Chromospheric activity properties and search for subdwarfs and extreme subdwarfs based on LAMOST stellar spectral survey |
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| Institution: | 1. College of Science/Department of Physics & NAOC-GZU-Sponsored Center for Astronomy Research, Guizhou University, Guiyang 550025, PR China;2. Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, PR China;3. Dept. of Physics and Astronomy, Butler University, Indianapolis, IN 46208, USA;4. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China;5. Nanjing Institute of Astronomical Optics & Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042, China;1. Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai 264209, China;2. Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, China;1. Department of Physics, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Terzio?lu Kampüsü, TR-17020 Çanakkale, Turkey;2. Department of Space Sciences and Technologies, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Terzio?lu Kampüsü, TR-17020 Çanakkale, Turkey;3. Astrophysics Research Centre and Observatory, Çanakkale Onsekiz Mart University, Terzio?lu Kampüsü, TR-17020 Çanakkale, Turkey;1. Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;2. National Astronomical Research Institute of Thailand, Chiang Mai 50200, Thailand;1. Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India;2. School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Amanaka G.E. Road, Raipur 492010, India;3. Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, GR-71003 Heraklion, Greece;4. ESL, Foundation for Research and Technology, Heraklion 71110, Greece;5. Department of Physics, The College of New Jersey, PO Box 7718, Ewing, NJ 08628-0718, USA |
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| Abstract: | Big data obtained from a stellar spectroscopic survey carried out using the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST, also known as Guo Shou Jing telescope) provide important information for studying chromospheric activity, variability of chromospheric activity, and chromospheric statistical properties, and for searching subdwarfs and extreme subdwarfs. Using as chromospheric activity indicator the Hα line, we detected 6391 active M stars among the 99741 stars in the M-star catalogue of the LAMOST survey. We also obtained the relationship between the fraction of active stars and the spectral types, which is consistent to previous results. We also studied the effects of activity on broadband photometric colors, and we did not see significant differences between active and inactive M stars. Using as spectroscopic molecular indicators the CaH123 and TiO5 lines, we found 1288 subdwarfs (including 120 active subdwarfs). We also found 15 extreme subdwarf (2 active extreme subdwarf) candidates. Our subdwarf candidates are slightly redder by about 0.05 mag in g-r compared with dwarfs using the g-r and r-i, and g-r and i-z color diagrams. Using our active M-star catalogue, we found that 898 stars exhibited Hα emission in at least two exposures (170 of them in at least three exposures). Among these 170 stars, 163 of them show variability in Hα emission on long timescales (more than 2.5 h). Furthermore, 34 stars show variability over short timescales (less than 2.5 h), and 29 actives show variability over both short and long time scales. |
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