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Nova Sagittae 1783, WY Sagittae

Nova in Sagitta

Right Ascension 19 : 32.7 (h:m)
Declination +17 : 45 (deg:m)
Distance 10,000 (ly)
Visual brightness 5.4 .. 20.7 (mag)

This nova which appeared in 1783 in the constellation Sagitta was discovered by the French astronomer D'Agelet (these observations have been discussed and published by B.A. Gould Washington Nat. Acad. Mem., Vol. 1, 1866). D'Agelet observed it on 3 days, July 26, 27 and 29, 1783 at mag 6, but calibration to today's magnitude system (Harvard visual scale) brings this up to mag 5.4 with an uncertainty of 0.4 mag.

After more than a century, several astronomers tried to recover D'Agelet's variable, or nova, between 1882 and 1908. A photographic search was made in July 1942 with the Mt.Wilson 60-inch reflector, and in June to July, 1950 with the 100-inch Hooker telescope of Mt.Wilson. From these photographs, the nova could be recovered as a White Dwarf star of between +18.6 and +19.5 mag which is exactly in the position of the nova, by H.F. Weaver of Lick Observatory (Weaver 1951). This identification was confirmed by M.M. Shara and A.F.J. Moffat by spectroscopic investigations which revealed a typical cataclysmic variable spectrum with strong Balmer, He I and He II emission lines superimposed on a continuous spectrum (Shara and Moffat 1982).

Shara and Moffat found deep eclipses of more than 2 magnitudes with a period of 1.0756 days (or an integer fraction of this), which must be the orbital period of the binary star system.



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Hartmut Frommert
Christine Kronberg