| Abstract : | Active M dwarfs of various sub-spectral types (M0-M9) show spectroscopic variability in various time scales. In most cases, such variabilities can be traced to internal dynamics of M dwarfs like magnetic activity,
energetic flaring events, their rotation periods etc. The variation in the strengths of prominent emission lines, such as H-alpha, is usually taken as a proxy of such variation. Most of these studies in the literature have explored the variability in H-alpha emission of M dwarfs at the time scale of 15-20 minutes with archival data; therefore, a uniform cadence is missing. Only a couple of systematic studies have explored the short-term (~5 minutes) H-alpha variability in M Dwarfs with uniform cadence. Here, we have performed the spectroscopic monitoring of 83 M dwarfs across several spectral types to study the variations in H-alpha and H-beta emissions on timescales of a few minutes. This project was undertaken as
one of the science characterization programs of the in-house developed MFOSC-P instrument with large samples as part of the Ph.D. thesis of the speaker. Low-resolution (resolution ~ 6 angstroms) spectral time series of 3-5 minutes cadence over 0.7-1.5 hours were obtained with MFOSC-P instrument on PRL 1.2m Mt. Abu telescope, covering H-beta and H-alpha wavelengths, for each of the sources. Coupled with the data available in the literature and archival photometric data from TESS and Kepler/K2 archives, this data set reveals interesting correlations between the variability in H-alpha/H-beta emissions with respect to 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. Other parameters like the star-spot filling factor,
H-alpha activity strength (L_H-alpha/L_bol), etc., are also derived and explored for such distributions. |
