Diversity of SNe II with CSM Interaction:(II-L vs. IIn vs. IIn-P vs. SLSN IIn)

Nathan Smith
University of Arizona/Steward Observatory, USA

OUTLINE
Diversity in Progenitors: Single star evolution with (sometimes unsteady)mass loss vs. Binary Evolution. Why the paradigm has shifted. Single stars,
stripped primaries, mass gainers, mergers, etc.
main point: SNe should be very diverse.
Diversity in interacting SN II properties and types: Observed properties(light curves, spectra). Diversity of inferred physical properties.
main point: many possible variables and wide range of each. Not simple.
Diversity in outburst/explosion mechanisms: pre-SN mass loss
mechanisms and links to various observed properties, explosions, constraints.
main point: many possibilities, but also limitations.
for reference, see my review on mass loss (Smith 2014, ARAA, 52, 487)
or my review on interacting SNe (Smith 2017, the handbook)Observed Massive Star Diversity
O type:O dwarfs, subdwarfs
O supergiants
Of, O(f), O((f))+, etc.
supergiants
Of?pe (peculiar = magnetic)
B type:B dwarfs
B supergiants
Be + HMXB
B[e]B[e] supergiants

Yellow:
Yellow supergiants
Yellow hypergiants
dense CSM (or not)RSG:
normal RSGs
(like Betelgeuse)
extreme RSGs
(like VY CMa)
Miras
OH/IR stars
symbiotic
super-AGB

Interacting binaries:
any of the above + any of the above, or NS or BH, range of period
massive blue stragglers, red stragglers, mergers, etc.

Observed core-collapse SN Diversity
Types Ib, Ic, Ic BL, IIb (IIb-e vs IIb-c), Ibn, Ibn/IIn, Icn, GRB, SLSN Ic
Types II-P, II-L, IIn-P, IIn (huge variety), SLSN IIn, SLSN II

WR:
WO, WC, WN
WNH
Ofpe/WN9
WN3/O3
WC+O binaries (WR140 etc)
He stars (weak winds)
LBV:
cool or hot
giant eruptions(Eta Car, SN impostors)
S Dor variability
microvariability
LBV candidates
CSM shells, or notA central issue in Massive Star Evolution:
SHEDDING THE HYDROGEN ENVELOPE
2 competing stories for how we make WR stars and stripped envelope SNe

winds
Binary RLOF

Requires high luminosity (high MZAMS)Works across all MZAMS

Stronger at higher Z (line-driven or dust)

Can work at low Z too

Observed classes are a monotonic time
sequence of progressive mass loss:

Observed classes are a result ofdifferent evolutionary paths:

O star è LBV è WR è SN Ibc
or RSG

Mass donor, mass gainer,common env., merger, etc.

Sana etal. 2012

M

REDUCED HOT &COOL WIND Mdots(Beasor talk)time

LOTS OF BINARIESBINARY INTERACTIONDOMINATES THE DIVERSITY
OF MASSIVE STARS AND
THEIR SNe(not Z-dependent steady winds)

Smith +11

Lyman +16
Drout +12

~2 M¤
TOO MANY SESNe andLOW EJECTA MASSWEIRD SNe, CSM
INTERACTION, ETC

Evolution and mass loss of massive single stars

LBV
120 M¤

In general, dense CSM isassociated with stars in
rapid transitional phases.

RSG
SN II-P/IIn

Wolf-Rayet

BSG/LBV
SN IIn/II-pec
YSG
SN II-L/IIb/IIn

60 M¤

SN Type Ibc
30-35 M¤

10-20 M¤
But with binaries, diversity comes from stripped primaries, mass gainers, mergers. So
these transitional SN types can occur across all initial masses, and at a variety of times
before core collapse (depending on separation).

RSG
SN II-P

Evolution and mass loss of massive single stars

RSG

Adapted from
Heger et al. 2003

MWR

WN

WC

Determined by assumed mass-loss rates in astellar evo code.

