J/A+A/669/A118ivo://CDS.VizieR/J/A+A/669/A118doi:10.26093/cds/vizier.36690118CDSWollmann J.Heinzel P.Kabath P.2024-11-28T20:01:41Z2023-01-20T11:40:50ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frlate-type-starsstellar-flaresvisible-astronomyspectroscopyStellar flares are energetic events occurring in stellar atmospheres. They have been observed on various stars using photometric light curves and spectra. On some cool stars, flares tend to release substantially more energy compared to solar flares. Spectroscopic observations have revealed that some spectral lines, aside from an enhancement and broadening, exhibit asymmetry in their profile. Asymmetries with enhanced blue wings are often associated with the presence of coronal mass ejections while the origin of the red asymmetries is currently not well understood. A few mechanisms have been suggested but no modeling has been performed yet. We observed the dMe star AD Leo using the 2-meter Perek telescope at Ondrejov observatory, with simultaneous photometric light curves. In analogy with solar flares, we model the H{alpha} line emergent from an extensive arcade of cool flare loops and explain the observed asymmetries using the concept of coronal rain. We solve the non-LTE radiative transfer in H{alpha} within cool flare loops taking into account the velocity distribution of individual rain clouds. For a flare occurring at the center of the stellar disc, we then integrate radiation emergent from the whole arcade to get the flux from the loop area. We observed two flares in the H{alpha} line that exhibit red wing asymmetry corresponding to velocities up to 50km/s during the gradual phase of the flare. Synthetic profiles generated from the model of coronal rain have enhanced red wings quite compatible with observations.2023A&A...669A.118Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/669/A118CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/637/A13 : AD Leo high resolution spectra (Muheki+, 2020)J/A+A/638/A5 : HD 285507 and AD Leo light and velocity curves (Carleo+, 2020)J/A+A/666/A143 : AD Leo RV and stellar activity indices (Kossakowski+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/669/A118https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/669/A118http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/669/A118https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/669/A118https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/669/A118http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/669/A118GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapAssociated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/669/A118OpticaldefaultJ/A+A/669/A118/listList of spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNxNumber of pixels along X-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableblambdaLower value of wavelength interval0.1nmem.wlfloatBlambdaUpper value of wavelength interval0.1nmem.wlfloatdlambdaSpectral resolution0.1nmspect.resolutiondoublesizeSize of FITS fileKibytephys.size;meta.fitsintspShow the spectrummeta.ref.urlcharFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar