Diagnosing nucleosynthesis production in supernovae

Anders Jerkstrand, MPI for Astrophysics Outline

1. Introduction to supernovae and their nucleosynthesis

2. Nebular phase modelling and the SUMO code

3. Results 1. Hydrostatic yields: Oxygen

4. Results 2. Explosive yields: Nickel

5. Outlook : Extending emission line modelling to kilonovae 6. Summary

2 Supernovae – the deaths of stars

1 Core-collapse of a massive star 2 Thermonuclear explosion of a as it runs out of fuel at the end of white dwarf exceeding the its life Chandrasekhar limit (1.4 M ⊙)

Hydrostatic

Explosive

www.phys.olemiss.edu hetdex.org More envelope stripping à Type IIP IIL IIb Ib Ic Ia

Rate 40% 10% 10% 5% 20% 25% 3 Supernovae – open questions

Stellar origins • Which stars explode as which Type of SNe? • How do H-poor SNe lose their H envelopes? How do He-poor lose their He?

Explosion physics and compact object formation • How does the explosion happen? Is the neutrino-mechanism the right one? MRI effects? • How are neutron stars and black holes formed? Which masses, spins, and kicks?

Nucleosynthesis • Which elements are made in which supernovae? • Which elements are mainly made by supernovae, and which by other sources?

Application as distance indicators • How do Type Ia supernovae work, and how accurately can we measure cosmological distances with them?

Exotic physics • Can the equation of state at high densities be constrained by SNe? • Do some supernovae form magnetars, quark stars, gamma-ray bursts? 4 More massive stars produce much more nucleosynthesis

6

) Thielemann 1996 ⊙ Nomoto 1997 M 5 Limongi 2003 Hirschi 2005 − no rot 4 Hirschi 2005 − with rot Woosley 2007 3

2 Variation with 1 stellar evolution Ejected oxygen mass ( physics

0 10 15 20 25 30 MZAMS(M⊙) 5 Two main supernova phases

Photospheric phase Nebular phase

Long escape time for radiation Short escape time for radiation à a diffusion light curve à a steady-state tail

Spectra probe Spectra probe surface layers all ejecta

Many lines Few lines excited and excited and signi- reduced optical depth --> ficant optical depth –> Mangitude Emission-line spectra Scattering spectra

Time Simple microphysics (~LTE) Complex microphysics (NLTE)

Transition epochs: H-rich SNe: ~150d, H-poor SNe: ~30d, Kilonovae: ~2d Elements currently diagnosed from supernova emission-line spectra

Hydrostatic production Explosive production (up to Mg) (Si and beyond)

Rapidly plummeting abundances à Elements over Zn too rare to be seen

See Jerkstrand 2017,chapter in Handbook of supernovae, for a review of key results 7 The SUMO code : a state-of-the-art forward modelling tool Jerkstrand+2011, 2012 Radioactive decay and gamma-ray thermalization Degradation of Compton electrons NLTE statistical equilibrium • Spencer-Fano Equation • 22 elements, first three ionization stages • Ionization, excitation, heating • 10,000 levels

Temperature Radiative transfer • Heating = cooling • Monte Carlo-based, Sobolev approximation, 300,000 lines

• Code is 1D but allows approximate treatment of mixing by virtual grid method.

Example of best-fitting explosion models (this one from KEPLER, Woosley & Heger 2007) to a Type IIP supernova.

8 A crucial challenge: considering 3D effects

3D simulation (Hammer+2010) C O Ni

Set-up in SUMO

• In Monte-Carlo codes, one option it to treat clumps in a statistical manner (Jerkstrand et al. 2011) • Use 3D simulations as guide to set up the probability functions using radial averages of distributions. 9 Treatment of molecules and dust Jerkstrand+2012

SN 2004et (AJ+2012)

Molecules: Dust: • Assume O/Si and O/C zones to • Apply a gray, time-dependent be mainly cooled by SiO and CO absorption coefficient. (a result from chemistry codes). • Value can be inferred from line • Can be tested in few cases (e.g. shifts and IR observations. SN 1987A, SN 2004et). 10 Oxygen : Standard Type II supernovae from explosions of MZAMS =10-17 M⊙ stars. M(O) = 0.1 – 1 M⊙. AJ+2015 (MNRAS)

• 10 Can be modelled quite

1987A 2002hh 2007it well with approximate 1988A 2004et 2012A 8 1990E 2006bp 2012aw mixing methods in 1D. 1999em 2006my 2012ec Co power) M

56 ZAMS 25 • “Red Supergiant 6 19 problem” (Smartt 2009) 4 appears confirmed.

15 2 • However, first object with 12 possibly M > 20 ~M ⊙ now

L([O I] 6300, 6364) (% of 0 discovered 150 200 250 300 350 400 450 500 Epoch (days) (Anderson+2018). Low metallicity (0.05 Z ⊙).