OUTLINE✔

Diversity in Progenitors: Single star evolution with (sometimes unsteady)mass loss vs. Binary Evolution. Why the paradigm has shifted. Single stars,
stripped primaries, mass gainers, mergers, etc.
Main point: Diversity in binary evolutionary paths dominates the diversityof stars and SNe, not monotonic scaling of mass-loss with MZAMS.
Wide diversity in binary evolution paths, even from 8-20 M¤ (single or widebinary, stripped primaries, gainers, mergers, mass ratios, period, etc).
Diversity in interacting SN II properties and types: Observed properties(light curves, spectra). Diversity of inferred physical properties.
main point: many possible variables and wide range of each. Not simple.
Diversity in outburst/explosion mechanisms: pre-SN mass loss
mechanisms and links to various observed properties, explosions, constraints.
main point: many possibilities, but also limitations.

CSM INTERACTION DIVERSITY
Observations

SNe IIn lightcurves – diversity
in L and duration
Huge range of CSM interaction
luminosity, from SLSNe IIn where CSM
interaction completely dominates,
down to cases where there is almost no
CSM interaction or it makes a minor
addition to L.
Also, huge range of total radiated energy:1049 erg < Erad < few x 1051 erg

Diversity of CSM interaction for SNe
IIn results from a range of CSM mass
and its radial distribution (more later)t
2003ma2010jlCSM INTERACTION DIVERSITY
Observations

SNe IIn lightcurves – diversity
in L and duration
TIMING: Huge range in onset or duration
Fleeting CSM interaction lasting for only a
few days (talk tomorrow by Bruch)
Delayed onset CSM interaction• Short delays (~40 days like 09ip)• Very long delays (years) like 14C, 87A,
etc (next talk by Dan)
Huge diversity in duration even for normal
SNe IIn. Some fade quickly (1998S),
some persist for decades (1988Z).

Diversity of CSM interaction for SNe
IIn results from a range of CSM mass
and its radial distribution (more later)t
2003ma2010jlCSM INTERACTION DIVERSITY
Observations

SNe IIn lightcurves – diversity
in L and duration
TIMING: Huge range in onset or duration
Fleeting CSM interaction lasting for only a
few days (talk tomorrow by Bruch)
Delayed onset CSM interaction• Short delays (~40 days like 09ip)• Very long delays (years) like 14C, 87A,
etc (next talk by Dan)
Huge diversity in duration even for normal
SNe IIn. Some fade quickly (1998S),
some persist for decades (1988Z).

Diversity of CSM interaction for SNe
IIn results from a range of CSM mass
and its radial distribution (more later)t
2003ma2010jlCSM INTERACTION DIVERSITY
Observations
CSM interaction for decades after SN traces
mass loss 5,000-20,000 yr before death.
Strong CSM interaction indicates 0.2-20 M¤ lost in relatively
short time intervals before core collapse in some cases.
Smith+09,+16
Smith+15

Mauerhan & Smith’12

Milisavljevic+12
Chandra+09
Turatto+93
Aretxaga+99
Smith+16

88Z Erad > 2e51 erg
05ip
PTF11iqb~10-3 M¤/yr

93J

98S

~10-4 M¤/yr

80K
REVERSE SHOCK (BROAD LINES, EJECTA)

1e4

Smith +16

CSM INTERACTION DIVERSITY
Observations

SNe IIn spectra
n for “narrow” really means “narrower thannormal SNe”
SN IIn spectra show narrow (< 1000 km/s)
and intermediate-width (1000-3000 km/s)
components with ranges of FWHMs andline shapes. Often P Cyg.
Can have broad (~3,000-15,000 km/s)
components at some phases (especiallylate).

Smith & Andrews 2020

ASASSN15ua(SLSN IIn)

Intermediate-width components evolvewith time, usually changing fromsymmetric Lorentzian shape at early times
to asymmetric, irregular, multi-component
at later times.

