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Episodic and High Mass Loss Events In Evolved Stars

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 Upper HR Diagram. The evidence for episodic high mass loss events.

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Episodic and High Mass Loss Events In Evolved Stars

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  1. 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

  2. The Upper HR Diagram The evidence for episodic high mass loss events

  3. In Evolved Massive Stars -- Luminous Blue Variables (LBVs) S Dor variability vs giant Eruptions -- Warm and Cool Hypergiants Humphreys and Davidson 1994

  4. 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)

  5. 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)

  6. The Cause of the Instability? Most explanations -- the star is near the Eddington Limit LEdd = 4pcGMsun/k , GEdd = const k (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) W = vrot/vcrit > 1, v2crit = (1 –G) GM/R 3. Vibration/Pulsation -- e mechanism (in the core) no longer considered applicable to evolved stars -- k 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

  7. Giant Eruptions and the Supernova Impostors Giant Eruption LBVs (Humphreys & Davidson (1994) -- increase their luminosity during the eruption! SN1954j

  8. Examples of reflection nebulae associated with LBVs (K. Weis) ejecta and atmospheres are N and He rich  Evolved post MS Same linear scale

  9. 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. Max luminosity 106.7 LsunTotal energy 1048.6 ergs Mass lost ~ 0.2 Msun An LBV or S Dor – type “eruption” First photographic spectra 1892- 93 (Walborn & Liller 1977, Humphreys et al. 2008

  10. 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 2nd eruption 50 yrs later SN1961v N1058 ~ -12 ? -16.5 ~ 1yr 2nd eruption 3 yrs later SN1954j N2403 - 7.5 < -11.6 ~ 1 yr V12, max. not observed P Cyg MW - 8 -11 ~ 6 yrs 2nd 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

  11. The Warm and Cool Hypergiants IRC+10420

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

  13. 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 ? * * * *

  14. Optically obscured, “cool” transients NGC 300 2008 OT SN2008s SN2010da 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 maximum Mv = -12.1 or -12.9 mag L = 1.1 x 107 Lsun T= 440K BB L = 3.5 x 104Lsun 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

  15. 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

  16. 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”

  17. A future meeting -- Outstanding Theoretical Problems in Massive Star Research Minnesota Instiute for Astrophysics and Fine Theoretical Physics Institute University of Minnesota October 2012 IMPOSTOR !

  18. 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)

  19. V37 in N2403, Tammann & Sandage 1968 SN 2009ip ATEL 2897, Oct 1, 2010

  20. Warm Hypergiants, post RSG evolution, the “Yellow” void, and a dynamical instability Variable A in M33 – a warm or cool hypergiant ~ 45 years in eruption!

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