High-resolution spectra of comet C/2013 R1 (Lovejoy)

Context. High-resolution spectra of comets permit deriving the physical properties of the coma. In the optical range, relative production rates can be computed, and information about isotopic ratios and the origin of oxygen atoms can be obtained. <BR /> Aims: The main objective of the work presented here was to obtain information about the chemical composition of comet C/2013 R1 (Lovejoy), a bright and long-period comet that passed perihelion (0.81 au) on 22 December 2013. <BR /> Methods: We used the HARPS-North echelle spectrograph at the 3.5 m telescope TNG to obtain high-resolution spectra of comet C/2013 R1 (Lovejoy) in the optical range immediately after its perihelion passage during four consecutive nights in the period December 23 to 26, 2013. <BR /> Results: Our results demonstrate the ability of HARPS-North to efficiently obtain cometary spectra. Very faint emission lines, such as those of [SUP]15[/SUP]NH[SUB]2[/SUB], have been detected, leading to a rough estimate of the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio in NH[SUB]2[/SUB]. The [SUP]12[/SUP]C/[SUP]13[/SUP]C ratio was measured in the C[SUB]2[/SUB] lines and is equal to 80 ± 30. The oxygen lines were studied as well (green to red line intensity ratios and widths), confirming that H[SUB]2[/SUB]O is the main parent molecule that photodissociates to produce oxygen atoms. This suggests that this comet has a high CO[SUB]2[/SUB] abundance. Relative production rates for C[SUB]2[/SUB] and NH[SUB]2[/SUB] were computed, but we found no significant deviation from a typical NH[SUB]2[/SUB]/C[SUB]2[/SUB] ratio. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.