Asteroseismology of Red Giants. Josefina Montalbán Université de Liège

Transcription

1 Asteroseismology of Red Giants Josefina Montalbán Université de Liège

2 Stellar oscillations Oscillation mode Variations of v r : spectroscopy Variations of luminosity: photometry

3 Basic properties Lamb Frequency: Brunt-Väisälä Frequency: p mode oscillatory if: or If not, evanescent pressure modes gravity modes g mode Mixed mode

4 Solar like oscillations Periods: minutes to hours Intrinsically damped but externally forced by turbulent convection Amplitudes ~ ppm/ tens of ppm G-K red giants

5 Solar-like oscillations Sun Comb-like spectrum BISON data Ulrich 1986; Brown 1991 Kjeldsen & Bedding 1995 Belkacem 2011

6 Solar like star Solar-like oscillations

7 L l log N, L ( Hz) Propagation diagram mixed modes evanescent zone N < < L more interactions for l=1 modes than for l=2 p cavity > N > L max g cavity < N < L N S 1 S M in He burning phase r/r

8 Pressure-gravity mixed character Modes trapped in the center: high E g dominant character Modes trapped in the envelope: low E acoustic dominant character Dziembowski et al. 2001; Christensen-Dalsgaard, 2004; Dupert et al Eggenberger et al. 2010; Mazumdar et al. 2010; Montalban et al. 2010

9 Spectrum properties PopI RGB Pressure dominated non-radial modes between two consecutive radial ones, separated by Δν l=2 modes better trapped in the acoustic cavity. Low degree of gravity-acoustic coupling. l=1 modes: more significant coupling of gravity and acoustic cavities. Dziembowski et al. 2001; Christensen-Dalsgaard, 2004; Dupret et al. 2009; Eggenberger et al. 2010; Mazumdar et al. 2010; Montalban et al. 2010

10 Spectrum properties PopI RGB Pressure dominated non-radial modes between two consecutive radial ones, separated by Δν l=2 modes better trapped in the acoustic cavity. Low degree of gravity-acoustic coupling. Δν l=1 modes: more significant coupling of gravity and acoustic cavities. Dziembowski et al. 2001; Christensen-Dalsgaard, 2004; Dupret et al. 2009; Eggenberger et al. 2010; Mazumdar et al. 2010; Montalban et al. 2010

11 Outline A. From acoustic modes Global parameters He abundance B. From mixed modes Evolutionary state Near core mixing processes Internal rotation and AM transport

12 Ensemble asteroseismology average seismic parameters: Stello et al. 2009, Miglio et al. 2009, Mosser et al. 2010,2011, Hekker et al. 2010, Chaplin et al. 2011, Kallinger et al. 2010

13 Ensemble asteroseismology Study of stellar populations (Miglio et al. 2009, 13, Hekker et al 2009, Mosser et al.2010, Chaplin et al. 2011, Corsaro et al. 2012, Basu et al ) Mass loss from clusters (Miglio et al. 2012) Cluster membership (Stello et al 2010, 11) Determination of log g spectroscopy (Morel & Miglio 2012; Creevey et al. 2013) R (Miglio 2012, Huber et al. 2012, White et al. 2012) M Age (but model dependent)

14 Population study of CoRoT RedG Model Model CoRoT CoRoT Sample dominated by Red Clump stars! max ~35 Hz D ~ 4 Hz Miglio et al Hekker et al Mosser et al. 2010

15 Ensemble seismology of G-K giants Radius + Teff apparent mag + BC L l d 2 L/l max and D with 2.4% and 0.6% (Mosser et al. 2010) T eff from 2MASS J and Ks photometry in EXODAT ( ~0.02 mag) + colour-t eff calibration (Alonso et al. 1999) (T eff )~ 190K Ks BC (Girardi et al. 2005) Galactic extinction (Drimmel et al. 2003) ( (Av) ~0.3) DISTANCE 10-15% uncertainty Miglio et al EDJ-Proc

16 3D map of G-K giants CoRoT LRs: ~ 3000 stars Mosser et al Kepler data: ~ stars et al. 2011, Stello et al. Hekker CoRoT LRa01+LRc01 => 2000 RGs with average seismic parameters LRa01 LRc01 9/25/2013 SF2A - Montpellier 2013

17 Early results: differential population studies Different distribution of M in the center and anticenter directions Different ages LRc01 sample older thanlra01 ZLRa01< ZLRc01 9/25/2013 SF2A - Montpellier 2013 Miglio et al MNRAS

