[APEX] axion arxiv post (astro)

[Jay Benesch]

in the unlikely case you missed it:

http://arxiv.org/abs/1403.2436

Potential solar axion signatures in X-ray observations with the 
XMM-Newton observatory
G. W. Fraser (1), A. M. Read (2), S. Sembay (2), J. A. Carter (2), E. 
Schyns (3) ((1) SSI Group, SRC, University of Leicester, UK, (2) Dept 
Physics and Astronomy, University of Leicester, UK, (3) Photonis, Brive, 
France)
(Submitted on 10 Mar 2014 (v1), last revised 13 Sep 2014 (this version, v2))

     The soft X-ray flux produced by solar axions in the Earth's 
magnetic field is evaluated in the context of ESA's XMM-Newton 
observatory. Recent calculations of the scattering of axion-conversion 
X-rays suggest that the sunward magnetosphere could be an observable 
source of 0.2-10 keV photons. For XMM-Newton, any conversion X-ray 
intensity will be seasonally modulated by virtue of the changing 
visibility of the sunward magnetic field region. A simple model of the 
geomagnetic field is combined with the ephemeris of XMM-Newton to 
predict the seasonal variation of the conversion X-ray intensity. This 
model is compared with stacked XMM-Newton blank sky datasets from which 
point sources have been systematically removed. Remarkably, a seasonally 
varying X-ray background signal is observed. The EPIC count rates are in 
the ratio of their X-ray grasps, indicating a non-instrumental, external 
photon origin, with significances of 11(pn), 4(MOS1) and 5(MOS2) sigma. 
After examining the constituent observations spatially, temporally and 
in terms of the cosmic X-ray background, we conclude that this variable 
signal is consistent with the conversion of solar axions in the Earth's 
magnetic field. The spectrum is consistent with a solar axion spectrum 
dominated by bremsstrahlung- and Compton-like processes, i.e. 
axion-electron coupling dominates over axion-photon coupling and the 
peak of the axion spectrum is below 1 keV. A value of 2.2e-22 /GeV is 
derived for the product of the axion-photon and axion-electron coupling 
constants, for an axion mass in the micro-eV range. Comparisons with 
limits derived from white dwarf cooling may not be applicable, as these 
refer to axions in the 0.01 eV range. Preliminary results are given of a 
search for axion-conversion X-ray lines, in particular the predicted 
features due to silicon, sulphur and iron in the solar core, and the 
14.4 keV transition line from 57Fe.