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CHALLENGES FOR STELLAR EVOLUTION AND PULSATION THEORY Jadwiga Daszyńska-Daszkiewicz Instytut Astronomiczny, Uniwersytet Wrocławski, POLAND JENAM Symposium.

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Presentation on theme: "CHALLENGES FOR STELLAR EVOLUTION AND PULSATION THEORY Jadwiga Daszyńska-Daszkiewicz Instytut Astronomiczny, Uniwersytet Wrocławski, POLAND JENAM Symposium."— Presentation transcript:

1 CHALLENGES FOR STELLAR EVOLUTION AND PULSATION THEORY Jadwiga Daszyńska-Daszkiewicz Instytut Astronomiczny, Uniwersytet Wrocławski, POLAND JENAM Symposium "Asteroseismology and stellar evolution" September 8, 2008, Vienna

2 DIVERSITY OF STELLAR PULSATION J. Christensen-Dalsgaard

3 Amplitude frequency [c/d] mode identification: osc →( n,,m ) ASTEROSEISMOLOGY

4 P S -- parameters of the model: the initial values of M 0, X 0, Z 0, the angular momentum (or V rot,0 ), age (or logT eff ) SEISMIC MODEL j,obs = j,cal ( n j, j, m j, P S,P T ) j,obs = j,cal ( n j, j, m j, P S,P T ) P T -- free parameters of the theory: convection, overshooting distance, parameters describing mass loss, angular momentum evolution, magnetic field

5 SOME OBSERVATIONAL KEY PROBLEMS

6 CLASSICAL CEPHEIDS primary distance indicators

7 Mass discrepancy problem for double mode Cepheids pulsational masses  evolutionary masses

8 Petersen Diagram (P 1 /P 0 vs logP 0 ) for  Scuti stars and double mode Cepheids LAOL & OPAL tables Moskalik i in, 1992 Christensen-Dalsgaard 1993

9 Mass discrepancy remains Keller 2008 mass loss ? internal mixing ? ML relation dependence Z dependence Keller, Wood 2006

10 double mode Cepheids models result from ignoring bouyancy in convectively stable layers ! Smolec R., Moskalik P., 2008 double mode solution is not found ! Growth rates:  0,1 - for the fundamental mode with respect to the first overton,  1,0 - for the first overton

11 another interesting facts (OGLE):  nonradial modes in Classical Cepheids  Blazhko Cepheids  1O/3O double-mode Cepheids  single mode 2O Cepheids  triple-mode Cepheids  eclipsing binary systems containing Cepheids Udalski, Soszyński Kołaczkowski, Moskalik, Mizerski

12 Period–luminosity diagrams for Classical Cepheids in the LMC OGLE Data Soszyński et al. 2008

13 B type main sequence pulsators M>8M  - progenitors of Type II Supernova (most  Cep’s) M<8M  – form CNO elements (most SPB stars)

14  Cep and SBB stars in Magellanic Clouds Pigulski, Kołaczkowski (2002) Kołaczkowski, 2004, PhD Kołaczkowski et al. (2006) Karoff et al. (2008) LMC Z=0.008 SMC Z=0.004

15 Pamyatnykh, Ziomek

16 Miglio, Montalban, Dupret

17  problem of mode excitation  uncertainties in opacity and element distribution  extent of overshooting distance  estimate of the interior rotation rate

18 Dziembowski, Pamyatnykh 2008

19 sdB stars  core helium burning phase  thin hydrogen envelope  final stage before white dwarfs

20 sdB PULSATORS Charpinet et al – theoretical predication Kilkenny et al – observational evidence Green et al – long period oscillations Fontaine et al – iron accumulation in Z-bump Fontaine et al – including radiative levitation

21 Inner structure and origin ?  single star evolution  binary star evolution -- common envelope evolution -- stable Roche-lobe overflow -- the merge of two He WD stars

22 sdO stars  C/O core  helium burning shell phase

23 Woudt, Kilkenny, Zietsman et al SDSS object: 13 independent frequencies (P= s) Rodriguez-Lopez, Ulla, Garrido, 2007 two pulsating candidates in their search (P=500s and 100 s) sdO PULSATORS Rodriguez-Lopez, Ulla, Garrido, 2007