Dickinson+23 (arXiv:2302.04958)

CSM INTERACTION DIVERSITY
Observations

SNe IIn spectra
Also show a lot of diversity in how much
CSM interaction contributes to spectrum.
Some have just a small amount of CSM
interaction emission added to an almost
normal SN II spectrum (like 09ip at somephases).
Some dominated by emission from theshock and CSM (006gy, 94W)

2006gy ≈ 1994W

2009ipCSM INTERACTION DIVERSITY
Inferred properties
Basic picture leads to complicated observations.
Four main zones in a simple shock:1. Pre-Shock CSM
2. Shocked CSM - behind forward shock(cooling makes this collapse in a SN IIn)
3. Shocked ejecta - reverse shock
4. Unshocked freely expanding ejecta
CONTINUUM PHOTOSPHERE• Moves through these zones with time.
• Can come from different zones at the same time.
• There can be no photosphere (late times, thin).
SPECTRAL LINES• Can be seen from any or all of these zones,
changing with time.
• Line profiles modified or hidden by electron
scattering, occultation by photosphere, or dust.
INFERRED VALUES• Vwind comes from narrow emission components
or narrow P Cyg (10-500 km/s)• VSN is forward shock speed, from int. width(usually 1000-30000 km/s)• L is luminosity generated by CSM interaction
SHOCK RADIATION PROPAGATES OUTWARD
AND INWARD, MODIFIES CSM AND EJECTA

3
•
1
1
V
L = wVSN3 = M SN22 Vw

Efficient conversion of KE

LightCSM INTERACTION DIVERSITY
Inferred properties
CSM Density and total mass: Wide range of CSM mass (depending on L and duration),
range 0.01-30 M⊙. (w range 1016-1019 g/cm)
Radial density distribution: Compact shells/inflated envelopes (fleeting CSM interaction),
inner cavities (delayed interaction), normal SNe IIn (10s-102s AU), very extended denseshells (103-104 AU). 𝜌(r) = 𝜌0r-2 may be a bad assumption.
CSM Speed: related to progenitor’s mass-loss speed. Typical range = 10-500 km/sec. Low
values are more common. Not always constant.
Duration of pre-SN mass loss: tpreSN = tobs (VCDS/VCSM). Ranges from weeks/months(fleeting CSM interaction) to millenia (persistent interactors). For most SNe IIn, bright phaseof light curve (few 102 d) traces several decades of strong pre-SN mass loss.
CSM Asymmetry: from specpol, line profiles, seeing fast SN ejecta, escaping radiation.
Many SNe IIn inferred to have very asymmetric CSM (i.e. disks, bipolar).
Explosion constraints: some constraints on ESN (i.e. ESN ≥ Erad), Mejecta, M(56Ni)
Other stuff: MZAMS from progenitor or environment (again: huge range), CSM clumpiness,
bumpy light curves, dust formation and dusty CSM, etc.

CSM INTERACTION DIVERSITY
Inferred properties
CSM Density and total mass: Wide range of mass(depending on L and duration), range 0.01-30 M⊙.
w range 1016-1019 g/cm.
You can fit pretty much any light curve if you choose
the right 𝜌(r). But it may be hard to do this and also
agree with velocities in observed spectra.

1, 6, 10, 20 M¤(van Marle +10)

10 M¤

•

increasing shell density (totalmass) increases the peakluminosity•

increasing the outer shell radius(also increasing total M)
increases duration

25 M¤

CSM INTERACTION DIVERSITY
Inferred properties

What we reallymeasure isrequired winddensityparameter (w),and then infer
Mdot fromadopted speed.

COMPARE:
Mdot and VW
inferred forinteracting SNe to
those of various
types of stars(from Smith 2014
review).

Down here weget bright radio
and X-rayemission.

