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Analysis of spectra of Type I Supernovae with radiative transfer models [Elektronische Ressource] / Stephan Hachinger. Gutachter: Wolfgang Hillebrandt ; Wolfram Weise. Betreuer: Wolfgang Hillebrandt

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Published 01 January 2011
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¨ ¨TECHNISCHE UNIVERSITAT MUNCHEN
¨MAX-PLANCK-INSTITUT FUR ASTROPHYSIK
Analysisofspectra
ofTypeIsupernovae
withradiativetransfermodels
StephanHachinger
Vollstandiger¨ AbdruckdervonderFakultat¨ fur¨ PhysikderTechnischenUniversitat¨
Munchen¨ zurErlangungdesakademischenGradeseines
DoktorsderNaturwissenschaften(Dr.rer.nat.)
genehmigtenDissertation.
Vorsitzender: Univ.-Prof. S.Bishop,PhD
Prufer¨ derDissertation:
1. Hon.-Prof. Dr. W.Hillebrandt
2. Univ.-Prof. Dr. W.Weise
DieDissertationwurdeam 01.06.2011 beiderTechnischenUniversitat¨
¨ ¨ ¨MuncheneingereichtunddurchdieFakultatfurPhysikam 08.07.2011
angenommen.2 AnalysisofspectraofTypeIsupernovaeContents
1 Introduction 13
1.1 SNobservations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.1.1 LightcurvesandcosmologicalapplicationofSNe . . . . . . . 14
1.1.2 Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.2 TheoryofTypeIaSNe(thermonuclearSNe) . . . . . . . . . . . . . . . 28
1.2.1 Observationalconstraints . . . . . . . . . . . . . . . . . . . . . 28
1.2.2 Progenitorsystems: somedetails;evolutionpriortoexplosion . 31
1.2.3 Finalstages,explosionandnucleosynthesis . . . . . . . . . . . 34
1.3 TheoryofTypeIb,IcandIISNe(core-collapseSNe) . . . . . . . . . . 38
1.3.1 Observationalconstraints . . . . . . . . . . . . . . . . . . . . . 39
1.3.2 Progenitorstarmodels . . . . . . . . . . . . . . . . . . . . . . 43
1.3.3 Explosionmodelsandnucleosynthesis . . . . . . . . . . . . . . 44
1.4 SNejectaafterexplosion–force-free,homologousexpansion . . . . . 50
2 Analysingspectrawithradiativetransfermodels 53
2.1 RadiativetransferinSNatmospheres . . . . . . . . . . . . . . . . . . . 53
2.1.1 Radiativetransfer: basicquantitiesandequations . . . . . . . . 53
2.1.2 OpacityandemissivityinSNe . . . . . . . . . . . . . . . . . . 55
2.1.3 Thestateoftheplasma . . . . . . . . . . . . . . . . . . . . . . 63
2.2 Radiativetransfer/spectrumsynthesiscode . . . . . . . . . . . . . . . 66
2.2.1 Conceptofthecode . . . . . . . . . . . . . . . . . . . . . . . 66
2.2.2 MainloopofthecodeandMCtransportloop . . . . . . . . . . 68
2.2.3 Formalintegralprocedure . . . . . . . . . . . . . . . . . . . . 72
2.2.4 TheNLTEextensiontothecode . . . . . . . . . . . . . . . . . 72
2.2.5 Spectralmodels: principles,modelling,abundancetomography 78
3 SNeIa: spectralanalysisofpeculiarobjects 83
3.1 SN2005bl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.1.1 Densityprofiles . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.1.2 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
3.1.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.1.4 Summary–analysisofthe1991bg-likeSN2005bl . . . . . . . 106
3.2 SN2009dc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.2.2 Observationsandobservationalparameters . . . . . . . . . . . 108
3.2.3 Densityprofile&risetime–earlytimemodels . . . . . . . . . 109
3.2.4 Tomographymodels . . . . . . . . . . . . . . . . . . . . . . . 1184 AnalysisofspectraofTypeIsupernovae
3.2.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
3.2.6 Summary–analysisofthe“Super-Chandrasekhar”SN2009dc . 136
4 SNeIIb/Ib/Ic:asequenceofspectralmodelsforstrippedCCSNe 139
4.1 ModelsfortheSNe2008axand1994I . . . . . . . . . . . . . . . . . . 139
