2. Stellar evolution a crash course

Size: px

Start display at page:

Download "2. Stellar evolution a crash course"

Brice Wright
5 years ago
Views:

1 2. Stellar evolution a crash course 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 1

2 Evolution of low mass stars 0.5M apple M apple 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 à post-agb (pagb): hot Central Stars of PN (CSPN) à White Dwarfs (WD): no energy sources, cooling supernovae in binaries 2

3 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 3

4 He-flash after flash stars on HB with central He burning and H burning shell 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 4

5 interior structure during evolution He-flash hydrodynamic Maeder, 2009 the nuclear H-burning shell moves outwards until He-burning ignites in the degenerate He-core 5

6 Concepcion 2007 NGC 300 Cycle 11 HST/ACS imaging Distance from TRGB Rizzi, Bresolin, Kudritzki et al., 2005, ApJ agrees with Cepheids

7 Concepcion 2007 Mager et al. (2008) NGC 300 Cycle 11 HST/ACS imaging TRGB distance (theory new) (m-m) 0 = MASER distance (Humphreys et al. 2013) TRGB (m-m) 0 = Comparison with MASER distance to Distance from TRGB Rizzi, Bresolin, Kudritzki et al., 2005, ApJ agrees with Cepheids your name NGC4258 M. Salaris, MIAPP 2014

8 TRGB detection (maximum likelihood methods) LF parametrised as noisy edge detection response The fitted parameters are m TRGB = [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] Makarov et al your name M. Salaris, MIAPP

9 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 T eff sequence 9

10 HORIZONTAL BRANCH MORPHOLOGY your name M. Salaris, MIAPP

11 globular cluster CMD Hansen & Kawaler,

12 globular cluster CMD RR Lyrae pulsators in HB Hansen & Kawaler,

13 RR Lyrae stars as distance indicators and stellar tracers Rolf Kudritzki SS 2015 RR Lyrae variables M4 Initial mass (MS): ~ M sun Mass (HB): ~ M sun Horizontal Branch (HB) Core He + Shell H burning [Fe/H] ~ (Smith, 2005) Old: >10 Gyr (GCs, halo, bulge) Main Sequence (MS) HB Maruzio s talk Stetson, VFB et al. (2014) 13 Guiseppe Bono, MIAPP 2014

14 Distance Rolf Kudritzki determination SS 2015 to M4 with optical, NIR and MIR photometry of RR Lyrae M4 CMDs Vittorio Francesco Braga 14 Garching, MIAPP, 11/6/2014

15 HB evolution Maeder,

16 Ingredients: He-core mass at He-ignition Convective-core mixing Bolometric corrections Star Formation histories/rgb mass loss HORIZONTAL BRANCH Core He-burning phase in old stellar populations M. Salaris, MIAPP 2014 your name 16

17 internal structure of AGB star Maeder,

18 AGB and post-agb evolution CSPN WD 18

19 Evolution of intermediate mass stars 2.5M apple M apple 8.0M 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 à post-agb (pagb): hot Central Stars of PN (CSPN) à WD cooling sequence supernova in binaries 19

20 evolution of a 7 M sun star Maeder,

luminous objects Maeder, 2009 pagb core mass luminosity

21 pagb evolution note: heavy influence of mass-loss, for instance, 7 M sun star has only 1 M sun left evolution time much faster for luminous objects Maeder, 2009 pagb core mass luminosity relationship simple fit formula by Paczynski, 1970 L L = M M

22 evolution of a 7 M sun star Maeder,

23 evolution of a 7 M sun star Cepheid instability strip Maeder,

24 instability strip Hayashi limit of low mass fully convective stars main sequence 24

25 Evolution of massive stars M 8.0M 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 M sun blue loops during He core burning Cepheid pulsators à post RSG evolution leads to à iron core collapse supernovae 25

26 Athens 2013 Blue supergiants objects in transition Brightest normal stars at visual light: L sun -7 M V -10 mag B1 A4 t ev ~ 10 3 yrs L, M ~ const. ideal to determine chemical compos. abundance grad. SF history extinction extinction laws distances of galaxies

27 MIAPP 2014 IR beacons in universe: red supergiants Brightest stars at infrared light: -8 M J -11 mag Advantage: AO supported MOS possible B1 A4 medium resolution J-band spectroscopy: atomic lines dominate à medium res. spectra ok K M à enormous potential with Keck/VLT, TMT/E-ELT beyond Local Group out to Coma cluster

28 structure of a massive star shortly before iron core SN collapse Maeder,

29 The bright and beautiful death of many stars: Supernovae Maeder,

30 light curves of supernova types and peak magnitudes Maeder,

31 The bright and beautiful death of many stars: Supernovae Maeder,

32 structure of a massive star shortly before iron core SN collapse Maeder,

33 Introduction Rolf Kudritzki SS 2015 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 Image: Mattila et al Stefan Taubenberger (MPA) Distance measurements with Type IIP supernovae

34 Observational data II: SNe IIP at intermediate redshift Rolf Kudritzki SS 2015 SNe IIP at the GTC 34 Stefan Taubenberger (MPA) Distance measurements with Type IIP supernovae

35 Phenomenology Strong Hydrogen lines --> Type II classification A long Plateau in their lightcurve A sharp fall A radioactive tail 35

36 Phenomenology Strong Hydrogen lines --> Type II classification A long Plateau in their lightcurve A sharp fall A radioactive tail Olivares et al

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

37 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 = and Mv = 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 M, but on the basis of the progenitors analysis, the accepted limit is of the order of M......Until now... 37

38 The bright and beautiful death of many stars: Supernovae Maeder,

39 Rolf Kudritzki SS 2015 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 39 A. Riess, 2012, Naples WS

40 Surveying the Universe with Type Ia Supernovae NOAO 4m image of SN 2011fe in M101 (T.A. Rector, H. Schweiker & S. Pakzad NOAO/AURA/NSF) SN 2014J in M82 (Marco Burali, Osservatorio MTM Pistoia) Saurabh W. Jha MIAPP The Extragalactic Distance Scale May 28,

41 SNIa background physics CSPN all stars with M apple 8M WD evolve into the cooling sequence of White Dwarfs 41

42 cooling sequence of WDs V.Weidemann and collaborators 42

43 White Dwarfs: extremely narrow mass distribution hm WD i 0.6M 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 0.8M apple M apple 8M 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 M 1.4M!!!

