= RW Dra Sergey Nikolaevich Blazhko (November - PowerPoint PPT Presentation

Сергей Николаевич Блажко = RW Dra Sergey Nikolaevich Blazhko (November 5(17), 1870 - February 11, 1956, Moscow)

The Blazhko effect: What is it?

Blazhko RR Lyrae stars in the Kepler field Great variety of light curve modulation period, strength and shape is seen in this sample.

The Kepler telescope A region of the extended solar neighborhood in the Cygnus-Lyra regions Layout of the 42 CCDs along the Orion arm of our galaxy has been chosen.

« Petite » mission CNES (MO) + Belgique + Allemagne + Autriche + Espagne + Brésil+ ESA 3 ème mission PROTEUS (minisat) Double programme : astérosismologie ET recherche de planètes extrasolaires CO nvection Lancement 27 décembre 2006 : Soyouz Starsem 2b depuis Baïkonour RO tation Orbite polaire circulaire à 896 km d’altitude T ransits Durée nominale : 2.5 ans

Time resolution effect on frequency detection Kolenberg et al. 2011 MNRAS 411, 878

Examples of Blazhko stars Katrien Kolenberg Elisabeth Guggenberger RR Lyr P B =39 d P B /P=70 http://www.univie.ac.at/tops/blazhko/Project.html

RR Lyr P B =39 d P B /P=70

V1127 Aql P B =27 d P B /P=76 Courbe de lumière montrant 2 cycles de pulsations de l’étoile RR Lyrae V 1127 Aql évoluant au cours du temps (en bleu), on observe parfaitement l’effet Blazhko. Au cours des 400 cycles (en rouge) observés par le satellite CoRoT, on distingue à la fois une modulation de l’amplitude (sur l’axe vertical des ordonnées), et une modulation de la période de pulsation (sur l’axe horizontal des abscisses).

MW Lyr P B =17 d P B /P=42 The Blazhko RR Lyrae star MW Lyr Jurcsik, J ., Sódor, Á., Hurta, Zs., Váradi, M., Szeidl, B., Smith, H. A., Henden, A., Dékány, I., Nagy, I., Posztobányi, K., Szing, A., Vida, K., Vityi, N. 2008, MNRAS , 391 , 164 - http://konkoly.hu/24/publications/

SS Cnc P B =5.3 d P B /P=14 Sergey Nikolaevich Blazhko The shortest modulation period Blazhko RR Lyrae star: SS Cnc J. Jurcsik, B. Szeidl, Á. Sódor, I. Dékány, Zs. Hurta, K. Posztobányi, K. Vida, M. Váradi, and A. Szing 2006, AJ , 132 , 61 - http://konkoly.hu/24/publications/

Why do some stars do it and others don‘t? Repeating cycles Blazhko modulation [mag] [mag] 50% 50% of RR Lyrae of RR Lyrae

Different types of RR Lyrae F = 1H 1O = 2H 2O = 3H 3O = 4H 4O = 5H 5O = 6H F 1O DM 2O Wils D.M.

OGLE-II and OGLE-III fields in the LMC ASAS

Spatial distribution of RR Lyrae stars in the LMC

RRab, RRa and RRb stars The new nomenclature of RR Lyrae stars: The classification of S.I. Bailey (1902) based on the shape of light curves: - RRa : increase of light very rapid. Decrease - RR0 = RRab , 70%, fundamental mode pulsator; - RR1 = RRc , 20%, first overtone pulsator; rapid, but much less rapid than the increase; - RR01 = RRd , 5%, double-mode pulsator F/1O; - RRb : increase of light moderately rapid. - RR2 = RRe , 5%, second overtone pulsator; Decrease is relatively slow and continues; - RR12 = double-mode pulsator 1O/2O; - RRc : low-amplitude and nearly sinusoidal light curves; - RR3 = third overtone pulsator; - RR23 = double-mode pulsator 2O/3O; RRa and RRb merged to ”ab” because the gradual transition between them made them almost - RR4 = fourth overtone pulsator; undistinguishable. - RR34 = double-mode pulsator 3O/4O; - RRab = RRa + RRb: large amplitude and - RR5 = fifth overtone pulsator; non-sinusoidal light curve; etc. a new type: - RRd : a rare type; double-mode pulsator.

Igor Soszynski U. Warsaw, Poland

RR Lyr: P=0.57 day RRab, RRa and RRb stars RRa P=0.625 day RRb The Bailey diagram: RRa RRb 0.625

The Blazhko effect

The explanation of the Blazhko effect??? Until today, after over 100 years of research, there were more than 10 explanations proposed but none is satisfactory. What is the correct explanation?... (K. Kolenberg) Today the Blazhko effect represents an ongoing challenge in variable-star research. Sergey Nikolaevich Blazhko

