COOL SUPERGIANT ENVELOPE STRUCTURE FROM 3D
RHD SIMULATIONS & EXPLOSIVE IMPLICATIONS
Jared A. Goldberg* — Radiation Hydrodynamics Review Talk, part 2
Munich Institute for Astro, Particle, and bio Physics, 27 February 2023
*Flatiron Research Fellow @ Center for Computational Astrophysics, Flatiron Institute, NY, USA
Email: goldberg@ucsb.edu
Web: jaredagoldberg.wordpress.com
Twitter: @aurimontem+ROADMAP:

1▸Motivation▸Large-scale convection in RedSupergiant envelopes asrevealed by 3D Simulations▸Shock Breakout in 3D RSGenvelopes▸Potential connections of (R)HDsims to Interacting SNe2CORE PROPERTIES DETERMINEEXPLOSION (ENERGY), REMNANTENVELOPE PROPERTIES DETERMINE
STELLAR OBSERVABLES AND
SUPERNOVA EMISSIONSN EMISSION IS DETERMINED BY THE LOCATION OF
THE SN PHOTOSPHERE + THE STRUCTURE OF THE
STAR NEAR THAT LOCATION

Stellar surface
matters!
Stellar Envelope(interior) matters!

Early Times

On the Plateau

Core structure + explosion
geometry + everything
matters!

Late Times

3

REMINDER: EARLY-TIME SN EMISSION SENSITIVE TO“SURFACE”

4▸ First ~20 days ofthe SN sensitive
to the shockcooling of theoutermost~0.01-0.1M☉▸ By day 50, seeinto the bulk ofthe ejecta

Models matching SN2017eaw at 6.85 pc

Day 50EARLY-TIME SN EMISSION SENSITIVE TO STELLAR“SURFACE”

Figure from Morozova+16▸ Outer density profile
variation between
stellar evolution codes,
input physics andprescriptions▸ Circumstellar material
often invoked tointerpret earlylightcurves -- requires
assumptions about thedensity profile

5

6

RSG ENVELOPES ARE
FULLY CONVECTIVE

7

CONVECTION ON EARTH▸ In the conventional picture ofconvection: hot, underdensematerial rises, and cold,
overdense material sinks.
▸ “Bubble” rises a mixing length
proportional to the pressure
scale height, ℓ= ⍺ H

Roaring boil:
Energy transport
by convection
Simmer:Energy transport
by thermal
diffusion

Image courtesy of finecooking.com
https://www.finecooking.com/article/whats-the-difference-between-asimmer-and-a-boil

CONVECTION IN THE SUN
Data courtesy of DKISTCONVECTION IN A RED SUPERGIANT

9

Reconstructed image

CO5BOLD simulations from website of Bernd Freytag; see also Chiavassa+2009, 2010a,b, 2011, 2012; Arroyo-Torres+15, Kravchenko+2018;
Norris+ 2021, & references therein & others. Image: ALMA image of Antares (alpha Sco)LARGE-SCALE CONVECTION MIGHT BE OBSERVABLE W/ 10GAIAChiavassa+2022: Few plumes à photocenter should bevariableà

Motion of a RSG photocenter in GAIA band

Though the detectability given current GAIA error floors isdebatable, see Kochanek 22

Figure from Chiavassa+2022

FURTHER 1D INSIGHTS TO MOTIVATE 3D WORK

11

▸ Assumptions about convection(especially mixing length alpha)strongly influence stellar radius*▸ Pressure scale height (H=P/𝜌g) isa significant fraction of the radius▸ Radiation and gas are both
important to pressure support▸ Envelope is loosely bound sochoice of modeling gravitational
potential for 3D matters!
Goldberg, Jiang, & Bildsten 2022a*see also Henyey+1965; Stothers & Chin 1995; Meynet & Maeder 1997; Massey etal 2003; Dessart+2013, Meynet+2015; Chun+2018; Joyce et al 2020; & more