Betelgeuse

Figure from
Smith (2016) inHandbook ofSupernovae

CSM INTERACTION DIVERSITY
Inferred properties
CSM Density and total mass: Wide range of CSM mass (depending on L and duration),
range 0.01-30 M⊙. (w range 1016-1019 g/cm)
Radial density distribution: Compact shells/inflated envelopes (fleeting CSM interaction),
inner cavities (delayed interaction), normal SNe IIn (10s-102s AU), very extended denseshells (103-104 AU). 𝜌(r) = 𝜌0r-2 may be a bad assumption.
CSM Speed: related to progenitor’s mass-loss speed. Typical range = 10-500 km/sec. Low
values are more common. Not always constant.
Duration of pre-SN mass loss: tpreSN = tobs (VCDS/VCSM). Ranges from weeks/months(fleeting CSM interaction) to millenia (persistent interactors). For most SNe IIn, bright phaseof light curve (few 102 d) traces several decades of strong pre-SN mass loss.
CSM Asymmetry: from specpol, line profiles, seeing fast SN ejecta, escaping radiation.
Many SNe IIn inferred to have very asymmetric CSM (i.e. disks, bipolar).
Explosion constraints: some constraints on ESN (i.e. ESN ≥ Erad), Mejecta, M(56Ni)
Other stuff: MZAMS from progenitor or environment (again: huge range), CSM clumpiness,
bumpy light curves, dust formation and dusty CSM, etc.

CSM INTERACTION DIVERSITY
Inferred properties
CSM Asymmetry: hidden (engulfed) CSM signatures
PTF11iqb: Disk-like geometry of CSM gets
enveloped by SN photosphere. (Smith+15)
Spectroscopic evolution
through 3 main phases:
1. Early CSM interaction(WR-like spectrum) inthick inner wind at ~10 AU.

Lightcurve:Type II-P + CSM int.

2. SN photosphere
expands to ~100 AU andengulfs CSM interaction.
CSM interaction (re)heats
ejecta.
3. SN continuum
photosphere recedes andexposes CSM interaction
again (multi-peaked
asymmetric Hα).

Possibly relevant for many SNe II-P and II-L light curves.

PTF11iqb: Weird, blue bump and double-peaked Hαat late times as it drops from plateau.

Smith+15

First few days (Type IIn)
Rphot ~ 10 AU
Strong CSM interaction
in equatorial disk.
Narrow emission can beseen by observer.

Disk can be
photoionized.
Narrow lines30-80 days (II-P)
Rphot ~ 100 AU
Strong CSM interaction inequatorial disk continues,
but is enveloped by opaqueejecta. Inside photosphere,
hidden.

?

?

Both CSM interaction (disk)
and radioactive decay(center) heat the ejecta.

But… CSM interaction
luminosity is now deposited
inside photosphere. Extra
source of heat, but nonarrow lines can be seen.

≥100 days

Strong CSM interaction in equatorial disk
continues, and may be exposed again
when photosphere recedes. Causing
asymmetric photosphere? Eventually
becomes optically thin.

Rphot recedes?

?

Both CSM interaction (disk)
and radioactive decay(center) heat the ejecta.

Disk has been swept up, accelerated to~2000 km/s or more, may be seen as
double-peaked line at late times.

>200 days
Rphot gone, nebular phase
Late phase CSM interaction dominates.

Strong CSM interaction in equatorial disk
continues, and is exposed again.

?

?

iPTF14hls:
Andrews & Smith 2018

This is Iair’s crazyimpossible SN. No
narrow lines duringmain 2 yr peak, butthen narrow + int.
width lines seen assoon as it fades.

Disk has been swept up, accelerated to~2000 km/s, may be seen as doublepeaked line at late times.
How long this lasts depends on extent of
disk…
e.g., SN 1998s, SN 1993J, etc.
also iPTF14hls

CSM INTERACTION DIVERSITY
Inferred properties
CSM Asymmetry: hidden CSM signatures
Disk-like geometry of CSM gets envelopedby SN photosphere. (Smith+15)
Spectroscopic evolution
through 3 main phases:
1. Early CSM interaction(WR-like spectrum) inthick inner wind at ~10 AU.

