U Scorpii erupts (and an update on V496 Scuti)
February 7, 2010
Nova in Latin means new. This is an apt name for a type of star that appears to brighten from out of nowhere. A small sub-class of these objects, called recurrent novae, have been observed to erupt on multiple occasions. U Scorpii is such an object having been observed in outburst in 1863, 1906, 1917, 1936, 1945, 1969, 1979, 1987, and 1999. Recent studies suggested another outburst was due in 2008-2010 and this study appears correct. On Jan 28, Barbara Harris of New Smyrna Beach, Florida imaged U Sco at a relatively bright magnitude of V = 8.05 (bright enough for binoculars and small telescopes). Only a night earlier Harris had measured its brightness at a dim V = 18.2.
U Scorpii is a “fast” nova meaning it rapidly decreases in brightness. The chart below shows the rapid decrease in brightness of roughly a magnitude per day. Though I didn’t attempt to observe the nova, Salvador Aguirre was able to observe it visually on 4 consecutive nights (the blue crosses on the chart below). The nova is now around magnitude 14 which is too faint for all but CCD-equipped astronomers.
Much more on the history and science of U Sco can be found at the AAVSO.
While U Sco is am example of a fast nova, another nova first seen in November is of the “slow” variety. V496 Scuti was an easy object for evening observers and I was able to observe it over the course of a few weeks. Unfortunately the object got too low to be seen from my backyard and I had to stop my observations. After a month or so too close to the Sun for any observers, the nova is once again visible. Surprisingly the nova is still a reasonably bright 9th magnitude and only ~1.5 to 2.0 magnitude fainter than at maximum. That’s a fading of 1.5 to 2.0 magnitude over a 2+ month period. Compare that with U Sco’s rate of ~1 magnitude per day. More on this object can be found on earlier Transient Sky posts here and here.