Relativistic simulations of compact object mergers for nucleonic matter and strange quark matter [Elektronische Ressource] / Andreas Ottmar Bauswein

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Technische Universit¨at Mu¨nchenPhysik DepartmentMax-Planck-Institut fu¨r AstrophysikRelativistic simulations ofcompact object mergersfor nucleonic matter andstrange quark matterAndreas Ottmar BausweinVollst¨andigerAbdruckdervonderFakult¨atfu¨rPhysikderTechnischeUniversit¨atMu¨nchenzur Erlangung des akademischen Grades einesDoktors der Naturwissenschaften (Dr. rer. nat.)genehmigten Dissertation.Vorsitzender: Univ.-Prof. Dr. R. Kru¨ckenPru¨fer der Dissertation:1. Priv.-Doz. Dr. H.-Th. Janka2. Univ.-Prof. Dr. W. WeiseDie Dissertation wurde am 25.11.2009 bei der Technischen Universit¨at Mu¨ncheneingereicht und durch die Fakult¨at fu¨r Physik am 29.01.2010 angenommen.Diese Arbeit ist meinen Eltern Maria und Ottmar gewidmet.3Contents1. Introduction 71.1. Physical context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.2. Observational consequences . . . . . . . . . . . . . . . . . . . . . . . . . 91.2.1. Gravitational-wave signals . . . . . . . . . . . . . . . . . . . . . . 91.2.2. Gamma-ray bursts . . . . . . . . . . . . . . . . . . . . . . . . . . 101.2.3. Nucleosynthesis aspects . . . . . . . . . . . . . . . . . . . . . . . 111.2.4. Signatures of strange quark matter . . . . . . . . . . . . . . . . . 111.3. Modeling compact star mergers . . . . . . . . . . . . . . . . . . . . . . . 121.4. Neutron star-black hole mergers . . . . . . . . . . . . . . . . . . . . . . . 141.5. Goals and outline of the thesis . . . . . . . . . . . .

Sujets

• Physik

Informations

• Publié par: technische_universitat_munchen
• Publié le: 01 janvier 2010
• Nombre de lectures: 17
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

TechnischeUniversita¨tMu¨nchen
PhysikDepartment
Max-Planck-Institutfu¨rAstrophysik

Relativisticsimulationsof
compactobjectmergers
fornucleonicmatterand
strangequarkmatter

AndreasOttmarBauswein

Vollsta¨ndigerAbdruckdervonderFakulta¨tfu¨rPhysikderTechnischeUniversita¨tMu¨nchen
zurErlangungdesakademischenGradeseines

DoktorsderNaturwissenschaften(Dr.rer.nat.)
genehmigtenDissertation.
Vorsitzender:Univ.-Prof.Dr.R.Kru¨cken
Pru¨ferderDissertation:

1.Priv.-Doz.Dr.H.-Th.Janka
2.Univ.-Prof.Dr.W.Weise

DieDissertationwurdeam25.11.2009beiderTechnischenUniversita¨tMu¨nchen
eingereichtunddurchdieFakulta¨tfu¨rPhysikam29.01.2010angenommen.

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3

Contents
1.Introduction7
1.1.Physicalcontext................................7
1.2.Observationalconsequences.........................9
1.2.1.Gravitational-wavesignals......................9
1.2.2.Gamma-raybursts..........................10
1.2.3.Nucleosynthesisaspects.......................11
1.2.4.Signaturesofstrangequarkmatter.................11
1.3.Modelingcompactstarmergers.......................12
1.4.Neutronstar-blackholemergers.......................14
1.5.Goalsandoutlineofthethesis........................15
1.6.Conventionsandnotations..........................16
2.Physicalmodelandnumericalimplementation17
2.1.Relativisticsmoothparticlehydrodynamicsandtheconformalatness
approximation.................................17
2.1.1.Initialdata..............................22
2.2.Simulatingneutronstar-blackholemergers.................22
2.2.1.Blackholesinnumericalrelativity..................23
2.2.2.Punctureblackholeintheconformalatnessapproach......25
2.2.3.Furtheraspectsofsimulatingblackholes..............29
3.Equationofstateofhigh-densitymatter33
3.1.Nuclearequationsofstate..........................33
3.2.Strangequarkmatterequationsofstate..................35
3.3.Thermodynamicalpropertiesandstellarstructure.............36
3.4.Somecommentsonstrangequarkmatter..................40
4.Simulations43
4.1.Generaloverview...............................43
4.2.Binarieswith1.2Mand1.35M.....................47
4.3.Binarieswith1.35Mand1.35M.....................50
4.4.Binarieswith1.8Mand1.8M......................52
4.5.Thermaleects................................52
5.Gravitationalwaves55
5.1.Characteristicfeatures............................55
5.2.Binaryparameterdependence........................59
5

oCtnnets5.3.Equationofstatedependenceandthermaleects.............64
5.4.Occurrenceofapromptcollapse.......................65
5.5.Gravitational-waveluminosity........................67

