Circumstellar gas and dust in 68 Ophiuchi (A0 IVe).
Waters, L. B. F. M.; Grady, C. A.; The, P. S.; van den Ancker, M. E.; Sandell, G.; van der Bliek, N. S.; Geballe, T. R.; Baas, F.; Van Winckel, H.; Oudmaijer, R. D.; Kester, D. J. M.; Bontekoe, T. R.; Vega, R.
Abstract
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 β 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 25μm by IRAS, but the data show no strong evidence for thermal emission from cool circumstellar dust grains. Observations at 450μm and 800μm 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 Hα and Brα. The Ca II λ 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.