Post on 20-Jan-2017
2. Stellar evolution – a crash course Rolf Kudritzki SS 2015
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Extragalactic stellar distance indicators need to be bright advanced stages of stellar evolution
• Red Giant Star (SFB) • Tip of Red Giant Branch (TRGB) • Horizontal Branch – RR Lyrae • post-AGB stars, Planetary Nebulae • Cepheid Stars • Blue Supergiant Stars
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Evolution of low mass stars 0.5M� M 2.5M�
main sequence (MS): H core burning à Red Giant Branch (RGB): H shell burning à He-flash: ignition of He core burning à Tip of RGB (TRGB) à Horizontal Branch (HB): He core burning H burning shell RR Lyrae pulsators à Asymptotic Giant Branch (AGB): He burning shell H burning shell àpost-AGB (pAGB): hot Central Stars of PN (CSPN) à White Dwarfs (WD): no energy sources, cooling supernovae in binaries
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Maeder, 2009
all low mass stars ignite He-flash at almost the same luminosity à tip of red giant branch but there is a metallicity dependence
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Maeder, 2009
all low mass stars ignite He-flash at almost the same luminosity à tip of red giant branch but there is a metallicity dependence
He-flash after flash stars on HB with central He burning and H burning shell
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Maeder, 2009
interior structure during evolution
the nuclear H-burning shell moves outwards until He-burning ignites in the degenerate He-core
He-flash hydro-dynamic
Con
cepc
ion
2007
NGC 300 Cycle 11 HST/ACS imaging
Distance from TRGB Rizzi, Bresolin, Kudritzki et al., 2005, ApJ agrees with Cepheids
Con
cepc
ion
2007
NGC 300 Cycle 11 HST/ACS imaging
Distance from TRGB Rizzi, Bresolin, Kudritzki et al., 2005, ApJ agrees with Cepheids your name
Mager et al. (2008)
TRGB
TRGB distance (theory new) (m-M)0=29.51 0.05 0.05 MASER distance (Humphreys et al. 2013) (m-M)0=29.40 0.06 0.06
Comparison with MASER distance to NGC4258 M. Salaris, MIAPP 2014
Rolf Kudritzki SS 2015
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TRGB detection (maximum likelihood methods)
The fitted parameters are
mTRGB = 21.79 [21.76, 21.83], RGB slope a = 0.36 [0.30, 0.43] RGB jump b = 0.44 [0.38, 0.50] AGB slope c = 0.13 [0.03, 0.24]
‘noisy’ edge detection response
LF parametrised as
M. Salaris, MIAPP 2014
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after the hydrodynamic He-flash stars with central He-burning and a H-burning shell assemble on the Horizontal Branch (HB) HB stars have roughly the same He-core mass but different envelope masses à Teff sequence
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HORIZONTAL BRANCH MORPHOLOGY
M. Salaris, MIAPP 2014
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globular cluster CMD
Hansen & Kawaler, 1994
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globular cluster CMD
RR Lyrae pulsators in HB
Hansen & Kawaler, 1994
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RR Lyrae stars as distance indicators and stellar tracers
RR Lyrae variables
Initial mass (MS): ~0.8-0.9 Msun
Mass (HB): ~0.6-0.8 Msun
Core He + Shell H burning
[Fe/H] ~ -2.5 – 0.0 (Smith, 2005)
Old: >10 Gyr (GCs, halo, bulge) Main Sequence (MS)
Horizontal Branch (HB)
Stetson, VFB et al. (2014)
M4
HB Maruzio’s talk
Guiseppe Bono, MIAPP 2014
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Vittorio Francesco Braga
M4 CMDsDistance determination to M4 with optical, NIR and MIR photometry of RR Lyrae
Garching, MIAPP, 11/6/2014
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HB evolution
Maeder, 2009
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HORIZONTAL BRANCH Core He-burning phase in old stellar populations
Ingredients: He-core mass at He-ignition Convective-core mixing Bolometric corrections Star Formation histories/RGB mass loss
M. Salaris, MIAPP 2014
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internal structure of AGB star
Maeder, 2009
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AGB and post-AGB evolution
CSPN
WD
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Evolution of intermediate mass stars
main sequence (MS): H core burning à Red Giant Branch (RGB): H shell burning à no He-flash: normal ignition of He core burning on RGB à blue loops during He core burning Cepheid pulsators à Asymptotic Giant Branch (AGB): He burning shell H burning shell àpost-AGB (pAGB): hot Central Stars of PN (CSPN) à WD cooling sequence supernova in binaries
