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White Dwarf Stars: Crystals and Clocks S.O. Kepler.

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Presentation on theme: "White Dwarf Stars: Crystals and Clocks S.O. Kepler."— Presentation transcript:

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2 White Dwarf Stars: Crystals and Clocks S.O. Kepler

3 White Dwarf Stars as Laboratories S.O. Kepler Department of Astronomy UFRGS - Brazil

4 Stellar Evolution Mass < 10 M sun : White Dwarf 10 M sun < Mass < 25 M sun : Neutron Star 10 M sun < Mass < 25 M sun : Neutron Star Mass > 25 M sun : Black Hole

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6 Planetary Nebula Observed by the Hubble Space Telescope

7 Sirius and the White Dwarf Sírius B

8 White dwarfs pulsate as they cool

9 Intensity Changes With Time Multiperiodic, P=71s to 1500s, amp=4 mma to 300 mma

10 Pulsating White Dwarfs n Internal structure of the white dwarf (SNIa progenitors) (SNIa progenitors) n Cooling timescale n Age of the oldest stars in our galaxy High energy and high density physics High energy and high density physics

11 Pulsating White Dwarfs n White Dwarfs ~ 6000 (doubled in 2004) n Variable~ 115 (tripled in 2004) n DOV T eff = K 10 known, M= -1 n DBV T eff = K 13 know, M= 8 13 know, M= 8 n DAV T eff = K 92 known, M=12 92 known, M=12 Structure – SNIa progenitors

12 Pulsations … Seismology

13 Pulsations/Seismology: Y 10 e Y 11

14 Pulsations are global

15 Observations: 1.6 m telescope Laboratório Nacional de Astrofísica Brasópolis, MG

16 Whole Earth Telescope

17 Mass determination n UV spectra n Optical spectra n T ef = K n Massa = 1,1 M sol 0,6 M Sol

18 Mass distribution 300 stars PG survey

19 SDSS We fit all 1872 DA white dwarfs in SDSS

20 SDSS T eff determination

21 SDSS log g determination

22 Transição de fase para cristal A parte pontilhada corresponde a P(líquido quântico)/P(gás ideal) > 1. Efeitos quânticos iônicos são importantes à direita desta linha (  1975

23 DAV instability strip Need high S/N spectra of variables and non-variables to refine Teff and log g Need to find more variables and non-variables to determine log g dependence

24 Most Massive Pulsating WD

25 BPM37093 – Diamond in the Sky! 10’ 2 o = 12 x 10’ 17 light yr distant (40 quadrillion km)

26 Light Curve

27 Crystallization O C

28 Pulsations Present

29 Period in seconds

30 Phase Diagram

31 Crystallized or not?

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33 BPM37093 in 1999

34 Super-Diamond? n Diamond n C crystal n FCC n 3,08A between atoms n 2 shared electrons n T < 8000 K n 10 K atm < P < 1,2x10 8 atm n BPM37093 n C crystal n BCC n 0,01A between nucleons n all electrons are free (degenerate) n T = 7 million K n P = 5x10 18 atm  = 36 Ton/cm 3  = 36 Ton/cm 3 n E ions > 2kT (quantized) n metallic quantum crystal o o

35 DBV instability strip Bárbara Castanheira - IUE

36 DBV GD 358

37 181 periodicities detected n Mass of each layer n M(R): Luminosity -> distance (1/10 uncertainty of parallax) (1/10 uncertainty of parallax) n Rotation law(r) [splitting (k)] n Magnetic field limit (6000 G) n 6 th order harmonics and combinations

38 Nuclear reaction rate Quantity of 22 Ne dependes mainly onQuantity of 22 Ne dependes mainly on  [C 12  16  Ne 20  Mg 24  ] NonResonantReaction T > 10 8 K and   g/cm 3 Uncertainty is around 50%!

