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2 nd 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 - PowerPoint PPT Presentation
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Marek BiesiadaDepartment of Astrophysics and Cosmology
University of SilesiaKatowice, Poland
2nd Vienna Central European Seminar on Particle Physics and Quantum Field Theory
“FRONTIERS IN ASTROPARTICLE PHYSICS”25-27 November 2005
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
• 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.
m o t i v a t i o n
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
Scheme of Evolutionary Track of a Star
in practice
three main sources of astrophysical
bounds:
•the Sun;
•supernova 1987A;
•red giants from globular clusters.
•H burning main-sequence star
•response of radiative interior to extra cooling - shrinking and Tc increase
•how can we measure Tc of the Sun?
•helioseismology - possibility to estimate Tc directly from the profile of cs
the s u n
From Raffelt, 1999
constraints comes from:
pulse duration
•energy budget
s u p e r n o v a 1 9 8 7 A
red giants from globular clusters
•RG - stars with degenerate He core/interior•on HB - stars with radiative core/interior
•additional cooling mechanism would actually cool down the interior of RG - there is no feedback between energy loss and pressure
•consequences:
•He-flash would be delayed
•star would spend less time on HB
•observational indicators
•height of RGB tip
•# density of stars on HB
the new tool
now!
from white dwarfs
•white dwarfs are degenerate stars composed of C and O with 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
dt
dTMc
dt
dUL WDV
th
Instability strips
on H-R diagram
ZZ Ceti
•relative simplicity
•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 of changes of the temperature and hence the fraction of luminosity attributed to hypothetical new energy loss.
what makes white dwarfs useful ?
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)
index adiabaticfirst theis lnln
ln1ln
ad
1
1
2
dpd
Γ
gAdr
pddr
dgN
h o w d o e s i t w o r k ?h o w d o e s i t w o r k ?
Brunt-Väisälä
frequency
for degenerate electron gas in non-zero temperature:
A~T2 so
1/P ~T i.e.
MTc
L
T
T
P
P
V
•conclusions• from the rate of period change one gets information about cooling rate
•when the star cools down - the period increases
First, if ... • the observed period increase rate POBS is significantly greater than
theoretically predicted (assuming standard physics ) PO
- this anomalous effect can be explained by an additional energy loss
channel LNEW
(Isern, Hernanz, Garcia-Berro ApJ 1992)
1O
OBSNEW
P
P
L
L
•the observed value POBS agrees with PO in the
sense that PO lies within, say 2 confidence
interval - one can derive a constraint on exotic
channel of energy loss
1
O
UPPERNEW P
PLL
second case
G117 - B15A
Main actor G117-B15A
•pulsating DAV white dwarf (ZZ Ceti)•discovered in 1976 McGraw & Robinson•global parameters•mass 0.56 M0
•Teff =11 620 K Bergeron 1995
•log(L/L0) = -2.8 i.e. L=6.18 1030 erg/sMcCook & Sion 1999
•Chemical composition: C:O = 20:80•Tc = 1.2 107 K Bradley 1995
•R = 9.6 108 cm
O C He H
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)
What have we done with G117-B15A ?
•we have used this approach to constrain the
compactification mass scale Ms in
Arkani-Hammed, Dimopoulos & Dvali (1998) model
•we have considered model with n=2 large extra dimensions
•and tested with G117-B15A
Biesiada & Malec PhysRevD 65, 2002
additional energy loss channel due to KK-graviton emission
relevant process - gravibremsstrahlung in static electric field of ions.
e
e
e
e
ee
e e
Gkk
Gkk
Gkk
Gakk
specific mass emissivity for this process calculated by Barger et al. Phys Lett B 1999
24
3751086.5 jj
s
e ZnM
nT
the upper 2 limit on POBS translates into a bound:
LL
P
PMZn
M
nTL
O
OBS
jjj
S
eKK
308.011086.5 2
2
375
the final result for the constraint on mass scale MS is:
23.14c
TeVM S
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
What have the others done with G117-B15A ?
• used G117-B15A to constrain the mass of an axion
•evolutionary and pulsational codes with axion emissivity added
•obtained bound to axion mass
Corsico et al. New Astron. 6, 2001
meVmax 2cos4
Corsico et al. New Astron. 6, 2001
Another issue - Varying G
• renewed debate over the issue whether the fundamental constants of nature (G, c, h or e) can vary with time
•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
MOTIVATION
Paper
M.Biesiada & B.MalecMNRAS 350, 644, 2004
Astroseismology
of
G117-B15A
Nature of oscillations: g-modes, Brunt - Väisälä frequency
Asymptotic form Rate of period change (classically)
Modification for varying G
CoolingResidual contraction
Here is the dependence on G
Idea: observed agrees with
theoretical (with some accuracy)
so
We obtain the bound
[Theoreticalmodel according to Salaris et al. 1997]
ALTERNATIVE BOUNDS ON VARYING G
1. Paleontological:
Teller 1948 assuming, that the Earth temperature is determined by energy fluxthrough 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 agoTearth would have been close to water boiling point - contradicted by existence of cambrian trylobits
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
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
4. Cosmology (Brans-Dicke Theory)
•CMB
•BBN
Copi et al. Phys Rev.Lett. 92 2004
Cyburt et al. 2004astro-ph/0408033
•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, Montgomery 2005 astro-ph/0510103
•pulsating White Dwarfs are becoming a new tool in astroparticle physics
PERSPECTIVES AND CONCLUSIONS