2.5M� M 8.0M�
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evolution of a 7 Msun star
Maeder, 2009
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pAGB evolution note: heavy influence of mass-loss, for instance, 7 Msun star has only 1 Msun left evolution time much faster for luminous objects
pAGB core mass – luminosity relationship simple fit formula by Paczynski, 1970 L
L�= 5.29 104
✓M
M�� 0.52
◆
Maeder, 2009
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evolution of a 7 Msun star
Maeder, 2009
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evolution of a 7 Msun star
Maeder, 2009
Cepheid instability strip
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instability strip
main sequence
Hayashi limit of low mass fully convective stars
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Evolution of massive stars
main sequence (MS): H core burning à blue supergiants (BSG): H shell burning à red supergiants (RSG): normal ignition of He core burning à M < 15 Msun blue loops during He core burning Cepheid pulsators à post RSG evolution leads to à iron core collapse supernovae
M � 8.0M�
Ath
ens
2013
Blue supergiants – objects in transition
B1–A4
Brightest normal stars at visual light: 105..106 Lsun -7 ≥ MV ≥ -10 mag tev ~ 103 yrs L, M ~ const. ideal to determine
• chemical compos. • abundance grad. • SF history • extinction • extinction laws • distances
of galaxies
MIA
PP 2
014
IR beacons in universe: red supergiants
B1–A4
Brightest stars at infrared light: -8 ≥ MJ ≥ -11 mag
K–M
medium resolution J-band spectroscopy: atomic lines dominate à medium res. spectra ok
à enormous potential with Keck/VLT, TMT/E-ELT beyond Local Group out to Coma cluster
Advantage: AO supported MOS possible
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Maeder, 2009
structure of a massive star shortly before iron core SN collapse
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The bright and beautiful death of many stars: Supernovae
Maeder, 2009
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Maeder, 2009
light curves of supernova types and peak magnitudes
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The bright and beautiful death of many stars: Supernovae
Maeder, 2009
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Maeder, 2009
structure of a massive star shortly before iron core SN collapse
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Type IIP supernovae - progenitors
Several direct detections of progenitors (e.g. Smartt et al. 2009):
mostly red supergiants
Mass range ~9 to ~18 M⊙
Core-collapse explosions of massive, H-rich stars
Introduction
Image: Mattila et al. 2010
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SNe IIP at the GTC
Observational data II: SNe IIP at intermediate redshift
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Phenomenology
● Strong Hydrogen lines --> Type II classification
● A long Plateau in their lightcurve
● A sharp fall
● A radioactive tail
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Phenomenology
● Strong Hydrogen lines --> Type II classification
● A long Plateau in their lightcurve
● A sharp fall
● A radioactive tail
Olivares et al. 2010
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SNe IIP in a nutshell
● The duration of the plateau is usually of the order of ~100 days, ranging between 80 and 120 days
● The initial velocity of the ejecta is of the order of 1-2 x 10^4 km/s
● The initial temperature is of the order of 1-2 x 10^4 K
● Peak luminosities commonly range between Mv = -15.5 and Mv = -18.5 mag --> how can we use them as distance indicators?
● The SN event is generated by the core-collapse of a massive star
● Progenitors are usually Red Supergiants (RSG, in some cases we have a BSG, such as SN 1987A)
● Their masses are expected
to be up to 25-30 M
, but on
the basis of the progenitors analysis, the accepted limit is
of the order of 15-18 M
...
...Until now...
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The bright and beautiful death of many stars: Supernovae
Maeder, 2009
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SNe Ia: Far-Reaching Candles
• CO White Dwarf in binary pushed to Chandrasekhar limit (fundamental physics)
Mass transfer, companion, time scales not well understood.
