strange Hb in Be (48 Per)

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#577859
Andy Wilson
Keymaster

Hi Kevin,

I’ve been doing spectroscopy for a couple of years now and I still get excited with each new spectrum. You never know what you will see and this is very true of Be stars. The hydrogen lines can be a complex mix of absorption and emission from the star and disc configurations which change over time.

I found 48 Per in the BeSS database. I’ve put a link below, though it does not look as though the link preserves all of the criteria I entered. You can select the H-beta region by entering 4861 in the wavelength. This shows pervious spectra with various mixes of absorption and emission of this line.

http://arasbeam.free.fr/spip.php?page=beam_splist2&etoile=HD 25940&lang=en

I’m not sure of the effect of rectification on the science value of a spectrum, so I avoid it. The BeSS standard uses the words ‘clearly advised against’ where it calls it ‘continuum normalisation’. For personal interest it is of course fine, and others with more knowledge may be able to advise on its effect. The bit where I am particularly unsure is its effect on line strength measurements, like equivalent width. This may not be big since the effects to the continuum on either side will be scaled by a similar amount, but I’ve never done an experimentation to discover the effect.

Similarly, for personal interest it is fine to use alternative methods to correct the response, but as soon as you want to do any science or submit to a database then a proper response correction is needed.

Best wishes,

Andy