EDP Sciences
Free access
Volume 423, Number 1, August III 2004
Page(s) L1 - L4
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20040193

A&A 423, L1-L4 (2004)
DOI: 10.1051/0004-6361:20040193


  $\eta$ Carinae: The 1998 brightening and the smearing-out effect

A. M. van Genderen1 and C. Sterken2

1  Leiden Observatory, Postbus 9513, 2300RA Leiden, The Netherlands
    e-mail: genderen@strw.leidenuniv.nl
2  Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium

(Received 15 March 2004 / Accepted 11 June 2004)

A comparison of broad-band photometry of the Homunculus (ground-based data) and of broad-band and narrow-band photometry of the central region (HST-based) from 1997 to 2003 reveals that, apart from the brightening in 1998, the Homunculus as well as the central star varied in a very similar way. This excludes smearing-out effects as an explanation for the difference between the brightening of the central region and that of the Homunculus during 1998. A plausible reason for the homologous light behaviour is enhanced extinction decrease in the line-of-sight to the central region during a global brightening occurring after the 1998.0 spectroscopic event. From 1998 to 2004 there is indeed a brightness excess of ~0 $\fm$3 between the Homunculus and the extrapolated secular brightening. We also illustrate that ground-based aperture photometry of the Homunculus is a reliable diagnostic tool for studying the variability of the central star.

Key words: technique: photometric - stars: individual:  $\eta$ Carinae - variables - supergiants

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© ESO 2004