Stellar iron core collapse in _424 3+1_425 general relativity and the gravitational wave signature of core-collapse supernovae [Elektronische Ressource] / von Christian David Ott

Christian David Ott

Sujets

• Astronomie

Informations

• Publié par: universitat_potsdam
• Publié le: 01 janvier 2006
• Nombre de lectures: 31
• Langue: English
• Poids de l'ouvrage: 45 Mo

Extrait

Stellar Iron Core Collapse in{3+1} General Relativity and
The Gravitational Wave Signature of Core-Collapse Supernovae
Dissertation
eingereichtander
Mathematisch-NaturwissenschaftlichenFakulta¨t
derUniversita¨tPotsdam
von
Christian David Ott
November2006Stellar Iron Core Collapse in{3+1} General Relativity and
The Gravitational Wave Signature of Core-Collapse Supernovae
Christian David Ott
Dissertation
Albert-Einstein-Institut
Max-Planck-Institutfu¨rGravitationsphysik
and
Mathematisch-NaturwissenschaftlicheFakulta¨t
Universita¨tPotsdam
2006Copyrightby
ChristianDavidOtt
2006/2007
This work is licensed under the Creative Commons Attribution-Noncommercial-
Share Alike 2.0 Germany License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc-sa/2.0/de/ or send a letter to Creative
Commons,543HowardStreet,5thFloor,SanFrancisco,California,94105, USA.
Cover figure: Color map of the specific entropy per baryon in the equatorial plane of a new-
born rapidly rotating and nonaxisymmetrically deformed neutron star at 90 ms after core
2bounce. Shownaretheinner100×100km . Thecolormaprangesfrom∼0.8 k /baryon(red)B
to∼6 k /baryon(darkblue/purple).BGravitationalwavestravelatthespeedofthought.
SirArthurEddington
Ihavenoideawhofirstcalculatedtheemissionofgravitationalradiationfrom
acollapsingstarwithrotation. RuffiniandWheeler mayhavebeen thefirst.
Itwascertainlyobvioustoeveryonewhothoughtaboutitthatacollapsing
starwithrotationwouldgiverise toastrongpulseofgravitationalwaves.
Imakenoclaimtohavethoughtofthisfirst.
FreemanDyson,
personalcommunication,
October2006
Idon’tconsidermyselfapessimist. Ithinkofapessimistassomeonewhois
waitingforittorain. AndIfeelsoakedtotheskin.
LeonardCohenAbstract
53Core-CollapseSupernovaearenature’sgrandestexplosions, liberating∼ 10 erg,thecolossalgrav-
itationalbindingenergyof aneutronstar. Mostof thisenergy,99%,isemittedinneutrinos, 1%goes
into the asymptotic explosion energy and becomes visible in the electromagnetic spectrum, and a
tinyfraction,perhapslessthanamillionth, isradiatedingravitationalwaves.
The work presented in this dissertation is concerned with the gravitational wave signature of core-
collapse supernovae. Previous studies have identified rotating iron core collapse, core bounce and
protoneutron star (PNS) ring-down pulsations, postbounce convection, anisotropic neutrino emis-
sion and postbounce nonaxisymmetric rotational instabilities as the primary processes and phases
fortheradiationofgravitationalwaves.
I perform the first ever calculations of rotating stellar iron core collapse in {3+1} general relativ-
ity(GR) that start out with presupernovamodels fromstellar evolutionary calculationsand include
a microphysical finite-temperature nuclear equation of state, an approximate scheme for electron
capturesduring collapse and neutrino pressureeffects. Based on the resultsof theses calculations, I
obtaintheto-datemostrealisticestimatesforthegravitationalwavesignalfromcollapse,bounceand
earlypostbounce phasesof core-collapsesupernovae. Myresultsshow that (1)the collapse, bounce
and early postbounce gravitational wave signal morphology is much more generic than previously
estimated,(2)thattherelevanceofrotationaleffectsismuchsmallerthanthoughtandthatrotational
“multiple” core bounce does not occur in the range of physically plausible initial rotation rates and
degreesofdifferentialrotation,and(3)thatallconsideredironcorerotationalconfigurationsundergo
collapse,bounce andPNSring-down inaxisymmetryandnone ofthese modelsreachratiosofrota-
tionalkinetictogravitationalpotentialenergy(β = T/|W|)sufficientlyhightoexperienceaclassical
MacLaurin-typebar-modeinstability at high-T/|W|. However, I find and analyzethe development
of nonaxisymmetric structures with a dominant m = 1 component that grow in a number of mod-
els due to a low-T/|W| dynamical rotational instability and whose quadrupole components lead to
prolongednarrow-bandgravitationalwaveemission,significantlyenhancingthegravitationalwave
signatureofrapidlyrotatingironcorecollapse.
I supplement my{3+1} GR simulations of rotating iron core collapse with 2D Newtonian neutrino
radiation-hydrodynamicsupernovacalculationsfocussingon: (1)Thelate-postbounce gravitational
waveemissioninmodelsofcore-collapsesupernovaewithslowlyornonrotatingprogenitorcores. I
findthat thedominant emission processinsuchmodelsmaybetheoscillations ofthe PNScorethat
are of predominantly g-mode character and that are excited hundreds of milliseconds after bounce
and typically last for several hundred milliseconds while emitting strong gravitational waves in a
narrowfrequency band. (2)The gravitational wave emission in accretioninduced collapse (AIC) of
massive O/Ne/Mg white dwarfs to neutron stars, based on the first AIC calculations starting with
rapidlyrotating 2Dequilibrium models. I find that efficient electron captureleadsto rapid collapse
largelyunaffectedbyrotationaleffects,butowing toverysmallinner cores,toonly modest gravita-
tional wave emission from core bounce and PNS ring-down despite strong rotational flattening. At
postbounce times the gravitational wave emission is dominated in amplitude by the low-frequency
emissionassociatedwithrotation-inducedanisotropiesintheneutrinoradiationfields.
Based on my results I surmise that the gravitational wave emission from rapidly rotating iron core
collapseandAICeventsshouldbedetectablealreadybyinitialLIGO-classobservatoriesthroughout
the Milky Way and with advanced LIGO-class observatories throughout the Milky Way and the
Magellanic Clouds. If persistent nonaxisymmetric deformations occur, detection to distances out to
the Virgo Cluster may be marginally possible. Nonrotating or slowly rotating core collapse does
not lead to a detectable gravitational wave signal from core bounce, but gravitational waves from
postbounceconvectionandshockdeformationsmaybedetectablebyadvancedLIGOs. InitialLIGOs
woulddetectstrongPNScoreoscillationsthroughout theMilkyWayandbeyond.