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 – typical In “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 StripWolf (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 L Edd = 4  cGM sun /  Edd = const  (L/L sun ) (M/M sun ) -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)  = v rot /v crit > 1, v 2 crit = (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 Duration ~ 7 yrs Increase ~ 2mag in apparent brightness Spectrum - F supergiant abs lines plus H and Fe II em. First photographic spectra (Walborn & Liller 1977, Humphreys et al Max luminosity L sun Total energy ergs Mass lost ~ 0.2 M sun An LBV or S Dor – type “eruption”

Supernova Impostors What are they –giant eruptions of evolved massive stars,LBVs, or ?? Obj. Galaxy M v (proj) M Bol max Duration Comment eta Car MW yrs 2 nd eruption 50 yrs later SN1961v N1058 ~ -12 ? ~ 1yr 2 nd eruption 3 yrs later SN1954j N < ~ 1 yr V12, max. not observed P Cyg MW ~ 6 yrs 2 nd eruption 55 yrs later V 1 N > 8 yrs ongoing ? SN1978 N : < -12 ~ 1 yr max. not observed SN1997bs M d SN1999bw N3198 ? d SN2000ch N : ~ 10d second eruption 2009 SN2001ac N3504 ? ~ 30d? SN2002kg N ~ 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) ~ > 1 yr ongoing ? SN2009ip N7259 ~ > 1 yr ongoing? SN2010da N300 ( -5.5) optically obscured SN2010dn N 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 M red transient SN 2008s (N6946) -- optically obscured progenitor N 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 ? *

NGC OT SN2008s SN2010da Optically obscured, “cool” transients Prieto 2008Prieto et al 2008Khan et al., Berger et al T= 350K BB L = 5.5 x 10 4 L sun, Mbol = -7.1 mag at maximum Mv = or mag L = 1.1 x 10 7 L sun T= 440K BB L = 3.5 x 10 4 L sun Mbol = -6.8 mag at maximum Mv = mag L = 3 x 10 7 L sun T= 890 K BB L = 1.3 x 10 4 L sun Mbol = -5.5 mag at maximum Mv = mag L = 1.1 x 10 6 L sun In “eruption” increased 100 – 1000 times

Spectra F-type supergiant absorption spectra plus strong H, Ca II and [CaII] emission– resemble IRC Bond et al 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 M sun ) ejections Large-scale convective activity  Magnetic Fields From polarization of OH, H 2 O, 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