The 16OH/18OH and OD/OH isotope ratios in comet C/2002 T7 (LINEAR)

The [SUP]16[/SUP]OH/[SUP]18[/SUP]OH and OD/OH isotope ratios are measured in the Oort-Cloud comet C/2002 T7 (LINEAR) through ground-based observations of the OH A [SUP]2[/SUP]Σ[SUP]+[/SUP] - X [SUP]2[/SUP]Π[SUB]i[/SUB] ultraviolet bands at 3063 à (0, 0) and 3121 à (1, 1) obtained with the Very Large Telescope (VLT) feeding the Ultraviolet-Visual Echelle Spectrograph (UVES). From the [SUP]16[/SUP]OH/[SUP]18[/SUP]OH ratio, we find [SUP]16[/SUP]O/[SUP]18[/SUP]O = 425 ± 55, equal within the uncertainties to the terrestrial value and to the ratio measured in other comets, although marginally smaller. We also estimate OD/OH from which we derive D/H = 2.5 ± 0.7à 10[SUP]-4[/SUP] in water. This value is compatible with the water D/H ratios evaluated in other comets and is marginally higher than the terrestrial value. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programme 073.C-0525).