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40 C(  )O S 300

41 Mode identification with HST Chromatic amplitude changes

42 GD358 mode identification HST n Bárbara Castanheira l = 1 for k=8 and 9 in 1996 l = 1 for k=8 and 9 in 1996 probably l = 1 for other modes in 2000 probably l = 1 for other modes in 2000

43 GD358 mode identification HST n Bárbara Castanheira l = 1 for k=8 and 9 in 1996 l = 1 for k=8 and 9 in 1996 probably l = 1 for other modes in 2000 probably l = 1 for other modes in 2000

44 PNNV – DOV instalibility strip

45 Period (sec) PG

46 Frequency (  Hz) All PG

47 PG : 101 pulsations detected n T eff = K n Total mass : ( / ) M Sun n M(R): Luminosity -> distance n Mass of external layers n no harmonics or linear combination (no convection zone) (no convection zone)

48 PG modes detected k=   P=21.43s M= M Sun J. Edu S. Costa

49 Direct Method dP/dt Period (s ) P=516s dP/dt=( )x s/s

50 But period increases with time! dP/dt=( ) x 10 –11 s/s 1s/300 years

51 Most stable optical clock known

52 DAV

53 G117-B15A 2004 P=215s

54 Stable? Time scale = 2.2 Gyr Pulsars with dP/dt = s/s have timescale 0.1 Gyr, but PSR B , with P=5.3 ms and dP/dt=1.8x s/s has timescale of 9.5 Gyr.

55 Axions m ax cos2  < 4 meV E vacuum >2,5GeV &

56 Axions m ax > 1  eV or  ax > 1 tan  ratio of the vacuum energy of the two Higgs fields

57 Gravitons? Biesada & Malec (2002) Phys Rev D, 65 dP/dt: the string mass scale M s > 14,3 TeV/c 2 for 6 dimensions for Kaluza-Klein gravitons. The limit is negligible for higher dimensions

58 Variable G? Asteroseismological bound on G/G from pulsating white dwarfs Omar G. Benvenuto, Enrique García-Berro, and Jordi Isern PHYSICAL REVIEW D 69, (2004).

59 Why do pulsation periods change? R = 9,6 x 10 8 cm, dR/dt = 1 cm/yr T nucleus =12 million K, dT/dt = 0.05 K/year DAV Cooling dominates!

60 Photon vs neutrino emission

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62 The Feynman diagram

63 Plasma neutrino (Weak interaction)

64 Two keys… n To excite the plasmon we must have n The plasma frequency is much higher for a degenerate gas, and increases with increasing density…

65 Effects of Neutrinos on Evolutionary Timescales EC GD 358

66 DBVs: dP/dt and Plasmon Neutrinos: 3-4!

67 Luminosity Function and Age of the Galaxy Age of the disk:  ± 2 yr Number of Stars Intensity

68 Age of the Universe Age = (11,5 ± 2,7) billion years Age of Universe = Age of disk + Halo + Formation of galaxy Age of disk + Halo + Formation of galaxy 9 ± 2 1,5 ± 1,5 1 ± 1 billion yr

69 HST: Galaxies formed 1 Gyr after Big-Bang

70 White dwarfs in globular cluster M – 8 days of exposure with HST Age= Gyr Age= Gyr Disk corrected we will do other globulars with SOAR

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72 Age of the Universe in 2004 CMB - WMAP = ( ) GyrCMB - WMAP = ( ) Gyr Hubble constant: 1/H = (12 + 1) GyrHubble constant: 1/H = (12 + 1) Gyr Globular clusters: ( ) GyrGlobular clusters: ( ) Gyr Radiactive decay: ( ) GyrRadiactive decay: ( ) Gyr Cooling of white dwarf stars: ( ) GyrCooling of white dwarf stars: ( ) Gyr Distances to SNIa: (0.63/h)Gyr, Distances to SNIa: (0.63/h)Gyr,  10 years ago only white dwarfs gave age smaller than 15 billion years: smaller than 15 billion years: SN1987A NGC6903CenA SNIa

73 Spectra of DA, DB and DO

74 Mode identification with SOAR

75 Find more variables Frequency (Hz) Fractional Amplitude P=647s; A=48mma (V=18.6) P=329s; A=22mma

76 Detection of extra-solar planets Spectroscopy: detection of radial velocity variation around the center of mass

77 G117-B15A 2004 P=215s

78 Jupiter around G117-B15A? P=11.86 years, a=5.2 UA

79 Saturn around? P=29.46 years, a=9.5 UA

80 Search for planetary companions monitoring changes in pulse arrival time due to motion of star around barycenter. Orbit around center of mass with planetary companion

81 Detection Limits on Orbits of the Planets Doppler Sectroscopic Method (Current Limits) Pulsating White Dwarf Method (Current Limits)

82 Region of Planet Detection Quantitative Theoretical Limits of Stability? Time Squared

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89 PMT CCD vs PMT

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91 Measured Amplitude Difference

92 Change in Amplitudes

93 Amplitude vs Wavelength

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95 CCD Data Analysis

96 That’s all folks!

97 Music?


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