Recurrent nova IM Normae | Astronomy & Astrophysics (A&A) (original) (raw)

A&A 391, L7-L9 (2002)

Letter to the Editor

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, This email address is being protected from spambots. You need JavaScript enabled to view it.

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 Mathematical equation: <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>R</mi><mo>=</mo><mn>17.0</mn></mrow><annotation encoding="application/x-tex">R=17.0</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6833em;"></span><span class="mord mathnormal" style="margin-right:0.00773em;">R</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">17.0</span></span></span></span> mag and Mathematical equation: <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>B</mi><mo>=</mo><mn>18.0</mn></mrow><annotation encoding="application/x-tex">B=18.0</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6833em;"></span><span class="mord mathnormal" style="margin-right:0.05017em;">B</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">18.0</span></span></span></span> 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.

Key words: novae, cataclysmic variables / stars: individual: IM Nor

© ESO, 2002

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