G. J. Ferland, J. Tomkin and J. H. Woodman, Department of Astronomy, University of Texas at Austin, write: "Low-noise, 0.8-A-resolution, time-resolved (10 min) observations of [O III] 4959 A and 5007 A in V1500 Cyg were obtained during Aug. 21-23 with a Reticon at the coude focus of the McDonald Observatory's 270-cm telescope. A 90-min set of observations shows no profile variations greater than 5 percent. Subsequent H-beta wide-filter observations (whose flux is dominated by [O III] with H-beta making a moderate contribution) show the intensity of the emission line to be constant to 2 percent. Photometric observations with a y filter (which our spectroscopic observation shows to be clear of emission lines) on the 76-cm telescope reveal variations of 0.4 magnitude, indicating that the continuum is the source of the photometric activity reported by other observers. Future photometry should strive to avoid the constant emission lines (the strongest being [O III] 4959 A and 5007 A and [N II] 6548 A and 6584 A) and concentrate on the continuum. The U filter is fairly clear of strong emission (O III, [Ne III] and [Ne V] contributing weakly). Another excellent bandpass would be a blue-sensitive photocathode (1P21 or bialkaline) combined with a blue-cutoff (cutoff past 5100 A) filter." Selected recent visual magnitude estimates: July 20.88 UT, 11.9 (R. Lukas, Wilhelm Foerster Observatory); 28.89, 12.0 (Lukas); Aug. 4.19, 11.6 (S. O'Meara, Harvard College Observatory); 11.23, 11.7 (O'Meara); 19.82, 12.2 (Lukas); 26.21, 11.7 (O'Meara).
International Astronomical Union Circular
- Pub Date:
- September 1976