J/ApJ/831/133ivo://CDS.VizieR/J/ApJ/831/133doi:10.26093/cds/vizier.18310133CDSHerczeg G.J.Dong S.Shappee B.J.Chen P.Hillenbrand L.A.Jose J.,Kochanek C.S.Prieto J.L.Stanek K.Z.Kaplan K.Holoien T.-S.,Mairs S.Johnstone D.Gully-Santiago M.Zhu Z.Smith M.C.Bersier D.,Mulders G.D.Filippenko A.V.Ayani K.Brimacombe J.Brown J.S.,Connelley M.Harmanen J.Itoh R.Kawabata K.S.Maehara H.Takata K.,Yuk H.Zheng W.2017-06-21T08:21:44Z2017-03-07T08:16:51ZCDS support team

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

cds-question@unistra.frvisible-astronomybroad-band-photometryyoung-stellar-objectsOutbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The ~3.5mag brightening in the V band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from ~10000K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000km/s. The wind and hot gas both disappeared as the outburst faded and the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H_2_ is detected in emission from vibrational levels as high as v=11, also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, though the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling.2016ApJ...831..133Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/831/133CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)II/321 : IPHAS DR2 Source Catalogue (Barentsen+, 2014)I/284 : The USNO-B1.0 Catalog (Monet+ 2003)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)J/MNRAS/458/3479 : SVM selection of WISE YSO Candidates (Marton+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/831/133https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/831/133http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/831/133https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/831/133https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/831/133http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/831/133GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tap3.322582951404819e-19 3.852589004194616e-19OpticaldefaultJ/ApJ/831/133/table2The ASAS-SN photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDJulian Date of the observationdtime.epochdoubleVmag[13.5/18] V band magnitudemagphot.mag;em.opt.Vfloate_Vmag[0.02/0.8] The 1{sigma} error in Vmagmagstat.error;phot.mag;em.opt.VfloatFlux[0.2/15] V band flux densityJyphot.flux.density;em.opt.Vfloate_Flux[0.1/0.5] The 1{sigma} error in FluxJystat.error;phot.fluxfloat