18 Constraining RGB mass loss

19 Outline A. From acoustic modes Global parameters He abundance B. From mixed modes Evolutionary state Near core mixing processes Internal rotation and AM transport

20 Signatures of local features quasi-discontinuity in the distribution of an equilibrium variable inside the star Deviations from constant Δν as oscillatory components in the frequencies of oscillation e.g. p-modes, helioseismology sharp variations of due to helium ionization envelope Helium abundance transition from convective to radiative transport at the base of the convective envelope depth of the convective envelope

21 Periodic components in ν Signature of an acoustic glitch in the star!! acoustic depth acoustic radius Period acoustic depth ( ) e.g. Gough 1990

22 The solar case Acoustic glitches Houdek & Gough, 2007 Ballot et al years GOLF observations Acoustic radius of base of the CZ 2 nd He ionization region Possible for other stars? e.g. Perez Hernandez & Christensen-Dalsgaard 1998 Roxburgh&Vorontsov, 1998 Monteiro et al. 1998, 2000 Mazumdar&Antia 2001 Ballot et al Basu et al Verner et al Houdek & Gough 2007 Mazumdar & Michel this conference

23 Acoustic glitches He burning 1.5Msun He II Cov Env. 1.5Msun in Ascending Red Giant Branch

24 HR 7349 : acoustic glitches Model 1.2 M sun Miglio et al A&A

25 Amplitude of the oscillatory signal vs. He abundance Broomhall et al. in preparation

26 Amplitude of the oscillatory signal vs. He abundance Y=0.25 Initial helium mass fraction Y=0.40 M=1.5M Initial helium mass fraction Y=0.28 & Y=0.25 Broomhall et al. in preparation

27 Outline A. From acoustic modes Global parameters He abundance B. From mixed modes Evolutionary state Near core mixing processes Internal rotation and AM transport

28 Asymptotic approximation p-mode frequencies constant frequency spacing g-mode periods constant period spacing Tassoul ApJS

29 Spectrum properties Number of modes by Tassoul 80 Interaction between p and g modes increases when the evanescent region decreases (see also Christensen-Dalsgaard 2011) Houdek 1999 Montalbán et al. 2012

30 Spectrum properties PopI RGB Pressure dominated non-radial modes between two consecutive radial ones, separated by Δν l=2 modes better trapped in the acoustic cavity. Low degree of gravity-acoustic coupling. Δν l=1 modes: more significant coupling of gravity and acoustic cavities. Dziembowski et al. 2001; Christensen-Dalsgaard, 2004; Dupret et al. 2009; Eggenberger et al. 2010; Mazumdar et al. 2010; Montalban et al. 2010

31 Spectrum properties Number of modes by Tassoul 80 Interaction between p and g modes increases when the evanescent region decreases (see also Christensen-Dalsgaard 2011) Houdek 1999 Montalbán et al IAU-GA-SpS13 ; 2013

32 Spectrum properties CLUMP 1.5Msun Pressure dominated non-radial modes between two consecutive radial ones, separated by Δν l=2 modes better trapped in the acoustic cavity. Low degree of gravity-acoustic coupling. l=1 modes: more significant coupling of gravity and acoustic cavities. Montalbán et al ApJ; AN; 2012 ApSS ; 2013 ApJ

33 Red giants: evolution 5 Msun 1.5 M R=12.3 R <D > = Msun 1 Msun Red-Clump log L/L = 1.76 log r c /<r> = 7.3 Yc = 0.25 DP~250s Mcc = 0.08M * RGB log L/L = 1.72 log r c /<r> = 8.3 Yc = 0.98 DP~80s

34 Echelle Diagram : RC vs RGB M=1.5 Msun l = 2 l = 0 l = 1 l = 2 l = 0 l = 1 RGB log L/L = 1.72 log c /< > = 8.3 Yc = 0.98 P~80s Montalbán et al. 2012; Red-Clump log L/L = 1.76 log c /< > = 7.3 Yc = 0.25 P~250s Mcc = 0.08M *

35 a b Frequency (µhz) Frequency (µhz) Echelle Diagram : RC vs RGB Frequency (µhz) Frequency (µhz) M=1.5 Msun l = 2 l = 0 l = 1 l = 2 l = 0 Frequency modulo µhz Frequency modulo µhz c c Frequency modulo µhz Frequency modulo µhz l = 1 Frequency (µhz) Frequency (µhz) RGB Frequency (µhz) d Frequency (µhz) d Frequency modulo 7.81 µhz Frequency modulo 7.81 µhz Frequency (µhz) Frequency (µhz) e e Red-Clump 0 Frequency modulo 3.53 µhz Frequency modulo 3.53 µhz Frequency modulo 4.10 µhz Frequency modulo 4.10 µhz

