The Be Star Newsletter, Volume 38 - January 2006

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An unexpected emission-line phase of HD 6226 detected Miroslav Slechta Astronomical Institute of the Academy of Sciences, CZ-251 65 Ondrejov, Czech Republic; email:  slechta@sunstel.asu.cas.cz Received: Jan 25, 2006;  Accepted: Jan 30, 2006 The Be star HD 6226 (SAO 36891, BD+46°245, R.A.2000=01:03:53.3587, Decl.2000=+47:38:32.262) is very interesting and seems to be more and more exciting object. We informed (Slechta et al., The Be Star Newsletter, earlier in the Volume 38, November 2005; for a short review on the history of its studies see therein) about detection of unexpected emission-line phase. However, this emission-line phase was quite short -- Charles T. Bolton (Dept. of Astronomy and Astrophysics, Univ. of Toronto, Ontario, Canada) secured spectrum of HD 6226 in December 17, 2005, in H region and found only a slight bump on the blue wing; the core was probably filled but without any visible structure (priv. communication). We should remark that Thomas L. Gandet (Lizard Hollow Observatory, Tucson, AZ, USA) photometrically observed HD 6226 in November 12, 2005, in V-band (priv. communication). He found none photometric variations (or they were of order of errors). Really, our spectrogram, secured in January 10, 2006 (this lag is due to the weather conditons) in H region, showed no emission but small bump on the blue wing, as it was mentioned by Charles T. Bolton. However, the new spectrogram secured in January 15, 2006, showed the emission in H again. The rapid evolution of emission phase was confirmed in January 22 when strong emission was found on secured spectrum -- see Fig.1. Thus the new emission phase started probably about January 10, 2006. Figure 1.  The H line profiles of HD 6226 obtained in January, 2006. Possible beginning of another emission phase. The last three consecutive spectra are quite poor due to the observational conditions. However, one can see that strength and profile of H emission has changed. It means that nowadays the behaviour of HD 6226 is quite dramatic and unpredictable. It is surprising in comparison with the behaviour in past years -- see Slechta & Skoda, 2005, Ap&SS, Vol. 296, Issue 1-4, pp. 179-182. In cited paper we presented our spectroscopic observation of HD 6226 during 2003. At the beginning of that stage, we found the object in an emission phase. The emission strength systematically decreased up to August 11, 2003, when the last emission was secured. The following spectrum, saved in August 25, 2003 (the pause was due to the weather), showed typically absorption profile of H without any emission remnants. This absorption phase continued up to October 28, 2003, when new strong emission line was detected. The emission phase was confirmed by Thomas L. Gandet in the H region (priv. communication). His spectrum (secured in October 1, 2003 via coude spectrograph attached to the 0.9m telescope at Kitt Peak) shows double-peaked emission pattern in the core of H, but not exceeding the level of continuum. The strength of the emission decreased up to January 14, 2004. Then the bad weather made impossible to observe the star up to March 22, 2004, when absorption spectrum was saved. The spectrum secured in March 30, 2004, confirmed absorption phase of HD 6226. The first autumn spectrum of HD 6226 was exposed in August 7, 2004, and showed new emission phase which continued up to April 3, 2005 (!). Then HD 6226 was not observable in Ondrejov up to autumn; the first spectrum exposed in August 19, 2005, showed absorption profile. The new unexpected emission was observed between October 28 and 29 as we announced in mentioned 38th Be Stars Newsletter. Then the emission disappeared and returned about January 10, 2006. Since this date the emission phase continued up to January 24, 2006, when we secured the last spectrum until now. Perhaps, it is premature to put a hypothesis on such dramatic change in the behaviour of this object. However, it is possible to say that the behaviour of the HD 6226 dramatically accelerated during the last year. It would be very interesting to observe the HD 6226 as often as possible and watch whether this epoch of instability is (or is not) impermanent and how long will remain. Acknowledgement This study was supported from the research plans J13/98: 113200004 K2043105, AV0Z 100/30501 and from the grants GA CR 205/2003/0788 and GA AV CR B/301/630/501.