Lightcurve:Type II-P + CSM int.

2. SN photosphere
expands to ~100 AU andengulfs CSM interaction.
CSM interactionluminosity(re)heats ejecta.
3. SN continuum
photosphere recedes andexposes CSM interaction
again (multi-peaked
asymmetric Hα).

Possibly relevant for many SNe II-P and II-L light curves.

Brief CSM interaction even in normal
SNe II-P with no narrow lines (not IIn)

Morozova et al. (2016, 2017, 2017) model
light curves of normal SNe II-P with SNEC
code, finding that CSM interaction isneeded to match the early peaks of many.
In sample of 20 well-observed nearby SNe
II-P and II-L, they find that 70% need CSM
shells with masses of 0.2-0.8 M¤ (mostly
within ~10 AU).
Implies strong mass loss of 0.01-0.1 M¤/yr
in just few years before explosion.

Anderson+14

Type II-P vs. Type II-L : A continuum?

Valenti et al. 2015, MNRAS, 448, 2608 (see also Valenti +2016; Anderson +2014; Arcavi +2012)••

Are SNe II-L just SNe II-P with CSM interaction?
How many SNe II-L would have IIn spectra if they were caught early after explosion?
SN II-L spectra have weaker P Cygni absorption, and they do tend to have brighter radio, etc.

II-P è II-L è IIn?

CSM INTERACTION DIVERSITY
Inferred properties

Type IIn-P subclass:(see Mauerhan et al. 2013, Smith 2013)

Type IIn spectra (nearly identical)
but with plateau light curves
SN 1994W
SN 2009kn
SN 2011ht
SN 1054 (?)
1. Sharp drop in L at ~120 days
2. Dense CSM (IIn spectra)
3. Low explosion energy (1050 erg)
but bright due to CSM interaction
4. Low inferred 56Ni mass
(0.007-0.02 M¤)

CSM INTERACTION DIVERSITY
Inferred properties
Asymmetry: extreme/exotic
SN 2010jp: a Type IIn-BL (Smith+12)(i.e. a broad-lined narrow-lined SN II)
somewhat underluminous (MV ~ -15.9 mag), but withextremely fast SN outflow (>20,000 km/s) andbizarre triple-peaked emission line profiles

CSM INTERACTION DIVERSITY
Inferred properties
Asymmetry: extreme/exotic
SN 2010jp: a Type IIn-BL (Smith+12)(i.e. a broad-lined narrow-lined SN II)
somewhat underluminous (MV ~ -15.9 mag), but withextremely fast SN outflow (>20,000 km/s) andbizarre triple-peaked emission line profiles
Is this a failed SN and a would-be GRB
choked by a hydrogen envelope?
Found in far outer
tidal arms of agalaxy merger(NGC2207/IC2163).

At very late times, SN is gone, but HST images
show a youngish (~8 Myr) cluster and r=30pc HII
region. MZAMS ~ 18-22 M⊙. Corgan et al. (2022)

CSM INTERACTION DIVERSITY
Inferred properties
CSM Density and total mass: Wide range of mass (depending on L and duration), range
0.01-30 M⊙. (w range 1016-1019 g/cm)
Radial density distribution: Compact shells/inflated envelopes (fleeting CSM interaction),
inner cavities (delayed interaction), normal SNe IIn (10s-102s AU), very extended denseshells (103-104 AU, persistent interaction like 88Z). generally 𝜌(r) = 𝜌0r-2 is a bad assumption.
CSM Speed: related to progenitor mass-loss speed. Range = 10-500 km/sec. Low values
are more common. not always constant.
Duration of pre-SN mass loss: tpreSN = tobs (VCDS/VCSM). Ranges from weeks/months(fleeting CSM interaction) to millenia (persistent interactors). For most SNe IIn, bright phaseof light curve traces several decades of strong pre-SN mass loss.
CSM Asymmetry: from specpol, line profiles, seeing fast SN ejecta, escaping radiation.
Many SNe IIn inferred to have very asymmetric CSM (i.e. disks, bipolar).
Explosion constraints: some constraints on ESN (i.e. ESN ≥ Erad), Mejecta, M(56Ni)
Other stuff: MZAMS from progenitor or environment (again: huge range), CSM clumpiness,
bumpy light curves, dust formation and dusty CSM, etc.

