Detection of doubly-deuterated methanol in the solar-type protostar IRAS 16293-2422 [Letter]

Parise, Berengere, Ceccarelli, C., Tielens, A. G. G. M., Herbst, E., Lefloch, B., Caux, E., Castets, A., Mukhopadhyay, I., Pagani, L. and Loinard, L. 2002. Detection of doubly-deuterated methanol in the solar-type protostar IRAS 16293-2422 [Letter]. Astronomy and Astrophysics 393 (3) , L49-L53. 10.1051/0004-6361:20021131

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Abstract

We report the first detection of doubly-deuterated methanol (CHD 2OH), as well as firm detections of the two singly-deuterated isotopomers of methanol (CH 2DOH and CH 3OD), towards the solar-type protostar IRAS 16293-2422. From the present multifrequency observations, we derive the following abundance ratios: $\rm [CHD_2OH]/[CH_3OH] = 0.2 \pm 0.1$, $\rm [CH_2DOH]/[CH_3OH] = 0.9 \pm 0.3$ , $\rm [CH_3OD]/[CH_3OH] = 0.04 \pm 0.02$. The total abundance of the deuterated forms of methanol is greater than that of its normal hydrogenated counterpart in the circumstellar material of IRAS 16293-2422, a circumstance not previously encountered. Formaldehyde, which is thought to be the chemical precursor of methanol, possesses a much lower fraction of deuterated isotopomers (~20%) with respect to the main isotopic form in IRAS 16293-2422. The observed fractionation of methanol and formaldehyde provides a severe challenge to both gas-phase and grain-surface models of deuteration. Two examples of the latter model are roughly in agreement with our observations of CHD 2OH and CH 2DOH if the accreting gas has a large (0.2-0.3) atomic D/H ratio. However, no gas-phase model predicts such a high atomic D/H ratio, and hence some key ingredient seems to be missing.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Uncontrolled Keywords:	ISM: abundances; ISM: molecules; stars: formation; ISM: individual: IRAS 16293-2422
Additional Information:	Pdf uploaded in accordance with publisher's policy at http://www.sherpa.ac.uk/romeo/issn/0004-6361/ (accessed 17/04/2014)
Publisher:	EDP Sciences
ISSN:	0004-6361
Date of First Compliant Deposit:	30 March 2016
Last Modified:	15 May 2023 01:09
URI:	https://orca.cardiff.ac.uk/id/eprint/52836

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