Letter to the Editor

A coincidence between a hydrocarbon plasma absorption spectrum and the λ5450 DIB

¹ Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands e-mail: wehres@strw.leidenuniv.nl
² Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
³ Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200B, 3000 Leuven, Belgium
⁴ Physics and Astronomy Department, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
⁵ National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 W. Saanich Road, Victoria, BC V9E 2E7, Canada
⁶ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁷ Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland

Received: 8 January 2010
Accepted: 4 February 2010

Abstract

Aims. The aim of this work is to link the broad λ5450 diffuse interstellar band (DIB) to a laboratory spectrum recorded through expanding acetylene plasma.

Methods. Cavity ring-down direct absorption spectra and astronomical observations of HD 183143 with the HERMES spectrograph on the Mercator Telescope on La Palma and the McKellar spectrograph on the DAO 1.2 m Telescope are compared.

Results. In the 543–547 nm region a broad band is measured with a band maximum at 545 nm and FWHM of 1.03(0.1) nm coinciding with a well-known diffuse interstellar band at λ5450 with an FWHM of 0.953 nm.

Conclusions. A coincidence is found between the laboratory and the two independent observational studies obtained at higher spectral resolution. This result is important, as a match between a laboratory spectrum and a – potentially lifetime broadened – DIB is found. A series of additional experiments were performed in order to unambiguously identify the laboratory carrier of this band, but this was not successful. The laboratory results, however, restrict the carrier to a molecular transient, consisting of carbon and hydrogen.