Stellar recipes for axion hunters

Abstract

Abstract. There are a number of observational hints from astrophysics which point to the existence of stellar energy losses beyond the ones accounted for by neutrino emission. These excessive energy losses may be explained by the existence of a new sub-keV mass pseudoscalar Nambu-Goldstone boson with tiny couplings to photons, electrons, and nucleons. An attractive possibility is to identify this particle with the axion -the hypothetical pseudo Nambu-Goldstone boson predicted by the Peccei-Quinn solution to the strong CP problem. We explore this possibility in terms of a DFSZ-type axion and of a KSVZ-type axion/majoron, respectively. Both models allow a good global fit to the data, prefering an axion mass around 10 meV. We show that future axion experiments -the fifth force experiment ARIADNE and the helioscope IAXO -can attack the preferred mass range from the lower and higher end, respectively. An axion in this mass range can also be the main constituent of dark matter.

Axion predictions in SO(10) × U(1)PQ models

“…figure 12. Intriguingly, for m A = O(10) meV and tan β 0.3, the axion in this model may explain at the same time recently observed stellar cooling excesses observed from helium burning stars, red giants and white dwarfs [77].…”

“…Note that the region in the N DW = 3 case has been derived under the assumption that the PQ symmetry is protected by a discrete symmetry, so that Planck scale suppressed PQ violating operators are allowed at dimension 10 or higher [69]. In the last two lines the projected sensitivities of various experiments are indicated [70][71][72][73][74][75][76][77].…”

“…In fact, we infer from the first line in figure 12 that the aforementioned phenomenological constraints result in an axion parameter region 2.6 × 10 15 GeV < f A < 3.0 × 10 17 GeV, 1.9 × 10 −11 eV < m A < 2.2 × 10 −9 eV, (6.4) 13 For the stellar cooling bound, we took the one on the photon coupling from horizontal branch stars in globular clusters [65]. The one on the nucleon coupling from supernova 1987A is presumably stronger, fA > 3×10 8 GeV, corresponding to mA < 0.02 meV [77], but suffers still from nuclear physics uncertainties.…”

Improved axion emissivity from a supernova via nucleon-nucleon bremsstrahlung

“…As evident from the figure, the SN bound is competitive with the RGB bound, however not dominating, except for low values of tan β. When compared with the expected IAXO potential [9,20], it is evident that helioscopes of the next generation have the capability to explore large regions of the axion parameter space that are not affected by the SN analysis. As stressed above, the results of our analysis should not be considered as a robust bound as we are not including the axion feedback on the star, which at these couplings is most likely non-negligible.…”

Gaia and the use of White Dwarfs as Advanced Physics laboratories

“…Axions with the properties described here not only would perturb the cooling of white dwarfs but they would also modify in a subtle way the evolution of other kind of stars. An extensive review can be found in Giannotti et al, (2017), while Sedrakian (2019) provides a recent analysis of the cooling by DFSZ axions of the neutron star in Cas A. Here only the two more restrictive tests are presented.…”