24 Iron levitation in the pure hydrogen medium Mode excited in the range P s

25 inner structure and origin ? „luminous” sdO  post-AGB stars „compact” sdO  post-EHB objects, descendants of sdBs  He-sdOs – the merger of two He WDs or deleyed core He flash scenario

26 sdOB pulsators – perfect object for testing diffusion processes hybrid sdOB pulsators - Schuh et al. 2006

27 Extreme helium stars

28 Detection of variability in hydrogen deficient Bp supergiants: V652 Her (P=0.108d), V2076 Oph (P= d)– Landlot 1975 Jeffery 2008 strange-mode instability – high L/M ratio Z-bump instability

29 Origin and connection (if any) between normal and the He-rich stars

30 helium-rich sdB star Pulsation in high order g-modes such modes should be stable Ahmad, Jeffery 2005

31 Hot DQ White Dwarf stars Carbon atmospheres with little or no trace of H and He new sequence of post-AGB evolution

32 Dufour, Liebert, Fontaine, Behara, 2007, Nature 450, 522 White dwarf stars with carbon atmospheres Six hot DQ White Dwarfs

33 Montgomery et al. 2008, ApJ 678, L51 SDSS J : A Prototype for a new class variable white dwarfs P=417.7 [s] from time-series potometry new class of pulsating carbon-atmosphere WDs (DQVs) or first cataclysmic variable with a carbon-dominated spectrum Period [s]

34 Fontaine, Brassard, Dufour, 2008, A&A 483, L1 Might carbon-atmosphere white dwarfs harbour a new type of pulsating star? Dufour, Fontaine et al. 2008, ApJ 683, L167 SDSS J : The first pulsating white dwarf with a large detectable magnetic field Unstable low-order g-modes for models with T eff from K to K, log g = 8.0, X (C) = X (He) = 0.5 Pulsation in hotter models can be excited if surface gravity is increased or if convective is more efficient

35 EVOLUTION OF PLANETARY SYSTEMS Planets around oscillating solar type stars e.g.  Ara Planets around compact pulsators V391 Peg, Silvotti et al. 2007

36 SOME THEORETICAL KEY PROBLEMS

37 OPACITIES determine the transport of radiation through matter  (T, , X i )

38 LAOL (Los Alamos Opacity Library) till ~1990 Simon (1982) suggestion that the opacity were at fault OPAL (OPAcity Library) F.J. Rogers, C.A. Iglesias i in ApJ 360, ApJ 397, 717; ApJS 79, Science 263, ApJ 456, 902 OP (Opacity Project) International team led by M.J. Seatona 1993 MNRAS 265, L MNRAS 279, MNRAS 360, 4 58, MNRAS 362, L1

39 Opacity in the  Cephei model (M=12 M , X=0.70, Z=0.02): OP (Seaton et al.) vs. OPAL (Livermore) vs. LAOL (Los Alamos) (< 1991) A. A. Pamyatnykh

40  (OPAL) as a function of logT and log  /T 6 3 (T 6 =T/10 6 ) Pamyatnykh 1999, AcA 49, 119 C/O bump

41 CONESQUENCES OF Z-BUMP   Seismic model of the Sun improved  Cepheids mass discrepancy  Cepheids mass discrepancy solved   pulsation of B type MS stars explained   sdB and sdO pulsation   pulsation of some extreme He stars OSCILLATION FREQUENCIES  TEST OF STELLAR OPACITY

42 NEW SOLAR CHEMICAL COMPOSITION Asplund, Grevesse, Sauval 2004, 2005

43 Comparison of the old and new solar composition A. A. Pamyatnykh

44 better agreement of solar metallicity with its neighbourhood No problem with B main sequence pulsators Pamyatnykh (2007): more Fe relative to CNO For AGS04 galactic beat Cepheid models are in better agreement with observations Buchler, Szabo 2007 Reduction of the lithium depletion in pre-main sequence stellar models gives better agreement with observations, Montalban,D’Antona 2006

