Letter to the Editor

Recurrent nova IM Normae

¹ Department of Astronomy, Kyoto University, Kyoto 606-8502, Japan
² Faculty of Science, Kyushu University, Fukuoka 810-8560, Japan
³ Center for Nova Studies, Casilla 5022 Renaca, Viña del Mar, Chile
⁴ Bronberg Observatory, PO Box 11426, Tiegerpoort 0056, South Africa

Corresponding author: T. Kato, tkato@kusastro.kyoto-u.ac.jp

Received: 26 March 2002
Accepted: 2 July 2002

Abstract

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  mag and  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.