H Emission Behavior of
 Cas Between 1976 and 1998

Long-term observations of the intensity behavior of the H emission line of the Be star disk  Cas carried out by the author between 1994 and 1998 - together with results of observations during the period from August 1971 to October 1989 by Horaguchi et al. (1994) - have led to more than twenty years of observations of the star's overall behavior.

As a result of discussions with experts of the IAU Working Group on Active B Stars, the idea of publication in the Be Star Newsletter developed. Above all, however, the examination results recently presented (Smith, Robinson, & Corbet 1998), concerning the X-ray production of the star and its correlation with the intensity behavior of the disk's H emission, were the cause for the results presented here. It is not necessary to go into detail on the generation of spectra and data reduction which led to the results as they have already been discussed in Pollmann (1997).

As an amateur astronomer, the author does not take the liberty of relating the results of his observations presented here to the exceptional features of the physics of the circumstellar star shell or the gas disk, but confines himself to explaining the results which can be directly derived from the behavior in the course of time.

1. A linear regression over the represented total period of more than twenty years allows the estimate of a yearly increase of the emissive power. To what extent the total increase of approximately 19 Å, (August 1971) to approximately 37 Å, (October 1998) is related to the X-ray activities referred to cannot be assessed here.

2. At JD 2449750 an eruption which lasted about four months could be observed which at its maximum of approximately 60 Å, was nearly twice as powerful as the base equivalent width of approximately 30 Å. To the knowledge of the writer, this eruption has not been confirmed by comparative measurements carried out by other observers.

The writer will continue to monitor  Cas and in due course it will be possible to again report here on the further behavior.

References:

Horaguchi, T. et al. 1994, PASJ, 46, 9-26

Smith, M., Robinson, R. D., & Corbet, R. H. D. 1998, ApJ, 503, 877-893

Pollmann, E. 1997, Be Star Newsletter, 32, 11-13