(cba:news) V380 Oph

Joe Patterson jop at astro.columbia.edu
Tue Aug 7 09:31:15 EDT 2012

Dear CBAers,

We're hoping to get an HST observation of V380 Oph, which has entered a 
low state, quite soon.  To do that we have to monitor it visually with 
sufficient depth to get an idea of how bright it is.  The fainter, the 
better... partly because it certifies that the white dwarf is dominating 
the light (the aim of the observation), and partly because a BRIGHT V380 
Oph will fry the detectors (and therefore be forbidden by NASA).

Snapshot magnitudes of V380 Oph are the main thing that's needed, rather 
than time series, which of course are our usual specialty.  And - again 
unusual for us - "it's too faint for me" is not really an appropriate 
reaction here.  Add frames, lengthen exposures, do whatever you need to 
measure the magnitude.  It's likely to be around magnitude 18-19, maybe 

The HST observation probably won't happen till mid-September, but to 
proceed with the planning, we need some knowledge of its variability 
pattern.  Some of these deep-low-state stars have brief flares by a 
couple of magnitudes, while others just sit there inert, faint, and 
unvarying.  Over the next few weeks, we need to learn more about V380 
Oph in that regard!

We'll also be trying this with big scopes, where S/N isn't a problem... 
but a few snapshots don't really answer the question.  We need to know 
the pattern of variability, and that's where CBAers can provide the answer.


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