Axion and neutrino bounds improved with new calibrations of the tip of the red-giant branch using geometric distance determinations

Abstract

The brightness of the tip of the red-giant branch (TRGB) allows one to constrain novel energy losses that would lead to a larger core mass at helium ignition and, thus, to a brighter TRGB than expected by standard stellar models. The required absolute TRGB calibrations strongly improve with reliable geometric distances that have become available for the galaxy NGC 4258 that hosts a water megamaser and to the Large Magellanic Cloud based on 20 detached eclipsing binaries. Moreover, we revise a previous TRGB calibration in the globular cluster ω Centauri with a recent kinematical distance determination based on Gaia data release 2. All of these calibrations have similar uncertainties, and they agree with each other and with recent dedicated stellar models. Using NGC 4258 as the cleanest extragalactic case, we thus find an updated constraint on the axion-electron coupling of g ae < 1.6 × 10 −13 and μ ν < 1.5 × 10 −12 μ B (95% C.L.) on a possible neutrino dipole moment, whereas ω Centauri as the best galactic target provides instead g ae < 1.3 × 10 −13 and μ ν < 1.2 × 10 −12 μ B. The reduced observational errors imply that stellar evolution theory and bolometric corrections begin to dominate the overall uncertainties.

More axions from strings

“…Existing experimental bounds and observational constraints (solid lines) on g aγγ as a function of the axion mass and the projected sensitivity of proposed experiments (dotted) are also shown. The limit on DFSZ models from white dwarfs and red giants ("WD/RG") is indicated for tan β = 1 [75] , while the supernova-1987a limit on such models ("SN1987a") spans the blurred region as tan β varies (the corresponding constraint on KSVZ models is m a < 15 meV) [70]. The post-inflationary region that we identify could also be probed by future experiments sensitive to the axion's couplings to matter [54,59].…”

“…Defined as L ⊃ − 1 4 g aγγ aFF in the low energy theory, where F is the electromagnetic field strength 18. The existing experimental and observational bounds shown are from ADMX[61,62], earlier cavity experiments "UF/RBF"[63,64], HAYSTACK[65], CAST[66], observations of horizontal branch starts "HB"[67], supernova 1987a "SN1987a"[68][69][70] (see however[71]) and red giants and white dwarf stars "RG/WD"[72][73][74][75]. The constraints on DSFZ axions from supernova 1987a, red giants and white dwarfs are model dependent via the mixing angle β.…”

“…The constraints on DSFZ axions from supernova 1987a, red giants and white dwarfs are model dependent via the mixing angle β. For those from white dwarfs and red giants we plot the limit from[75] for tan β = 1. The limit from supernova 1987a is m a < 0.02 eV for tan β = 1 and this barely weakens for smaller tan β but it…”

What if ALP dark matter for the XENON1T excess is the inflaton

“…Here we have adopted the decay rate into photons based on the anomaly-free ALP DM model [3,17]. On the other hand, the cooling argument based on the tip of red-giant branch stars places a tight bound on g φe < 1.60 (0.82) × 10 −13 at 95% (68%) CL, and the gray shaded region shows the 2σ excluded region, and the red dotted line is the 1σ bound [25]. 6 The RG cooling bound gives a lower bound on the fraction of ALP DM as r 0.01.…”

“…The red shaded region is preferred by the cooling of white dwarf stars. The gray region and the red dashed line represent the bound from the cooling of the tip of the red-giant branch [25] at 2σ and 1σ level, respectively.…”