Most uniform standard candle at this luminosity scale
• Empirical and theoretical calibrations give MV=-19 mag, explain yield of IME
• Identified by strong Si II, absence of H in spectra, come in late/early type hosts
A. Riess, 2012, Naples WS
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NOAO 4m image of SN 2011fe in M101 (T.A. Rector, H. Schweiker & S. Pakzad NOAO/AURA/NSF)
Saurabh W. Jha MIAPP The Extragalactic Distance Scale May 28, 2014
Surveying the Universe with Type Ia Supernovae
SN 2014J in M82 (Marco Burali, Osservatorio MTM Pistoia)
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SNIa background physics
all stars with evolve into the cooling sequence of White Dwarfs
M 8M� CSPN
WD
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cooling sequence of WDs
V.Weidemann and collaborators
White Dwarfs: extremely narrow mass distribution
without mass-loss stars with such masses cannot have evolved from the main sequence within Hubble time
from the HRDs of open clusters we know that all stars with have formed WDs The mass spectrum observed can be roughly explained by IMF and stellar evolution with mass-loss applying Reimers – formula Note: no WD with masses !!!
hMWDi ⇡ 0.6M�
0.8M� M 8M�
M� � 1.4M�
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The Physics of White Dwarfs
the equation of state (EOS) of WDs is different from normal stars because of their much higher densities: 0.6 solar masses confined within earth-like radius mean particle distance << de Broglie wavelength quantum nature (fermions!) of matter important: 1. Pauli principle: only one particle per quantum state 2. Fermi distribution of energies instead Maxwell/
Boltzmann 3. different EOS
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�B =hp
2⇡mkT
r0 = n� 13n =
N
V=
1
r30
f(✏) =1
e(�⌘+ ✏kt ) + 1
↵ = 2
de Broglie wavelength
particle separation
energy distribution
degeneracy parameter for �B � r0
spin degeneracy of electrons
⌘ =1.21
↵
✓�B
r0
◆2
/ n23
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strong degeneracy of free electrons in WD electrons provide pressure acting against gravity different EOS
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f(✏) =1
e(�⌘+ ✏kt ) + 1
✏/kT
Fermi energy
P ⇠ n53
eWD EOS: degenerate matter pressure de-coupled from temperature
✏f ⇠ n23
e
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Mass – radius relationship of WDs dP
dr= �G
Mr
r2⇢
dP
dr⇠ P0 � Pc
R� 0= �Pc
R⇠ �M
R2⇢̄
⇢̄ ⇠ M
R3
Pc ⇠M2
R4
Pc ⇠ ⇢̄53 ⇠ M
53
R5
R ⇠ M� 13
hydrostatic equilibrium
on the other hand: EOS
(1)
(2)
combine (1) and (2)
WD radii shrink with increasing mass!!!!
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with higher mass Fermi energy increases and particles become relativistic
R ⇠ M� 13 ⇢̄ ⇠ M2
✏f � mec2
✏f ⇠ ⇢23
✏ = m0c2(1 +
p2
m0c2)
12 p = m0v(1�
v2
c2)�
12
relationship between energy and momentum p changes
P = A2⇢43 (1�B2⇢
� 23 )
relativistic EOS at higher mass
The Chandrasekhar limit of WDs
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P = A0M2
R4⇢ = B0
M
R3combining eq (1) and
with relativistic EOS yields
R =B
130
B122
M13
r1� M
MCh
MCh =
✓A2
A0
◆ 32
B20 ⇡ 1.4M�
at the Chandrasekhar mass MCh the radius is zero
no higher masses than MCh possible !!!
The Chandrasekhar limit of WDs
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relativistic degeneracy
WD Mass radius relationship
Close to the Chandreasekhar limit: We will show in the next chapter that such configurations are unstable collaps and explosive carbon burning Supernova explosion
P ⇠ ⇢43
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Scenario for SNIa supernova explosions
WD in binary system is accreting mass approaching Chandrasekhar limit and explodes as SNIa Since explosion happens always at same mass, released energy (luminosity) should be the same Bright standard candle !! ??
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SNe Ia: Far-Reaching Candles
• CO White Dwarf in binary pushed to Chandrasekhar limit (fundamental physics)
Mass transfer, companion, time scales not well understood.
Most uniform standard candle at this luminosity scale
• Empirical and theoretical calibrations give MV=-19 mag, explain yield of IME
• Identified by strong Si II, absence of H in spectra, come in late/early type hosts
A. Riess, 2012, Naples WS
Rolf Kudritzki SS 2015
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NOAO 4m image of SN 2011fe in M101 (T.A. Rector, H. Schweiker & S. Pakzad NOAO/AURA/NSF)
Saurabh W. Jha MIAPP The Extragalactic Distance Scale May 28, 2014
Surveying the Universe with Type Ia Supernovae
SN 2014J in M82 (Marco Burali, Osservatorio MTM Pistoia)
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May 18, 1998
Ca
Fe
S
Si
Si
Fe
intermediate mass elements are fused from C and O during the explosion
ejecta travels at ~10,000 km/s
March 14, 1997
What is a Type Ia Supernova?
