Exploring the short-term variability of Hα and Hβ emissions in a sample of M Dwarfs

Abstract

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 aring 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 Hβ emissions on short-time scales. Low-resolution (resolution ∼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 Hβ 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 statisticallysignificant 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.