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Let there Be stars

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Anthony Rodda's picture
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Last seen: 3 weeks 6 days ago
Joined: 01/09/2014 - 14:15
Let there Be stars

Hi All,

When Andy and Kevin stated that they were always pleasantly surprised by what they find when they process spectra it was a lovely bit of British understatement.

Like Kevin I thought I'd chase a few Be stars.  I simply queried the BeSS database for "Be's around Castor" ran the output through Astroplanner and picked a few that had low spectra numbers (but enough to provide comparisons).

Dumb questions follow below plots...

All targets use the same response curve from the same B2 star.  My plots are blue in the top 2 and green in the lower.  The other plots are from BeSS for comparison.  And I chose comparison spectra from observers as close to my setup as I could see (just a quick scan).

 

Top two spectra are flat, without rectification.  They correspond (roughly) with the existing examples, so I'm not a mile away.  Clearly not a black body in form and more like a DN disc in outburst.  What's the correct science explanation?

The third/fourth are close but the blue end is adrift in plot four.  I appreciate the existing spectra aren't flux calibrated nor 'standardised' but is the blue-ward difference in plot 4 just what we've discussed previously - differences in technique, star/slit placing, altitude, etc.?

Regards

T

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Robin Leadbeater's picture
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Last seen: 11 hours 15 min ago
Joined: 05/03/2014 - 00:50
Be star continuum shape

Hi Tony,

I am not a Be star expert but I would have expected the continuum to be that of the corresponding B star ie a typical hot star spectrum rising towards the blue end. On that basis the flat spectra and that one which dips down at the blue end look strange to me. The stars may be reddened by interstellar extinction though I suppose. For a more experienced view you could ask on the ARAS forum.

Cheers

Robin

Anthony Rodda's picture
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Last seen: 3 weeks 6 days ago
Joined: 01/09/2014 - 14:15
That's what gets me Robin...

Thanks for responding.  If I'd produced those spectra in isolation I'd have doubted my technique, sanity, etc. (which was my reason for asking) but they're pretty close to what's in BeSS already so these are replicable observations.  I'm very curious.  I'll post a separate thread asking if anyone (BAA) is posting to BeSS...  Andy, David, etc may be able to comment/help.