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Photometry of close pairs

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Vitobs
Vitobs's picture
Photometry of close pairs

I think many have problems with photometry of close pairs of stars for subtracting the brightness of the component from the total brightness. If for bright stars it is not difficult to determine the brightness of components in catalogs, then for faint stars 14-17m this is a problem.
Now in the VizieR published photometry from Pan-STARRS DR1, it is ideal for faint stars. Is there a table for correcting g,r,i,z,y-magnitudes of Pan-STARRS into V Johnson's photometry?

Vitali Nevski

Sebastian Otero
Sebastian Otero's picture
Transformations

In the spreadhseet I provide, you can use add the g an r Pan-STARRS1 photometry to the SDSS g and r columns.
You can also add r in the CMC15 r mag column and determine V from 2MASS colors.
ot results will slightly differ, you can use the one more cosnistent with the other catalogues. Transformations are not so accurate since errors in one of the sources spread easily to the final result.
The above is valid for IPHAS and VPHASDR2 r values too.

Cheers,
Sebastian

PS: I have found that Pan-STARRS1 tend to give results slightly fainter than the other sources (~0.1 mag.).

CTX
CTX's picture
Pan-STARRS as a BVRI Source

Last Year I did a study of five surveys containing data within the M67 FOV and then comparing those five surveys against a 6th survey, the Hendon Naval Observatory Data for the M67 FOV. 

One of those five surveys was Pan-STARRS and part of the effort was to also simply determine the Efficacy of this survey as a BVRI source for sequence creation. 

The Methodology finally adopted:

16 comparrison stars were sourced directly froma Pan-STARRS catalog search URL, cetered on the M67 coordinates; only those stars with a minimum of three epoch detections in the g flter (ng) were used:

http://archive.stsci.edu/panstarrs/search.php

using the mean aperture magnitudes for the g,r & I filters (i.e, gMeanAPMag)

The conversions to BVRI were accomplished with the use of transformations suggested by Jester et al. (2005) as sourced through SDSS:

http://www.sdss3.org/dr8/algorithms/sdssUBVRITransform.php

When  Rc-Ic < 1.15

B-V = 0.98*(g-r)+0.22

V-R = 1.09*(r-i)+0.22

Rc-Ic = 1.00*(r-i)+0.21

B = g+0.39*(g-r)+0.21

V = g-0.59*(g-r)-0.01

Compared with the Hendon Data, the average magnitude differences for the Pan-STARRS data for the BVRI filters in this limited survey:

B = .097

V  = .056

Rc = .022

Ic = .040

I am comfortable using Pan-STARRS as a sequence source within the range of ~ V = 14.5-18.5, provided there is no Hendon or SDSS faint data available for a given FOV.

Tim Crawford

Vitobs
Vitobs's picture
Many thanks to all!

Many thanks to all!

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