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We present results on simultaneous observations of Class I methanol masers at 25, 36, and 44 GHz towards 22 Galactic targets carried out with the Effelsberg 100-m telescope. The study investigates relations between the hyperfine (HF) structure of the torsion–rotation transitions in CH |$_3$| OH and maser activity. By analysing the radial velocity shifts between different maser lines together with the patterns of the HF structure based on laboratory measurements and quantum-chemical calculations, we find that in any source only one specific HF transition forms the maser emission and that this transition changes from source to source. The physical conditions leading to this selective behaviour are still unclear. Using accurate laboratory rest frequencies for the 25 GHz transitions, we have refined the centre frequencies for the HF multiplets at 36, 44, and 95 GHz: |$f_{\scriptscriptstyle 36} = (36169.2488\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz. |$f_{\scriptscriptstyle 44} = (44069.4176\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz, and |$f_{\scriptscriptstyle 95} = (95169.4414\pm 0.0003_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz. Comparison with previous observations of 44 GHz masers performed 6–10 yr ago with a Korean 21-m Korean Very Long Baseline Interferometry Network telescope towards the same targets confirms the kinematic stability of Class I maser line profiles during this time interval and reveals a systematic radial velocity shift of |$0.013\pm 0.005$|  km s |$^{-1}$| between the two telescopes. [ABSTRACT FROM AUTHOR]

We intend to use stellar models with and without α-enhancement, as well as asteroseismic analysis, to study two α-enhanced stars, KIC 7976303 and KIC 8694723. For the α-enhanced models, we adopt [α/Fe] = 0.2 and 0.4. For the evolved subgiant KIC 7976303 with mixed modes, the α-enhanced models fit the observations better than the models without α-enhancement, and point to a star with M = 1.20 ± 0.02M⊙, t = 4.88 ± 0.08Gyr, R = 2.04 ± 0.01 R⊙ and L = 5.07 ± 0.05 L⊙. For the post turn-off star KIC 8694723, we find that the models fit the observations well in all three cases ([α/Fe] = 0.0, 0.2 and 0.4). According to the observed metal abundances, only α-enhanced models are used to estimate the stellar parameters, which are M = 1.13 ± 0.06M⊙, t = 5.47 ± 0.43Gyr, R = 1.55 ± 0.13 R⊙ and L = 3.18 ± 0.26 L⊙. Our α-enhanced models indicate that KIC 7976303 has a larger mass and younger age than in previous works based on standard models. Furthermore, the differences of estimated mass and age between the three cases are~0.1M⊙ and ~0.5-1.3Gyr. These results suggest that we include α-enhancement in the modelling of α-enhanced stars, such as members of globular clusters and metal-poor stars in the disc and in the halo. [ABSTRACT FROM AUTHOR]