Letter to the Editor

Deep transient optical fading in the WC9 Star WR 106

¹ Department of Astronomy, Kyoto University, Kyoto 606-8502, Japan
² Variable Star Observers League in Japan (VSOLJ), 2-7-10 Fujimidai, Toyohashi City, Aichi 441-8135, Japan
³ Variable Star Observers League in Japan (VSOLJ), 65-1 Oohinata, Saku-machi, Nagano 384-0502, Japan
⁴ Faculty of Science, Kyushu University, Fukuoka 810-8560, Japan

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

Received: 6 August 2002
Accepted: 22 August 2002

Abstract

We discovered that the WR9-type star WR 106 (HDE 313643) underwent a deep episodic fading in 2000. The depth of the fading ( mag) surpassed those of all known similar “eclipse-like" fadings in WR stars. This fading episode was likely to be produced by a line-of-sight episodic dust formation rather than a periodic enhancement of dust production in the WR-star wind during the passage of the companion star though an elliptical orbit. The overall 2000 episode was composed of at least two distinct fadings. These individual fadings seem to more support that the initial dust formation triggered a second dust formation, or that the two independent dust formations occurred by the same triggering mechanism rather than a stepwise dust formation. We also discuss on phenomenological similarity of the present fading with the double fading of R CrB observed in .