J/A+A/667/A7ivo://CDS.VizieR/J/A+A/667/A7doi:10.26093/cds/vizier.36670007CDSMunari U.Masetti N.Walter F.M.Williams R.E.Hambsch F.-J.Frigo A.,Valisa P.2024-11-28T20:01:10Z2022-10-28T09:37:49ZCDS support team

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

cds-question@unistra.frnovaeinfrared-photometryvisible-astronomybroad-band-photometryspectroscopyWe report about the fast Nova Sgr 2016 N.4 being surprisingly trapped in a long-lasting and bright plateau (Delta(I)>=10mag above quiescence), six years past the nova eruption. Very few other novae experience a similar occurring. We have carried out an intensive observing campaign collecting daily BVRI photometry, monthly high-resolution optical spectroscopy, and observed the nova in ultraviolet and X-rays with Swift at five distinct epochs. The bolometric luminosity radiated during the plateau is L(bol)~4200L_{sun}_ (scaled to the distance of the Galactic Bulge), corresponding to stable nuclear burning on a 0.6M_{sun}_ white dwarf. A stable wind is blown-off at FWZI~1600km/s, with episodic reinforcement of a faster FWZI~3400km/s mass-loss, probably oriented along the polar directions. The collision of such winds could power the emission detected in X-rays. The burning shell has an outer radius of ~25R_{sun}_ at which the effective temperature is ~7600K, values similar to those of a F0 II/Ib bright giant. The Delta(m)<1mag variability displayed during the plateau is best described as chaotic, with the irregular appearance of quasi-periodic oscillations with a 15-17 days periodicity. A limited amount of dust (~3x10^-11^M_{sun}_) continuously condense at T(dust)~1200K in the outflowing wind, radiating L(dust)~52L_{sun}_.2022A&A...667A...7Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/667/A7CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/667/A7https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/667/A7http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/667/A7https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/667/A7https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/667/A7http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/667/A7GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tap3.322582951404819e-19 3.852589004194616e-19OpticalInfrareddefaultJ/A+A/667/A7/table1BVRI photometry of nova V5856 Sgr collected in 2021 and 2022recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian date (HJD-2459000)dtime.epochfloatDateDate (UT) of the observation (YYYY-MM-DD.ddd)time.epochnullableVmagV magnitudemagphot.mag;em.opt.Vfloate_VmagError on Vmagmagstat.error;phot.magfloatB-V? B-V colormagphot.color;em.opt.B;em.opt.Vfloatnullablee_B-V? Error on B-V colormagstat.error;phot.color;em.opt.BfloatnullableV-R? V-R colormagphot.color;em.opt.V;em.opt.Rfloatnullablee_V-R? Error on V-R colormagstat.error;phot.color;em.opt.VfloatnullableR-I? R-I colormagphot.color;em.opt.R;em.opt.Ifloatnullablee_R-I? Error on R-I colormagstat.error;phot.color;em.opt.RfloatnullableJ/A+A/667/A7/spectrumSpectrum (fig. 2)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaHeliocentric wavelength0.1nmem.wl;pos.heliocentricdoubleFluxFlux (in erg/cm^2^/s/{AA}10mW.m**-2.nm**-1phot.fluxdouble