11 Oxygen: Same picture for hydrogen-poor (Type Ib/IIb) SNe: these appear to be mainly mass donors to a companion from low-mass progenitor range (10-20 M ⊙). AJ+2015 (A&A), Ergon+2015 (A&A) 0.04 1993J 2008ax 2011dh 0.03

0.02

MZAMS: 17 0.01

([O I] 6300, 6364), normalized 13 L 0 12 100 200 300 400 500 600 Time (days) 12 Oxygen : Very large production only in a rare class of superluminous supernovae AJ+2017 (ApJ)

f=filling factor

Too cold Too ionized

• Independent support from large inferred Mg masses (1 - 10 M ⊙) from standard recombination lines theory. • Implication: Some high-mass stars do explode somehow (but most probably collapse directly to black holes) 13 Low-velocity Type II SNe: match models for 8-10 M ⊙

progenitors AJ+2018 16 3.0 10− × Ca II SN 2008bk +531d Ha ) 1 2.5 9 M model − ⊙ ˚ A OI 2 2.0 −

cm CI

1 1.5 Fe II − 1.0 Mg I (erg s Na I Fe II Ni II λ

F 0.5

0.0 4000 5000 6000 7000 8000 9000 Wavelength (A)˚ Data: Maguire+2012

• Mg, O, Na, C lines all strong à Fe core progenitors, not ONeMg cores (more later)

14 The progenitor landscape (local Universe, Z ~ Z ⊙) from inferred hydrostatic nucleosynthesis yields

IIb/Ib LIGO BHs Couch&Franss (not Donor on 1996 AJ+2015 PISNe Few known, SNe SLSNe Ic

detected) all GRB SNe Ic AJ+2017, Nicholl Sub- Normal Dessart+2017 +2017 Single or (not lum. Mazzali+2001, IIP Maeda+2006 instability

receiver - AJ+2012,2014, AJ+2018 (in prep). Pulsational (not detected) ECSN IIP AJ+2018 2015 Pair detected) Lisakov+2018

8 10 20 30 40 100 130 M ZAMS 10 Nickel: a unique tracer of the innermost layers and the explosion

• Forward modelling shows Fe and Ni lines formed in LTE and optically thin à can use analytic method.

16 Nickel: a unique tracer of the innermost layers and the

explosion AJ+2015 (MNRAS)

• Average ratio ≥ solar. If true in larger sample, Type Ia SNe must make Ni/Fe ≤ solar → constraints on both core-collapse and thermonuclear explosions models.

• But sometimes significantly larger than solar: what does it mean?

17 Nickel: a unique tracer of the innermost layers and the explosion AJ,Magkotsios,Timmes+2015 (ApJ) TORCH simulations, vary electron fraction Ye, tempesature, density Ni/Fe in solar Ni/Fe in solar Ye = 0.499 Ye = 0.497

• Solar production requires Ye ~ 0.499, whereas supersolar requires Ye ~ 0.497.

18 Nickel: The Ni/Fe ratio tells us which progenitor layer was explosively burned AJ,Magkotsios,Timmes+2015 (ApJ)

• Can help on constraining mass cuts used in galactic chemical evolution models and understand late shell burning physics. For example, KEPLER grid gives [Ni/Fe]=+0.1-0.3 dex

depending on piston location (Woosley & Heger 2007). 19 Kilonovae

43 Smartt, Chen, Jerkstrand et al. Nature 2017 : First ) 42

-1 observed event (At2017gfo) 41 M ej 0.017 0.034 v Metzger 2010 : First ej 0.2c 0.2c κ 0.1 0.1

theoretical prediction Log L (erg s 40 β -1.3 -1.0 χ2 2.6 2.1 red 39 10-1 100 101 Days since explosion

Production sites for the r-process elements?

Makers of short gamma-ray bursts? 20 NSF/LIGO From supernovae to kilonovae From supernovae to kilonovae

SNe KNe Homology ~1 day ~10 sec

Mass 1-10 Msun ~0.01 Msun Velocity 0.01c (0.1-0.3)c Powering 56Ni r-process Composition Z=1-30 Z=40-90 t_peak 10 days 1 day rho_peak 10-10 g/cm3 10-14 g/cm3

Much lower densities than SNe —> NLTE more important 21 Kilonovae: the challenge to understand the spectra

Models, three different ejecta. AT 2017gfo: observed spectra

Courtesy E. Pian Tanaka+2017 22 Summary • Stellar element production and supernova explosion physics can be directly diagnosed by nebular-phase spectroscopy of supernovae to determine their yields and morpjology. • H, He, C, N, O, Ne, Na, Mg, Si, S, Cl, Ar, K, Ca, Fe, Co, Ni have so far been diagnosed to various extents. • The SUMO code provides state-of-the-art synthetic spectra of explosion models. • Oxygen (An important diagnostic of hydrostatic burning yields):

• Type II SNe produce 0.1-1 M ⊙ O and appear to arise from 8-17 M ⊙ stars. • Nickel: (An important diagnostic of explosive burning): • A sample of CCSNe show mostly solar Ni/Fe, but sometimes several times larger. • This may be explained by which progenitor layer provided the main explosive silicon burning fuel: oxygen (gives solar Ni/Fe) or silicon (gives supersolar Ni/Fe). • Kilonovae: The community is currently transitioning tools to model ejecta from neutron star mergers. Can we identify these as the main sources of r-process elements in the Universe? 23 THANK YOU FOR LISTENING Reserve slides

24 Testing explosion models through line profiles AJ+2018 ×10−16 −17 2.0 4 ×10 Hα 1.5 1997D 3 [Fe II] 7155, 7172 1997D Model Model 1.0 2

0.5 1 7155 7172

0.0 0 −3000 −2000 −1000 0 1000 2000 3000 −3000 −2000 −1000 0 1000 2000 3000 −1 Shift (km s ) Shift (km s−1)

3D tests now in preparation.