4.1.1 SN2008ax–aSNIIb . . . . . . . . . . . . . . . . . . . . . . 142
4.1.2 SN1994I–aSNIc . . . . . . . . . . . . . . . . . . . . . . . . 148
4.2 Modelsequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
4.2.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
4.2.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
4.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
4.3.1 Heatom,rateequilibriainaHe I/He II-dominatedplasmainSNe164
4.3.2 HestateintheSN2008axmodel;evolutionofthelines . . . . . 166
4.3.3 Tests: modificationsofthe“SNIb/Ic”model . . . . . . . . . . 169
4.3.4 Summary–ourresultsandSNIb/Icprogenitormodels . . . . . 170
5 Conclusionsandoutlook 173Astrophysicaltermsandnotation
In this thesis, we follow the usual terminology in astrophysics and supernova physics.
Termslesscommoningeneralphysics,orusedinadifferentsensethaninotherbranches
ofphysics,areprinteditalicthefirsttimetheyareused. Termswhichcannotbeguessed
from the context and which are easily misinterpreted or for which it is hard to find a
clear definition in a basic textbook (Unsold¨ &Baschek 2001), are explained below in
Table 1. We kindly ask the reader to consult this table when in doubt. Equations are
alwayswrittenincgsunits(gaussianunits,cf.Jackson1998). Otherunitsareusedonly
if common in astrophysics. Unusual symbols and non-cgs units which appear in our
formulaearelistedinTable2. Usageofonesymbolformorethanonequantityhasbeen
allowedinafewcases.
Table1: Technicaltermsinastrophysicsandsupernovaphysics.
term meaning
atomicline line of an atom or ion, corresponding to a transition between
discreteenergylevels
co-moving,lagrangian referstothe co-movingframe
co-movingframe, A coordinate system moving locally with the hydrodynamic
lagrangianframe flow; the transformation from the static (eulerian) to the co-
movingframechangeswithtimesuchthateachfluidelement
retains its coordinate. A transformation from a global static
toaglobalco-movingsystemneednotbelinear.
dustextinction see reddening
envelope outer layers of a star (often used as an opposite to the term
core)
extragalactic notwithintheMilkyWay
Fe-groupelements scandium(Sc)andheavierelementsuptonickel(Ni)
IME/intermediate- elements heavier than oxygen (O) and lighter than scandium
masselements (Sc)
galactic withintheMilkyWay
He(giant)star a star which has lost its H envelope (usually as a result of
binaryevolution),butretaineditsHe
LTE localthermodynamicequilibrium6 AnalysisofspectraofTypeIsupernovae
Table1: (contd.) Technicaltermsinastrophysicsandsupernovaphysics.
term meaning
NLTE,non-LTE non – local-thermodynamic-equilibrium, i.e. a state (of the
plasmaandtheradiationfield)outofLTE
metal anyelementheavierthanhelium
observedwavelength wavelengthatwhichlineradiationisobservedbyanobserver
immersed in air – this wavelength will differ from the rest
wavelength (see below) if emitting material moves with re-
specttotheobserver
opticalspectrum spectrum of an astronomical source of light covering at least
the optical wavelength range (but normally also extending
intothenearinfrared)
restwavelength atomiclinewavelengthmeasuredinalaboratory(inair)
reddening Attenuation of light from an astrophysical source by dust;
usually leads to a particularly strong suppression of blue ra-
diation. When needed we assume a Cardellietal. (1989)
extinction curve with R = 3.1 (standard Milky-Way-likeV
dust).
scattering in radiative transfer: absorption and re-emission of a photon,
preserving the photon’s energy in the rest frame of the ab-
sorber – only the energy-preserving nature is relevant here;
the exact properties of the physical process is irrelevant and
alsothetarget(atom,freeelectron,...)