1936 The first explanation of the Blazhko effect by Miss H. A. Kluyver

1) a 2:1 resonance between the fundamental radial mode and the second overtone (Kluyver 1936 ;Walraven 1955; Borkowski 1980) 2) The changing aspect of a magnetic oblique rotator-pulsator (Balazs-Detre 1959; Balazs-Detre & Detre 1962; Christy1966; Cousens 1983; Shibahashi 2000) 3) non-adiabatic splitting of a radial mode (Ledoux 1963) 4) Tides in a binary system (Fitch 1967) 5) a resonance between a radial mode and an unobservable nonradial mode (Vandakurov1967; Cox 1993; Kovacs 1995) 6) a resonance between a radial mode and an observable nonradial mode (Fahlman 1971; time Cox 1993;Kovacs 1995;Van Hoolst et al. 1998; Nowakowski & Dziembowski 2003; Dziembowski & Mizerski 2004) 7) Pairing of binary companions of RR Lyrae types ab and c (Kinman & Carretta 1992) 8) mode mixing as a Blazhko mechanism (Clement et al. 1997; Clementini et al. 2004) 9) a 2:1 resonance between the fundamental radial mode and the third overtone (Borkowski 1980;Moskalik 1986; Goranskii 1989) 10) Binary light-time effects (Jurcsik et al. 2002) 11) Changes in the structure of the outer convective zone, due to an irregular variation of the magnetic field (Stothers 2006) 12) Fundamental mode destabilized by a 9:2 resonant interaction with the 9th overtone (Buchler & Kollath 2011 ) full references are given by Stothers 2006 ApJ 652, 643 & Smolec et al. 2011 MNRAS 414, 2950

Interprétations de l'effet Blazhko : Modèles magnétiques  Ces modèles supposent que ces étoiles ont un champ magnétique incliné par rapport à l'axe de rotation (cf. modèles de rotateur oblique des étoiles Ap). Le mode fondamental radial est déformé pour donner une composante quadripôle dont l'axe coïncide avec l'axe magnétique.  La période Blazhko est supposée être égale à la période de la rotation de l'étoile. (K. Kolenberg)  Un champ magnétique 1kG serait nécessaire pour qu'une modulation d'amplitude soit observable.  Un champ de 1.5kG a été observé par certains observateurs mais il n’a pas été confirmé par d'autres (rien au dessus de 130 G). (see Kolenberg & Bagnulo 2009 A&A 498, 543) From Jean-François Le Borgne - La Rochelle 2006

Summary of explanations for the Blazhko effect by Katrien Kolenberg Until 2006, very simplified picture!

non-Blazhko star A new fact that any model must explain today: KIC 3866709 = V715 Cyg Continuous and accurate observations of the CoRoT and Kepler space telescopes revealed many new small frequencies in addition to the usual RR Lyrae pattern (fundamental and Blazhko periods). Blazhko star These small frequencies are irregular from one cycle to the other. KIC 7671081 = V450 Lyr From Jon Jenkins, Kepler Co-Investigator, New York Times story (2011 Jan 30)

The Blazhko effect

Location of RRab Blazhko stars in the HRD FOBE First Overtone Blue Edge Blazhko FBE star Fundamental Blue Edge Pietrynski, G., Thompson, I. B., Gieren, W., et al. 2010, Nature, 468, 542 FORE First Overtone Red Edge non Blazhko FRE star Fundamental Red Edge Gillet 2013 A&A

The key process: the first overtone shock RR Lyr Fokin & Gillet 1997 A&A 325, 1013

Formation region of s3 Formation region of s3’ Collision of shocks: s4+s3 & s3’ The main shock Formation region of s4 Formation region of s1 Fokin & Gillet 1997 A&A 325, 1013

RR Lyr Collision of shocks: s4+s3 & s3’ Fokin & Gillet 1997 A&A 325, 1013

The key process: the first overtone shock s3’ - s4 : accumulated weak compression waves (buzz waves) at the sonic point during the beginning of the atmospheric compression produce shock s4. - s3 : associated with the stop of the hydrogen recombination front near the phase of maximum expansion. - s3’ : might be generated by the perturbation of the fundamental mode by the transient first overtone? - s2 : produced by the κ -mechanism that occurs in helium subphotospheric layers. - s1 : produced by the κ -mechanism that occurs in hydrogen subphotospheric layers.  There are 5 shock waves in RR Lyr during a pulsation cycle. Fokin & Gillet 1997 A&A 325, 1013

The velocity of s3’ is weak: Mach number ∼ 2.5 Mach number =20 Fokin & Gillet 1997 A&A 325, 1013

The second required process: the decrease of the average effective temperature MW Lyr Blazhko maximum P B =17 d P B /P=42 Amplitude = 6915 – 6850 = 65 K How to explain the variation in average effective temperature <T eff >?

Ratio of the emergent radiative flux F RN to the total energy of the shock wave C 2 Mach number Rankine-Hugoniot equation for energy: 2 4 6 F F 1 1 + + = + + = R R 2 2 u h u h cste 1 2 ρ ρ 1 1 2 2 2 u 2 u 1 1 2 2 Definition: F 1 ≡ + + 2 R C u h ρ 2 2 u ≡ h enthalpy        ≡ + + + + + C E E E E W E 2 k tr x I R 1 p p γ − ρ ρ 1 When the shock velocity increases, its radiative losses increase rapidly. Fadeyev & Gillet 2001 A&A 368, 901