36 Period spacing in red giants Bedding et al Kepler Core Helium burning phase H-shell burning RGB CoRoT Mosser et al. 2011

37 Theoretically observable period spacing Montalbán et al KASC5; 2013 ApJ

38 observed period spacing < P> obs

39 Observed period spacing From red giants observed by Kepler Stello et al. 2013, ApJ

40 Outline A. From acoustic modes Global parameters He abundance B. From mixed modes Evolutionary state Near core mixing processes Internal rotation and AM transport

41 Mass of He-core DP follows the mass of He core M < 1.6M overshooting during MS does not change the mass of the degenerate He core M of star with minimum He core decreases if central mixing during MS (see also, Sweigart et a. 90, Girardi 1999, Castellani et al 2000) Minimum DP occurs at lower stellar mass. Ov=0.2Hp => DM ~ 0.2 Msun Observable ΔP also follows The mass of the He core Montalbán et al IAU-GA-SpS13; 2013 ApJ

42 ΔP vs He-core mass No Overshooting Z=0.02 Y=0.278 Z=0.02 Y=0.278 No Overshooting Overshooting M 2.3 M 2.1 M 2.5 M 2.2M 2.4M RGB RGB Montalbán et al IAU-GA-SpS13; KACK5; 2013 ApJ

43 ΔP vs He-core mass Z=0.02 Y=0.278 No Overshooting Overshooting and max + Period spacing + metallicity RGB 2.2M 2.4M Mixing during the MS evolutionary phase Montalbán et al IAU-GA-SpS13; KACK5; 2013 ApJ

44 Convective core mixing during central He-burning CC Asymptotic period spacing for models with overshooting during the He-burning Montalbán et al. 2013, ApJ

45 Overshooting during He central burning No over Overshoot adiab. 0.2 Hp Montalbán et al. 2013, ApJ

46 Asymptotic ΔP & convective core during central He-B phase From observed DP to asymptotic one Direct relation between asymptotic DP And radius of convective core Montalbán et al Mosser et al. 2012; Christensen-Dalsgaard 2012

47 Convective core size during He central burning phase Montalbán et al. 2013, ApJ

48 Outline A. From acoustic modes Global parameters He abundance B. From mixed modes Evolutionary state Near core mixing processes Internal rotation and AM transport

49 Internal rotation Dipole g modes => smaller rotational splitting than p modes

50 Internal rotation

51 Internal rotation The Sun García et al. 2007

52 Internal rotation g p g Beck et al See also Deheuvels et al Differential rotation with the core rotating 10 times faster than the surface

53 Internal rotation

54 Evolution and transport of angular momentum Rotating models predict steep rotation profiles (e.g. Palacios et al. 2006; Eggenberger et al. 2010; Marques et al. 2013) An additional mechanism for the transport of angular momentum is needed. From seismic constraints Δν rot wings/δν rot centre = 1.5 Its efficiency should be ν add = cm 2 s -1 Eggenberger, Montalban & Miglio 2012 Vini = 50 km/s: δνrot = 32.8 μhz and δνrot wings/δνrot centre = 2.5 Vini = 1 km/s: δνrot= 1.6 μhz and δνrot wings/δνrot centre = 2.4 Observations: δνrot= 0.135±0.008 μhz and δνrot wings/δνrot centre = 1.5

55 Solar-like oscillations across the HR diagram COROT KEPLER Straka et al. 2006, Carrier et al. 2005, Guenther 2004, Kjeldsen et al. 2003, Di Mauro et al 2002, Christensen-Dalsgaard et al. 1995, Kjeldsen et al 1995, Provost et al. 2006, Claudi et al. 2005, Eggenberger et al. 2004, Martic et al. 2004, Eggenberger&Carrier 2006, Bedding et al. 2006, Carrier&Eggenberger 2006, Bouchy et al. 2005, Bazot et al. 2005, Bedding et al Carrier et al. 2001, D Antona et al 2005 Chaplin & Miglio 2013

56 Red giants with solar-like oscillations in stellar clusters NGC6633 HD HD HD Stello et al Poretti et al. 2013

57 Summary A. From acoustic modes Global parameters: M, R, etc BUT calibration with stellar clusters He abundance => multiple populations B. From mixed modes Evolutionary state: check with clusters Near core mixing processes: mixing processes during MS phase for transition mass Size of mixed region in He burning low mass stars Internal rotation and AM transport : chemical elements abundances / rotation