Letter to the Editor

 Car: the optical features at the 2003.5 low-excitation event

¹ Leiden Observatory, Postbus 9513, 2300RA Leiden, The Netherlands
² Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
³ Alvine Estate, Vintage Lane, RD 3, Blenheim, New Zealand
⁴ Casilla 5022, Reñaca, Viña del Mar, Chile

Corresponding author: A. M. van Genderen, genderen@strw.leidenuniv.nl

Received: 2 October 2003
Accepted: 31 October 2003

Abstract

UBV and BVR photometry of η Car during the 2003.5 low-excitation event – the considered periastron passage of a binary – is presented. The light and colour curves show a number of features, which were also seen at previous periastron passages: a light maximum of long duration with a superimposed flare-like event which is temporarily interrupted by an eclipse-like dip, and a steep decline in the color index. The R brightness reached a minimum at the time of mid X-ray totality, probably implying that the Hα emission line reached a minimum. The source of the optical flare-like event is probably not the same as the one causing the the X-ray radiation. It is tempting to consider the epoch of the R minimum and the mid- X ray totality – which roughly coincides with the UBV minimum – as the central moment of the 2003.5 low-excitation event.