Marek Biesiada Department of Astrophysics and Cosmology University of Silesia Katowice, Poland

1. 2nd Vienna Central European Seminar on Particle Physics and Quantum Field Theory “FRONTIERS IN ASTROPARTICLE PHYSICS” 25-27 November 2005 Pulsating White Dwarfs as a Tool for Astroparticle Physics Marek Biesiada Department of Astrophysics and Cosmology University of Silesia Katowice, Poland

2. Outline of the talk • Astrophysics as a source of bounds on exotic physics • Astroseismology of WDs - a new tool for astroparticle physics • Some bounds from G117-B15A star • Perspectives and Conclusions

3. m o t i v a t i o n • modern astrophysics is a great success of standard physical theories in explaining properties of stars and stellar systems • stars can be used as sources of constraints for non standard physical ideas • some of these bounds turn out to be more stringent than these coming from direct physical experiments.

4. i d e a weakly interacting particles (axions, Kaluza-Klein gravitons, etc. ) can be produced in stellar interiors and escape freely they become an additional channel of energy loss from stellar interiors new channel of energy loss would modify stellar evolution e.g. Raffelt G., Annu.Rev.Nucl.Particle Sci.,49, 1999

5. Scheme of Evolutionary Track of a Star

6. in practice • three main sourcesof astrophysical bounds: • the Sun; • supernova 1987A; • red giants from globular clusters.

7. the s u n • H burning main-sequence star • response of radiative interiorto extra cooling - shrinking and Tcincrease • how can we measure Tcof the Sun? • helioseismology- possibility to estimateTcdirectly from the profile ofcs

8. From Raffelt, 1999

9. s u p e r n o v a 1 9 8 7 A constraints comes from: •  pulse duration • energy budget

11. red giants from globular clusters • RG - stars with degenerate He core/interior • onHB-stars with radiative core/interior • additional cooling mechanism wouldactually cool downthe interior of RG- there is no feedback between energy loss and pressure • consequences: • He-flashwould bedelayed • star would spendless timeon HB • observational indicators • height of RGBtip • # densityof stars on HB

12. the new tool from white dwarfs • white dwarfsare degenerate stars composed of Cand Owith thin He and H outer layers • WD history is simple: the only thing the star can do is to cool down emitting photons • luminosity of the WD is given by Mestel cooling law now!

13. Instability strips on H-R diagram ZZ Ceti

14. what makes white dwarfs useful ? • relativesimplicity • some of them become pulsating stars - the so called ZZ-Ceti variables • advances in asteroseismology - possibility to identify various modes of pulsation and to measure their periods with great accuracy • an opportunity to estimate the rate ofchanges of the temperatureand hence the fraction of luminosity attributed to hypothetical new energy loss.

15. h o w d o e s i t w o r k ? from the theory of stellar oscillations it turns out that white dwarfs can support non-radial oscillations the excited g-modes have frequencies (proportional to) Brunt-Väisälä frequency

16. for degenerate electron gasin non-zero temperature: A~T2so 1/P ~Ti.e. • conclusions • from therate of period changeone gets information about cooling rate • when the star coolsdown - the period increases

17. First, if ... • theobserved period increase rate POBSis significantly greater than theoreticallypredicted (assuming standard physics )PO - this anomalous effect can be explained by an additional energy loss channel LNEW (Isern, Hernanz, Garcia-Berro ApJ 1992)

18. second case • theobserved valuePOBSagrees with POin the sense that POlies within, say 2 confidence interval- one can derive a constraint on exotic channel of energy loss

19. G117 - B15A

20. Main actor G117-B15A • pulsating DAV white dwarf (ZZ Ceti) • discovered in 1976 McGraw & Robinson • global parameters • mass 0.56 M0 • Teff =11 620 KBergeron 1995 • log(L/L0) = -2.8 i.e. L=6.18 1030 erg/s • McCook & Sion 1999 • Chemical composition: C:O = 20:80 • Tc = 1.2 107K Bradley 1995 • R = 9.6 108 cm C He H O

