球状星团M 22中的CV1：通过X射线观测和光谱学确认其性质
CV1 in the globular cluster M 22: confirming its nature through X-ray observations and optical spectroscopy
摘要：
上下文在球状星团中观测到的激变变星与在野外观测到的相比，似乎显示出爆发的缺乏。人们提出了许多解释，包括低质量转移率和/或中等磁场意味着白矮星的质量高于在磁场中观察到的平均质量。或者，这种明显的缺乏可能只是一种选择偏见。目标。我们研究了球状星团M22中一个新的激变变星CV 1的多波长数据，试图限制它的周期和磁性，目的是了解球状星团激变变星是否与野外观测到的激变变星有本质的不同。方法.我们使用钱德拉ACIS-S的亚弧秒分辨率来识别与CV1对应的X射线，并分析X射线光谱，以确定最能描述该源的光谱模型。我们还研究了激变变星典型发射线的低分辨率光谱。在每个单独的光谱中互相关联的H α线也允许我们搜索轨道运动。结果X射线光谱揭示了一个最适合高温韧致辐射模型的源，X射线未吸收光度为1.8e32 erg/s（0.3-8.0 keV），这是典型的激变变星。光学光谱显示巴耳末发射线，这是吸积盘的指示。在Halpha发射线的潜在径向速度检测和CV1的周期提出。结论.这些观察结果支持CV鉴定。径向速度测量表明，CV1可能有一个约7小时的轨道周期，但CV1的进一步更高分辨率的光谱学需要明确地建立这个CV的性质和它的轨道周期。
英文摘要：
Context. Observations of cataclysmic variables in globular clusters appear to show a dearth of outbursts compared to those observed in the field. A number of explanations have been proposed, including low mass-transfer rates and/or moderate magnetic fields implying higher mass white dwarfs than the average observed in the field. Alternatively this apparent dearth may be simply a selection bias. Aims. We examine multi-wavelength data of a new cataclysmic variable, CV1, in the globular cluster M 22 to try to constrain its period and magnetic nature, with an aim at understanding whether globular cluster cataclysmic variables are intrinsically different from those observed in the field. Methods. We use the sub-arcsecond resolution of the Chandra ACIS-S to identify the X-ray counterpart to CV1 and analyse the X-ray spectrum to determine the spectral model that best describes this source. We also examine the low resolution optical spectrum for emission lines typical of cataclysmic variables. Cross correlating the Halpha line in each individual spectrum also allows us to search for orbital motion. Results. The X-ray spectrum reveals a source best-fitted with a high-temperature bremsstrahlung model and an X-ray unabsorbed luminosity of 1.8e32 erg/s (0.3-8.0 keV), which are typical of cataclysmic variables. Optical spectra reveal Balmer emission lines, which are indicative of an accretion disc. Potential radial velocity in the Halpha emission line is detected and a period for CV1 is proposed. Conclusions. These observations support the CV identification. The radial velocity measurements suggest that CV1 may have an orbital period of ~7 hours, but further higher resolution optical spectroscopy of CV1 is needed to unequivocally establish the nature of this CV and its orbital period.
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