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Spectral characteristics of GCAS eruptive variables

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Spectral characteristics of GCAS eruptive variables

Could someone either give me a reference or a direct answer to the question as to whether stars of type GCAS (in my particular instance V0568 Cyg) are characterized by H-beta and higher emission lines?  V0568 Cyg is a potential target of opportunity for my DSLR photometry program, but I won't bother with it if the star is strongly emissive in the spectral region covered by the DSLR green channel but not by Johnson V.

Thanks in advance for your assistance!



PS - The answer. in The Astrophysical Journal Supplement Series, 50:55-84, 1982 September, is  Yes.  Full Balmer series is present.

Robin Leadbeater
V568 Cyg spectra

Hi Stephen,

Several spectra of V568Cyg can be found in the Pro-Am  Be Star database BeSS.

Only H alpha is in net emission




Olivier Thizy
Olivier Thizy's picture
V568 Cyg spectrum



I just took a spectrum of V568 Cyg and not only Halpha is in emission but also Hbeta and Hgamma (see attached). The FITS file is also attached in ZIP archive.

My spectrum has been uploaded on BeSS database but there is lot of backlog in the validation process (I have more than 700 spectra waiting for approval at the moment).


Note also that BeSS spectra are easily visible on ARASBeAm (may be easier for a quick look):

Just look for V568 Cyg and you have access to spectra in BeSS in graph view...





Robin Leadbeater
V568 H Beta

Hi Olivier,

Yes there is emission in the core of the Balmer absorption lines but except at H alpha the EW of the full line is still positive. (ie except at H alpha there is a net absorption)   I dont know if the core emission would be a problem for V photometry measurements though.




Thanks Oliver and Robin!  It is clear that one should never do DSLR photometry on GCAS stars.

Ciel dégagé  (c'est vrai?)


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