Radiative Transfer in Relativistic Accretion-Disk Winds

Radiative transfer in a relativistic accretion disk wind is examined under the plane-parallel approximation in the fully special relativistic treatment. For an equilibrium flow, where the flow speed and the source function are constant, the emergent intens

PASJ:Publ.Astron.Soc.Japan,1–??,

c2008.AstronomicalSocietyofJapan.

RadiativeTransferinRelativisticAccretion-DiskWinds

JunFukue

AstronomicalInstitute,OsakaKyoikuUniversity,Asahigaoka,Kashiwara,Osaka582-8582

fukue@cc.osaka-kyoiku.ac.jp

(Received00;accepted00)

Abstract

arXiv:0711.1387v1 [astro-ph] 9 Nov 2007

Radiativetransferinarelativisticaccretiondiskwindisexaminedundertheplane-parallelapproxi-mationinthefullyspecialrelativistictreatment.Foranequilibrium ow,wherethe owspeedandthesourcefunctionareconstant,theemergentintensityisanalyticallyobtained.Insuchanequilibrium owtheusuallimb-darkeninge ectdoesnotappear,sincethesourcefunctionisconstant.DuetotheDopplerandaberratione ectsassociatedwiththerelativisticmotionofwinds,however,theemergentintensityisstronglyenhancedtowardthe owdirection.Thisistherelativisticpeakinge ect.Wethuscarefullytreatandestimatetheappearanceofrelativisticwindsandjets,whenweobservetheminanarbitrarydirection.

Keywords:accretion,accretiondisks—astrophysicaljets—gamma-raybursts—radiativetransfer—relativity

1.Introduction

Accretiondisksarenowwidelybelievedtobeenergysourcesinvariousactivephenomenaintheuniverse(seeKatoetal.2007forareview).Relatingtoenergeticaccretiondisks,accretiondiskwindshavebeenextensivelyexaminedinconnectionwithastrophysicaljetsandout ows:inbipolarout owsfromyoungstellarobjects(YSOs),inout owsfromcataclysmicvariables(CVs)andsupersoftX-raysources(SSXSs),inrelativisticjetsfrommicroquasars(µQSOs),activegalacticnuclei(AGNs),quasars(QSOs),andingamma-raybursts(GRBs).Inparticular,intenseradiation eldsofluminoussupercriticalaccretiondisksmayberesponsibleforrelativisticjetsfromsuper-Eddingtonsources,suchasluminousµQSOs,GRS1915+105andSS433,luminousQSOs,3C273,andenergeticGRBs(see,e.g.,Fukue2004forreferences).Furthermore,energeticemissionsfromrelativisticjetshavebeenexamined,relatingto,e.g.,gamma-rayblazarsandgamma-raybursts(Dermer,Schlickeiser1993,2002;Dermer1998;B¨ottcher,Dermer2002;Dermeretal.2007).

Insuchcircumstances,radiativetransferinaccretiondiskwindsaswellasaccretiondisksbecomesmoreandmoreimportant.Radiativetransferinthestandarddiskhasbeeninvestigatedinrelationtothestructureofastaticdiskatmosphereandthespectralenergydistributionfromthedisksurface(e.g.,Meyer,Meyer-Hofmeister1982;Cannizzo,Wheeler1984).Furthermore,grayandnon-graymodelsofaccretiondiskswereconstructedundernumericaltreatments(Kˇriˇz,Hubeny1986;Shaviv,Wehrse1986;Adametal.1988;Mineshige,Wood1990;Rossetal.1992;Shimura,Takahara1993;Hubeny,Hubeny1997,1998;Hubenyetal.2000,2001;Davisetal.2005;Huietal.2005)andunderanalyticalones(Hubeny1990;Artemovaetal.1996;Fukue,Akizuki2006a).

Radiativetransferintheaccretiondiskwind,ontheotherhand,hasnotbeenwellconsideredbothinthenon-relativisticandrelativisticregimes.Forexample,transformationpropertiesofdiskradiation eldsintheproperframeofarelativisticjetwereexaminedby,e.g.,DermerandSchlickeiser(2002).Intheseearlierworks,however,theradiation eldsaresettobeexternalsources,andtheradiationtransferwasnotconsidered.Recently,radiativetransferinamovingdiskatmospherewas rstlyinvestigatedinthesubrelativisticregime(Fukue2005a,2006a),andintherelativisticregime(Fukue2005b,2006b;Fukue,Akizuki2006b).Inthesestudies,however,onlytheradiativemomentswereobtainedunderthemomentformalism,andthespeci cintensitywasnotsolved.Hence,inFukue(2007)thespeci cintensityfromanaccretiondiskwindwasobtainedinthesubrelativisticregime,wherethe owspeedvisoftheorderof(v/c)1.

Inthispaper,http://doc.guandang.netly,weexamineradiativetransferintherelativisticaccretiondiskwind,whichisassumedtoblowo fromtheluminousdiskintheverticaldirection(plane-parallelapproximation),withtherelativisticspeeduptotheorderofc.

Inthenextsectionwedescribethebasicequations.Insection3,weshowanalyticalsolutionsofthespeci cintensity.The nalsectionisdevotedtoconcludingremarks.

Radiative transfer in a relativistic accretion disk wind is examined under the plane-parallel approximation in the fully special relativistic treatment. For an equilibrium flow, where the flow speed and the source function are constant, the emergent intens

22.

RelativisticRadiativeTransferEquation

J.Fukue[Vol.,

Letussupposealuminous atdisk,deepinsidewhichgravitationalornuclearenergyisreleasedviaviscousheatingorotherprocesses.Theradiationenergyistransportedintheverticaldirection,andthediskgas,itself,alsomovesintheverticaldirectionasadiskwindduetotheactionofradiationpressure(i.e.,plane-parallelapproximation).Forsimplicity,inthepresentpaper,theradiation eldisconsideredtobesu cientlyintensethatboththegravitational eldof,e.g.,thecentralobjectandthegaspressurecanbeignored.Wealsoassumethegrayapproximation,wheretheopacitiesdonotdependonthefrequency.Asfortheorderofthe owvelocityv,weconsiderthefullyspecialrelativisticregime.

Theradiativetransferequationsaregiveninseveralliteratures(Chandrasekhar1960;Mihalas1970;Rybicki,Lightman1979;Mihalas,Mihalas1984;Shu1991;Katoetal.1998,2007;Peraiah2002;Castor2004).Thera-diativetransferequationinthefullyrelativisticformisgivenin,e.g.,theappendixEofKatoetal.(2007)ingeneralandverticalforms.

Inageneralformtheradiativetransferequationintheinertial( xed)frameisexpressedas

4 abs1v·lv·l 3sca

1 +(l· )I=ργ κ0+κ0γ1

t4π

2

v·l3v·l

γ41

4πcc2

2

v·lv·lv·l

+1

c2cc2c

2

vivjPijv·lij2

+liljcP 2γ1

c1 v2/c2)istheLorentzfactor.Intheleft-handside

thefrequency-integratedspeci cintensityIandthedirectioncosinelarequantitiesmeasuredintheinertia …… 此处隐藏：17982字，全部文档内容请下载后查看。喜欢就下载吧 ……