6.Massejectionofstrangestarmergers

73

7.Simulationsofmixedbinaries79
7.1.Head-oncollisions...............................79
7.2.Quasi-equilibriumorbits...........................83
7.3.Mergingcompactstar-blackholebinaries..................84

8.Summary,conclusionsandoutlook

59

A.Thermaleectsinneutronstarmergersimulations99
A.1.Temperaturephenomenology.........................99
A.2.Approximatetreatmentofthermaleects..................103

B.Mass-radiusrelationsofneutronstars

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111

1.Introduction

1.1.Physicalcontext

Starsmoremassivethan8solarmassesendtheirhydrostaticevolutionwithasupernova
explosion.Theremnantsofsucheventsareeitherablackhole(BH)forthemostmassive
progenitorstarsoracompactstar,commonlyreferredtoasneutronstar(NS).Thetrue
natureofthelatterhasremainedamysterysincethediscoveryoftheseobjects.Besides
acompositionofmainlyneutrons,moreexoticphaseshavebeenproposedtooccurin
compactstars[59,66].Theremayevenbethepossibilitythattheseobjectsareinreality
quarkstars.Accordingtothestrangematterhypothesis[25,164]amixtureofup,down
andstrangequarksmayformthetrueandabsolutegroundstateofmatterandifthis
hypothesisweretrue,compactstarswouldbeso-calledstrangestars(SSs)consistingof
thishigh-densitystrangequarkmatterratherthanNSmatter[59,66].Itturnsoutthat
SSsareinmanywayssimilartoNSs,forexampleinthemassrangeandcompactness,
andthereforetheycanbeconsideredasanalternativetoNSsinaccordancewiththe
observedpropertiesofknowncompactstars[3,59,65,66,160].Throughoutthisthesis
thetermcompactstarreferstoeitheraNSoraSS.
Theoreticalconsiderationscannotexcludethestrangematterhypothesisandthusthe
existenceofSSsbecauseofuncertaintiesontheequationofstate(EoS)ofhigh-density
matterandthephenomenonofquarkconnement[59,66,159,160].Also,theEoSof
ordinaryNSmatterabovenuclearsaturationdensity,2.71014g/cm3,isuncertain
becauseofmanydicultiesintreatingthenuclearmany-bodyproblem[66,89,159].
Furthermore,severalnuclearparameters,whichareusedintheoreticaldescriptions,are
notwellmeasured.Theseobservationaldataaredeterminedatdensitieswhichare
accessiblebylaboratoryexperiments,butathigherdensitiesrelevantforNSstheycan
onlybeextrapolated.Becauseofthisignoranceofthenatureofthetruehigh-density
EoSmanydierentEoSswereproposed,employingdierentmicrophysicalmodelsand
adoptingvariousexperimentaldata.
Toconstraintheuncertaintiesofthephysicsofcompactstars,astronomicalobserva-
tionsprovideauniquepossibilityandopenthefantasticavenuetostudynuclearand
particlephysicsatcelestialobjectsasaninterplaybetweenvariouseldsofresearch.
Somemassesofcompactstarsareknownverywellbytimingthearrivalofradiosignals
ofpulsarsasmembersinbinarysystems[150].Allotherstellarpropertiesareratherun-
certain,includingradiusmeasurements.Thisisunfortunate,becauseforinstanceonly
onewelldeterminedpointofthemass-radiusrelation,whichisentirelygivenbythe
EoS,wouldputtightconstraintsontheEoSandwouldeventuallyalsodecidewhether
SSsexist[66,89].

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1.nItroudtcoinFigure1.1.:Cumulativeshiftoftheperiastrondemonstratingtheorbitaldecayofthe
binarypulsar1913+16duetotheemissionofGWs.InNewtoniangravitynosucheect
ispredicted(horizontalsolidline).Figuretakenfrom[161].

Thisthesisisintendedtoexploretheastrophysicalconsequencesofdierenthigh-
densityEoSsinthecontextofcompactstarmergersincludingmodelsthatdescribe
absolutelystablestrangequarkmatter.Inparticular,itisexaminedifthemergersof
SSscouldyieldobservationalsignaturesthatallowonetodistinguishthemfromcolliding
.sSNAtthetimeofwritingthisthesisabouttenbinariescomposedoftwocompactstarsare
knowninourgalaxy(seethecompilationin[117,150]),amongthemthefamousHulse-
Taylorpulsar[161].Theobservationofthisbinaryprovedforthersttimeindirectly
theexistenceofgravitationalwaves(GWs)(seeFig.1.1),whichwerepredictedby
Einsteinalreadyin1918[44]butarestillwaitingfortheirdirectdetection[33].The
orbitalparametersinthedoublecompactstarsystemscanbemeasuredveryprecisely
byradiotelescopes,anditisfoundthattheorbitsofthesebinariesdecayinaway

8

12..Osbreavtoianlocsnqeeucnsepredictedbygeneralrelativity[86,95].ThisisduetotheemissionofGWs,whichcarry
awayenergyandangularmomentum.Thedecreaseoftheorbitalseparationonatime
scaleofabout100-1000Myrs