45 Basu & Antia, 2007, astro-ph Conspiracy at work: better is worse

46 ROTATION

47 Achernar: the ratio of the axes is 1.56 ± 0.05

48 1. Structure (spherical symetry broken) 2. mixing (meridional circulation, shear instabilities, diffusion, transport, horizontal turbulence) distribution of internal angular momentum (the rotation velocity at different depths) 3. mass loss from the surface enhanced by the rapid rotation (the centrifugal effect) Laplace, Jacobi, Lioville, Riemann, Poincare, Kelvin, Jeans, Eddington, von Zeipel, Lebovitz, Lyttleton, Schwarzachild, Chandrasekhar, Kippenhahn, Weigert, Sweet, Öpik, Tassoul, Roxgurgh, Zahn, Spruit, Deupree,Talon, Maynet, Maeder, Mathis and many others

49 Maynet, Maeder, 2000 Evolutionary tracks for non–rotating and rotating models

50 Maynet, Maeder, 2000 The evolution of  ( r ) during the MS evolution of a 20M  star

51 Stars can reach the break-up velocity Maynet, Maeder, 2000 M=20 Z=0.004

52 The third order expression for a rotationally split frequency Dziembowski, Goode 1992 Soufi, Goupil, Dziembowski 1998 Mathis Goupil et al EFFECTS OF ROTATION ON PULSATION

53 Pamyatnykh 2003 M=1.8 M , T eff =7515 K, Vrot=92 km/s.

54  j -  k   ; j = k  2 ; m j = m k (  >>  ) rotational mode coupling    perturbation approach fails EFFECTS OF ROTATION ON PULSATION

55 rotational mode coupling Daszyńska-Daszkiewicz et al a k - contributions of the k -modes to the coupled mode eigenfunction of an individual mode is a linear combination complex amplitude of the flux variation Soufi, Goupil, Dziembowski 1998

56 Description of slow modes (  ~  )  the traditional approximation Townsend(2003) Townsend(2003)  Expansion in  Expansion in Legendre function series Lee, Saio (1997) Lee, Saio (1997)  2D code (Savonije 2007)

57 Rotation confines pulsation towards the stellar equator Townsend 1997 Hough functions

58 Rotation complicates identification of pulsational modes diagnostic diagrams become dependent on (i,m,V rot ) Coupled modes: Daszyńska-Daszkiewicz et al Slow modes: Townsend 2003, Daszyńska-Daszkiewicz et al. 2007

59 Solar rotation J. Christensen-Dalsgaard

60  =  (r) profile The rotational splitting kernel, K  the  =  (r) profile The rotation rate increases inward, e.g. Goupil, Michel, Lebreton, Baglin 1993 (GX Peg) Dziembowski, Jerzykiewicz 1996 (16 Lac) Aerts, Toul, Daszynska et al (V836 Cen) Pamyatnykh, Handler, Dziembowski, 2004 ( Eri) Eri Dziembowski, Pamyatnykh 2008 ( Eri,12 Lac) For the Eri model from Pamyatnykh, Handler, Dziembowski, 2004

61 Dziembowski & Pamyatnykh 1991, A&A 248, L11 Modes which are largely trapped in the region surrounding the convective core boundary can measure the extend of the overshooting. E k =  2  2 V836 Cen – first evidence of the core overshooting in  Cep star Aerts, Toul, Daszyńska et al., 2003, Science 300, 1926

62 Miglio, Montalban, Noels, Eggenberger 2008 Properties of high order g-modes in SPB and  Dor stars Effects of mixing processes on  P models of 1.6M  with X c =0.3, =1

63 IMPACT OF PULSATION ON ROTATIONAL EVOLUTION Talon, Charbonnel 2005 Internal gravity waves contribute to braking the rotation in the inner regions of low mass stars Townsend, MacDonald 2008 Pulsation modes can redistribute angular momentum and trigger shear-instability mixing in the   zone The evolution of  in the  gradient zone transport by (,m)=(4,-4) g-modes

64 COVECTION  Convection transports energy  Mixing and overshooting convective flows  convection affects stellar spectra  stochastic convective motions excite stellar oscillation  role of convection in heating of stellar chromospheres  Convection + differential rotation  stellar activity

65 MLT theory of stellar convection Böhm-Vitense 1958 full-spectrum turbulence theory of convection Canuto, Goldman, Mazzitelli 1996 (CGM)

66 Fractional heat flux carried by covection in the local MLT and in the Gough’s nonlocal, time-dependent convection formalisms, M=1.8 M , log T eff = 3.860, log L = 1.170