May 18, 1998
strong evidence that SN Ia are explosionsof carbon-oxygen white dwarfs
but big questions about companion star, white dwarf mass and explosion process SN 1998bu in M96
S.W. Jha, 2014, MIAPP WS
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The Groundbreaking Work: Calán/Tololo
Hamuy et al. (1996a,b)
1996AJ....112.2391H
1996AJ....112.2398H
S.W. Jha, 2014, MIAPP WS
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SN Ia are standardizable candles,with emprically derived corrections:
light curve-shape correction(aka the Phillips 1993 relation)
color-correction(including dust reddening/extinction,
e.g. Riess et al. 1996, 1999)
light curve fitters (in use today):MLCS2k2 (Jha, Riess, & Kirshner 2007)
SALT2 (Guy et al. 2007)SiFTO (Conley et al. 2008)
BayeSN (Mandel et al. 2009, 2011)SNooPy (Burns et al. 2011)
Gaussian Process (Kim et al. 2013, 2014)...
Standardizing the Candles
S.W. Jha, 2014, MIAPP WS
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MLCS2k2 light-curve fitsJha, Riess, & Kirshner (2007)
6
0
1000
2000
-20 -10 0 10 20 30 40 50 60
0
1000
2000
-20 -10 0 10 20 30 40 50 60
SN 2005ff z=0.09
g
r
i
Tobs - 53634.7
Flu
x
0
1000
2000
-20 -10 0 10 20 30 40 50 60
0
200
400
600
-20 -10 0 10 20 30 40 50 60
0
200
400
600
800
-20 -10 0 10 20 30 40 50 60
SN 2005fb z=0.18
g
r
i
Tobs - 53632.8
Flu
x
0
200
400
600
-20 -10 0 10 20 30 40 50 60
0
100
200
-20 -10 0 10 20 30 40 50 60
0
100
200
300
-20 -10 0 10 20 30 40 50 60
SN 2005fr z=0.29
g
r
i
Tobs - 53633.4
Flu
x
0
100
200
-20 -10 0 10 20 30 40 50 60
0
25
50
75
-20 -10 0 10 20 30 40 50 60
0
50
100
150
-20 -10 0 10 20 30 40 50 60
SN 2005gq z=0.39
g
r
i
Tobs - 53646
Flu
x
0
100
200
-20 -10 0 10 20 30 40 50 60
Fig. 1.— Light curves for four SDSS-II SNe Ia at different redshifts: SN 2005ff at z = 0.09, SN 2005fb at z = 0.18, SN 2005fr atz = 0.29, and SN 2005gq at z = 0.39. The passbands are SDSS g (top), r (middle), and i (bottom). Points are the SMP flux measurements(flux = 10(11−0.4m), where m is the SN magnitude) with ±1 σ photometric errors indicated. Solid curves show the best-fit mlcs2k2 modelfits (see §5.1), and dashed curves give the ±1 σ error bands on the model fits. The Modified Julian Date (MJD) under each set of lightcurves is the fitted time of peak brightness for rest-frame B-band.
SNANA: Kessler et al. (2009b)“scene-modeled” multi-color light curves, with fits for light curve shape and dust extinction
Holtzman et al. (2008)
Si
MLCS2k2 light curve fits
SN 1999cp and SN 2002cr, both in NGC 5468μ = 33.46 ± 0.07 mag μ = 33.49 ± 0.10 mag
KAIT BVRI photometry Ganeshalingam et al. (2010)
S.W. Jha, 2014, MIAPP WS
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Si
~6 to 10% distance precision per object -- average this down with pN
Standardizing the Candles
Jha, Riess, & Kirshner (2007)
S.W. Jha, 2014, MIAPP WS
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q0, 1998: High-z SNe Ia; Acceleration (q0<0), Dark Energy!
Riess et al. 2007
Not just supernovae require “dark energy”…
A. Riess, 2012, Naples WS
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