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标题：Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira
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作者：Supriyo Ghosh ; Soumen Mondal ; Ramkrishna Das 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：155
期号：5
页码：1-13
DOI：10.3847/1538-3881/aab902
语种：English
出版社：American Institute of Physics
摘要：We describe the time-dependent properties of a new spectroscopically confirmed Mira variable, which was discovered in 2013 as MASTER-Net Optical Transient J212444.87+321738.3 toward the Cygnus constellation. We have performed long-term optical/near-infrared (NIR) photometric and spectroscopic observations to characterize the object. From the optical/NIR light curves, we estimate a variability period of 465±30 days. The wavelength-dependent amplitudes of the observed light curves range from ΔI∼4 mag to ΔK∼1.5 mag. The (J − K ) color index varies from 1.78 to 2.62 mag over phases. Interestingly, a phase lag of ∼60 days between optical and NIR light curves is also seen, as in other Miras. Our optical/NIR spectra show molecular features of TiO, VO, CO, and strong water bands that are a typical signature of oxygen-rich Mira. We rule out S- or C-type as ZrO bands at 1.03 and 1.06 μm and C2 band at 1.77 μm are absent. We estimate the effective temperature of the object from the Spectral Energy Distribution, and distance and luminosity from standard Period–Luminosity relations. The optical/NIR spectra display time-dependent atomic and molecular features (e.g., TiO, Na I, CaI, H2O, CO), as commonly observed in Miras. Such spectroscopic observations are useful for studying pulsation variability in Miras.
关键词：infrared: stars;methods: observational;stars: AGB and post-AGB;stars: late-type;stars: variables: general;techniques: spectroscopic