Volume 634, February 2020
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||31 January 2020|
Letter to the Editor
Searching for water ice in the coma of interstellar object 2I/Borisov⋆
European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
2 Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA
3 Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
4 Southwest Research Institute, Boulder, CO 80302, USA
Accepted: 10 December 2019
Aims. Interstellar objects passing through our Solar System offer a rare opportunity to probe the physical and chemical processes involved in solid body and planet formation in extrasolar systems. The main objective of our study is to search for diagnostic absorption features of water ice in the near-infrared (NIR) spectrum of the second interstellar object 2I/2019 Q4 (Borisov) and compare its ice features to those of the Solar System icy objects.
Methods. We observed 2I in the NIR on three separate occasions. The first observation was made on 2019 September 19 UT using the SpeX spectrograph at the 3m IRTF and again on September 24 UT with the GNIRS spectrograph at the 8m GEMINI telescope; the last observation was made on October 09 UT with IRTF.
Results. The spectra obtained from all three nights appear featureless. No absorption features associated with water ice are detected. Spectral modeling suggests that water grains, if present, comprise no more than 10% of the coma cross section. The comet consistently exhibits a red D-type like spectrum with a spectral slope of about 6% per 1000 Å, which is similar to that of 1I/’Oumuamua and is comparable to Solar System comets.
Key words: techniques: spectroscopic / comets: individual: 2I/Borisov
The spectra are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/634/L6
© ESO 2020
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