Beata Malec University of Silesia

1. Beata Malec University of Silesia White dwarf constraints on dark matter particles XXXIII International Conference of Theoretical Physics MATTER TO THE DEEPEST: Recent Developments in Physics ofFundamental Interactions, Ustroń’09

2. Outline of the talk • Introductory remarks • Context - dark matter problem, • Astrophysical constraints on exotic physics • White dwarfs in perspective G117-B15A as a tool for astroparticle physics • WD constraints on : • multidimensional ADD model • scalar WIMP-nucleon cross section • Conclusion and perspectives MATTER TO THE DEEPEST

3. Dark Matter in the Universe Pioneers: Oort 1923, Zwicky 1925 Gravitational lensing by galaxies and clusters (giant arcs) Flat rotation curves in galaxies X-ray emission from clusters MODERN COSMOLOGY LSS CMBR BBN b = 0.042 m = 0.29 ± 0.04 MATTER TO THE DEEPEST

4. Dark Matter in the Universe MATTER TO THE DEEPEST

5. Motivation and ideas • Modern astrophysics is a great success of standard physical theories in understanding stellar structure and evolution • Stars serves as a source of constraints on non standard ideas • Some of these constraints turn out to be more stringent than laboratory ones First idea: weakly interacting particles (axions, Kaluza-Klein gravitons, etc.) produced in hot and dense stellar interior are steaming freely – in effect we have additional cooling channel and modification of evolutional time-scales Second idea: If a star is immersed in a halo of supersymmetric dark matter it can have consequences on the course of its evolution MATTER TO THE DEEPEST

6. In practice • Three main source of astrophysical constraints:(previously considered mainly in the context of additional cooling channels) • Sun (helioseismology) additional cooling – increase of Tc • Globular clusters main observables • Height of RGB tip above HB • Number density of stars onHB • Supernova 1987A • Duration of  pulse • Energy budget MATTER TO THE DEEPEST

7. New tool – pulsating White Dwarfs (WD) • White dwarfs are degenerate stars , consist of C and O, they could also have thin outher He and H layers. • WD history is simple: the only one thing they can do is to cool down. • Luminosity is fairly well described by Mestel cooling law • Some of them are pulsating stars- so called ZZ-Ceti variables asteroseismology - gives opportunity to record many pulsational modes and to measure them with great accuracy MATTER TO THE DEEPEST

8. How it works? From the theory of stellar oscillations it is known that WD can support non radial oscillations excited g-modes have frequencies (proportional to) Brunta-Väisäla frequency for degenerate electron gas at non-zero temperature: A~T2 so 1/P ~T then • inferences • from the rate of period change one can estimate cooling rate • when star is cooling its period increases MATTER TO THE DEEPEST

9. Pulsating White Dwarf G117-B15A Other names RY LMi WD 0921+352 • discovered (as variable) in 1976 (McGraw & Robinson) • Global parameters • mass 0.59 M0 • Teff =11 620 K(Bergeron 1995) • log(L/L0) =-2.8tzn. L=6.18 1030 erg/s (McCook & Sion 1999) • R = 9.6 105 cm • Tc = 1.2 107K Chemical composition: C:O = 20:80 (Bradley 1995) C : O = 17 : 83 (Salaris et al. 1997) MATTER TO THE DEEPEST

10. Pulsational properties/features: excited modes – g-modes– non-radial oscilations 215.2 s 271 s 304.4 s Kepler et al. 1982 Rate of period change is precisely measured for the mode 215. 2 s (Kepler et al. 2000) (Kepler et al. 2005) Change of the period gives information about cooling rate ! MATTER TO THE DEEPEST

11. Systematic effects (secular): • residual gravitational contraction – negligibly small • core crystalization –DAV stars are too hot • proper motion effect (Pajdosz 1995) Proper motion van Altena et al. 1995 Theoretical prediction of the Salaris (1997) model Corsico et al. 2001 MATTER TO THE DEEPEST

12. Energetic constraint Excellent agreement between theory and the observed rate of period change -> a source of constraints It restricts possibility of new energy sources or cooling channels In the Mestel law approximation Energetic constraints on exotic sources in G117 – B15A MATTER TO THE DEEPEST

13. ADD Model • World is multidimensional: gravity acts in n+4dimensions, all other interactions „confined” to 4-dim „brane” • One can build low-energy effective theory of K-K gravitons interacting with S.M. fields [Barger et al. 1999, Cassisi et al. 2000] emission rate Observed rate of change of period Theoretical rate of change of period MATTER TO THE DEEPEST

14. Comparison of bounds • LEP  Ms > 1 TeV/c2 • SUN  Ms > 0,3 TeV/c2 • Globular Clusters  Ms > 4 TeV/c2 • SN1987A  Ms > 30-130TeV/c2 • WD G117-B15A  Ms > 8,8 TeV/c2 MATTER TO THE DEEPEST

15. Stars are immersed in the Galactic darkhalo What are the consequences ? MATTER TO THE DEEPEST

16. Accretion of dark matter Capture rate Barometric distribution of WIMPs sets in Majorana particles - -> annihilate Stady state: accretion and annihilation rates are equal Additional luminosity Spergel & Press 1985 Gould 1987 MATTER TO THE DEEPEST

17. In the supersymmetric model of WIMPs (neutralino) One can obtain the upper bound on nucleon scatering cross section MATTER TO THE DEEPEST

18. Recapitulation • Pulsating white dwarf G117 – B15A is a nice tool for astroparticle physics: • Long sequence of observational data (fotometric and spectroscopic) • Well calibrated astroseismologically • Pulsational mode 215 s – one of the most stable clocks in nature (the most stable „optical clock”) MATTER TO THE DEEPEST

19. MATTER TO THE DEEPEST

20. MATTER TO THE DEEPEST

21. additional energy loss channel due to KK-graviton emission relevant process - gravibremsstrahlung in static electric field of ions. Gkk Gkk e e e e Gkk e e e Gkk e MATTER TO THE DEEPEST

22. 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: MATTER TO THE DEEPEST