Abstract.We report the detection of the 405 nm band of interstellar C3 in absorption toward HD 210121. The abundance of triatomic carbon is approximately 1/17 of that of diatomic carbon in the same diffuse molecular cloud. Rotational levels of C3 up to J = 14 are seen in this cloud. The rotational excitation of C3 in the interstellar medium may reflect a competition between inelastic collisions, formation and destruction of the molecule, and radiative pumping in the far-infrared. The abundance of C3 is compared with chemical models. Attention is called to molecular properties that need to be better determined.

Abstract.To investigate the presence of small scale structure in the spatial distribution of H 2 molecules we have undertaken repeated FUSE UV observations of the runaway O9.5V star, HD 34078. In this paper we present five spectra obtained between January 2000 and October 2002. These observations reveal an unexpectedly large amount of highly excited H 2 . Column densities for H 2 levels from (v = 0, J = 0) up to (v = 0, J = 11) and for several v = 1 and v = 2 levels are determined. These results are interpreted in the frame of a model involving essentially two components: i) a foreground cloud (unaffected by HD 34078) responsible for the H 2 (J = 0, 1), CI, CH, CH + and CO absorptions; ii) a dense layer of gas (n 10 4 cm −3 ) close to the O star and strongly illuminated by its UV flux which accounts for the presence of highly excited H 2 . Our model successfully reproduces the H 2 excitation, the CI fine-structure level populations as well as the CH, CH + and CO column densities. We also examine the time variability of H 2 absorption lines tracing each of these two components. From the stability of the J = 0, 1 and 2 damped H 2 profiles we infer a 3σ upper limit on column density variations ∆N(H 2 )/N(H 2 ) of 5% over scales ranging from 5 to 50 AU. This result clearly rules out any pronounced ubiquitous small scale density structure of the kind apparently seen in HI. The lines from highly excited gas are also quite stable (equivalent to ∆N/N ≤ 30%) indicating i) that the ambient gas through which HD 34078 is moving is relatively uniform and ii) that the gas flow along the shocked layer is not subject to marked instabilities.

We present data from high-dispersion echelle spectra and simultaneous uvby photometry for γ Doradus. These data were obtained from several sites during 1994 November as part of the MUSICOS-94 campaign. The star has two closely-spaced periods of about 0.75 d and is the brightest member of a new class of variable early F-type stars. A previously suspected third period, very close to the other two, is confirmed. Previous observations indicated that sudden changes could be expected in the spectrum, but none were found during the campaign. The radial velocities rule out the possibility of a close companion. The phasing between the radial velocity and light curve of the strongest periodic component rules out the starspot model. The only viable mechanism for understanding the variability is nonradial pulsation. We used the method of moments to identify the modes of pulsation of the three periodic components. These appear to be sectorial retrograde modes with spherical harmonic degrees, (ℓ, m), as follows: f 1 = (3,3), f 2 = (1,1) and f 4 = (1,1). The angle of inclination of the star is found to be i ≈ 70 • .

Abstract. As part of our efforts to unveil extragalactic large-scale structures behind the southern Milky Way, we here present redshifts for 764 galaxies in the Hydra/Antlia, Crux and Great Attractor region (266 . A total of 947 galaxies have been observed, a small percentage of the spectra (N = 109, 11.5%) were contaminated by foreground stars, and 74 galaxies (7.8%) were too faint to allow a reliable redshift determination. With MEFOS we obtained spectra down to the faintest galaxies of our optical galaxy survey, and hence probe large-scale structures out to larger distances (v < ∼ 30 000 km s −1 ) than our other redshift follow-ups using the 1.9-m telescope at the South African Astronomical Observatory (Kraan-Korteweg et al. 1995;Fairall et al. 1998;Woudt et al. 1999) and the 64-m Parkes radio telescope (Kraan-Korteweg et al. 2002). The most distinct large-scale structures revealed in the southern Zone of Avoidance are discussed in context to known structures adjacent to the Milky Way.