The 2000 outburst of the recurrent nova CI Aquilae: Optical spectroscopy^*

¹ Department of Experimental Physics and Astronomical Observatory, University of Szeged, Dóm tér 9., Szeged 6720, Hungary
² Guest Observer at Konkoly Observatory
³ University of Toronto, David Dunlap Observatory, Richmond Hill, Canada
⁴ Mt. Suhora Observatory of the Pedagogical University, Cracow, Poland

Corresponding author: L. L. Kiss, l.kiss@physx.u-szeged.hu

Received: 14 September 2000
Accepted: 13 November 2000

Abstract

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 (-) hydrogen and iron profiles suggest an early expansion velocity of 2000-2500 km s^-1. The Hα evolution is followed from = -0.6 d to +53 d, 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 =. The available visual and CCD-V observations are used to determine t₀, t₂ and t₃. The resulting parameters are: , d, d. The recent lightcurve is found to be generally similar to that observed in 1917 with departures as large as 1-2 mag in certain phases. This behaviour is also typical for the U Sco subclass.