Episodic and High Mass Loss Events In Evolved Stars Roberta M. Humphreys University of Minnesota...
-
Upload
candace-hudson -
Category
Documents
-
view
213 -
download
0
Transcript of Episodic and High Mass Loss Events In Evolved Stars Roberta M. Humphreys University of Minnesota...
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 ?
*
*
* *
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