Pulsating Stars & Spectrocopy Denis GILLET Directeur de recherche au CNRS Observatoire de Haute Provence denis.gillet@oamp.fr
An outstanding laboratory Our Galaxy: 100 billion stars about a star The Sun on 100,000 is pulsating
Stellar pulsation
Stable (ordinary star) & Unstable (pulsating star) Initially pushing below the limit cycle equilibrium radius value deadening limit cycle
RR Lyrae star 70% H R * = 40 000 000 km 29.9% He 0.1% other Iben 1971 PASP 83, 697
10,000 K 40,000 K The he κ - me mecha hanism photosphere three - body recombinat ion : + + + → + * H H e e e with kinetic energy Chapter 6
• hydrogen ionization zone (H H + and He He + ) T = 10,000 – 15,000 K • helium II ionization zone (He + He ++ ) T = 40,000 K The insta instability ility strip strip n f 1 o u s n t p d u - If the star is too hot, the ionization a o l m v zones will be too near the surface to s e e drive the oscillations. a n r t t t - This accounts for the “ blue edge ” I a o of the instability strip. o l n n - The “ red edge ” is probably due to e the onset of convection.
Atmospheric dynamics of pulsating stars
RR Lyr T eff = 7175 K M = 0.6 M sun L = 62 L sun 90 layers opacity with Fe Fokin & Gillet 1997 A&A 325, 1013
RR Lyr Fokin & Gillet 1997 A&A 325, 1013
RR Lyr the density decreases of one million times! Fokin & Gillet 1997 A&A 325, 1013
5 shock waves in RR Lyr – their velocity Mach number =20 Fokin & Gillet 1997 A&A 325, 1013
Comparaison de la dynamique atmosphérique dans le cas d'une pulsation classique (small amplitudes) et dans le cas d'une pulsation de fortes amplitudes (atmosphere with shock waves). From Ernst A. Dorfi Universität Wien.
Dynamique extrême de l'atmosphère d'une supergéante pulsante subissant des chocs de très forte intensité conduisant à des phénomènes de perte de masse sporadiques. From Ernst A. Dorfi Universität Wien.
Types of Waves www.astro.uwo.ca/~jlandstr/planets/webfigs/earth/slide1.html
Longitudinal Waves In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. Transverse Waves In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. Water Waves or in Solids Water waves are an example of waves that involve a combination of both longitudinal and transverse motions. Standing wave In the pipe, the particles oscillate back and forth, right and left, though they are not all moving in the same direction at the same time; some are moving to the right while others are moving to the left. http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html
Shocks in a protostellar jet Here is an animation of a theoretical model of a protostellar jet like the one from HH47. The material in the jet cools rapidly, causing it to break up into clumps and "bullets". (From Jim Stone, http://www.astro.princeton.edu/~jstone/pjets.html)
The weak shock: viscous shock front ~ mean free path unperturbed shock gas wake ρ 1 ρ 2 T 1 T 2 1 T 1 Maxwellian velocity distribution T 2 Compression rate ρ γ + 2 ( 1 ) M η ≡ 2 = 1 2 2 u u ρ ρ + γ − + = + 2 1 2 2 ( 1 ) M h h 1 1 1 2 2 2 1 p p ≡ + γ + h 1 γ − ρ ρ η → → ∞ 1 if M ρ γ − 1 1
The strong shock: Hypersonic/Radiative shock wave
Hydrodynamic and radiative shocks Précurseur radia tif T ρ
The compression excitation ionization in the shock wake translational Fadeyev & Gillet 2001 A&A 368, 901
From Alpher & Greyber 1958
Radiative and full-radiative shocks F r ≠ 0, P r ≅ 0, E r ≅ 0 F r ≠ 0, P r ≠ 0, E r ≠ 0 or
From R.A. Gross 1968
From where did emission lines come?
What does happen when the radiative flux photoionize the preshock region ?
M 1 = 6.5 ρ γ + 2 ( 1 ) M 2 η ≡ = 1 ρ ρ + γ − 2 2 ( 1 ) M 1 1 γ + 1 η → → ∞ if M ρ γ − 1 1 Fadeyev & Gillet 2001 A&A 368, 901
Final compression ratio ρ N / ρ 1 at the postshock outer boundary X N of shock Fadeyev & Gillet 2001 A&A 368, 901
3D simulation of shock wave with turbulence using detailed chemistry. M = 4.156 Mt = 0.25. Master of science in aerospace engineering by H.Narayanan Nagarajan 2009 University of Texas at Arlington.
KVA
Spectrum behaviors Emission lines Absorption lines Continuum
Origin of stellar photons ?
