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Optical spectroscopy of comets using Hanle Echelle Spectrograph (HESP)

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dc.contributor.author Aravind, K
dc.contributor.author Venkataramani, Kumar
dc.contributor.author Ganesh, Shashikiran
dc.contributor.author Surya, Arun
dc.contributor.author Sivarani, T
dc.contributor.author Sahu, D. K
dc.contributor.author Unni, Athira
dc.contributor.author Bhardwaj, Anil
dc.date.accessioned 2024-06-21T08:15:51Z
dc.date.available 2024-06-21T08:15:51Z
dc.date.issued 2024-05
dc.identifier.citation Monthly Notices of the Royal Astronomical Society, Vol. 530, No. 1, pp. 393–404 en_US
dc.identifier.issn 0035-8711
dc.identifier.uri http://hdl.handle.net/2248/8487
dc.description Open Access. en_US
dc.description This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
dc.description.abstract Observing the vibrational/rotational lines in a comet’s optical spectrum requires high-resolution spectroscopy, as they are otherwise seen as a blended feature. To achieve this, we have obtained medium and high-resolution (R (λ/λ) = 30 000 and 60 000) spectra of several comets, including C/2015 V2 (Johnson), 46P/Wirtanen, 41P/Tuttle–Giacobini–Kresak, ´ and 38P/Stephan–Oterma, using the Hanle Echelle Spectrograph (HESP) mounted on the 2-m Himalayan Chandra Telescope (HCT) in India. The spectra effectively cover the wavelength range 3700–10 000 Å, allowing us to probe the various vibrational bands and band sequences to identify the rotational lines in the cometary molecular emission. We were also able to separate the cometary Oxygen lines from the telluric lines and analyse the green-to-red (G/R) forbidden oxygen [O I] ratios in a few comets. For comets C/2015 V2, 46P, and 41P, the computed G/R ratios, 0.04 ± 0.01, 0.04 ± 0.01, and 0.08 ± 0.02, respectively, point to H2O being a major source of Oxygen emissions. Notably, in the second fibre pointing at a location 1000 km away from the photocentre of comet 46P, the G/R ratio reduced by more than half the value observed in the first fibre, indicating the effects of quenching within the inner coma. We also measured the NH2 ortho-to-para ratio of comet 46P to be about 3.41 ± 0.05 and derived an ammonia ratio of 1.21 ± 0.03 corresponding to a spin temperature of ∼26 K. With these, we present the results of the study of four comets from different cometary reservoirs using medium and high-resolution optical spectroscopy, emphasizing the capabilities of the instrument for future cometary studies. en_US
dc.language.iso en en_US
dc.publisher Oxford University Press on behalf of Royal Astronomical Society en_US
dc.relation.uri https://doi.org/10.1093/mnras/stae666
dc.rights © 2024 The Author(s).
dc.subject Methods: observational en_US
dc.subject Techniques: spectroscopic en_US
dc.subject Comets: general en_US
dc.title Optical spectroscopy of comets using Hanle Echelle Spectrograph (HESP) en_US
dc.type Article en_US


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