Current Minimum of the Hα Equivalent Width in π Aqr
Observations note of the German VdS-Spectroscopy-Group*
Ernst Pollman
Emil-Nolde-Straße 12, 51375 Leverkusen, Germany
email:
ernst-pollmann@t-online.de
Received: Oct 16, 2007; Accepted: Oct 27, 2007
Based on data published by Dachs et al. in 1986, Bjorkman et al. (2002)
concluded that the last maximum in the emission strength in π Aqr
was between 1980 and 1985. In their paper, Bjorkman et al. also
reported the discovery of an observed extra emission embedded inside
the absorption profile of Hα and suggested that this is
evidence for the existence of a companion star.
Despite data gaps due to a non-visible period, the recent maximum was
clearly determined by the German VdS-Spectroscopy-Group to be
within the narrow time window of 27 October 2005 (± 2d). But
the Hα emission during the last maximum
(EW  7.5 Å ,
cf. Fig. 1) seems to be minute compared to that in the 1980s in which
EWs of up to 40 Å were observed.
Figure 1. Development of the Hα line profile between 10/2004 and 10/2007.
The current intensity of the Hα emission
(EW 1−2 Å)
suggests that π Aqr is on its way back to a quasi-normal
B-phase (Fig. 2). Should this trend prevail, the monitoring of the
Hα absorption line would be of specific interest for us because
of the up coming possibility of detecting the extra emission
discovered by Bjorkman et al. (2002), as the spectral resolution of our apparatus
has been improved considerably. The observations so far have been
carried out with telescopes between 20 and 40 cm aperture and spectral
resolutions R 8000−14000. With telescopes
comprising aperture more than 40 cm and spectrometers with a minimum resolution
of 15000, it should be possible in the near future to provide good scientific
data to support the professional community.
Figure 2. Time behavior of the Hα EW and V/R between 10/2004 and 10/2007.
References:
Bjorkman, K.S., et al. 2002, ApJ, 573, 812
Dachs, J. 1986, A&AS, 63, 87
*
VdS:
Vereinigung der Sternfreunde Deutschland
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