Type-Ia Supernova SN 1995D in NGC 2962: Optical V, R, and I Band Photometry and Spectra

摘要

OpticallightcurvesintheV,R,andIbands,starting10daysbeforethemaximumlight,andtheopticalspectraneartotheVmaximumphaseofsupernovaSN1995DinNGC2962arepresented.Thespectratakenneartotheopticalmaximumaresimilartotheprototypicaltype-lasupernovaSN1981B,andshownotraceoftheinterstellarNalDline.Theexpansionvelocityatthemaximumphasewas10000?±200kms-1.ThesupernovareachedmaximumlightintheIbandaboutfourdaysearlierthanintheVband.Adistinctsecondarypeakisobservedinthe/bandabout30daysaftertheVmaximum.Thissecondarypeakoccurredaboutoneweekdelayedfromthepublishedtemplatelightcurve.AclearshoulderisdetectedintheRbandlightcurvecorrespondingtothesecondarypeakintheIband.Theinitialrateofdeclineisslow[?”m15(V)=0.66mag],anditissuggestedthatthesupernovabelongstoagroupoftheintrinsicallybrightesttype-lasupernovae.FromtheinitialdecliningrateintheVband,weestimatedtheabsolutemagnitudeMvtobea?’18.8?±0.3mag,andthedistancemodulusoftheparentgalaxy(NGC2962)tobe32.2?±0.3mag.