Absorption by carbon monoxide in the spectrum of quasar SDSS J000015.16+004833.2 is investigated in order to derive a constraint on the temporal variation of the proton-to-electron mass ratio , \mu .
The spectrum was recorded using VLT/UVES , and it was partially corrected for long-range wavelength scale distortions using the supercalibration technique .
Eight vibrational CO singlet-singlet bands belonging to the \textrm { A } ^ { 1 } \Pi - \textrm { X } ^ { 1 } \Sigma ^ { + } electronic absorption system , and the perturbing d ^ { 3 } \Delta - \textrm { X } ^ { 1 } \Sigma ^ { + } ( 5 , 0 ) singlet-triplet band are detected in the damped Lyman- \alpha system at z _ { \textrm { \scriptsize abs } } \simeq 2.52 .
The spectra are modelled using a comprehensive fitting technique , resulting in a final value of \Delta \mu / \mu = ( 1.8 \pm 2.2 _ { \textrm { \scriptsize { stat } } } \pm 0.4 _ { \textrm { % \scriptsize { syst } } } ) \times 10 ^ { -5 } , which is consistent with no variation over a look-back time of \sim 11.2 Gyrs .