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

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3. Results

Fig. 1 shows the images of HD 97300 obtained in the four CAM narrow-band filters centered at 6.0 µm (lw4), 6.8 µm (lw5), 11.3 µm (lw8) and 14.9 µm (lw9). The morphology of the object is very similar in the four filters: we can see extended emission centered on the star and an elliptical ring of size [FORMULA] around it. This same morphology is also seen in the CVF images at all frequencies, with very similar characteristics.

[FIGURE] Fig. 1. Logarithmic grey scale images of HD 97300 of the four narrow-band filters. The images are re-sampled to [FORMULA] pixel scale. The numbers in the lw5 image indicate the positions of the CVF spectra shown in Fig. 2. The full line in the lw8 image at P.A. =[FORMULA] gives the direction along which the intensity profiles have been measured (see Fig. 4).

The ring is not symmetric around the star, but is much more extended in the SE than in the NW direction. The position of the star in our images coincides with the emission peaks seen near the center in lw4 and lw5, and with the secondary peak of the emission seen in lw8, roughly at the same position. In the lw8 and lw9 filters we detect a second peak of emission, about [FORMULA] north of the star.

Fig. 2 shows CVF spectra between 5.8 and 13.8 µm in 8 positions roughly aligned along P.A. = [FORMULA]. This line intersects the star, as well as the emission minimum and the ring seen in the SE direction. The location of the 8 positions is indicated in Fig. 1. In all positions, we detect strong IEBs over a weak continuum. This confirms the results of Prusti et al. (1994) who found that their mid IR multi-aperture photometry was consistent with extended emission from non-thermally heated species.

[FIGURE] Fig. 2. CVF spectra of HD 97300 in the 8 positions shown in Fig. 1. Position 4 is closest to the star; Position 6 coincides roughly with the minimum of emission seen in the images; position 7 with the ring. The background emission has been measured in the upper-left corner of the imaged area. Each spectrum has been measured over a single pixel, i.e., over an area of [FORMULA]. The uncertainties are typically smaller than a few %. Data are shown by diamonds and the best-fit models by the full lines.

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© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998