Speaker
Nicolas Viaux
(Pontificia Universidad Católica de Chile)
Description
Stellar evolution is quite sensitive to the inclusion of new low-mass particles (such as axions or neutrinos with novel electromagnetic properties) which have weak interactions with matter. Such particles escape almost freely without having interactions with matter, implying changes in the evolution and properties of the star by achieving a new energy loss channel. These changes produced by these new low-mass particles or neutrinos with novel electromagnetic properties have a direct impact on the way that the star loses energy. So, the evolution path and physical properties of a star when considering these new particles (or neutrinos with novel electromagnetic properties) are different if compared with the case in which such particles are not considered, leaving a window open to put constraints when comparing them with observations of stars.
In this work, new constraints in the light of the most recent data from globular clusters (GC) and updated stellar evolution codes are presented, paying special attention to the systematic and statistical uncertainties in order to make an easy comparison between terrestrial and astronomical constraints.
Specifically, we study the impact of the neutrino magnetic moment (NMM) and axions on the tip of the red giant branch (TRGB). The latter has been identified as a sensitive indicator of exotic energy loss mechanisms in low-mass stellar interiors.
Enhanced neutrino emission due to NMM and axion emission for different coupling strengths with electrons has been implemented in our stellar evolution code, PGPUC. Then, for both cases, we have computed stellar evolution tracks, to reach the TRGB for the GC: M5 (NGC5904) and M3 (NGC5272). This GC the best candidate of GCs where we imposed stringent criteria that provide us with clean color-magnitude diagrams and straightforward interpretation of the results.
Summary
We have confronted both theoretical and observational results with which constraints on the NMM and the axion-electron coupling are obtained using GC. For the NMM we obtained $\mu_{\nu} < using 2.6\times 10^{-12}\mu_{\rm B}$ (68%C.L.), where $\mu_{\rm B} \equiv e/2m_{e}$ (with $\hbar =c=1$) is the Bohr magneton and $\mu_{\nu} < 4.5 \times 10^{-12}\mu_{\rm B}$ (95% C.L.). For the axion-electron coupling we obtained $g_{aee} < 2.6 \times 10^{-13}$ (68% C.L.) and $g_{aee} < 4.3 \times 10^{-13}$ (95% C.L.). These constraints are the most stringent upper limits with confidence levels available so far.
Author
Nicolas Viaux
(Pontificia Universidad Católica de Chile)
Co-authors
Dr
Achim Weiss
(Max-Planck-Institut für Astrophysik)
Dr
Aldo Valcarce
(Pontificia Universidad Católica de Chile)
Dr
Georg Raffelt
(Max Planck Institut fuer Physik)
Javier Redondo
(LMU/MPP Munich)
Dr
Márcio Catelan
(Pontificia Universidad Católica de Chile)
Dr
Peter Stetson
(National Research Council (Canada))
