Near-infrared colors of asteroid 2012a€‰DA14 at its closest approach to Earth: Observations with the Nishiharima Infrared Camera (NIC)

摘要

WepresenttheresultsofourJHKsphotometryofasteroid2012a€‰DA14atitsclosestapproachtoEarthon2013February15.Possiblespectralchangesassociatedwithresurfacingbyplanetaryencountersareofgreatinterest.TheEarthflybyof2012a€‰DA14providedarareopportunitytoinvestigatethiseffect.OurobservationswereconductedusingtheNishiharimaInfraredCamera(NIC)attachedtothe2.0a€‰mNayutatelescopeattheNishi-HarimaAstronomicalObservatory.Despitetheextraordinarilyfastskymotionofuptonear50a€3a€‰sa?’1,thetelescopesuccessfullytrackedtheasteroid.TheNICachievementofthree-bandsimultaneousobservationsallowedustoreliablydeducethecolorsofthisfast-movingobject.Thederivednear-infraredrelativereflectancesareflat,whichisconsistentwiththeclassificationoftheasteroidasL-type.TheJ??a?’HandH??a?’Kscolorsat0.5a€“1a€‰hraftertheclosestapproacharecomparedwiththoseobservedbydea€‰Le?3n(2013,Aamp;A,555,L2)at??a??a€‰10a€‰hraftertheclosesttime.Wedidnotdetectcolorchangessignificantlyexceedingthephotometricerrors,whichare??a??a€‰0.1a€‰mag.ThisprojecthasdemonstratedthepotentialoftheNICasathree-bandsimultaneousimager,especiallyforobservationsofrapidlytime-variablephenomena.