Activities in M dwarfs show spectroscopic variability over various time scales ranging from a few seconds to several hours. The time scales of such variability can be related to internal dynamics of M dwarfs like magnetic activity, energetic flaring events, their rotation periods, etc. The time variability in the strengths of prominent emission lines (particularly Hα ) is mostly taken as a proxy of such dynamic behavior. In this study, we have performed the spectroscopic monitoring of 83 M dwarfs (M0-M6.5) to study the variations in Hα and H\b{eta} emissions on short-time scales. Low-resolution (resolution around 5.7 angstroms) spectral time series of 3-5 minutes cadence over 0.7-2.3 hours were obtained with MFOSC-P instrument on PRL 1.2m Mt. Abu telescope, covering H\b{eta} and Hα wavelengths. Coupled with the data available in the literature and archival photometric data from TESS and Kepler/K2 archives, various variability parameters are explored for any plausible systematics with respect to their spectral types, and rotation periods. Though about 64% of our sample shows statistically significant variability, it is not uniform across the spectral type and rotation period. Hα activity strength (LHα/Lbol) is also derived and explored for such distributions.
Exploring Young Stellar Variability with Gaia DR3 light curves
University of Geneva（日内瓦大学）；Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Research Network (HUN-REN)（孔科利天文台，匈牙利研究网络（HUN-REN）地球科学研究中心）；CSFK, MTA Centre of Excellence（CSFK，马塔卓越中心）；University of Szeged（塞格德大学）；Universität Wien（维也纳大学）；Natural History Museum Vienna（维也纳自然史博物馆）
Three-dimensional dynamical evolution of cloud particle microphysics in sub-stellar atmospheres I. Description and exploring Y-dwarf atmospheric variability
The orbital kinematics of eta Carinae over three periastra with a possible detection of the elusive secondary's motion
船底座η双星是最接近超大质量恒星的例子，它可能是在19世纪中期的大爆发中通过合并形成的。我们的目的是确认和改进的运动学使用的光谱数据集与CTIO 1.5米望远镜在2008年至2020年的时间段，涵盖三个近星点通道的高偏心轨道。我们测量的H-α和H-β，其中的径向速度和轨道运动学的主要恒星的H-β发射线使用平分线的方法测量线的变化。在远离近星点的阶段，我们观察到He II 4686的发射与主星相反，与可能的沃尔夫-拉叶伴星一致，尽管发射线看起来很窄。这可能是第一次探测到来自伴星的辐射。
Exploring the long-term temporal variability in polarization through multi-epoch optical spectro-polarimetry - Part II: A sample of symbiotic and red-giant stars
Physical Research Laboratory（物理研究实验室）；Indian Institute of Technology Gandhinagar（甘地纳加尔印度理工学院）；Johns Hopkins University（约翰斯·霍普金斯大学）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德航天飞行中心）
Exploring the long-term temporal variability in polarization through multi-epoch optical spectro-polarimetry - Part I: A sample of Herbig Ae/Be and classical Be stars
Physical Research Laboratory（物理研究实验室）；Indian Institute of Technology Gandhinagar（甘地纳加尔印度理工学院）
Even More Rapidly Rotating Pre-Main Sequence M Dwarfs with Highly Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and Upper Centaurus-Lupus Associations
An Automated tool to detect variable sources in the Vista Variables in the V\'ıa Láctea Survey. The VVV Variables (V$^{4}$) catalog of tiles d001 and d002