44 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 44

45 B = h p 2 mkt de Broglie wavelength n = N V = 1 r 3 0 r 0 = n 1 3 particle separation 1 f( ) = e ( + kt ) +1 = B / n 2 3 =2 r 0 energy distribution degeneracy parameter for B r 0 spin degeneracy of electrons 45

46 strong degeneracy of free electrons in WD electrons provide pressure acting against gravity different EOS 46

47 f( ) = 1 e ( + kt ) +1 /kt f n 2 3 e Fermi energy P n 5 3 e WD EOS: degenerate matter pressure de-coupled from temperature 47

48 dp dr = GM r r 2 Mass radius relationship of WDs dp dr P 0 P c R 0 = P c R hydrostatic equilibrium M R 2 P c M 2 R 4 (1) M R 3 on the other hand: EOS P c 5 3 M 5 3 R 5 (2) combine (1) and (2) R M 1 3 WD radii shrink with increasing mass!!!! 48

49 The Chandrasekhar limit of WDs R M 1 3 M 2 with higher mass Fermi energy increases and particles become relativistic = m 0 c 2 (1 + p2 f 2 3 m 0 c 2 ) 1 2 p = m 0 v(1 f m e c 2 v 2 c 2 ) 1 2 relationship between energy and momentum p changes P = A (1 B2 2 3 ) relativistic EOS at higher mass 49

50 combining eq (1) P = A 0 M 2 with relativistic EOS yields R = B M 1 B M Ch = The Chandrasekhar limit of WDs A2 A 0 r 1 M M Ch R B M and = B 0 M R 3 at the Chandrasekhar mass M Ch the radius is zero no higher masses than M Ch possible!!! 50

51 WD Mass radius relationship relativistic degeneracy Close to the Chandreasekhar limit: We will show in the next chapter that such configurations are unstable P 4 3 collaps and explosive carbon burning Supernova explosion 51

52 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!!?? 52

Most uniform standard candle at this luminosity scale Empirical and theoretical calibrations give MV=-19

53 Rolf Kudritzki SS 2015 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 53 A. Riess, 2012, Naples WS

54 Surveying the Universe with Type Ia Supernovae NOAO 4m image of SN 2011fe in M101 (T.A. Rector, H. Schweiker & S. Pakzad NOAO/AURA/NSF) SN 2014J in M82 (Marco Burali, Osservatorio MTM Pistoia) Saurabh W. Jha MIAPP The Extragalactic Distance Scale May 28,

55 What is a Type Ia Supernova? intermediate mass elements are fused from C and O during the explosion ejecta travels at ~10,000 km/s March 14, 1997 May 18, 1998 Ca Fe Fe S Si Si SN 1998bu in M96 S.W. Jha, 2014, MIAPP WS strong evidence that SN Ia are explosions of carbon-oxygen white dwarfs but big questions about companion star, white dwarf mass and explosion process 55

56 The Groundbreaking Work: Calán/Tololo Hamuy et al. (1996a,b) 56 S.W. Jha, 2014, MIAPP WS

Standardizing the Candles SN Ia are standardizable candles, with emprically derived corrections: light curve-shape correction (aka the Phillips 1993 relation) color-correction (including dust

57 Standardizing the Candles 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) Krisciunas et al. (2006) 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) S.W. Jha, 2014, MIAPP WS

S.W. Jha, 2014, MIAPP WS MLCS2k2 MLCS2k2 light-curve light curve fits fits scene-modeled multi-color light curves, with fits for light curve shape and dust extinction KAIT

29 2000 600 200 400 1000 0 g 200 0 g 100 0 g 800 300 2000 1000 0 r 600 400 200 0 r 200 100 0 r Flux 2000 1000 0 i -20-10 0 10 20 30 40 50 60 Flux 600 400 200 0 i μ = 33.46 ± 0.

58 S.W. Jha, 2014, MIAPP WS MLCS2k2 MLCS2k2 light-curve light curve fits fits scene-modeled multi-color light curves, with fits for light curve shape and dust extinction KAIT Holtzman et BVRI al. (2008) photometry SNANA: Kessler Ganeshalingam et al. (2009b) Jha, et Riess, al. &(2010) Kirshner (2007) SN 2005ff z=0.09 SN 2005fb z=0.18 SN 2005fr z= g g g r r r Flux i Flux i μ = ± 0.07 mag μ = ± 0.10 mag T obs T obs SN 1999cp and SN 2002cr, both in NGC 5468 Si Flux i T obs

59 Standardizing the Candles Jha, Riess, & Kirshner (2007) Si ~6 to 10% distance precision per object -- average this down with p N 59 S.W. Jha, 2014, MIAPP WS

60 q 0, 1998: High-z SNe Ia; Acceleration (q 0 <0), Dark Energy! Riess et al Not just supernovae require dark energy 60 A. Riess, 2012, Naples WS

61 61

62 62

Chapter 8: Simple Stellar Populations

Chapter 8: Simple Stellar Populations Simple Stellar Population consists of stars born at the same time and having the same initial element composition. Stars of different masses follow different evolutionary