Hydrodynamical simulations of the jet in the symbiotic star

In papers I and II in this series, we presented hydrodynamical simulations of jet models with parameters representative of the symbiotic system MWC 560. These were simulations of a pulsed, initially underdense jet in a high density ambient medium. Since th

Received2007February28;accepted2007April04

APreprinttypesetusingLTEXstyleemulateapjv.10/09/06

HYDRODYNAMICALSIMULATIONSOFTHEJETINTHESYMBIOTICSTARMWC560

III.APPLICATIONTOX-RAYJETSINSYMBIOTICSTARS

MatthiasStuteandRaghvendraSahai

JetPropulsionLaboratory,CaliforniaInstituteofTechnology,4800OakGroveDrive,Pasadena,CA91109,USA

Received2007February28;accepted2007April04

arXiv:0704.2240v1 [astro-ph] 17 Apr 2007

ABSTRACT

InpapersIandIIinthisseries,wepresentedhydrodynamicalsimulationsofjetmodelswithparametersrepresentativeofthesymbioticsystemMWC560.Theseweresimulationsofapulsed,initiallyunderdensejetinahighdensityambientmedium.Sincethepulsedemissionofthejetcreatesinternalshocksandsincethejetvelocityisveryhigh,thejetbowshockandtheinternalshocksareheatedtohightemperaturesandshouldthereforeemitX-rayradiation.Inthispaper,weinvestigateindetailtheX-raypropertiesofthejetsinourmodels.WehavefocusedourstudyonthetotalX-rayluminosityanditstemporalvariability,theresultingspectraandthespatialdistributionoftheemission.TemperatureanddensitymapsfromourhydrodynamicalsimulationswithradiativecoolingpresentedinthesecondpaperareusedtogetherwithemissivitiescalculatedwiththeatomicdatabaseATOMDB.ThejetsinourmodelsshowextendedandvariableX-rayemissionwhichcanbecharacterizedasasumofhotandwarmcomponentswithtemperaturesthatareconsistentwithobservationsofCHCygandRAqr.TheX-rayspectraofourmodeljetsshowemissionlinefeatureswhichcorrespondtoobservedfeaturesinthespectraofCHCyg.Theinnermostpartsofourpulsedjetsshowironlineemissioninthe6.4–6.7keVrangewhichmayexplainsuchemissionfromthecentralsourceinRAqr.WeconcludethatMWC560shouldbedetectablewithChandraorXMM-Newton,andsuchX-rayobservationswillprovidecrucialforunderstandingjetsinsymbioticstars.

Subjectheadings:circumstellarmatter—hydrodynamics—ISM:jetsandout ows–binaries:sym-biotic–methods:numerical—X-rays:ISM

1.INTRODUCTION

Highlycollimatedfastout owsorjetsarecommoninmanyastrophysicalobjectsofdi erentsizesandmasses:activegalacticnuclei(AGN),X-raybinaries(XRBs),youngstellarobjects(YSO),pre-planetaryneb-ulae(PPN),supersoftX-raysourcesandsymbioticstars.Inthelasttwoobjects,thejetengineconsistsofanac-cretingwhitedwarf.Insymbioticstars,thecompanionisaredgiantundergoingstrongmassloss.Morethanonehundredsymbioticstarsareknown,butonlyabouttensystemsshowthepresenceofjets.ThemostfamoussystemsareRAquarii,CHCygni,andMWC560.

RAquarii,withadistanceofabout200pc,isoneofthenearestsymbioticstarsandawellknownjetsource.Thejethasbeenextensivelyobservedintheopticalandatra-diowavelengths(e.g.Solf&Ulrich1985;Itshowsarichmorphol-ogy,e.g.aseriesofparallelfeaturesinthejetandthecounter-jet,extendingtoafewhundredAUeach.Thisisahintofpulsedejectionofbothjets.Furthermore,RAqristhe rstjetinasymbioticsystem,whichwasde-tectedinX-raysuKelloggetal.2001).Kelloggetal.(2001)foundpeaksofOVIIat0.57keVinboththeNEandSWjetsandapeakofNVIat0.43keVonlyintheNEjet.ThespectraareconsistentwithasoftcomponentwithkT～0.25keV.ThecentralsourceshowsasupersoftblackbodyemissionwithkT～0.18keVandaFeKαlineat6.4keVwhichsuggeststhepresenceofahardsourcenearthehotstar.Recently,reportedon veyearsofobservationswithChandraandwereable

Electronicaddress:Matthias.Stute@jpl.nasa.gov

tomeasurethepropermotionofintheNEjetofabout600kms 1.investigatedtheX-rayemissionfromtheinner500AUofthissystem.In1984/85,CHCygnishowedastrongradiooutburst,duringwhichadouble-sidedjetwithmultiplecompo-nentswasejectedThisevental-lowedanaccuratemeasurementofthejetvelocitynear1500kms 1.InHSTobservations2002),arcscanbedetectedthatalsocouldbeproducedbyepisodicejectionevents.X-raywas rstde-tectedbyEXOSAT(Leahy&Taylorandsubse-quentASCAobservationsrevealedacomplexX-rayspec-trumwithtwosoftcomponents(kT=0.2and0.7keV)associatedwiththejet,(7.3keV)andaFeKαlineTheyinter-pretedthehardcomponentasthermalemissionbyma-terialbeingaccretedontothewhitedwarfandthesoftcomponentaseithercoronalemissionfromthegiantstaroremissionsfromshocksinthejets.AnalysisofarchivalChandraACISdatabyGalloway&Sokoloski(2004)re-vealedfaintextendedemissiontothesouth,alignedwiththeopticalandradiojetsseeninHSTandVLAob-servations.Wheatley&KallmanreanalyzedtheASCAdataandinterpretedthesoftemissionasscatter-ingofthehardcomponentinaphoto-ionizedmediumsurroundingthewhitedwarf.Theyclaimthatnoothersourcesthantheaccretingwhitedwarfarerequiredtoexplainthespectrum.Theobviousexistenceofthejet,however,andfurthermoretheapparentdeclineofthehardX-raycomponentobservedwiththeUS-JapaneseX-raysatelliteSuzakubyMukaietal.togetherwiththelackofacorrespondingdeclineinthesoftcom-ponent,suggestthatthisinterpretationisimplausible.