Circumstellar gas and dust in 68-ophiuchi (a0-ive)
Waters, L Vandenancker, Me Baas, F Vanderbliek, Ns Bontekoe, Tr Geballe, Tr Grady, Ca Kester, Djm Oudmaijer, Rd Sandell, G The, Ps Vega, R Van Winckel, Hans #
Astronomy and astrophysics vol:299 issue:1 pages:173-178
We present photometry and spectroscopy of the A0IVe star 68 Ophiuchi, for which Vidal-Madjar et al. (1993) suspected the presence of a circumstellar disc of material similar to that found around beta Pic. The UV and optical continuum agrees well with a Kurucz model with parameters that are consistent with the spectral type. 68 Oph is detected at 12 and 25 mu m by IRAS, but the data show no strong evidence for thermal emission from cool circumstellar dust grains. Observations at 450 mu m and 800 mu m also indicate that there is no strong dust component. Intermediate and high resolution optical and near-IR spectra of 68 Oph confirm that the star is surrounded by a gaseous disc, seen in H alpha and Br alpha. The Ca II lambda 3933.7 line shows a broad photospheric absorption line with two narrow, blue-shifted absorption lines near line centre, one of which is also found in Na I. These absorption lines are probably of interstellar origin. We conclude that 68 Oph does not show properties observed in other proto-planetary sytems, such as red-shifted absorption features in spectral lines and a strong dust continuum.