Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Constraining meV Axion Dark Matter with ALMA Observations of the Galactic Center Magnetar SGR 1745-2900

Javier De Miguel, Evanthia Hatziminaoglou, Frédéric Poidevin, Nanda Rea, Daniel L. Walker, Davide De Grandis, Jaime Prieto-Polo

Abstract

We report a mm-wave search for axions from the magnetar SGR 1745-2900, based on 4.8 h of ALMA observations. No statistically significant features are detected between 133.99-135.78, 135.91-137.70, 145.99-147.78, and 147.99-149.78 GHz. Interpreting this null result via resonant conversion with a state-of-the-art star model and the dark-matter density expected at the Galactic Center, we constrain the axion-photon coupling at the level of $g_γ\gtrsim 2\times10^{-13}$ GeV$^{-1}$ within 0.55-0.62 meV, accessing for the first time the QCD axion parameter space near the meV scale.

Constraining meV Axion Dark Matter with ALMA Observations of the Galactic Center Magnetar SGR 1745-2900

Abstract

We report a mm-wave search for axions from the magnetar SGR 1745-2900, based on 4.8 h of ALMA observations. No statistically significant features are detected between 133.99-135.78, 135.91-137.70, 145.99-147.78, and 147.99-149.78 GHz. Interpreting this null result via resonant conversion with a state-of-the-art star model and the dark-matter density expected at the Galactic Center, we constrain the axion-photon coupling at the level of GeV within 0.55-0.62 meV, accessing for the first time the QCD axion parameter space near the meV scale.

Paper Structure

This paper contains 5 sections, 4 equations, 4 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Observations, data Reduction and analysis
  3. Results
  4. Conclusions
  5. Acknowledgements

Figures (4)

  • Figure 1: ALMA 2-mm continuum of the GC before (top) and after (bottom) Sgr A* subtraction; the cyan ellipse marks the synthesized beam at the astrometry position of SGR 1745--2900.
  • Figure 2: Top: raw ON–source spectrum toward SGR 1745–2900 (blue) and averaged OFF reference (orange), shown per spectral window (SPW; vertical dotted lines). Bottom: differenced spectrum, ON–$\langle$OFF$\rangle$ (purple), and its high–pass (hp) filtered version (green). Masked channels are marked in red with shaded regions indicating their extent.
  • Figure 3: Left: distribution of SNR across frequency after applying the matched–filter pipeline. Horizontal dashed lines indicate the zero level and the $3.5\sigma$ detection threshold (red). Right: histogram of SNR values for all accepted channels (black), compared to a rescaled Gaussian with mean $\mu$ and standard deviation $\sigma$ (red dashed).
  • Figure 4: 95% CL constraints on $g_{\gamma}$ from ALMA observations of SGR 1745–2900, shown for three NS configurations. The blue shaded area corresponds to a light star $(M_*,R_*,B_0) = (1.17\,\mathrm{M}_\odot,\,12.54\,{\rm km},\,8.4\times10^{14}\,{\rm G})$; the red area to the canonical NS $(1.40\,\mathrm{M}_\odot,\,12.59\,{\rm km},\,9.52\times10^{14}\,{\rm G})$; and the red filled region to a heavy model $(2.10\,\mathrm{M}_\odot,\,12.53\,{\rm km},\,1.14\times10^{15}\,{\rm G})$. For all three configurations we assume $P=3.76$ s Mori:2013yda, $v_0=236$ km s$^{-1}$Bower:2014tea, $\theta\simeq20^{\circ}$, $\theta_m \simeq 10^{\circ}$, $\varepsilon \approx 0.9$ and a Beloborodov magnetosphere with $\pazocal{M} \simeq 50$ and $\gamma_p \simeq 2$Beloborodov_2012Beloborodov_2013. The ambient axion density is $6\times10^8\,\mathrm{GeV\,cm^{-3}}$McMillan_20162018AA...619A..46L. Results are compared with CAST limits PhysRevLett.133.221005CAST:2017uph and globular–cluster bounds Ayala:2014pea2022JCAP...10..096D. The phenomenologically preferred axion window is shown in beige DiLuzio:2016sbl, together with benchmark QCD–axion models (KSVZ, DFSZ) PhysRevLett.43.103Shifman1980CanCEDINE1981199osti_7063072.