Table2: Lesscommonsymbolsandnon-cgsunitsusedinthisthesis.
symbol meaning
−8˚ ˚ ˚A Angstrom, 1A = 10 cm. Whenever wavelengths of spec-
˚tralfeaturesarementioned,anotationlike“1234.5A”implies
that1234.5isthe observed wavelength
˚B B filter band [3700–5500A; for detailed shapes of filter
bandpassesseee.g.Bessell(1990)]
::: prefixes denote small quantities, or increments of
quantities.
d luminositydistance,i.e.thedistanceinferredfromtheratioofL
the radiation fluxF sentoutandreceivedfromanobject
51foe 10 erg[(tentothe)fifty-oneerg]Astrophysicaltermsandnotation 7
Table2: (contd.) Lesscommonsymbolsandnon-cgsunitsusedinthisthesis.
symbol meaning
dFF,F ,F ,f,... radiation flux (F = : flux per unit frequency; F : analo- d
gous): energytransportedbyabeamofradiationperunittime
andperunitareaperpendiculartothebeam
˚1234.5 1234.5A. Whenever wavelengths of spectral features are de-
notedlikethis,1234.5istobetakenasthe restwavelength.
˚I I filter band [7000–8750A; for detailed shapes of filter
bandpassesseee.g.Bessell(1990)]
dII,I intensity(I = : frequency-dependentspecificintensity) d
:::I,:::II,::: Ionisation stages (e.g. Si I, Si II, :::) – I refers to a neutral
atom, IItoaionwithachargeof+e, IIItoaionwithacharge
of +2e. Negative ions are denoted in the standard notation,
−e.g.OH .
L luminosity: power[erg/s]ofaradiationsource
::: analogousto::: ,seethere
ly light year –
171ly=c365.25d86400s=d9.46110 cm.
M totalmass
M,m,mag Magnitudes, a logarithmic measure for the brightness of a
source of light. The relative magnitude m of an astrophys-
ical source of light – as seen from earth – is defined us-
Fing the star Vega as a reference: m[mag] = 2.5log( ),
FVega
where F is the measured flux of the radiation. The absolute
magnitude M is the relative magnitude at which an object
would appear if it would be 10pc away from the observer.
It is equivalent to a luminosity, and can be calculated as:
F rM[mag] = 2.5log( ) 5log( ).
F 10pcVega
M ,m magnitudeinthefilterbandXX X
::: as subscript to a function denotes the frequency as an ar-
gument to the function. This notation is commonly used in
radiative transfer, where e.g. a frequency-dependent intensity
isdenotedasI (:::).
pc Parsec–thedistance(perpendiculartotheorbitalplane)from
which the mean radius of the Earth’s orbit around the Sun is
observedtosubtendanangleof1”. 1pc3.26ly.
˚R R filter band [5600–8500A; for detailed shapes of filter
bandpassesseee.g.Bessell(1990)]8 AnalysisofspectraofTypeIsupernovae
Table2: (contd.) Lesscommonsymbolsandnon-cgsunitsusedinthisthesis.
symbol meaning
˚U U filter band [3100–4100A; for detailed shapes of filter
bandpassesseee.g.Bessell(1990)]
˚V V filter band [4800–6600A; for detailed shapes of filter
bandpassesseee.g.Bessell(1990)]
Z metallicity: abundanceof metals(seeTable1)
∗::: Ansuperscriptasteriskattachedtosomequantitydenotesthe
valueof this quantity in local thermodynamic equilibrium (at
temperatureT).
::: Asubscriptattachedtoaquantitydenotesthevalueforthe
sun(e.g.sunmass: M ).