marek biesiada department of astrophysics and cosmology university of silesia katowice, poland

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