21. Pulsating properties: • excited fundamental modes • 215.2 s 271 s 304.4 s • Kepler et al. 1982 • Accurate measurement of the rate of change of • 215.2 s mode period • Kepler et al. 2000 theory predicts dPO/dt = 3.9 10-15 s/s ( Córsico et al. 2001)

23. What have we done with G117-B15A ? Biesiada & Malec PhysRevD65, 2002 • we have used this approach to constrain the compactification mass scaleMsin • Arkani-Hammed, Dimopoulos & Dvali (1998) model • we have considered model withn=2large extra dimensions • and tested withG117-B15A

24. additional energy loss channel due toKK-gravitonemission relevant process -gravibremsstrahlungin static electric field of ions. Gakk Gkk e e e e Gkk e e e Gkk e

25. specific mass emissivity for this process calculated by Barger et al. Phys Lett B 1999 the upper 2 limit on POBS translates into a bound: the final result for the constraint on mass scale MS is:

26. comparison with other bounds • LEP Ms > 1 TeV/c2 • The Sun Ms > 0,3 TeV/c2 • Red Giants Ms > 4 TeV/c2 • SN1987A Ms > 30-130TeV/c2 • White Dwarf Ms > 14,3 TeV/c2

27. What have the others done with G117-B15A ? Corsico et al. New Astron.6, 2001 • used G117-B15A to constrain the mass of an axion • evolutionary and pulsational codes with axion emissivity added • obtained bound to axion mass

28. Corsico et al. New Astron.6, 2001

29. Another issue - Varying G • renewed debate over the issue whether the fundamental constants of nature (G, c, h or e) can vary with time

30. MOTIVATION • Dirac’s Large Number Hypothesis • Brans-Dicke Theory • Theories with higher dimensions, superstring theories, M-theory etc. • Claims that fine structure constant might vary • Webb & Murphy 2001 • Gravity constant G: • historically the first considered as varying

31. Paper M.Biesiada & B.Malec MNRAS 350, 644, 2004 Astroseismology of G117-B15A

32. Nature of oscillations: g-modes, Brunt - Väisälä frequency Here is the dependence on G Rate of period change (classically) Asymptotic form Modification for varying G Residual contraction Cooling

33. Idea: observed agrees with theoretical (with some accuracy) [Theoretical model according to Salaris et al. 1997] so We obtain the bound

34. ALTERNATIVE BOUNDS ON VARYING G 1. Paleontological: Teller 1948 assuming, that the Earth temperature is determined by energy flux through a sphere of radius = the radius of the Earth orbit Tearth ~ G2.25 M01.75 if M0 =const. , then if G were 10% higher 300 mln. yrs ago Tearthwould have been close to water boiling point - contradicted by existence of cambrian trylobits

35. 2. Celestial Mechanics Moon - Earth system (LLR) < 8 •10-12 yr-1 Williams et al. 1996 Solar System (Viking) (2 ± 4 )•10-12 yr-1 Hellings et al. 1983 binary pulsars PSR 1913+16 (1.10 ± 1.07 )•10-11 yr-1 Damour & Taylor 1991 PSR B1913+16 (4 ± 5 )•10-11 yr-1 Kaspi et al. 1994

36. 3. Astrophysics • helioseismology - p-modes spectrum: classical vs. Brans-Dicke Theory • < 1.6 •10-12 yr-1 Guenther et al. 1998 • Globular Clusters („cluster age < age of the Universe”) • (-1.4 ± 2.1) •10-12 yr-1 Del’Innocenti et al. 1996 • pulsating White Dwarfs • 4. •10-10 yr-1 Biesiada & Malec 2004 • Benvenuto et al. 2004

37. 4. Cosmology (Brans-Dicke Theory) • CMB • BBN Cyburt et al. 2004 astro-ph/0408033 Copi et al. Phys Rev.Lett. 92 2004

38. PERSPECTIVES AND CONCLUSIONS • besides G117-B15A, another DAV star with dPO/dt measured is R548 (ZZ Ceti) • for P0=213 s • Mukadam et al.Baltic Astron. 2003 • besides DAV, hot DBV stars can be used to test plasmon neutrinos and axions • Kim, Winget, Montgomery2005 astro-ph/0510103 • pulsating White Dwarfs are becoming a new tool in astroparticle physics