The chromospheres of classical Cepheids. II - High-resolution profiles of the Mg II h and k lines. III - A search for transition region emission lines
The chromospheres of classical Cepheids. II - High-resolution profiles of the Mg II h and k lines. III - A search for transition region emission lines
复制标题
经典造父变星的色球层。
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
S. Parsons
中科院分区：
文献类型：
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作者：
E. Schmidt;S. Parsons
利用IUE长波照相机高分辨光谱研究了5颗造父变星中每一颗的Mg Ⅱ h线和k线在2900 A附近的轮廓。发射特征通常出现在两条谱线的中心，由于星际或星周气体的存在，也有中心吸收特征，这些特征通常是多重的，可能起源于也可能不起源于一个至少是恒星半径的十分之几的区域。虽然它的平均辐射通量低于类似温度和光度的不变星，但它的最大辐射强度与瞬时温度一致。在本文的第二部分中，我们注意到，在短波长区域，对于样本中最短周期的星星，Delta Cep，几乎没有发现明显的色球发射。为了探测辐射或降低通量，在五颗恒星中的三颗在几个关键阶段获得了较长的曝光时间。虽然强度，当检测到时，是类似于不变的，在其他地方的上限表明比在不变的恒星中观察到的流量更小。
The profiles of the Mg II h and k lines near 2900 A are studied on the basis of IUE long wavelength camera high resolution spectra for a number of phases of each of five Cepheids. An emission feature often appears at the centers of the two lines, and there are central absorption features as well, due to interstellar or circumstellar gas, which are often multiple and may or may not originate in a region which is at least several tenths of a stellar radius in extent. While the mean flux of the emission is lower than for nonvariable stars of similar temperature and luminosity, the maximum strength of the emission is in keeping with the instantaneous temperature. In the second part of this paper, it is noted that little significant chromospheric emission could be found in the short wavelength region for the shortest period star in the sample, Delta Cep. In order to detect the emissions or place lower limits on the fluxes, longer exposures have been obtained at several critical phases for three of the five stars. While the strength, when detected, is similar to that of nonvariables, the upper limits at other places indicate smaller fluxes than those observed in nonvariable stars.