Axion mass limit from observations of the neutron star in Cassiopeia A

Abstract

Direct Chandra observations of a surface temperature of isolated neutron star in Cassiopeia A (Cas A NS) and its cooling scenario which has been recently simultaneously suggested by several scientific teams put stringent constraints on poorly known properties of the superfluid neutron star core. It was found also that the thermal energy losses from Cas A NS are approximately twice more intensive than it can be explained by the neutrino emission. We use these unique data and well-defined cooling scenario to estimate the strength of KSVZ axion interactions with neutrons. We speculate that enlarged energy losses occur owing to emission of axions from superfluid core of the neutron star. If the axion and neutrino losses are comparable we find c 2 n m 2 a ∼ 5.7 × 10 −6 eV 2 , where m a is the axion mass, and c n is the effective Peccei-Quinn charge of the neutron. (Given the QCD uncertainties of the hadronic axion models, the dimensionless constant c n could range from −0.05 to 0.14.)

Diffusive nuclear burning in cooling simulations and application to new temperature data of the Cassiopeia A neutron star

“…Constraining cooling models with multiple temperature observations can provide fundamental knowledge on the properties of the NS interior, such as critical temperatures for superconductivity and superfluidity (e.g., Shternin et al 2011;Page et al 2011;Ho et al 2015). Other possibilities include fast or rotationally induced neutrino cooling (Negreiros et al 2013;Taranto et al 2016), magnetic field decay (Bonanno et al 2014), slow thermal relaxation (Blaschke et al 2012(Blaschke et al , 2013, stellar fluid oscillations (Yang et al 2011), and transition to axions or quark matter (Noda et al 2013;Sedrakian 2013;Leinson 2014;Hamaguchi et al 2018).…”

Axion cooling of neutron stars. II. Beyond hadronic axions

“…We do not attempt to fit the transient behavior of the Cas A, as has been done in Refs. [16,17], since the data on rapid cooling is inconclusive [48,50]. In any FIG.…”

“…The transient behavior of the Cas A has been studied in Refs. [16,17] to this end and useful limits were obtained assuming that the data reflect per se the fast cooling of this object. The cooling behavior of peculiarly "hot" CCO HESS J1731-347 has been analyzed in the context of axionic cooling in Ref.…”

Distinguishing axion models with IAXO

“…Similarly, supernovae [28,52] and neutron stars [53] set stringent limits on an axion-nucleon coupling. Neutron stars also provide a hint towards the existence of ALPs [53,54]. However, Helioscopes are not sensitive to these couplings and they cannot be inferred from g aγ and g ae in a model-independent way.…”