25 The nebular phase : our window on stellar nucleosynthesis

• 100d – 1000d post explosion Exponential tails discovered by • Baade+1945. Emission lines from all nuclear burning regions • Data collection rate: ~5-10 per year (<1% of all discovered SNe). • Current amount of objects: ~50- 100 0 100 200 300 400

H Type IIP SN (2012aw)

Ca Ca O C Mg Na Fe K

26 1. Mixing : Virtual grid method Setup in SUMO Jerkstrand+2011

Impact probability Clump radius

2 Ri pi = 2 i Ri Good method for strong-mixed P Impact angle 1 Type II SNe µ = z Ni 0.9 ONeMg He H 0.8 Filling factor, clump type i 0.7

0.6

0.5 1/3 0.4 Hammer+2010 3Vfi 0.3 (3D CCSN sim.) Ri = Density (normalized for each element) 0.2 4⇡N

0.1 ✓ ◆

0 0 1000 2000 3000 4000 5000 6000 Number of27 clumps Vel [km/s] X of each type Available late-time spectral models for Type II SNe

Explosion energy ~30-50% of all CCSNe Jerkstrand+2011, 2012, 2014 (SUMO) 1E51 Dessart+2011, 2013, 2015 (CMFGEN)

Lisakov+2017

1E50 Maguire+2012

Jerkstrand, Ertl, Janka et al. 2018: First spectral simulation of neutrino-exploded ejecta

8 10 12 15 20 25

MZAMS

28 Nebular data sample of SLSN Ic now 3

Jerkstrand+2017 z=0.11-0.16

200-250d: • SN 2015bn virtual clone of SN 2007bi (see also iPTF13ehe (Yan+2015) z = 0.34 Nicholl+2016). PS1-14bj (Lunnan+2016) z= 0.52 iPTF15esb (Yan+2017) z = 0.22 • LSQ14an: additional [O II] and [O III] lines iPTF16bad (Yan+2017) z= 0.25 (see also Lunnan+2016 for PS1-14bj case) Gaia16adp (Kangas+2017) z=0.10 Can start to make detailed model comparisons, e.g. find best-fitting MZAMS 15 10− 1.2 × O MZAMS =12M (M(O)=0.5 M ) ⊙ ⊙ H MZAMS =25M (M(O)=3 M ) 1.0 ⊙ ⊙ SN 2012aw ) 1 − 0.8 ˚ A

2 Ca − cm

1 0.6 − Mg

0.4

Flux (erg s Fe Na Fe Ca 0.2 C K

0.0 4000 5000 6000 7000 8000 9000 10000 Wavelength (A)˚ AJ+2014. 30 Type II supernovae. Breakthrough a few year ago: Model spectra start to agree quite well with observed spectra

10 ! 250 d SN 2012aw 5 15 M⊙ model ) 1 −

˚ A 0

2 4

− 332 d [Ca II] Ca II [O I] cm 2 Mg I] [O I] Na I [Fe II] 1 OI − 0 369 d erg s 2 15

− 1

(10 0 λ

F 451 d 0.5

0 3000 4000 5000 6000 7000 8000 9000 10000 λ (A)˚

AJ+2014. See also Dessart+2013. 31 32 However: is SN 2016bkv the first discovered electron-capture SN? Hosseinzade+(incl. AJ) 2018

O I 8447 [C I] 8727, only strong pumped by Ca in Fe core models Bowen fluorescence only in ECSN models SN 2016bkv

Fe-CCSN model nickel lines? “ECSN” model

33 34 An exception: Electron capture supernovae have Ni/Fe >> solar. But no SN yet observed shows

this..well Crab? AJ, Ertl, Janka+2018

×10−17 4.0 ×10−17 4.0 SN 1997D +350d SN 1997D +350d 3.5 58 56 Ni/ Ni 0 times solar 3.5 58Ni/56Ni 0 times solar 58 56 Ni/ Ni 3 times solar 58 56 3.0 Ni/ Ni 3 times solar

58 56 [Ni II] 6667 3.0 ) Ni/ Ni 20 times solar 58 56 1 ) Ni/ Ni 20 times solar 1 − − ˚ A 2.5 [Ni II] 7412 ˚ A

2 2.5 2 − [Ni II] 7378 − cm

2.0 cm

1 2.0 1 − − 1.5 1.5 (erg s (erg s λ λ F 1.0 F 1.0

0.5 0.5

0.0 0.0 6600 6620 6640 6660 6680 6700 6720 6740 7300 7320 7340 7360 7380 7400 7420 7440 Wavelength (A)˚ Wavelength (A)˚

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