Spectral analysis of 636 white dwarf-M star binaries from the sloan digital sky survey
Spectral analysis of 636 white dwarf-M star binaries from the sloan digital sky survey
复制标题
DOI：
10.1051/0004-6361:200810632
复制
发表时间：
2009-03
影响因子：
6.5
通讯作者：
R. Heller;D. Homeier;S. Dreizler;R. Ostensen
中科院分区：
文献类型：
--
作者：
R. Heller;D. Homeier;S. Dreizler;R. Ostensen
上下文。我们提供了来自斯隆数字巡天(SDSS)第六次数据发布(DR6)的857颗白矮星(WD)-M双星的目录，其中大部分是以前识别的。对于其中的636颗恒星，我们完成了光谱分析，得出了它们的恒星成分和它们与地球的距离的基本参数。目标。我们试图通过完成光谱分析来测量这些系统的基本参数。我们建议测试通常应用于拟合过程的模型，并约束系统可能和适当的演化场景。方法：研究方法。我们使用χ2最小化技术来分解每个组合谱并得到其分量的独立参数估计。随机排列的可能性被降级为统计意义不大，因此，我们使用二元组分的物理相互作用作为输入参数。此外，我们还检查了SDSS中相应的光度学数据，以找到光学分辨系统。结果。在我们的光谱样本中，有41个恒星对在它们各自的SDSS图像中被光学分辨。对于这些系统，我们还得到了它们的最小真空间间隔和轨道周期的下限，通常约为104年。167对恒星的光谱显示出显著的氢发射，在大多数情况下没有额外的He I或He II特征。我们还发现，在636wd中，有20个适合于DO，其中16个的TWD ff约为40000K。此外，我们还识别了70个质量小于0.1M�的次级极低质量天体(VLMO)，它们是候选的亚星伴星。结论。尽管各种选择效应可能起了作用，但6.4%的WD-M恒星双星的轨道间距约为500AU，是恒星双星系统演化模型的判据。在167个有氢发射的光谱中，8个已经被发现是后公共包络双星(PCEB)，4个是在M矮星上有强辐射过程的系统。剩下的155颗发射巴尔默的双星可能含有一颗活跃的M矮星(DM)，相当于24.4%。DO超标的原因很可能是由于DB-DO系列中的额外WD，但没有完成详细的装配。M星比WD分量更接近地球的趋势可能是由于低估了理论上的M星半径。
Context. We present a catalog of 857 white dwarf (WD)-M binaries from the sixth data release (DR6) of the Sloan Digital Sky Survey (SDSS), most of which were previously identified. For 636 of them, we complete a spectral analysis and derive the basic parameters of their stellar constituents and their distances from Earth. Aims. We attempt to measure fundamental parameters of these systems by completing spectral analyses. We propose to test models typically applied in fitting procedures and constrain likely and appropriate evolutionary scenarios for the systems. Methods. We use a χ 2 minimization technique to decompose each combined spectrum and derive independent parameter estimates for its components. The possibility of alignment by chance is demoted to statistical insignificance, hence, we use physical interaction of the binary constituents as input parameter. Additionally, we check the corresponding photometric data from the SDSS to find optically resolved systems. Results. Forty-one of the stellar duets in our spectroscopic sample are optically resolved in their respective SDSS images. For these systems, we also derive a minimum true spatial separation and a lower limit to their orbital periods, typically which are some 10 4 yr. Spectra of 167 stellar duets show significant hydrogen emission and in most cases no additional He i or He ii features. We also find that 20 of the 636 WDs are fitted to be DOs, with 16 measured to have T WD eff around 40 000 K. Furthermore, we identify 70 very low-mass objects (VLMOs), which are secondaries of masses smaller than about 0.1 M� , to be candidate substellar companions. Conclusions. Although various selection effects may play a role, the fraction 6.4% of WD-M star binaries with orbital separations of around 500 AU is a criterion for evolutionary models of stellar binary systems. Of the 167 spectra with hydrogen emission, 8 had already been found to be post-common envelope binaries (PCEBs) and 4 are systems with strong irradiation processes on the M dwarf. The remaining 155 Balmer-emitting binaries probably harbor an active M dwarf (dM), corresponding to a fraction of 24.4%. The excess of cool DOs is most likely due to additional WDs in the DB-DO Teff range, for which no detailed fitting was completed. The trend of the M stars being closer to Earth than the WD component is probably due to an underestimation of the theoretical M star radii.