First Detection of Micro-Structures in O Star Winds (The Last Run with the Reticon)

T. Eversberg, S. Lépine and A.F.J. Moffat, Département de Physique, Université de Montréal.

Background and Observations

Blobs are well established in the winds of Wolf-Rayet stars (Moffat & Robert, 1992) and are believed to represent supersonic, compressible turbulence (Henriksen 1994) driven by radiative instabilities (Owocki 1994). In O star winds only indirect evidence has been found so far, e.g., via Einstein X-ray observations (Chlebowski et al. 1989). The apparently brightest O-star in the sky, Puppis, happens also to be Of, i.e. it has a relatively strong wind. It is an obvious first target for search of blobs in the winds of OB-stars, if they should exist. We observed Pup at the f/8.2 Coudé focus during the two nights of 10/11 and 12/13 December 1995. Using the red Coudé train and image slicer, the 1800 l/mm holographic grating and the Reticon 1872 array as a detector, we obtained a S/N 1000/0.03 Å pixel in 10 minutes on a total range of 60 Å centered on HeII 4686 Å. The Reticon 1872 detector has been decomissioned after this run. The data reduction was carried out using IRAF with a Reticon reduction package developed by D. Bohlender and G. Hill, which includes the baseline reduction, flatfielding, heliocentric correction and wavelength calibration with a Thorium-Argon comparison spectrum. The FWHM of the Th-Ar lines covers ~2 pixels and the wavelength shift over the night is negligibly small.

Results

The wind of Puppis shows spectral substructures (Fig. 1, and Eversberg, Lépine, Moffat 1996, henceforth ELM) similar to those seen in the winds of Wolf-Rayet stars, which are the likely descendents of Of stars. These substructures are likely the consequence of excess emission from clumps in the wind. We note the following:

Acknowledgements

The authors would like to thank Dr. Grant Hill for making available the Reticon Reduction Package. T.E. is grateful for full financial aid from the Ev. Studienwerk/Germany which is supported by the German Government. S.L. acknowledges support from NSERC (Canada) for a doctoral scholarship. A.F.J.M. thanks NSERC and FCAR (Quebec) for financial assistance.

References

Chlebowski, T., Harnder, F.R., Sciortino, S., 1989, ApJ, 341, 427

Eversberg, T., Lépine, S., Moffat, A.F.J., 1996 (ELM), in: ``WR Stars in the Framework of Stellar Evolution'', 33rd Liège Int. Astroph. Coll., 1996

Henriksen, R.N., 1994, ApSpSc, 221, 25

Kudritzki, R.-P., Simon, K.P., Hamann, W.-R., 1983, A&A, 118, 245

Moffat, A.F.J., Michaud, G., 1981, ApJ, 251, 133

Moffat, A.F.J., Robert, C., 1992, in: "Nonisotropic and Variable Outflows from Stars", A.S.P. Conference Series, Vol.22, eds. L. Drissen, C. Leitherer & A. Nota, p.203

Owocki, S.P., 1994, ApSpSc, 221, 3

Puls, J., Kudritzki, R.-P., Herrero, A., Pauldrach, A.W.A., Haser, S.M., Lennon, D.J., Gabler, R., Voels, S.A., Vilchez, J.M., Wachter, S., Feldmeier, A., 1995, A&A, in press

Robert, C., 1992, Ph.D. Thesis, Département de Physique, Université de Montréal





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