To Be or not to Be (sorry)

To Be or not to Be (sorry)

Postby Andrew Smith » Fri Oct 03, 2014 12:57 pm

Following a valid challenge from Thierry Garrel I outline some criteria that would allow the identification of classical Be stars from the more general categories of B stars showing emission.
This is based on my reading of the paper "Classical Be stars" by Thomas Rivinius et al Astron Astrophys Rev (2013) 21:69.

I am no expert and this is given as a starter for 10 and I invite corrections and comment.

Criteria to Be.

1) Shows Balmer line(s) in emission (or has done in the past).
2) Non super-giant star.
3) High resolution spectra of Balmer lines does not show P Cygni or inverse P Cygni profiles.
4) High resolution spectra do not show forbiden emission lines
5) Does not show a strong infrared excess.
6) Does not have a Roche lobe filling companion.
7) Does not have variability in which the circumstellar environment shows variability with strictly the same period as the photosphere.

It seems to me that criteria 1 to 4 can be tested by amaturs using our spectroscopes and or literature searches.
While criteria 5-7 may be available to literature searches I am not sure about direct observation by us? Builds on this would be welcome.

Regards Andrew
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Re: To Be or not to Be (sorry)

Postby Andrew Smith » Fri Oct 03, 2014 4:17 pm

It would seem criteria 5(infrared excess) can be looked at from the h_k data from the 2MASS catalog http://irsa.ipac.caltech.edu/applicatio ... index.html

Allen & Swings 1976 AA 47 293-302 are quoted in The Astrophysics of Emission-Line Stars by Kogure & Leung as saying "The H-K color takes the values of -0.1 - +0.5 in ordinary Be stars."

Doing this for HD181751 give an h-k = -0.0090 which together with data that Robin and Thierry Garrel posted make it a very good candidate.

Regards Andrew
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Re: To Be or not to Be (sorry)

Postby Thierry Lemoult » Sun Oct 05, 2014 9:38 pm

Andrew, i post a quote of this excellent work on the ARAS web page . http://www.astrosurf.com/aras/be_candidate/auto-be-candidate.html The criteria need of course to be discuss.
Thierry
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