Is HS 240 an interstellar bubble ?
Abstract
We present radio, optical, and infrared observations of the galactic H II region HS 240 = S 119 round the O 7.5V star 68 Cyg. No evidence is found that the extended nebular structure ma y have formed under the action of a strong stellar wind. The measured emission line strengths are typical for a low-excitation nebula. The electron temperature, derived from optical line widths, is (7500 +/- 1000)K. The large scale emission measure distribution is rather uniform, with an average electron density of ~ 2 cm^-3^. There are indications that at least part of the gas is concentrated in small clumps of densities not higher than ~ 100 cm^-3^. The measured dust colour temperature is 41 K averaged over the whole H II region. The infrared emission distribution - not ring-like but centered on the star - demonstrates that the inner region is not a wind-blown cavity. We show that due to the high peculiar velocity of 68 Cyg the wind front may not reach further than ~ 1 pc from the star, i.e. less than 5% of the radius of the H II region, and a bow shock instead of a bubble is created. We present high-resolution IRAS data where this bow shock is indeed visible.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1989
- Bibcode:
- 1989A&A...221..311W
- Keywords:
-
- Astronomical Spectroscopy;
- H Ii Regions;
- Interstellar Matter;
- O Stars;
- Stellar Winds;
- Cosmic Dust;
- Electron Density (Concentration);
- Emission Spectra;
- Infrared Astronomy Satellite;
- Spectral Line Width;
- Astrophysics