Download WHITE DWARFS AS A SOURCE OF CONSTRAINTS ON EXOTIC …

Beata Malec
University of Silesia
XXXIII International Conference of Theoretical Physics
MATTER TO THE DEEPEST: Recent Developments in Physics of
Fundamental Interactions, Ustroń’09
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
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Dark Matter in the Universe
Pioneers: Oort 1923, Zwicky 1925
X-ray emission from clusters
MODERN
COSMOLOGY
Flat rotation curves in galaxies
Gravitational lensing by
galaxies and clusters
(giant arcs)
LSS
CMBR
BBN
b = 0.042
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m = 0.29 ± 0.04
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Dark Matter in the Universe
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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
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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 on HB
Supernova 1987A
Duration of  pulse
Energy budget
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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
dU
dT
th
L

 

c
M
V
WD
dt
dt
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
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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



d
ln
1
d
ln
p


N


g



gA
dr


1dr


2
for degenerate electron gas at non-zero temperature:
A~T2
1/P ~T
so
then
P
T
L
 
P
T
cV MT
inferences
 from the rate of period change one can estimate cooling rate
 when star is cooling its period increases
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Pulsating White Dwarf G117-B15A
 discovered (as variable) in 1976
(McGraw & Robinson)
Other names
RY LMi
 Global parameters
 mass 0.59 M0
 Teff =11 620 K (Bergeron 1995)
 log(L/L0) = -2.8
tzn. L=6.18 1030 erg/s
WD 0921+352
(McCook & Sion 1999)
 R = 9.6 105 cm
 Tc = 1.2 107 K
Chemical composition:
C:O = 20:80
(Bradley 1995)
C : O = 17 : 83
(Salaris et al. 1997)
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Pulsational properties/features:
excited modes – g-modes– non-radial oscilations
215.2 s
271 s
Kepler et al. 1982
304.4 s
Rate of period change is precisely measured
for the mode 215. 2 s
12


O

C


T


PE

P
P
E
max
(Kepler et al. 2000)
2
(Kepler et al. 2005)
Pobs  4.27  0.801015 ss 1
Change of the period gives information about cooling rate !
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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
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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
L  LX
L
Pobs

Ptheor
P
T
L
 
P
T
cV MT
 P

P
obs theor
L
X

P
theor
Energetic constraints on exotic sources in G117 – B15A
erg
L

0
.
126
L

1
.
298

10
X
s
30
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ADD Model
World is multidimensional: gravity acts in n+4 dimensions,
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
T
n

5
.
86

10
n
Z

dla
n

2


M
T
n

9
.
74

10

n
Z

dla
n

3


M
GB
GB
3

75
2
e
4 jj
s
4

91
2
e
5 jj
s
LKK 
M WD
  dm
0
Observed rate
of change of
period
erg
s
erg
L2  4.531021
s
erg
LGCP  2.141024
s
LGB  81029
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n
2

 M
n 
Pl
R
  n2
c M
s 
n
Theoretical
rate of change
of period
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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
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Stars are immersed in the Galactic dark halo
What are the consequences ?
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Accretion of dark matter
Capture rate
Spergel & Press 1985
Gould 1987
 eff   si 
i
MW D
3
X i Ai
mp
Barometric distribution of WIMPs sets in
1/ 2


3Tc

rx  
2

G

m
c dm 

rx  82km
Majorana particles - -> annihilate
Stady state: accretion and annihilation rates are equal
Additional luminosity
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In the supersymmetric model of WIMPs (neutralino)
One can obtain the upper bound on nucleon scatering cross
section

2
.08

10
cm
si

37 2
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Recapitulation
o Pulsating white dwarf G117 – B15A is a nice tool for
astroparticle physics:
o Long sequence of observational data
(fotometric and spectroscopic)
o Well calibrated astroseismologically
o Pulsational mode 215 s – one of the most stable clocks in
nature (the most stable „optical clock”)
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1/ 2


3Tc

rx  
 2G c mdm 
rx  82km
 eff
MW D
3
  si 
X i Ai
mp
i
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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
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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:



T
n
P
OBS


L

5
.
86

10
n
Z

M


1
L

0
.
30

L





M 
P
O

3

75
2
e
KK
j
2j
j
S


the final result for the constraint on mass scale MS is:
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