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  Low Resolution spectra of Be  Star   BD +55 521   (Vmag 10.6)   20-22 Sept 2008


The only spectra of BD +55 521 currently in the ARAS BeAm database date from January 2003, so an update is overdue. Two low resolution spectra were measured  on 20th and 22nd September 2008 using the Star Analyser grating. While not showing the detailed line profile, it should be possible to estimate if  the strength of the H alpha emission line has changed significantly.

 

The risk of interference from background stars and spectra increases as the technique is extended  to fainter stars.  Before imaging, the Digitized Sky Survey image of the area was examined to determine the best orientation of the camera to minimise such problems. After imaging, the actual spectrum position was overlaid on the DSS image to check for interfering stars.   A bright spot can just be seen in the spectrum at the H alpha wavelength. (An interfering star can also be seen to the left of the H alpha wavelength, overlapping the spectrum. This was removed in the final spectrum plot. There are no stars visible in the DSS image at the H alpha position)




The Star Analyser spectra were reduced in the usual way and finally normalised using a fit to the continuum.  The 2003 spectrum from the OHP ELODIE database was normalised in the same way and Gausian filtered to match the Star Analyser resolution for comparison.

At high resolution, the 2003 ELODIE spectrum shows emission features in the H alpha line (see below).  When filtered to simulate the resolution of the Star Analyser  spectrum however, the net effect is of a slight overal absorption centred at the H alpha wavelength.  By contrast, the two Star Analyser spectra recorded in September 2008 show a distinct emission feature at this position. This suggests that there may have been a significant increase in the strength of H alpha emission in this star since 2003. A higher resolution spectra would be required to investigate the detailed nature of the change but the star is too faint to measure this using the Three Hills Observatory LHIRES III spectrograph. 


A high resolution plot of the H alpha region from the 2003 spectrum in the ELODIE Archive

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