2001A&A...366..858K

We present low- and medium resolution spectra of the recurrent nova CI Aquilae taken at 14 epochs in May and June, 2000. The overall appearance is similar to other U Sco-type recurrent novae (U Sco, V394 CrA). Medium resolution (λ/Δλ≃7000-10000) hydrogen and iron profiles suggest an early expansion velocity of 2000-2500km/s. The Hα evolution is followed from Δt=-0.6d to +53d, starting from a nearly Gaussian shape to a double peaked profile through strong P-Cyg profiles. The interstellar component of the sodium D line and two diffuse interstellar bands put constraints on the interstellar reddening which is estimated to be E(B-V)=0.85±0.3mag. The available visual and CCD-V observations are used to determine t₀, t₂ and t₃. The resulting parameters are: t₀=2451669.5±0.1, t₂=30±1d, t₃=36±1d. The recent lightcurve is found to be generally similar to that observed in 1917 with departures as large as 1-2mag in certain phases. This behaviour is also typical for the U Sco subclass.