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Astron. Astrophys. 339, 134-140 (1998)

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A ring of organic molecules around HD 97300 *

R. Siebenmorgen 1, A. Natta 2, E. Krügel 3 and T. Prusti 1

1 ISO Science Operations Centre, Astrophysics Division of ESA, Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid, Spain
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
3 MPIfR, Auf dem Hügel, D-5300 Bonn, Germany

Received 27 April 1998 / Accepted 8 July 1998


This paper presents spectro-photometric images of the pre-main-sequence Herbig AeBe star HD 97300 in the mid-IR obtained with ISOCAM on board of ISO. The images show extended emission, an elliptical ring structure of size about 0.045[FORMULA]0.03 pc as well as two peaks of emission, separated by about [FORMULA] (240 AU). One of the two peaks coincides with the position of HD 97300, while the other may be an embedded companion. The data show that the emission in this region is dominated by the infrared emission bands centered at 6.2, 7.7, 8.7, 11.3 and 12.5 µm, with a very small contribution from continuum emission at longer wavelengths. We fit the spectra with a dust model including organic molecules such as polycyclic aromatic hydrocarbons, very small graphite and very small silicates, as well as large grains. The fit to the ISOCAM data is very good if one applies a classical oscillator model for the infrared emission bands. Our fitting procedure allows us to estimate the total mass of the ring, which is [FORMULA]0.03[FORMULA]. Its possible origin is briefly discussed.

Key words: circumstellar matter – star: formation – stars: individual: HD 97300 – stars: pre-main sequence – infrared: ISM: lines and bands

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) with the participation of ISAS and NASA.

Send offprint requests to: rsiebenm@iso.vilspa.esa.es

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© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998