Datatype: da0 CCD

The Delta a photometric system has be designed by Maitzen to detect photometrically peculiar stars (Ap). The original system is based on photoelectric photometry. The da CCD system is the realisation of the original da system with a CCD detector. It uses three filters g1, g2 and y and the parameter a is defined as

a = g2 - [(g1 + y) / 2].

Δa is computed relatively to a linear relation : a versus (B-V) or (b-y) or (g1-y).

For young open clusters with differential reddening, dereddened magnitudes and indices have been used, and a new datatype, da0ccd, has been introduced.

Record structure

No:Star number
Ref:Data source
V0:Unreddened V magnitude
a0:Dereddened a parameter
g1-y0:Dereddened g1-y colour index
Da0:Deviation from the normal relation
ebv:E(B-V) colour excess

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Last Update: 22 January 2006