OUR 3D RSG ENVELOPE SIMULATIONS

12𝝅𝟑𝝅▸ Semi-global (𝜃= 𝟒 − 𝟒 , ɸ= 0 − 𝜋)Radiation-Hydrodynamic (RHD)
simulations of RSG envelopes usingAthena++▸ 300 – 400R☉ inner boundary,

motivated by 16M☉ MESA model▸ Gravity included with g = G Mencl/r2▸ Equation of State is ideal gas +radiation▸ Full RHD solution (see Jiang+ 2021)
w/ OPAL opacities as function ofdensity, T, Z=0.02

𝝅𝟑𝝅▸ 𝜃= 𝟒− 𝟒▸ ɸ= 0 − 𝜋

STEADY STATE BEHAVIOR

13

FLUID STRUCTURE▸ Large-scale plumes extend deep
within the envelope

14

LARGE-SCAL CONVECTION, OVERTURN TIME ~300-500
DAYS

Goldberg, Jiang, Bildsten (2022a, ApJ)

15

CONVECTIVE PROPERTIES

16▸ Flat entropy profile ininterior w/ increasing
super-adiabaticity▸ Convection dominates theenergy transport▸ The turbulent motions
contain significant kinetic
energy density and thus
contribute to the pressure
support of the the outerenvelope layers
Goldberg, Jiang, & Bildsten 2022a

17FLUID PROPERTIES▸ 3D outer density structure ismuch more extended than 1Dmodel, with fluctuations, due inpart to pressure from turbulent
kinetic motions▸ Opacity, Temperature

distributions are bimodal oneach side of the H opacity peakTRANSITIONARY TO LOSSY CONVECTION▸ Below some opticaldepth, radiation isable to carry a large
amount of the flux
▸ Here, that happens athigh optical depth (afew hundred)▸ At that location, local
L > LEdd due to thelarge H opacity

18

DIFFERENT TURBULENT FLUID MOTIONS@ SURFACE VS INTERIOR▸ Not only is convection
inefficient near thestellar surface, but at
tau < tau_crit, the fluid
motions in no longer
resemble MLT; Cold,dense (opaque!) stuff
rises!

This is also seen in models of OB Stars!
(left panels = work led by William Schultz)

19

ROADMAP:

20▸Motivation▸Large-scale convection in RedSupergiant envelopes asrevealed by 3D Simulations▸Shock Breakout in 3D RSGenvelopes▸Potential connections of (R)HDsims to Interacting SNeINTRINSIC RISE OF THE SUPERNOVA IS VERY QUICK!
‣ "Shock Breakout” (SBO) occurs where 𝜏 = !⁄"$‣ For shock velocities of ~3000 km/s, this is 𝜏 ~100
‣ Intrinsic rise time is set by the diffusion time

‣ = 10s of minutes for typical 1D stellar models (with outerdensities ~10-9 g/cm3)‣ Aside: Intrinsic rise time gets longer at lower density. Theshorter apparent rise in optical bands for SBO in a CSM islikely a result of a brighter breakout overall convolved withfaster cooling from a larger area

35

HOPE FOR CONSTRAINING R WITH SHOCK BREAKOUT?

22‣ In the spherical picture, when tdiff is small and R is large, observed duration issmeared out over the light travel time, tltt=R/c, which is half an hour for
800R☉ RSG
Time = t0 + R/c

R

Shussman+2016

Time = t0

See also: Nakar & Sari 2010, Katz+2012,
Shussman+2016, Kozyreva+2020, and manyothers

OBSERVATIONAL LANDSCAPE‣ Very few events (~3 serendipitousSNLS-04D2DCLow-density breakout from Schawinski+08

GALEX detections), hundreds
expected from ULTRASAT (2026)‣ Includes SNLS-04D2dc(Schawinski+08; Gezari+2008) andPS1-13arp (Gezari+15, revisited byHaynie & Piro 2020 – See Anna’stalk!)‣ Observed events show SBO

durations of longer than ~6 hours >>(1000R☉)/c, often attributed to adense wind, or to SBO at lower
densities than 1D stellar models
exhibitDense wind from Gezari+08

23

THE 3D OUTER ENVELOPE

24▸ For shock velocities of ≈3000
km/s, SBO happens at 𝜏 ≈100

▸ In 3D simulations, shallower
density profile & material at
low densities à SBO at lower
ρ, enough to lengthen thepredicted diffusion time to~an hour
▸ Large-scale plumes à varietyof ”surface” radii spanning
ΔR~100R☉

