Stars as Laboratories for Fundamental Physics - MPP Theory Group

234 Chapter 6
Fig. 6.13. Contours of Q 1 /Q 3 and Q 2 /Q 3 defined by Eq. (6.93) in the plane
defined by the plasma frequency ω P and a “typical” electron velocity v ∗
discussed in Sect. 6.3. See Fig. 6.3 for contours of v ∗ and ω P in the T -ρplane.
(Adapted from Haft, Raffelt, and Weiss 1994.)
6.5.6 Astrophysical Bounds on Neutrino Electromagnetic
Properties
The plasma decay process is the most important neutrino emission
process for a large range of temperatures and densities. Moreover,
it has an observable impact on the cooling of hot white dwarfs, and
on the core mass at helium ignition in low-mass red giants. For a
neutrino millicharge e > ν ∼ 10 −14 e and a dipole moment µ > ∼ 10 −12 µ B the
nonstandard plasmon decay rates in Eq. (6.94) begin to compete with
the standard one if the plasma frequency is around 10 keV. Therefore,
neutrino millicharges or dipole moments of this magnitude will have
observable effects on these stars and thus can be excluded.