Episodic and High Mass Loss Events In Evolved Stars Roberta M. Humphreys University of Minnesota...
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Transcript of Episodic and High Mass Loss Events In Evolved Stars Roberta M. Humphreys University of Minnesota...
![Page 1: Episodic and High Mass Loss Events In Evolved Stars Roberta M. Humphreys University of Minnesota Intermediate Luminosity Red Transients Space Telescope.](https://reader036.fdocuments.net/reader036/viewer/2022070410/56649ed25503460f94be1a5d/html5/thumbnails/1.jpg)
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
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The evidence for episodic high mass loss events
The Upper HR Diagram
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In Evolved Massive Stars -- Luminous Blue Variables (LBVs)
S Dor variability vs giant Eruptions
-- Warm and Cool Hypergiants
Humphreys and Davidson 1994
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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)
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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)
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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
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Giant Eruptions and the Supernova Impostors
Giant Eruption LBVs (Humphreys & Davidson (1994) -- increase their luminosity during the eruption!
SN1954j
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Examples of reflection nebulae
associated with LBVs (K. Weis)
ejecta and atmospheres are N and He rich Evolved post MS
Same linear scale
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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”
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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
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The Warm and Cool Hypergiants
IRC+10420
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Warm Hypergiants, post RSG evolution, the “Yellow” void, and a dynamical instability
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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
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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
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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”
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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 !
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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)
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V37 in N2403,
Tammann & Sandage 1968
SN 2009ip
ATEL 2897, Oct 1, 2010
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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