Recent analysis of the first ROTSE-III dark run has uncovered an interesting transient event which we designate ROTSE3 J015118.59-022300.1. This object is absent in images taken on 10/11/01 to limiting magnitudes of R~18.2. It is also absent from skyview images, scanned SERC plates from the USNO PMM archive, and from the USNO A2.0 catalog.
On 10/13/01 the object appears at R=13.9, after which it fades rapidly, falling by more than 2 magnitudes over a period of 13 days. The onset time is in the 1.9 days between the 10/11 and 10/13 images. Assuming a time of 1 day, the transient fades with a power law index of around -0.9. The latest ROTSE-III observation (10/26/01 at 09:10:21.97 UT) shows the transient at R=16.2. We estimate the current R magnitude (11/01/01) to be 16.5-17.5.
Thanks to Steve Shectman at Magellan, we have a quick spectrum. The object is not at high redshift, and appears to be a CV. The exact classification of the type of CV remains uncertain.
It could be a fast nova (NA) in the halo. Fast novae are intrinsically bright. For this event the scaling relations in Duerbeck (1981 PASP 93, 165) would predict a peak absolute magnitude around MV~-8.5. The observed peak brightness of 13.9 suggests a distance modulus of 22, and a distance of ~300 kpc. The high galactic latitude of this event suggests that extinction is not the explanation. If it is a fast nova, it is an unusual one.
It is also possible that it is a dwarf nova, though the increase in brightness is rather extreme. Also, its absence in the plates scanned by the USNO PMM machine (12 epochs from 1953-1997) requires a low duty cycle.
The position of the object is (J2000):
|RA: 27.827476||DEC: -2.3834|
|L: 190.62224||B: -40.740092|
Five figures provide additional information. They can be found at