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HST target SDSS J164248.52+134751.4 at 16.5 CV

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Enrique de Miguel's picture
Enrique de Miguel
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Joined: 2011-04-04

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

Unfiltered mag
WGR's picture
WGR
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Joined: 2010-08-17

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

"Unfiltered us usually about
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FRF
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Joined: 2010-08-09

"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.

V = CV
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WGR
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Hello


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

 

Gary

CV vs V
Enrique de Miguel's picture
Enrique de Miguel
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Joined: 2011-04-04

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

 

 

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