Stellar parameters of Be stars observed with X-shooter
Stellar parameters of Be stars observed with X-shooter
复制标题
X-shooter观测到的Be星的恒星参数
DOI：
10.1051/0004-6361/201731536
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发表时间：
2017
影响因子：
6.5
通讯作者：
M. Abo
中科院分区：
文献类型：
--
作者：
A. Shokry;T. Rivinius;A. Mehner;C. Martayan;W. Hummel;R. Townsend;A. M'erand;B. Mota;D. Faes;M. A. Hamdy;M. Beheary;K. Gadallah;M. Abo
目标。对数千颗地球光谱的X-Shooter档案中的Be和Be壳星进行了浏览，以求得到恒星的基本参数和统计性质，特别是对于研究较少的晚型Be星，并将Be现象扩展到早期A星。方法：研究方法。使用BCD方法的改进版本，利用Balmer不连续参数来确定有效温度和表面重力。这种方法最适合于晚B星。通过对目标的镁II谱线进行轮廓拟合，得到目标的投影转速，并对光谱进行视觉检查，以确定是否存在特殊的特征，如红外钙三重态或双巴尔默不连续的存在。测量了Balmer线的当量宽度，但由于在确定光球层贡献方面存在不确定性，因此仅在Be星的一个小样本中可用于确定纯辐射贡献。结果。在X-Shooter大地标准恒星档案中总共发现了78颗Be星，其中48颗以前没有报道过，其中大多数是晚期类型的。证实了晚型比早型恒星具有更多的稀疏盘和更小的变化量的总趋势。相对较亮的(V>；8.5)额外Be星的数量相对较多(48颗)，这让人们对晚类型Be星的统计数据产生了一些怀疑；它们比目前认为的更常见：Be/B星的比例可能不太依赖于光谱亚型。
Aims. The X-shooter archive of several thousand telluric star spectra was skimmed for Be and Be-shell stars to derive the stellar fundamental parameters and statistical properties, in particular for the less investigated late type Be stars, and the extension of the Be phenomenon into early A stars. Methods. An adapted version of the BCD method is used, utilizing the Balmer discontinuity parameters to determine effective temperature and surface gravity. This method is optimally suited for late B stars. The projected rotational velocity was obtained by profile fitting to the Mg ii lines of the targets, and the spectra were inspected visually for the presence of peculiar features such as the infrared Ca ii triplet or the presence of a double Balmer discontinuity. The Balmer line equivalent widths were measured, but due to uncertainties in determining the photospheric contribution are useful only in a subsample of Be stars for determining the pure emission contribution. Results. A total of 78 Be stars, mostly late type ones, were identified in the X-shooter telluric standard star archive, out of which 48 had not been reported before. The general trend of late type Be stars having more tenuous disks and being less variable than early type ones is confirmed. The relatively large number (48) of relatively bright (V > 8.5) additional Be stars casts some doubt on the statistics of late type Be stars; they are more common than currently thought: The Be/B star fraction may not strongly depend on spectral subtype.