Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes

In this work, we present the results of an observational study of 2I/Borisov carried out with the 10.4-m Gran Telescopio Canarias (GTC) and the 3.6-m Telescopio Nazionale Galileo (TNG), both telescopes located at the Roque de Los Muchachos Observatory, in the island of La Palma (Spain). The study includes images in the visible and near-infrared, as well as visible spectra in the 3600-9200 Å wavelength range. N-body simulations were also performed to explore its orbital evolution and Galactic kinematic context. The comet's dust continuum and near-infrared colours are compatible with those observed for Solar system comets. From its visible spectrum on the nights of 2019 September 24 and 26, we measured CN gas production rates Q(CN) = (2.3 ± 0.4) × 1024 mol s-1 and Q(CN) = (9.5 ± 0.2) × 1024 mol s-1, respectively, in agreement with measurements reported by other authors on similar nights. We also obtained an upper limit for the C2 production rate of Q(C2) < (4.5 ± 0.1) × 1024 mol s-1. Dust modelling results indicate a moderate dust production rate of ∼50 kg s-1 at heliocentric distance rh = 2.6 au, with a differential power-law dust size distribution of index ∼-3.4, within the range reported for many comet comae. Our simulations show that the Galactic velocity of 2I/Borisov matches well that of known stars in the solar neighbourhood and also those of more distant regions of the Galactic disc. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
J. dL. and M. P. acknowledge financial support from the project ProID2017010112 under the Operational Programmes of the European Regional Development Fund and the European Social Fund of the Canary Islands (OP-ERDF-ESF), as well as the Canarian Agency for Research, Innovation and Information Society (ACIISI), and the project AYA2017-89090-P of the Spanish Ministerio de Econom´ıa y Competitividad’ (MINECO). C. dl F. M. and R. dl F. M. thank S. J. Aarseth for providing one of the codes used in this research and for comments on the implementation of non-gravitational forces in the calculations, and A. I. Gomez ´ de Castro for providing access to computing facilities. Part of the calculations and the data analysis were completed on the Brigit HPC server of the ‘Universidad Complutense de Madrid’ (UCM), and we thank S. Cano Alsua for his help during this ´ stage. This work was partially supported by the Spanish MINECO under grant ESP2017-87813-R. In preparation of this paper, we made use of the NASA Astrophysics Data System, the ASTROPH e-print server, the MPC data server, and the SIMBAD and VizieR databases operated at CDS, Strasbourg, France. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https: //www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement. L. M. L. acknowledges the financial support from the State Agency for Research of the Spanish MCIU through the Centro de Excelencia Severo Ochoa Program under grant SEV-2017-0709 and from the research project PGC2018-099425-B-I00. F. M. acknowledges financial support from the Spanish Plan Nacional de Astronomia y Astrofisica LEONIDAS project RTI2018-095330-B-100 and the Centro de Excelencia Severo Ochoa Program under grant SEV2017-0709. N. P. A. acknowledges funds through the SRI/FSI project ‘Digging-Up Ice Rocks in the Solar System’ and the Center for Lunar and Asteroid Surface Science funded by NASA’s SSERVI program at the University of Central Florida. M. D. P. acknowledges funding from the Prominent Postdoctoral Program of the University of Central Florida. A. C. S.-F. acknowledges CAPES (Coordenac¸ao de Aperfeic ˜ ¸oamento de Pessoal de N´ıvel Superior – Brasil) for financing, in part, this study (Finance Code 001). Based on observations made with the Gran Telescopio Canarias (GTC) and the Italian Telescopio Nazionale Galileo (TNG), both installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof´ısica de Canarias, in the island of La Palma. The TNG is operated by the Fundacion´ Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica). We thank E. Poretti for the allocation of Director’s Discretionary Time at TNG.