[vsnet-alert 15991] Re: Next HST observations: HS2214+2845 (V513 Peg) & OT J213806.6+261957

[Brian Skiff]

On Mon, 2013-07-15 at 16:50 -0400, Robert J. Modic wrote:
> Boris,
> 
> Those SDSS u/g/r images OT J213806.6+261957 really make it
> clear which one is the CV!
> 
> By the way, has anyone ever measured the Johnson/Cousins mags
> and colors for the companions of both HS2214+2845 and
> OT J213806.6+261957?  Perhaps with a larger scope (ie., WIYN, HST)?
> I know that most observers report combined magnitudes for these
> stars, but it would be nice to be able to subtract the light of the
> companions for a more accurate result.


     There is SDSS photometry for both stars (the SDSS telescope
is 2.5-m aperture).  SDSS DR9 shows that the photomtery is 
'clean' (they think it's reliable) for the companion of
OT J213806.6+261957:

filter    mag    unc
  u     16.828  0.008
  g     15.484  0.003
  r     14.987  0.003
  i     14.839  0.003
  z     14.757  0.004

...I'd take the nominal errors with a grain of salt,
and multiply by pi or some other number depending on
how skeptical you are.

     For the companion to HS 2214+2845, the values are
similarly:

  u     18.343  0.017
  g     17.268  0.005
  r     16.873  0.004
  i     16.708  0.005
  z     16.611  0.010


     There are formulae to transform these figures to
UBVRI, but I find you can get very close to Johnson V
(within a couple percent) just from:  V = (g+r)/2.



\Brian