William Liller

Recurrent nova IM Normae

We detected the second historical outburst of the 1920 nova IM Nor. Accurate astrometry of the outbursting object revealed the true quiescent counterpart having a magnitude of R = 17.0 mag and B = 18.0 mag. We show that the quiescent counterpart shows a noticeable variation. From the comparison of light curves and spectroscopic signatures, we propose that IM Nor and CI Aql comprise a new class of recurrent novae bearing some characteristics similar to those of classical novae. We interpret that the noticeable quiescent variation can be a result of either high orbital inclination, or the presence of high/low states. If the second possibility is confirmed by future observations, IM Nor becomes the first recurrent nova showing state changes in quiescence. Such state changes may provide a missing link between recurrent novae and supersoft X-ray sources.

The Ages of Globular Clusters Derived from BVRI CCD Photometry

Main sequence photometry has been obtained in the BV system for at least 36 galactic globular clusters (Peterson 1986). One of the most important objectives for these continued researches by several astronomical groups has been that of determining the ages of globular clusters. During the past five years, a general consensus has emerged that the spread in age among the known galactic globular clusters could be as small as 1 billion years; Burstein (1985) suggests that the average age of these objects lies between 14 and 17 Gys.