simeq 5\times 10^{15}$ cm $^{-3}$的氦等离子体中的发射。在两个系统中均检测到超过$30$氮和超过$10$氖发射线。此外，PDMATHAMT氮吸收线仅见于GP Com。这些谱线的径向速度变化与中心氦辐射分量具有相同的相位和速度幅值。中心氦发射分量的半振幅很小，与GP Com吸收分量的相位和振幅一致，以及测得的斯塔克效应表明，中心氦发射分量，即所谓的中心尖峰，与吸积白矮星上的一个起源一致。我们使用亮点和中心尖峰的动力学来约束两个系统的二元参数，并找到GP Com的$9.6$-$42.8$ M $_{\rm Jupiter}$和V396 Hya的$6.1$ - $30.5$ M $_{\rm Jupiter}$的供体质量。我们发现一个上限的旋转速度的吸积体的$v_{\rm rot}<46$公里的$^{-1}$的GP Com和$v_{\rm rot}<59$公里的$^{-1}$的V396 Hya排除了快速旋转吸积体在这两个系统。
英文摘要：
We present time-resolved spectroscopy of the AM CVn-type binaries GP Com and V396 Hya obtained with VLT/X-Shooter and VLT/UVES. We fully resolve the narrow central components of the dominant helium lines and determine radial velocity semi-amplitudes of $K_{\rm spike} = 11.7\pm0.3$ km s$^{-1}$ for GP Com and $K_{\rm spike} = 5.8\pm0.3$ km s$^{-1}$ for V396 Hya. The mean velocities of the narrow central components show variations from line to line. Compared to calculated line profiles that include Stark broadening we are able to explain the displacements, and the appearance of forbidden helium lines, by additional Stark broadening of emission in a helium plasma with an electron density $n_e\simeq 5\times 10^{15}$ cm$^{-3}$. More than $30$ nitrogen and more than $10$ neon lines emission lines were detected in both systems. Additionally, $20$ nitrogen absorption lines are only seen in GP Com. The radial velocity variations of these lines show the same phase and velocity amplitude as the central helium emission components. The small semi-amplitude of the central helium emission component, the consistency of phase and amplitude with the absorption components in GP Com as well as the measured Stark effect shows that the central helium emission component, the so-called central-spike, is consistent with an origin on the accreting white dwarf. We use the dynamics of the bright spot and the central spike to constrain the binary parameters for both systems and find a donor mass of $9.6$ - $42.8$ M$_{\rm Jupiter}$ for GP Com and $6.1$ - $30.5$ M$_{\rm Jupiter}$ for V396 Hya. We find an upper limit for the rotational velocity of the accretor of $v_{\rm rot}<46$ km s$^{-1}$ for GP Com and $v_{\rm rot}<59$ km s$^{-1}$ for V396 Hya which excludes a fast rotating accretor in both systems.
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