CSM INTERACTION DIVERSITY
Inferred properties

MAIN POINT:

CSM Density and total mass: Wide range ofObservations
mass (depending
onIIn
L and
duration),
range
of
SNe
show
HUGE
diversity
0.01-30 M⊙. (w range 1016-1019 g/cm)
in CSM properties (M, R, duration, asymmetry)and explosion properties.
Radial density distribution: Compact shells/inflated envelopes (fleeting CSM interaction),
2s AU), very extended dense
inner cavities (delayed interaction), normal SNe
IIndiversity(10s-10makesThisthem-2hard to understandshells (103-104 AU, persistent interaction like 88Z).
generally
𝜌(r)
=
𝜌0we
r is
a bad assumption.
with a simple model. “IfassumeX ,we find Y .” But X is probably not true at all,
CSM Speed: related to progenitor mass-loss so….
speed. NeedRange
= 10-500
km/sec. Low
valuesdetailed
observations
to constrain
are more common. not always constant.
multiple properties (light curves alone have too
many free parameters).
Duration of pre-SN mass loss: tpreSN = tobs (VCDS/VCSM). Ranges from weeks/months(fleeting CSM interaction) to millenia (persistentinteractors).
For most
IIn,tobright
Whatevermechanism
weSNe
invokemakephase
thisof light curve traces several decades of strongCSM
pre-SN
mass
loss.
must match this diversity, or we needmultiple mechanisms.
CSM Asymmetry: from specpol, line profiles, seeing fast SN ejecta, escaping radiation.
Many SNe IIn inferred to have very asymmetric CSM (i.e. disks, bipolar).
Explosion constraints: some constraints on ESN (i.e. ESN ≥ Erad), Mejecta, M(56Ni)
Other stuff: MZAMS from progenitor or environment (again: huge range), CSM clumpiness,
bumpy light curves, dust formation and dusty CSM, etc.

OUTLINE✔

Diversity in Progenitors: Single star evolution with (sometimes unsteady)mass loss vs. Binary Evolution. Why the paradigm has shifted. Single stars,
stripped primaries, mass gainers, mergers, etc.
Main point: Diversity in binary evolutionary paths dominates the diversityof stars and SNe, not monotonic scaling of mass-loss with MZAMS.
Wide diversity in evolutionary paths, even from 8-20 M¤ (single or widebinary, stripped primaries, gainers, mergers, mass ratios, period, etc).

✔

Diversity in interacting SN II properties and types: Observed properties(light curves, spectra). Diversity of inferred physical properties.
main point: many possible variables and wide range of each. Not simple.
Diversity in outburst/explosion mechanisms: pre-SN mass loss
mechanisms and links to various observed properties, explosions, constraints.
main point: many possibilities, but also limitations.

CSM INTERACTION DIVERSITY
Eruption/Explosion mechanisms

Some potential mechanisms to produce the CSM in interacting SNe.
How well do they match SN IIn properties and diversity?
Pulsational Pair Instability
8-11 M⊙ (ecSNe or whatever)
Wave driving
Pre-SN Binary Interaction

CSM INTERACTION DIVERSITY
Eruption/Explosion mechanisms
Pulsational Pair Instability (Woosley17, HW02, Renzo+20, talk by Farmer/Renzo/Marchant)
Pros:• Was actually predicted before SLSNe IIn became a hot topic.
• Can make high-L, long-duration, interaction-powered events with wide
diversity in observed properties (Woosley 2017, Renzo+20)• Gives a good explanation for SN 1961V (Woosley & Smith 2022)
Cons:• Should be super-rare (because of IMF) – not enough for most SNe IIn• can’t match wide range of progenitor masses for SNe IIn• velocities don’t match most observed SNe IIn at all(too fast for CSM, too slow for ejecta)• First pulse removes any H envelope, so faster ejecta in 2nd pulse should be
H-poor (doesn’t match most SNe IIn that show broad H𝛼)• First pulse is most energetic (so if a SN IIn looks like a smaller pre-SN outburst
followed by what looks like a ccSN, it aint a pPISN)• No reason to expect asymmetric CSM

