Possible detection of coronal mass ejections on late-type main-sequence stars in LAMOST medium-resolution spectra
Abstract
Context. Stellar coronal mass ejections (CMEs) are the main source of the stellar space weather and they could affect the habitability of neighboring planets. Large-sample time-domain spectral data are currently unavailable for the detection of stellar CMEs. Aims. This work aims to detect stellar CMEs from spectra continuously observed through the LAMOST Medium-Resolution Spectroscopic Survey (LAMOST-MRS). Our sample includes 1,379,408 LAMOST-MRS spectra of 226,194 late-type main-sequence stars (T _{eff} < 6000 K, log[g/(cm s -2)] > 4). Methods. We first identified stellar CME candidates by examining the asymmetry of Hα lines, and then performed double Gaussian fitting for Hα contrast profiles (differences between CME spectra and reference spectra) of the CME candidates to analyze the temporal variation of the asymmetric component. Results. Four stellar CME candidates were detected, one of which originates from a G-type Sun-like star, and the other three are from M-type dwarfs. The Mg I triplet (5168.94 Å, 5174.13 Å, 5185.10 Å) and the Hα line of candidate 1 exhibit a blue wing enhancement, and the corresponding Doppler shift of this enhancement shows a gradually increasing trend. The host star of candidate 2 is a G5-type Sun-like star. The emission of the Hα blue wing of this candidate gradually increases, and the corresponding maximum Doppler velocity is close to the stellar surface escape velocity. The Hα line shows an obvious blue wing enhancement in candidate 3. In candidate 4, the Hα line shows an obvious red wing enhancement, and the corresponding maximum Doppler velocity exceeds the surface escape velocity of the host star. The lower limit of the CME mass was estimated to be 8.84 × 1017 g to 3.02 × 1020 g for these four candidates.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1381L