该【collapsars as a major source of r-process elements daniel m. siegel资料 】是由【dt83088549】上传分享，文档一共【23】页，该文档可以免费在线阅读，需要了解更多关于【collapsars as a major source of r-process elements daniel m. siegel资料 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。:..Letterhttps:///-019-1136-0Collapsarsasamajorsourceofr-,2,3,4*,JenniferBarnes1,2&,2Theproductionofelementsbyrapid?neutron?capture(r-process)electroncapturereactionsonprotons.(Theprotonfractionisdefinedinneutron-starmergersisexpectedtheoreticallyandissupportedastheratioinnumberdensitiesofprotonstoallbaryons—protonsandbymultimessengerobservations1–3ofgravitational-waveeventneutrons—and,forhistoricalreasons,isreferredtoastheelectronfrac-GW170817:thisproductionrouteisinprinciplesufficienttotion,Ye.)retionrates(see?Methods),neutrinoaccountformostofther-,6delayedamildlydegeneratestate(η?=?μe/(kBT)?≈?1,where?kBistheBoltzmannretiondiskformedaroundthenewlyconstantandTisthetemperature;?Fig.?1);thiselectrondegeneracybornblackhole7–10asthedominantsourceofheavyr-processsuppressespositroncreationandthusreducestheopposingrateofmaterialfromthatevent9,(thesupernova-triggeringcollapseofrapidlypreservedinthediskoutflows,whichexpandtolargeradiisufficientlyrotatingmassivestars),-processelements12,,aswellasthephasesfollowingcollapse,whilethehotproto-neutronstarisstillpres-hemicalenrichmentofeuropiumrelativetoironoverentbeforeblackholeformation20,21;however,onlyasmallfractionoflongertimescales15,16,retedmass,andthusofthewindejecta,occursduringthisactingatlowstellarmetallicitiesthanwithneutron-,itisreasonableyieldsufficientr--unboundfromtheinnerregionofcollapsardisksissimilartothatinstarmergers,thelargeramountofmaterialejectedpereventneutron-,,asexpectedontheoret-collapsarsmaysupplymorethan80percentofther-(theisotropicWehaveperformedasuiteofthree-dimensional,general-relativisticγ-parable).Thediskwindohydrodynamic(MHD)simulationsofneutrino-re-?inferredfromtheGW170817positionscharacteristicofcollap-kilonovathentranslatesintoanaveragecollapsarr-processyieldofupsars(Fig.?1)inordertoquantifythenucleosynthesisproductsofthetoabout1M(see?Methods).-unboundoutflowsfromthedisk(see?Methods).retedatdifferentratesduringthedifferentdiskmasses,retionratesourdisksimulationsretionratesexperiencedatdifferentepochsintheshowgiverisetor-processejecta(see?Methods).-processthethermodynamictrajecto-neutron-starmergerscenariosdifferinthatthecollapsardiskoutflowsriesoftracerparticlestrackingtheunboundmatterusinganr-processencounterrampressurefrominfallingmaterialofthestellarenvelope;heirdetailednucleosyntheticyields,however,simpleanalyticargumentsaswellasprevioussimulations12accountingfortheabsorptionofelectronneutrinosandantineutri-(see?Methods).Thelargeroutflowyieldpercollapsarismoreaccretionratesintherange>s?1??s?1(whereMisthansufficienttomakeupfortheirlowercosmicallyaveragedrateasthesolarmass),paredtoneutron-starmergers,thusimplicatingcollapsarsasthecalesoflongγ-raybursts(monlyinvokedasresultingfromdominantsiteofthesecond-andthird-peakr-processinourGalaxyretion12),wefindthatthewindandSolarSystem(see?Methods).ejectaareneutron-richandrobustlysynthesizebothlightandheavyObservationalsignaturesofther-processincollapsarsshouldber-processnuclei,?