CSM INTERACTION DIVERSITY
Eruption/Explosion mechanisms
Pulsational Pair Instability (Woosley17, HW02, Renzo+20, talk by Farmer/Renzo/Marchant)
Pros:• Was actually predicted before SLSNe IIn became a hot topic.
• Can make high-L, long-duration, interaction-powered events with wide
diversity in observed properties (Woosley 2017, Renzo+20)• Gives a good explanation for SN 1961V (Woosley & Smith 2022)

V L
Cons:
• Should be super-rare (because of IMF) – not enough for most SNe IIn• can’t match wide range of progenitor masses for SNe IIn• velocities don’t match most observed SNe IIn at all(too fast for CSM, too slow for ejecta)• First pulse removes any H envelope, so faster ejecta in 2nd pulse should be
H-poor (doesn’t match most SNe IIn that show broad H𝛼)
Woosley & Smith 22• First pulse is most energetic (so if a SN IIn looks like a smaller pre-SN outburst
followed by what looks like a ccSN, it aint a pPISN)• No reason to expect asymmetric CSM

CSM INTERACTION DIVERSITY
Eruption/Explosion mechanisms
8-11 M⊙ (ecSNe or whatever) (WoosleyHeger15, Nomoto84/87,etc.)
Pros:• Expect dense H-rich CSM (sAGB wind or ejected by flashes)• Gives a good explanation for SNe IIn-P or other events (Crab) with low
explosion energy, low initial masses, low 56Ni masses, but high L• Maybe not super-rare because of IMF
Cons:• Can’t explain high-mass CSM, high progenitor masses• Can’t explain any of the luminous or super-luminous SNe IIn, or long-lasting
events (like 88Z) – CSM mass budget is not high enough• No reason to expect asymmetric CSM

CSM INTERACTION DIVERSITY
Eruption/Explosion mechanisms
Wave driving (Quataert & Shiode12, SQ14, Fuller17, Wu&F21, talks by Wu & Fuller)
Pros:• Really neat idea, natural outcome of last pre-SN burning phases• Might gives a good explanation for some short-duration events (brief inflationor puff of mass loss right before core collapse)Cons:• Only works for ~1 yr before core-collapse or less; not viable to explain thevast majority of SNe IIn and SLSNe IIn (where strong mass loss is several
years/decades/centuries before core collapse).
• Can it give an explosive ejection of large CSM mass?
• No reason to expect asymmetric CSM

CSM INTERACTION DIVERSITY
Eruption/Explosion mechanisms
Pre-SN Binary Interaction (Smith & Arnett 2014)
Pros:• We know that most massive stars are in binaries or triples or more.
• Expected to happen anyway as all stars swell (some fraction of binaries will
be caught interacting with wide companion in 10-104 yr before core collapse)
and also naturally explains delayed-onset CSM interaction.
• Can be combined with any of the previous that might inflate the envelope
shortly before core collapse to trigger immediate pre-SN mass loss (SA14)• Pre-SN merger can drive even the most extreme CSM of SLSNe IIn• Works across all initial masses, not just high or low• Also works with compact (NS/BH) companions (Fryer+98,Chevalier12,Schroeder+20)• Favors Type II because H envelopes are big• slow CSM should be the norm
• Can potentially account for full diversity in the inferred SN IIn properties• Only mechanism that obviously predicts strong asymmetry in CSM
Cons:• free parameter heaven• are there enough (?) systems caught in RLOF right before SN, or do we needto combine with other pre-SN inflation?