Other
Scientific paper
Nov 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997pasp..109.1285e&link_type=abstract
Publications of the Astronomical Society of the Pacific, v.109, p.1285
Other
2
Scientific paper
This study deals with the relationship between the absolute visual magnitude at maximum and the rate of decline (MMRD or M_v -- t_3) for classical novae. Considering the most reliable data including the nebular expansion parallax method for 24 galactic novae, we find that there are two distinct kinds of galactic novae. Slopes of very fast and fast novae were found from a least-squares fit to their MMRD relation. The values of these two slope angles are similar. A similar result was found for moderately fast and slow novae, whose mean slopes differ by only a small amount. Therefore very fast novae can be grouped with fast novae, and moderately fast novae can be grouped with slow novae, so that we have only two separate novae groups. These two groups of novae are distinguished from each other by the Eddington luminosity. Our conclusions agree well with those of Duerbeck (1981, PASP, 93, 165), based on the light curves of approximately 100 galactic novae. Considering numerical nova model calculations (Livio 1992, ApJ, 393, 516), it seems that there is a good agreement between the observed and the theoretical MMRD relation. Moreover, we applied the same classification method to novae in M31 (Massimo and Livio, 1995, ApJ, 452, 704), and found the same two separate groups. We also determined expansion parallaxes for QZ Aur, V1974 Cyg, FH Ser, XX Tau, RW UMi, and QU Vul, and expansion velocities for Nova Aql 1995, V1974 Cyg and FH Ser. These results were found from H-alpha imaging and spectroscopic observations made by the author and A.Bianchini and T.Iijima (University of Padova), using the 1.82- and 1.22-m telescopes at the Ekar and Asiago Observatories. When we compare our images with those in the literature, we can obtain expansion parallaxes for QU Vul, QZ Aur, V1974 Cyg, and RW UMi. Shell diameters in the light of H-alpha for QU Vul, QZ Aur, V1974 Cyg and RW UMi were found to be 0.82, 0.83, 0.76 and 2.94 arcsec, respectively (epoch 1994-5). The literature gives nebular expansion parallaxes for 22 galactic novae. To these we can now add expansion parallaxes for QZ Aur and QU Vul, thus increasing the number to 24. Two high-dispersion spectra of FH Ser and N Aql 1995, and a low-dispersion spectrum of V1974 Cyg, give the following expansion velocities: 425 +/- 25, 675 +/- 25, and 1600 +/- 100 km/s, respectively. (c) Society of (SECTION: Dissertation Summaries)
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