Indications of Electron-to-Proton Mass Ratio Variations in the Galaxy. II. 3 mm Methanol Lines Toward Sgr B2(N) and (M)

Differential measurements of the fundamental constant $$\mu = {{m}_{e}}{\text{/}}{{m}_{p}}$$ (the electron-to-proton mass ratio) for two sources near the Galactic Center—the Sgr B2(N) and B2(M) molecular clouds—suggest that $$\mu $$ is lower in these clouds than its laboratory value. Based on observations of methanol (CH 3 OH) emission lines in the 80–112 GHz range (data from the IRAM 30-m telescope), a weighted mean value $$\langle \Delta \mu {\text{/}}\mu \rangle $$ $$ \equiv $$ $$\langle ({{\mu }_{{{\text{obs}}}}} - {{\mu }_{{{\text{lab}}}}}){\text{/}}{{\mu }_{{{\text{lab}}}}}\rangle = ( - 2.1 \pm 0.6) \times {{10}^{{ - 7}}}$$ ( $$1\sigma $$ ) was obtained for Sgr B2(N) at the sample size $$n = 9$$ . This value of $$\Delta \mu {\text{/}}\mu $$ has the same sign as the result of recent measurements of methanol lines in the higher frequency range of 542–543 GHz (data from the Herschel space telescope) for Sgr B2(N): $$\langle \Delta \mu {\text{/}}\mu \rangle = ( - 4.2 \pm 0.7) \times {{10}^{{ - 7}}}$$ (sample size $$n = 2$$ ).