Nature of NML Cygnus
We suggest that H II region observed near NML Cygnus, a highly evolved mass-losing giant, results from the photoionization of the outflow by the luminous, hot stars in the Cyg OB2 association. NML Cyg is at a projected distance of 100 pc from Cyg OB2, but because all of these objects are near the center of the X-ray emitting superbubble in Cygnus where the hydrogen is mostly ionized, the Lyman continuum photons probably can travel this far without appreciable absorption. The observed structure of the H II region matches this hypothesis quite well. This picture provides the first reasonably precise estimate of the distance to NML Cyg: 2 kpc. At this distance, the star has a luminosity of 5 x 10/sup 5/ L/sub sun/ and a minimum mass loss rate of 6.4 x 10/sup -5/ M/sub sun/ yr/sup -1/. We conclude that NML Cyg is a massive (50 M/sub sun/) star in a highly evolved state. It is likely that it will soon become a supernova and contribute to the general expansion of the superbubble. Before doing so, however, it may endure a phase as a W-R star. If it remains a mass-losing supergiant when it does explode, there may be enough dust around it that it would be optically inconspicuous even if interstellar extinction were negligible. The possiblity that infrared supernovae are common would be very important for understanding the rate of stellar explosions, the formation of pulsars, and nucleosynthesis in the Galaxy.
- Research Organization:
- Department of Astronomy, UCLA. Department of Astronomy, Columbia University
- OSTI ID:
- 5838284
- Journal Information:
- Astrophys. J.; (United States), Vol. 267:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
THE PROTOPLANETARY DISKS IN THE NEARBY MASSIVE STAR-FORMING REGION CYGNUS OB2
OPTICAL PHOTOMETRIC GTC/OSIRIS OBSERVATIONS OF THE YOUNG MASSIVE ASSOCIATION CYGNUS OB2