[vsnet-alert 15991] Re: Next HST observations: HS2214+2845 (V513 Peg) & OT J213806.6+261957
bas at lowell.edu
Tue Jul 16 06:40:16 JST 2013
On Mon, 2013-07-15 at 16:50 -0400, Robert J. Modic wrote:
> 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
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
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.
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