ΔR

Goldberg, Jiang, & Bildsten, 2022b

THE 3D BRERAKOUT SHELL TOPOGRAPHY

DCA
B

25

vr

3D SHOCK PROPAGATION:▸ Initially sphericalshock corrugates ininhomogeneouslayers▸ Asymmetries lead to
ΔR ~100R☉ spread in
SBO locationlog(ρ)

26

BREAKOUT AT LOCATIONS AT DIFFERENT TIMES

27

SHOCK BREAKOUT LIGHTCURVES
R/c ~ .5 hours▸Duration set by tcross = ΔR/vshock~ 3-6 hours (> R/c) as different patches break out

28

HOW THIS MODIFIES THE LUMINOSITY
We can estimate the characteristic (peak) luminosity

Where E0 is the energy contained in radiation beyond 𝜏<c/vsand t is the relevant timescale.

Shell volume
Shock Energy density

IF the relevant timescale is the diffusion time across a spherical “breakout shell”;
then29

WHEN SHOCK-CROSSING TIME DOMINATES

30

We can estimate the characteristic (peak) luminosity

Where E0 is the energy contained in radiation
beyond 𝜏<c/vs and t is the relevant timescale
For

Smearing effect in outer layers à~(3-10)x fainter SBO, different
scalings with vsh and Eexp!

Goldberg, Jiang, & Bildsten, 2022b

arXiv:2206.04134

ADDITIONAL PREDICTION:
MULTIPLE PHOTON TEMPERATURES

T – tau relations spanning different lines of sight at the time of peak Lbol

31

SBO TAKEAWAYS

32▸Early LCs, and especially SBO, issensitive to (3D?) outer structure, whicheven for ”barren” RSG envelopes isdominated by large-scale 3Dconvective plumes▸An initially-spherical shock does notbreak out all at once: rise time set by~ΔR/vshock▸Leads to longer SN rise w/ shallower
fall, compared to explosions of 1Dmodels

(a)

(b)

ROADMAP:33▸Motivation▸Large-scale convection in RedSupergiant envelopes asrevealed by 3D Simulations▸Shock Breakout in 3D RSG
envelopes▸Potential connections of (R)HDsims to Interacting SNeCONNECTION: POSSIBLE IMPRINT OF 3D CONVECTION ON 34
CSM STRUCTURE
Benny Tsang+2022

Where in the pre-deposition star did
the outburst mass come from?

35CONNECTION: YELLOW SUPERGIANT CONVECTION & RHD
MASS LOSS‣ Yellow Supergiants have beenobserved to be IIb progenitors‣ Some may undergo cepheid-likepulsations depending on the surface
temperature and He opacity peak
‣ He rich due to the need to eat into
the H-burning shell to achieve low
envelope masses (~0.05 – 0.5 Msun)

3D YELLOW SUPERGIANT MODELS UNDERWAYPRELIMINARY36

QUANTIFYING YELLOW SUPERGIANT MASS LOSS

‣ Episodic outbursts dominate mass loss (* in the one modelwe have)YRANIMILERP37QUANTIFYING YELLOW SUPERGIANT MASS LOSS

‣ The mass ejection episodes vary in strength, but typical massloss seem to be ~10-6 Msun at a rate of ~a couple per year

PRELIMINARY38

YELLOW SUPERGIANT OUTER DENSITY STRUCTURE

39‣ Shocks and natural clumpy structure in outer atmosphere; variety
in density structure at different times

HSPA
SNTORPMILE

YRA
NIA
fewan
gle sna-av psera hotge s,

A FEW DISCUSSION POINTS:

40‣ What would be most useful for observers from the 3Dsimulations?

‣ Are dense CSM’s extending to multiple thousands of solar
radii (which are not achieved ab-initio in the 3D sims)
required by SN observations?

‣ Are there other probes of early-timeasymmetry? Would we expect
significant polarization?

‣ Please add your own thoughts!

WHERE DO WE GONOW?