CG Canis Majoris (CG CMa) was discovered by Verlooy on Franklin-Adams plates taken in 1934. CG CMa was considered to be a U Gem star or a possible classical nova, one of most distant in our Galaxy.

Duerbeck (1987) identified the possible quiescent counterpart, a star around magnitude 16.4. The cataclysmic classification, however, became less likely when Zwitter and Munari (1995) took the spectrum of the suggested quiescent counterpart, which showed an isolated white dwarf.

After observing this star for only two months I detected an outburst on February 22, 1999 at magnitude 13.7 – the first recorded outburst since it’s discovery in 1934 on photographic plates! CCD observations revealed that the outbursting object was about 2.5 arc seconds east of the suggested quiescent star.

The field of CG CMa in 1989 (R band, at minimum) and in 1999 (I band, at outburst). North is on top and west to the right. The dwarf nova is the eastern component of the close double star in the centre of the image. The field size is about 80″×80″. At minimum, no counterpart is seen down to R=22m


A spectrum of CG CMa was obtained with the 2.5-m Isaac Newton telescope on 1999 February 22.94 (UT), in the early stages of the outburst. The spectrum is quite typical of SU UMa-type dwarf novae at superoutburst. (IBVS 4759)

CCD observations revealed that CG CMa is a short period SU UMa-type dwarf nova, rather than a classical nova. No further outbursts have been recorded since the 1999 detection.

Light curve of my visual observations from the outburst detection.

The figure below shows the overall light curve of the 1999 outburst of CG CMa obtained from the Kyoto University, Japan.

Co-authored published paper on CG CMa

CCD Photometry of the 1999 Outburst of CG CMa. 1999IBVS.4760..IK

Back to Light curves


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