J/A+A/668/A111ivo://CDS.VizieR/J/A+A/668/A111doi:10.26093/cds/vizier.36680111CDSMaas A.Ilin E.Oshagh M.Palle E.Parviainen H.Molaverdikhani K.,Quirrenbach A.Esparza-Borges E.Murgas F.Bejar V.J.S.Narita N.,Fukui A.Lin C.-L.Mori M.Klagyivik P.2024-11-06T20:01:29Z2022-12-13T08:21:20ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsvisible-astronomysloan-photometryStellar flares emit thermal and non-thermal radiation in the X-ray and UV regime. Although high energetic radiation from flares is a potential threat to exoplanet atmospheres and may lead to surface sterilization, it might also provide the extra energy for low mass stars needed to trigger and sustain prebiotic chemistry. Despite the UV continuum emission being constrained partly by the flare temperature, few efforts have been made to determine the flare temperature for ultra-cool M-dwarfs. We investigate two flares on TRAPPIST-1, an ultra-cool dwarf star that hosts seven exoplanets of which three lie within its habitable zone. The flares are detected in all four passbands of the MuSCAT2 instrument allowing a determination of their temperatures and bolometric energies. We analyze the light curves of the MuSCAT1 and MuSCAT2 instruments obtained between 2016 and 2021 in g, r, i, zs-filters. We conduct an automated flare search and visually confirmed possible flare events. The black body temperatures are inferred directly from the spectral energy distribution (SED) by extrapolating the filter-specific flux. We study the temperature evolution, the global temperature, and the peak temperature of both flares.Results. White-light M-dwarf flares are frequently described in the literature by a black body with a temperature of 9000-10000K. For the first time we infer effective black body temperatures of flares that occurred on TRAPPIST-1. The black body temperatures for the two TRAPPIST-1flares derived from the SED are consistent with T_SED_=7940^+430^_-390_K and T_SED_=6030^+300^_-270_K. The flare black body temperatures at the peak are also calculated from the peak SED yielding T_SEDp_=13620^+1520^_-1220_K and T_SEDp_=8290^+660^_-550_K. We update the flare frequency distribution of TRAPPIST-1 and discuss the impacts of lower black body temperatures on exoplanet habitability. Conclusions. We show that for the ultra-cool M-dwarf TRAPPIST-1 the flare black body temperatures associated with the total continuum emission are lower and not consistent with the usually adopted assumption of 9000-10000K in the context of exoplanet research. For the peak emission, both flares seem to be consistent with the typical range from 9000-14000K, respectively. This could imply different and faster cooling mechanisms. Further multi-colour observations are needed to investigate whether our observations are a general characteristic of ultra-cool M-dwarfs. This would have significant implications for the habitability of exoplanets around these stars because the UV surface flux is likely to be overestimated by the models with higher flare temperatures.2022A&A...668A.111Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/668/A111CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/156/178 : NIR transmission spectra of TRAPPIST-1 planets (Zhang+, 2018)J/AJ/156/218 : Transit light curves of TRAPPIST-1 planets (Ducrot+, 2018)J/A+A/640/A112 : TRAPPIST-1 transit timings (Ducrot+, 2020)J/A+A/650/A138 : TRAPPIST-1 analogue stars TESS light curves (Seli+, 2021)J/A+A/658/A133 : TRAPPIST-1 h NIR spectrum (Gressier+, 2022)J/A+A/658/A170 : TRAPPIST-1 best-fit parameters (Teyssandier+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/668/A111https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/668/A111http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/668/A111https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/668/A111https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/668/A111http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/668/A111GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/668/A111/flare1Flare 1 griz datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimezTime for z band (JD-2454833)dtime.epochdoubleFluxz? Flux in z band in normalized unitsphot.mag;em.opt.IdoublenullableTimei? Time for i band (JD-2454833)dtime.epochdoublenullableFluxi? Flux in i band in normalized unitsphot.mag;em.opt.IdoublenullableTimer? Time for r band (JD-2454833)dtime.epochdoublenullableFluxr? Flux in r band in normalized unitsphot.mag;em.opt.RdoublenullableTimeg? Time for g band (JD-2454833)dtime.epochdoublenullableFluxg? Flux in g band in normalized unitsphot.mag;em.opt.BdoublenullableJ/A+A/668/A111/flare2Flare 2 griz datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimezTime for z band (JD-2454833)dtime.epochdoubleFluxz? Flux in z band in normalized unitsphot.mag;em.opt.IdoublenullableTimei? Time for i band (JD-2454833)dtime.epochdoublenullableFluxi? Flux in i band in normalized unitsphot.mag;em.opt.IdoublenullableTimer? Time for r band (JD-2454833)dtime.epochdoublenullableFluxr? Flux in r band in normalized unitsphot.mag;em.opt.RdoublenullableTimeg? Time for g band (JD-2454833)dtime.epochdoublenullableFluxg? Flux in g band in normalized unitsphot.mag;em.opt.Bdoublenullable