【学术报告】
～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～ 
报告题目：Comprehensive characterisation of L subdwarfs

报告人：张曾华

报告人单位：Instituto de Astrofisica de Canarias

报告时间：2016年8月30日（周二）上午10:30-11:30

报告地点：小学校会议室

报告语言：中文

报告摘要：

L subdwarfs are metal-poor counterpart of L dwarfs in the Galactic halo and thick disk. Only about 40 L subdwarfs reported in the literatures. I have conducted a search for L subdwarf candidates within the UKIDSS and SDSS. 34 of my candidates were confirmed as L subdwarfs spectroscopically at optical and/or near infrared wavelengths with VLT, GTC and Magallen. I examined the spectral types and metallicity subclasses classification of known L subdwarfs, and established a new classification scheme of L subdwarfs. I estimate temperatures and metallicities of 30 late type M and L subdwarfs by comparing their spectra to BT-Settl models. I find that L subdwarfs have temperatures between 1500 K and 2700 K, which are higher than similarly-typed L dwarfs by around 100-400 K depending on different subclasses and subtypes. I constrained the metallicity ranges of subclasses of M, L and T subdwarfs. I also discussed the spectral type and absolute magnitude relationships for L and T subdwarfs. Then I will briefly introduce two of my observational programme on L subdwarfs. I followed up 18 L subdwarfs with X-shooter on the VLT for more detailed model comparison and radial velocity measurements. I am leading a 3-years programme to measure parallaxes of 20 L subdwarfs with the 10.4m GTC telescope (comparing only 6 L subdwarfs have parallaxes in the literature). This programme is involving 123 hours of GTC time, and completing in a year.

～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～
请全体师生踊跃参加!

本通知也可以在云台学术报告网页看到：

http://www.ynao.cas.cn/xwzx/xstg/

申请安排学术报告的同事请参见台学术报告管理办法：

http://www.ynao.cas.cn/xwzx/xstg/gzzd/

大样本恒星演化研究组

云南天文台学术委会　　

邀请方联系人：韩占文

8月26日