Exploring the short-term variability of H{\alpha} and H\b{eta} emissions in a sample of M Dwarfs

TL;DR

This study investigates short-term spectroscopic variability of Hα and Hβ emissions in 83 M dwarfs, revealing significant variability linked to stellar activity, rotation, and spectral type, using time-series spectroscopy and archival data.

Contribution

It provides the first extensive short-term spectroscopic monitoring of M dwarfs focusing on Hα and Hβ variability, combining new observations with archival data.

Findings

64% of M dwarfs show significant variability

Variability correlates with spectral type and rotation period

Hα activity strength varies across the sample

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 flaring events, their rotation periods, etc. The time variability in the strengths of prominent emission lines (particularly H{\alpha} ) 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 H{\alpha} 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 H{\alpha} 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. H{\alpha} activity strength (LH{\alpha}/Lbol) is also derived and explored for such distributions.