Spectrum of the OH triplet at 2514 GHz. The absorption feature at ν<−60 km s^-1 is the blue-shifted wing of the second triplet at 2509 GHz observed in the lower sideband of the receiver. The red solid line represents the best fit and it is given by the sum of the spectra of all velocity components used in Sect. 4.2; green, blue, and cyan lines are the synthetic spectra of the absorption features at –13.2 km s^-1, +7.3 km s^-1, and +20.2 km s^-1, respectively; the two grey lines represent the spectra of the emission components at +34.3 km s^-1 and 55.1 km s^-1.