<p><strong>Abstract</strong></p>
<p>During the journey through the solar system, interstellar comet 2I/Borisov has been observed spectroscopically by most of the largest telescopes on Earth, enabling comparative studies of its chemical composition versus solar system comets. Already a few weeks after the discovery, the detection of the CN (0-0 band) in the coma has been reported [1]. Subsequent detections of C<sub>2</sub> suggested a significant depletion of this molecule [2,3], however, later evolution of C<sub>2</sub> placed it close to the typical values [4]. Pre-discovery images of 2I/Borisov showing this object to be active when far away from the sun indicated that its activity is driven by low-temperature volatiles, later confirmed by the detection of a high abundance of CO [5,6]. High abundance was also reported for NH<sub>2</sub> [4]. The water production rates derived from the detection of [OI] 6300 A line [7] were consistent with SWIFT/UVOT observations [8].</p>
<p>Here we report our spectroscopic observations of 2I/Borisov from VLT X-Shooter. We collected over 10 hours of data on UT 2020 January 28th, 30th, and 31st obtaining the deep spectrum of this object taken around the time of its maximum brightness. The spectrum covers an unprecedented wavelength range of 300 - 2500 nm that comprises numerous characteristic cometary emissions. The excellent sensitivity of the spectrum, combined with the decent spectral resolution provided by X-Shooter over the entire, enormous wavelength range makes the collected material unique.</p>
<p><br /><strong>Acknowledgements</strong></p>
<p>Authors are grateful for support from the National Science Centre of Poland through SONATA BIS grant number 2016/22/E/ST9/00109 to M.D.</p>
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<p><strong>References</strong></p>
<p>[1] Fitzsimmons, A., Hainaut, O., Meech, K. et al.: Detection of CN Gas in Interstellar Object 2I/Borisov, ApJL, Vol. 885, L9, (2019)<br />[2] Kareta, T., Andrews, J., Noonan, J. et al.: Carbon Chain Depletion of 2I/Borisov, ApJL, Vol. 889, L38, (2020)<br />[3] Lin, H., Lee, C., Gerdes, D. et al.: Detection of Diatomic Carbon in 2I/Borisov, ApJL, Vol. 889, L30, (2020)<br />[4] Bannister, M., Opitom, C., Fitzsimmons, A. et al.: Interstellar comet 2I/Borisov as seen by MUSE: C<sub>2</sub><sub>,</sub> NH<sub>2</sub> and red CN detections, https://arxiv.org/abs/2001.11605, (2020)<br />[5] Bodewits, D., Noonan, J., Feldman, P. et al.: The carbon monoxide-rich interstellar comet 2I/Borisov, NatAst, (in press)<br />[6] Cordiner, M., Milam, S., Biver, N. et al.: Unusually high CO abundance of the first active interstellar comet, NatAst, (in press)<br />[7] McKay, A., Cochran, A., Dello Russo, N. et al.: Detection of a Water Tracer in Interstellar Comet 2I/Borisov, ApJL, Vol. 889, L10, (2020)<br />[8] Xing, Z., Bodewits, D, Noonan, J. et al.: Water Production Rates and Activity of Interstellar Comet 2I/Borisov, ApJL, Vol. 893, L48, (2020)</p>
Interpretation of heliocentric water production rates of comets