Optical depth τ and spectral line formation Stellar Atmosphere τ increasing
c = + ξ = ∆ λ × 2 2 line width V λ th ξ 2 E 1 ≈ = turb 2 E 5 V th th
H H Type spectral : A7 V ~ 2 masses solaires H H He I He I Type spectral : B8 V ~ 3 masses solaires
The behaviour of the line strength
A schematic illustration of circulation in a 20 solar mass star with an initial rotational velocity of 300 km/s. From Meynet & Maeder 2002
Stellar tomography Jean-Francois Donati - 25/10/2006 - http://www.ast.obs-mip.fr/article.php3?id_article=457 A star hosting a surface dark spot close to the equator, If the spot is located close to the pole, spectral lines spectral line profiles are affected throughout their whole are only affected in their core regions. width as the spot is carried around the star by rotation.
RR Lyrae @ R = 27,000 and 2.5 m H α - 2.5 m telescope Las Campanas Observatory - R = 27,000 -Time resolution: 3-10 min - S/N = 20 - 3500-9000 A The evolution of H α profiles during pulsation cycles for WY Ant and XZ Aps, as well as for RV Oct based on many more observations, can be viewed as GIF animations in slides 83–86 of the PowerPoint file HNRLecture2009 at ftp: //ftp.obs.carnegiescience.edu/pub/gwp/HNRLecture. George W. Preston
RV Oct in April 2007 I(H α )/I(He) = 1.75/1.20 = 1.46 max λ 5876 (HeI) max Preston 2011 AJ 141:6, 1
Helium-Sodium show ! | 300 km/s | weak jump AS Vir LOOK! D3 IS-NaI IS NaI strong shift | 300 km/s | RV Oct Preston 2011 AJ 141:6, 1
RR Lyr @ R = 65,000 and 3.6 m - 3.6 m telescope CFHT Observatory -R = 65,000 -Time resolution: 7 min -S/N = 180 - 210 - 3000-10100 A Observations by Gillet, Fabas, Lèbre, 2013, A&A
RR Lyr - R = 65,000 - 3.6 m CFHT - Time resolution: 7 min - S/N = 200 The Schwarzschild mechanism in RR Lyr
The Schwarzschild mechanism in RR Lyr RR Lyr H α Gillet, Fabas, Lèbre, 2013, A&A in press
The Schwarzschild mechanism ⇒ A line doubling phenomenon H α RR Lyr: R = 27,000 and 2.5 m - 2.5 m telescope Las Campanas Observatory - R = 27,000 -Time resolution: 3-10 min - S/N = 20 - 3500-9000 A Preston, G.W. 2011 AJ George W. 141 1 P t
The Schwarzschild mechanism 1953, Trans. IAU, 8, 811 The line doubling ⇒ presence of a shock wave in the atmosphere
Emission lines: Produced by the shock
0.911 RR Lyr HeI 5875 Gillet, Fabas, Lèbre, 2013, A&A
0.911 RR Lyr HeI 5875 Gillet, Fabas, Lèbre, 2013, A&A
0.911 RR Lyr HeII 4686 Gillet, Fabas, Lèbre, 2013, A&A
0.911 RR Lyr HeII 4686 Gillet, Fabas, Lèbre, 2013, A&A
AS Vir : inset boxes surround HeII and HeI emission lines in 3 successive spectra H α HeI HeII 0.870 0.896 0.909 0.917 0.925 0.934 0.942 0.950 0.978 5870 5875 5880 5885 6550 6560 6570 6580 4680 4685 4690 wavelength (A) Preston 2011 AJ 141:6, 1
Detection of helium emissions was confirmed in June and November 2012 by Thierry Garrel with its 35 cm and a spectro to R = 11,000! LES RÉSULTATS DE THIERRY GARREL : - Les 15/6, 24/6 , 6/11/2012, HeI est en émission (pour seulement quelques minutes) quand H α est à son intensité maximale. - Le 24/6 montre HeI 5876 et HeI 6678 simultanément en émission; seul HeI 5876 est observé en émission les 15/6 et 6/11. - Le 24/6 , l’intensité de H α est plus forte que les 15/6 et 6/11. Le résultat le plus intéressant trouvé par Thierry GARREL est qu'il y a presque un quart (0.23) de période Blazhko entre les observations des 15/6 et 24/6 . DONC l‘émission de l'hélium est présente très longtemps (peut-être pendant la moitié la période Blazhko). Il sera donc facile de la détecter lorsqu'elle est là. Un autre résultat intéressant : il y a au moins 1,5 année de visibilité de l’HeI (CFHT observation July 4, 2011). Animation of spectra of RR Lyr during maximum by Thierry Garrel for HeI 5875 and neutral sodium NaD on 2012-06-16 and 2012-06-24
High resolution spectrum of Procyon - F5 IV
High resolution spectrum of Sun - G2 V
High resolution spectrum of Arcturus - K1 III
Recommend
More recommend