67 main-sequence A-type star ( T eff =8000 K, log g =4.00, [M/H]=0) Steffen M IAUS 239, 36 3D versus 1D vertical velocity [km/s] H+HeI convection zone HeII convection zone Radiative layer between two convection zones is mixed

68 Pulsating stars with „convection problem”  Scuti  Doradus Classical Cepheids RR Lyrae Red giants V777Her, ZZ Cet White dwarfs ( V777Her, ZZ Cet )

69 Convective–flux freezing approximation F conv =const during pulsation cycle

70 pulsation-convection interactions Unno 1967 Gough 1977 Solar-like stars – Houdek, Goupil, Samadi  Scuti,  Doradus -Xiong, Houdek, Dupret, Grigahcène, Moya Classical Cepheids, RR Lyr – Feuchtinger, Stellingwerf, Buchler, Kollath, Smolec Pulsating Red Giants – Xiong, Deng, Cheng DB (V777 Her) white dwarfs – Quirion, Dupret

71 Dupret et al M =1.6 M , T eff = 6665 K,  = 1.8, mode =0, p 1

72 MASS LOSS Important for late evolutionary phases and for massive stars mostly empirical mass-loss formulae are used Hot stars  Radiation-driven wind Cool and luminous stars  Dust-driven wind

73 pulsation and mass loss coupling Red giants (Mira and SR) – Wood 1979, Castor 1981 mass loss: stellar pulsation & radiation pressure on dust grains d M /d t - P relation Knapp et al. 1998

74 pulsation and mass loss coupling Massive stars (OB MS, W-R stars), LBV Howarth et al – wind variability in  Oph Kaufer 2006 – B0 supergiant (HD 64760) pulsation beat period observed in H  Owocki et al Townsend 2007

75 GW Vir stars Constraints on mass loss from the red-edge position different mass loss laws Quirion, Fontaine, Brassard 2007

76 not only pulsation frequencies not only pulsation frequencies can probe stellar interior can probe stellar interior photometric and spectroscopic observables

77 input from pulsation calculation: input from pulsation calculation: linear nonadiabatic theory: the f parameter linear nonadiabatic theory: the f parameter the ratio of the bolometric flux variation to the radial displacement at the photosphere level Theoretical photometric amplitudes and phases: input from atmosphere models: derivatives of the monochromatic flux over T eff and g derivatives of the monochromatic flux over T eff and g limb darkening coefficients: h (T eff, g) limb darkening coefficients: h (T eff, g)

78 The flux derivatives over T eff and log g depend on:   microturbulence velocity,  t   metallicity, [m/H]   models of stellar atmospheres, NLTE effects

79 The f parameter is very sensitive to:   global stellar parameters   chemical composition   element mixture, mixing processes   opacity   subphotospheric convection

80 multicolor photometry + radial velocity data simultaneous determination of and f from observations

81 Comparison of theoretical and empirical f values yields constraints on MEAN STELLAR PARAMETERS STELLAR ATMOSPHERES INPUT PHYSICS

82 f - a new asteroseismic probe sensitive to subphotospheric layers and complementary to pulsation frequency

83 Ocillation spectrum of FG Vir 67 independent frequencies ! Breger et al. 2005

84 Empirical and theoretical f values. Model: MLT, Model: MLT, convective flux freezing approximation Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653 Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653

85 Empirical and theoretical f values. Model: non-local, time-dependent formulation of MLT due to Guenter Houdek Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653 Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653

86 OSCILLATION SPECTRUM OF ERI Jerzykiewicz i in., 2005, MNRAS 360, independent frequencies

87 Comparison of the empirical and theoretical f values Comparison of the empirical and theoretical f values for the dominant frequency ( =0 mode) of Eri Daszyńska-Daszkiewicz et al. 2005, A&A 441, 641 Daszyńska-Daszkiewicz et al. 2005, A&A 441, 641

88 Seismic model with the new solar composition added DIFFUSION ???

89 CONCLUSIONS  more realistic treatment of macro- and microphysics in stellar modelling  more parallel photometric and spectroscopic observations  Ideal seismic stellar models should account not only for all measured frequencies but also for associated pulsation characteristics Asteroseismology helps:  Asteroseismology helps: - to solve the equation observation =theory - to avoid - to avoid more date=less understanding


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