Thelight curve of nova DM Geminorum, plotted from data presented by Shapley. When multiple values were listed with exactly the same time, they were averaged before plotting.[2]
DM Geminorum also known asNova Geminorum 1903 was anova which erupted in the constellationGemini in 1903. It was discovered byHerbert Hall Turner at theGreenwich Observatory on aCarte du Cielphotographic plate taken on 16 March 1903. Post-discovery examination of earlier photographs of the region taken at theHarvard College Observatory showed that the star was fainter thanapparent magnitude 9 on 2 March 1903, and magnitude 5.1 on 6 March 1903, making it visible to the naked eye at that time.[3] It had a conspicuous red color due to strongHα line emission.[4] By 1 April 1903 it had faded to magnitude 8.5.[5] By 1989 it had reached visual magnitude 17.38.[6]
DM Geminorum faded from peak brightness by 2 magnitudes in just 6 days, making it a "very fast nova".[7]
All novae are binary stars, with a "donor" star orbiting awhite dwarf. The two stars are so close together that matter is transferred from the donor to the white dwarf. High speedphotometry done with the 1.2 meter telescope at theWhipple Observatory show a small amplitude (0.25 magnitude peak-to-peak) oscillation with a period of 2 hours and 57 minutes, which is probably the orbital period of the binary system. In addition, brightness variations with a period of 22 minutes are also seen in this star'slight curve. The star's spectrum and brightness variations are similar to what is seen inintermediate polars.[8]
^Schmidt, Theodor (January 1957). "Die Lichtkurven-Leuchtkraft-Beziehung Neuer Sterne. Mit 8 Textabbildungen".Zeitschrift für Astrophysik.41: 182.Bibcode:1957ZA.....41..182S.
