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HST target SDSS J164248.52+134751.4 at 16.5 CV

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Enrique de Miguel
HST target SDSS J164248.52+134751.4 at 16.5 CV

Stack of 4 x 120 s unfiltered images show this target at 16.50(3) CV at 2012-10-01 19:20:52 UT. This is 2 magnitudes brighter than the brightness of this object at quiescence.

 

Enrique de Miguel

CBA, Spain

WGR
WGR's picture
Unfiltered mag

Hello Enrique

Are you can comparing these unfilted magnitudes(CV)  with the exisitng filtered (V) magnitudes in the AAVSO database/LCG?  Unfiltered us usually about 2 mags brighter than filtered V. 

 

Gary

FRF
FRF's picture
"Unfiltered us usually about

"Unfiltered us usually about 2 mags brighter than filtered V."

It may be the case for LPVs, but not for cataclysmic (blue) stars. Btw other observers also measured this variable around 16.2-16.5V recently.

Enrique de Miguel
CV vs V

Hi Gary,

Yes, I'm comparing unfiltered (CV) mags with V mags of comp stars from the corresponding AAVSO sequence. How these CV mags compare with standard V mags depends on the observer's setup. From past tests where I've measured the transformation coefficients from CV to standard V mags, I know that when using comp stars with typical (B-V) colors (say, ~0.7-0.8), my CV mags are about 0.25-0.30 mags too faint (I'm considering here that the target of interest is a cataclysmic variable, with typical B-V ~ 0). Of course, the bluer the comp star, the better CV mags will match V mags. 

 Incidentally, this HST target has faded ~0.75 mag since my last measurement 24 h ago and it's currently at 17.27(4) CV. 

Enrique

 

 

WGR
WGR's picture
V = CV

Hello

It does look like for these objects, V = CV; even thought the comp stars look like B - V = 0.6.  Very Interesting.

 

Gary

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