Search for flares and associated CMEs on late-type main-sequence stars in optical SDSS spectra

Abstract

This work aims to detect and classify stellar flares and potential stellar coronal mass ejection (CME) signatures in optical spectra provided by the Sloan Digital Sky Survey (SDSS) data release 14. The sample is constrained to all F, G, K, and M main-sequence type stars, resulting in more than 630,000 stars. This work makes use of the individual spectral exposures provided by the SDSS. An automatic flare search was performed by detecting significant amplitude changes in the $H\alpha$ and $H\beta$ spectral lines after a Gaussian profile was fit to the line core. CMEs were searched for by identifying asymmetries in the Balmer lines caused by the Doppler effect of plasma motions in the line of sight. We identified 281 flares on late-type stars (spectral types K3 to M9). We identified six possible CME candidates showing excess flux in Balmer line wings. Flare energies in $H\alpha$ were calculated and masses of the CME candidates were estimated. The derived $H\alpha$ flare energies range from $3\times 10^{28}-2\times 10^{33}$ erg. The $H\alpha$ flare energy increases with earlier types, while the fraction of flaring times increases with later types. Mass estimates for the CME candidates are in the range of $6\times 10^{16}-6\times 10^{18}$ g, and the highest projected velocities are $\sim 300-700$ km/s. The low detection rate of CMEs we obtained agrees with previous studies, suggesting that for late-type main-sequence stars the CME occurrence rate that can be detected with optical spectroscopy is low.

Contains 22 pages and 21 figures. Properties of the flaring stars and the derived parameters of the flares are available at CDS

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Cited by in corpus (19)

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• Detection of Flare-induced Plasma Flows in the Corona of EV Lac with X-ray Spectroscopy
• Possible detection of coronal mass ejections on late-type main-sequence stars in LAMOST medium-resolution spectra
• Stellar Coronal Mass Ejections
• Sun-as-a-star Analysis of H$\alpha$ Spectra of a Solar Flare Observed by SMART/SDDI: Time Evolution of Red Asymmetry and Line Broadening
• Detection of Flare-associated CME Candidates on Two M-dwarfs by GWAC and Fast, Time-resolved Spectroscopic Follow-ups
• A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N: Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations in the context of the solar-stellar connection
• A Superflare on YZ Canis Minoris Observed by Seimei Telescope and TESS: Red Asymmetry of H$\alpha$ Emission Associated with White-Light Emission
• MHD study of extreme space weather conditions for exoplanets with Earth-like magnetospheres: On habitability conditions and radio-emission
• Red Asymmetry of H${}_{\alpha }$ Line Profiles during the flares on the active RS CVn-type star II Pegasi
• Observations and modeling of spectral line asymmetries in stellar flares
• Flaring-associated Complex Dynamics in Two M-dwarfs Revealed by Fast, Time-resolved Spectroscopy
• Spectroscopic observations of flares and superflares on AU Mic
• Solar and stellar flares: frequency, active regions and stellar dynamo
• A huge-amplitude white-light superflare on a L0 brown dwarf discovered by GWAC survey
• Activity of Selected Solar Twins
• Doppler-shifted Signatures in the Chromospheric Line Profiles of II Pegasi
• Investigating Possible Stellar Coronal Mass Ejections in M-type Dwarfs Using the CARMENES DR1 Spectra
• A Possible Stellar CME Event Associated with a Long-duration Optical Flare on the RS CVn-type Star UX Arietis