≈?195(Figs.?1,2;see?Methods).Previousstudiesofsupernovaearepoweredbythelargequantity(?)ofradi-retiondisksdidnotfindthesynthesisofsuchnucleiindiskoactivenickel(56Ni),synthesizedmainlyduringtheinitialexplosionoutflows,?3M?of56Nicanbeandneutrons12insteadofself-consistentlyevolvingtheprotonfrac-generatedfromthecollapsardiskwindsatlatetimes,butonlyoncetionundercharged-currentweakinteractions,retionratedropsbelowther-processthreshold,<10?3M?s?1modelsassumedthediskwindstobeentirelyneutrino-driven,inwhich(see?Methods).Nearpeaksupernovalight,theradioactiveheatingratecaseoutflowingmatterabsorbedmanyelectronneutrinosgeneratedof56Nigreatlyexceedsthatofr-processnuclei,makingitpossibletofromthediskandexperiencedhighratesofpositroncaptures17,18‘hide’thelatterinGRBsupernovalightcurvesandspectra,depending(see?Methods).onhowefficientlyther-processproductsaremixedoutwardsintotheposedofapproximatelyhigh-velocitylayersoftheexplosion(Fig.?3;see?Methods).Thepres-equalnumbersofneutronsandprotons,matterisdrivenonceinenceofhigh-opacitylanthanideelements23deeperwithintheejectaoaneutron-richstate(protonfraction05.)bycouldneverthelessbevisibleasexcessnear-infrared(NIR)emission1DepartmentofPhysics,ColumbiaUniversity,NewYork,NY,,ColumbiaUniversity,NewYork,NY,,Waterloo,Ontario,,Guelph,Ontario,Canada.*e-mail:******@|VOL569|NAtUre|241:..reSeArCHLetterac04He56Ni0M1)]?2?1r-processM2s?2?4(MLightr-processM3fb56Ni?6M1?44Helog(abundance)M2log[MBlackhole?8M3?6formation -rayburstSolarr-process?10012345650100150200Totalfallbackmass,Mfb(M)(km)?50?50?500?1?2log(degeneracy)?50050?50050?50050Diskmidplane(km)Diskmidplane(km)Diskmidplane(km)|˙ign≈10??31Msmildelectrondegeneracy(η?=?μe/(kBT)?≈?1;lowerhalfa,retionrate(Mfb,onalogarithmicscale)ofplots,colourscaleontheright)isestablished,whichdrivesthediskretedmass,retionstagesM12,,MM3midplaneneutron-rich(protonfractionYe05.;upperhalfofplots,coloursimulatedhere(see?Methods).Verticaldottedlinesindicateinitialblackholescaleontheright).c,Abundancedistributionsofnucleisynthesizedintheretionprocesspoweringtheγ-(seekey;dotsrepresentHorizontalbandsindicatethedifferentnucleosyntheticregimesofthedisktheobservedSolarSystemabundances).AboveMign,aheavyr-processuptooutflowsasidentifiedfromthesimulations,?around195isobtained(,MM12),whereasbelowb,Simulationsnapshotsofthedisk’sequatorialplaneforthethreeMarapidtransitiontooutflowsrichin56Niand4Heisobserved()M.retionstages,showingthataboveacriticalthresholdofign3atlatetimes(Fig.?3).Althoughsuchanexcessmay,inprinciple,bedegeneratewithothereffects,thepresenceofr-processelementsmaybinationwithNIRspectraandfutureobserva-tionsofneutron--processelementsarepinneddownempiricallybyobservationsoffutureneutron-starmergers(‘pure’r-processsources)—forexample,bytheJamesWebbSpaceTelescope—similar(butnarrower,owing?1tothelowerejectavelocity)linefeaturescouldbesoughtinlate-,theearly-time‘MHDsupernova’?2phaseoftheexplosion24isprobablyalreadyruledoutasa?heavyFirstr-processsite;unlikeinthedelayeddiskwindscenariodescribedhere,Secondhigh-opacity?r-processmaterialgeneratedduringtheexplosionphase?3MignThirdwouldnecessarilybemixedtohighvelocitieswiththe56NiinawaypatiblewithpresentobservationsofGRBsuper-56Ninovae(Fig.?3).log(massfraction)?44HeCollapsarsasthedominantsourcesoftheGalacticr-processhelpalleviateseveraloftheobservationalchallengesforneutron--standingquestionwhethertheaveragedelay?5Midplaneneutron-richrequiredforbinaryneutronstarstocoalesceafterstarformationissuf-NeutrinoradiationimportantMidplaneYe -processabundancesinmetal-poorhalostars,thatis,thosepollutedbyjustafewgenerationsofstars.?1??2??3??4hem-log[accretionrate(Ms?1)]ountforcosmicstructuregrowth25,26,|retionorconsideringalternativeformationchannelsathighredshift27,-peak(red;atomicmassnumberA?≈?80),,bycontrast,occurprimarilyinsecond-peak(blue;A?≈?130)andthird-peak(green;A?≈?195)r-processlow-metallicityenvironments28andthuswouldbeover-representednucleisynthesizedinthediskoutflowsareshown,aswellas56Ni(cyan)amongthefirstgenerationsofstars,providinganaturalexplanationandhelium(4He;purple)massfractions,retionregimesfortheobservedcarbon-enhancedmetal-poorstarswithhighr-processM1,M2andM3(fromlefttoright).Asharptransitionfromaheavy29r-processregimeto56Ni-˙≈10??31Ms,verticaldashedline,isapparentThemostdirectcurrentevidenceforasingler-esign(see?Methods).Uncertaintiesinthenucleosyntheticyieldsshowtherangefromtheultra-faintdwarfgalaxyReticulumII,whichwaspollutedofvaluesobtainedbyusingtwodifferenttreatmentsofneutrinoemissionearlyinitshistorybyarare,high--(see?Methods).retionratearebracketedbythestarmergerindeedprovidesahighr-processyield,thesupernovarangeofvaluesattainedduringthesimulationperiodusedtomonitortheretionrate(see?Methods;ExtendedDataFig.?3).242|NAtUre|VOL569|9MAY2019:..,D.,Metzger,B.,Barnes,J.,Quataert,E.&Ramirez-Ruiz,-starmergersfromagravitational-,80–84(2017).),?1neutronstarmergerLIGO/,optical,andnear-,L17(er1042t=5days(2017).,D.,Perego,A.,Zappa,F.&Bernuzzi,:jointconstraintonLt=,L29(2018).ández,R.&Metzger,=,b10502–517(2013).?20J?2t=,O.,Bauswein,A.,Pulpillo,.,Goriely,S.&Janka,H.-.?,541–567(2015).RNormalized ux+offsett=,.&Metzger,-dimensionalgeneral-relativistic?retiondisksfromneutron?14t=45daysstarmergers:outflowsandr-,?12231102(2017).ABmagnitudeB+2t=ández,R.,Tchekhovskoy,A.,Quataert,E.,Foucart,F.&Kasen,D.?10Long-retiondisks:,?83373–3393(2019).02040605,00010,00015,00020,,.&Metzger,-dimensionalGRMHDsimulationsofDaysWavelength(?)neutrino-,|Thesignaturesofr-(2018).Shownaresyntheticphotometryandspectraformodelsofr-process-,.&Woosley,:gamma-rayburstsandexplosionsin“failedsupernovae”.,262–289(1999).,K.,Narayan,R.&Piran,-,341–361(2005).outwardmixingofr-processmaterialwithradioactive?nickel56Ni?,.,Frebel,A.,Chiti,A.&Simon,-,,610–613(2016).distributionofr-processmaterialtracksthedistributionof56Ni,?té,-,230(2017).inthecollapsarwindmodel,ther-,K.,Beniamini,P.&Piran,-,paredr-processnu
collapsars as a major source of r-process elements daniel m. siegel资料 来自淘豆网www.taodocs.com转载请标明出处.