THE OUTFLOWING WIND OF V1057 CYGNI
- Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States), E-mail: herbig@ifa.hawaii.edu
In 1970-1971, V1057 Cyg rose from about m {sub pg} {approx} 16 to a peak near 10.5 mag. It has subsequently faded to about B = 15, and although it appeared to be a T Tauri star (TTS) before the outburst, it now resembles a rather peculiar rapidly rotating G-type supergiant. Before the outburst, it showed unmistakable evidence of high-velocity outflow (by the suppression of emission Ca II {lambda}3968 by the P Cyg absorption component of H{epsilon} {lambda}3970). Such outflow absorptions are currently found at many strong lines (H{alpha}, Na I D{sub 1,2}, K I {lambda}{lambda}7664, 7698, Ca II {lambda}{lambda}8498, 8662, ...). The same phenomenon has since been observed in a number of other FUors near maximum light, suggesting that it is a FUor characteristic that clearly differs from the outflows found in TTSs. The Li I resonance line at 6707 A is relatively weak, and on high-resolution spectra obtained between 1997 and 2008 showed variable absorption structure on its shortward side that probably represents wind structure that is lost in the stronger lines. In addition, a narrow emission line at 6707 A persists throughout the series and is the counterpart of the sharp emission lines that occur near the centers of many of the broad stellar absorption lines (v sin i = 55 km s{sup -1}) and that were responsible for the line-splitting phenomenon formerly regarded as evidence of a Keplerian disk. Given the evidence of a quasi-permanent outflow at V1057 Cyg, the hypothesis is advanced that a FUor outburst may be the result of a rapidly rotating TTS having contracted to a point of rotational instability, at which time it sheds enough material and angular momentum to resume contraction, until the next such event.
- OSTI ID:
- 21255674
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 138, Issue 2; Other Information: DOI: 10.1088/0004-6256/138/2/448; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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