RR Telescopii

RR Telescopii is a symbiotic nova in the southern constellation Telescopium. It was recorded on photographic survey plates as a faint variable star between photographic magnitude (m_pg) 9 to 16.6 from 1889 to 1944. In late 1944 the star began to brighten, increasing by about 7 magnitudes, from m_pg ≈ 14 to brighter than 8. Brightening continued with a diminished rate of increase after early 1945, but the overall outburst was not noted until the star was seen at about 6.0, the threshold of naked eye brightness, in July 1948. At that time it was given the designation Nova Telescopii 1948. Since mid-1949 it has declined in brightness slowly, albeit accompanied by some remarkable changes in its spectrum, and as of August 2013 it had faded to visual magnitude around 12.

RR Telescopii was periodically observed in a survey program by the southern station of Harvard College Observatory starting in 1889, as well as other southern observatories begun at later dates. Williamina Fleming in 1908 reported variations in brightness between about magnitude 9 and 11.5, and suggested it might be the same type of star as SS Cygni. In later plates it showed modest irregular variability between m_pg 12.5 and 14, up to about 1930. At that time it began slow periodic variations in brightness between magnitudes 12 and 16; the period of these variations was 387 days, and the star could be characterized as a peculiar semi-regular variable. No spectra seem to have been taken of the star prior to outburst, since it was too faint to be included in the Henry Draper Catalog and was undistinguished until outburst.

In 1944 the periodic variations broke off, and RR Tel brightened by more than 7 magnitudes over the course of about four years. Starting about m_pg 14 in late 1944, survey plates recorded it brighter than magnitude 8 early in 1945, and the star was observed at m_pg 7.4 in September–October 1946, 7.0 in March 1948, and 6.0 in July 1948. In 1948 it was noticed, and received the designation Nova Tel 1948. In July 1949 the star began fading slowly. The information about RR Tel's pre-outburst behavior as seen in the Harvard survey plates was published in February 1949, and the already long duration of the outburst, years as opposed to days or weeks, made it very clear that RR Tel had to be very different from the novae which had been previously observed; it was called a slow nova in acknowledgement of that not understood difference.