共生星冷星光谱分类

SPECTRAL CLASSIFICATION OF THE COOL COMPANIONS OF SYMBIOTIC STARS

在近红外波段（λλ8100-8725A），对10颗共生星，27颗K－M型比较星进行了分辨本领信噪比S／N＞100的光谱观测，对晚于M2的晚型星，出现了TiO三重头（λλ8432，8442，8452A）吸收带，发现吸收带深度对温度（即光谱型）很敏感而对重力（即光度级）不敏感．用最小二乘法拟合了光谱型对TiO吸收带深度的曲线，拟合曲线的标准方差为0．22光谱分型，并由此给出6颗合晚于M2巨星的共生星光谱型.另外还测量了该波段上的CaII三重线、FeI、TiI、NaI等众多谱线的等值宽度．发现CaII三重线对光度级很敏感，FeI、TiI线对光度级较敏感，而NaI线相对不太敏感．同时，这些线的等值宽度也随恒星光谱型在变化，特别是光谱型晚于M3的恒星必须考虑光度级与光谱型两方面的效应．给出了10颗较亮的共生星的光度级，都是巨星，并无亮巨星或超巨星特征．

In the near infrared band (λλ8000 to 8725A), the spectra of 10 S-type symbiotic stars and 27 K-M type comparison stars have been observed with a moderate dispertion of 33Amm-1, the resolving power signal to noise raho S/N> 100. The triple-headed absorphon band of TiO (λλ8432, 8422 and 8452A)emerges when the star is later than Mi, we measured the depth of the TiO absorption band, it's very sensihve to the temperature (i.e.spectral type)and unsensihve to the gravity (i. e. luminosity class), we fit a curve of the spectral type against the absorption depth of TiO with σ = 0.22 of a subtype. The spectral types of the six symbiohc stars which include a giant later than M2 have been classifled. We also measured the EW of the infrared CaII triplet (λλ8498, 8542, 8662A ) and many Fe I, Ti I, Na I lines in this band, and found out that the IR triplet of CaII is sensihve to luminosity, so is the Fi I, Ti l, the Na I is rqahvely insensihve, simultaneously, the EW of line also changes with the spectral type of star, even when the star is later than M3. So we must consider both effects. Based on the quantity measurement and the comparision to the standard stars, the luminosity classes of 10 symbiohc stars have been given. All the ten bright symbiohc stars are class III giant none of them presentS the features of bnght giant or supergiant. A simple discussion is also made.