Episodic and High Mass Loss Events

In Evolved Stars

Roberta M. Humphreys

University of Minnesota

Intermediate Luminosity Red Transients

Space Telescope Science Institute, June 2011

The evidence for episodic high mass loss events

The Upper HR Diagram

In Evolved Massive Stars -- Luminous Blue Variables (LBVs)

S Dor variability vs giant Eruptions

-- Warm and Cool Hypergiants

Humphreys and Davidson 1994

So what is an LBV?

Distinguished by their photometric and spectroscopic variability

In quiescence – hot, luminous star, sp. types late O to mid B, Of/WN7 Some emission lines H, He I, Fe II, P Cyg profiles mass loss rates – typicalIn “eruption” – rapid rise in apparent visual brightness -- weeks – months apparent shift in sp. type ( late A to early F) or apparent temp -- shift in bolometric correction ~ constant luminosity but … (abs. bol. mag.) star develops, slow, dense, optically thick wind

mass loss rate increases ~ 10 x (10-5 Msun/yr)

this optically thick wind stage may last years -- decades

R127 (Walborn et al. 2008)

S Doradus or LBV Instability Strip Wolf (1989)

Note – in “eruption” – all about same temp ~ 7500 – 8000K

Davidson (1987) – opaque wind model (as opacity and mass loss rate increase, temperature approaches a minimum)

The Cause of the Instability?

Most explanations -- the star is near the Eddington Limit

LEdd = 4cGMsun/Edd = const (L/Lsun) (M/Msun) -1

Opacity modified limit is temperature dependent

1. opacity – modified Eddington Limit (Davidson, Lamers, Appenzeller)

as temp decreases, opacity increases (“bi-stability jump”, Pauldrach & Puls 1990 Lamers et al 1995)

2. Omega limit -- add rotation to the Eddington Limit (Langer)

= vrot/vcrit > 1, v2crit = (1 –) GM/R

3. Vibration/Pulsation -- mechanism (in the core) no longer considered applicable to evolved stars -- mechanism in the envelope periods of weeks to months

4. Sub-photospheric – violent mode or strange mode instabilities Glatzel et al, Guzik, Stothers & Chin Caused by increase in opacity due to Fe at base of photosphere leading to ionization induced instability

Giant Eruptions and the Supernova Impostors

Giant Eruption LBVs (Humphreys & Davidson (1994) -- increase their luminosity during the eruption!

SN1954j

Examples of reflection nebulae

associated with LBVs (K. Weis)

ejecta and atmospheres are N and He rich Evolved post MS

Same linear scale

Eta Car’s Second or lesser eruption 1888 -- 1895

Duration ~ 7 yrs

Increase ~ 2mag in apparent brightness

Spectrum - F supergiant abs lines plus H and Fe II em.

First photographic spectra 1892- 93 (Walborn & Liller 1977, Humphreys et al. 2008

Max luminosity 106.7 LsunTotal energy 1048.6 ergs

Mass lost ~ 0.2 Msun

An LBV or S Dor – type “eruption”

Supernova Impostors

What are they –giant eruptions of evolved massive stars ,LBVs , or ??

Obj. Galaxy Mv(proj) MBolmax Duration Comment

eta Car MW -9.5 -- -10 -14.5 20yrs 2 nd eruption 50 yrs later

SN1961v N1058 ~ -12 ? -16.5 ~ 1yr 2 nd eruption 3 yrs later

SN1954j N2403 - 7.5 < -11.6 ~ 1 yr V12, max. not observed

P Cyg MW - 8 -11 ~ 6 yrs 2 nd eruption 55 yrs later

V 1 N2366 -5.6 - 12 > 8 yrs ongoing ?

SN1978 N1313 -7.5: < -12 ~ 1 yr max. not observed

SN1997bs M66 -8.1 -13.8 30d

SN1999bw N3198 ? -12 30d

SN2000ch N3432 -10.7: -12.7 ~ 10d second eruption 2009

SN2001ac N3504 ? -13.7 ~ 30d?

SN2002kg N2403 -7.4 -11.3 ~ 2 yrs? = V37

SN2008S N6946 -(6.6) -13 < 1 yr optically obscured

N300 – OT (2008) -(7.1) -12 to -13 < 1 yr optically obscured

U2773 – OT (2009) ~-7.8 -12.8 > 1 yr ongoing ?

SN2009ip N7259 ~ -10 -14.5 > 1 yr ongoing?

SN2010da N300 ( -5.5) -10.4 optically obscured

SN2010dn N3184 -12.9 optically obscured ?

N3437 –OT (2011) -13.6

The Warm and Cool Hypergiants

IRC+10420

Warm Hypergiants, post RSG evolution, the “Yellow” void, and a dynamical instability

The Intermediate-Luminosity Red Transients

A small group of stars, a range of initial masses?, different origins for their instability/outbursts?

What they have in common – cool/red, evolved

V838 Mon

V4332 Sgr

V1309 Sco

M31 Red Var

M85 2006 red transient

SN 2008s (N6946) -- optically obscured progenitor

N300 2008 OT -- optically obscured progenitor

SN 2010da (N300) -- optically obscured progenitor

SN 2010dn (N3194) -- optically obscured progenitor?

Binary merger (V1309 Sco)

Photospheric instability?

Supernova or failed supernova ?

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NGC 300 2008 OT SN2008s SN2010da

Optically obscured, “cool” transients

Prieto 2008 Prieto et al 2008 Khan et al., Berger et al. 2010

T= 350K BB L = 5.5 x 104 Lsun, Mbol = -7.1 mag

at maximumMv = -12.1 or -12.9 mag

L = 1.1 x 107 Lsun

T= 440K BB

L = 3.5 x 104 Lsun Mbol = -6.8 mag

at maximum Mv = -13.6 mag

L = 3 x 107 Lsun

T= 890 K BB

L = 1.3 x 104 Lsun

Mbol = -5.5 mag

at maximum Mv = -10.4 mag

L = 1.1 x 106 Lsun

In “eruption” increased 100 – 1000 times

Spectra

F-type supergiant absorption spectra plus strong H, Ca II and [CaII] emission– resemble IRC+10420

Bond et al. 2009

Berger et al. 2009

A post RSG star (supergiant OH/IR star), post AGB(OH/IR or C star), on a blue-loop

Electron-capture SN (Thompson et al. 2009)

Failed SN ?

Binary interactions? SN2010da (SGXB, Binder et al. 2011)

Photospheric instability (super-Edd wind (Smith et al.2009, Bond et al. 2009)

Heger: “ the stars (on a blue loop) are not happy”

Outstanding Theoretical Problems in Massive Star Research

A future meeting --

Minnesota Instiute for Astrophysics and

Fine Theoretical Physics Institute

University of Minnesota October 2012

IMPOSTOR !

3D Morphology and History of Asymmetric Mass Loss Events and Origin of Discrete Ejecta

Arcs and Knots are spatially and kinematically distinct; ejected in different directions at different times; not aligned with any axis of symmetry.

They represent localized, relatively massive

(few x 10-3 Msun) ejections Large-scale convective activity Magnetic Fields

From polarization of OH, H2O, SiO

masers (Vlemmings et al. 2002, 2005)

V37 in N2403,

Tammann & Sandage 1968

SN 2009ip

ATEL 2897, Oct 1, 2010

Variable A in M33 – a warm or cool hypergiant ~ 45 years in eruption!

Warm Hypergiants, post RSG evolution, the “Yellow” void, and a dynamical instability