The content of the file gK
In many cluster fields there are red giants that may be cluster members.
This assumption is based on their magnitudes and colours which make them
fall more or less at the right place where they are expected if they were
cluster members.
The selection of probable red giant members has been done by using a
V magnitude cutoff and the stars brighter than the limit have been considered.
No red limit has been imposed, but, on the blue side, candidates have been
considered when they were redder than the colour corresponding to the
half distance between the top of the main sequence and the red giant clump.
The reason for this criterion is to include possible binary stars formed
by a bright main sequence star and a red giant.
To make the investigation easier, information for the stars which are
potentially cluster red giants are collected in the file gK.
This file is used by the commandgk
The file content is described below.
- star identification, according to the adopted numbering system
- membership probability (data type prob)
- membership estimate according the analysis of
- - proper motion
- The estimate is positive (+) if the probability is larger than .75,
negative (-) if it is smaller than .50 and doubtful (?)
if the condition .50 < prob < .75 is filled
- - radial velocity
- The estimate is positive if the mean radial velocity of a star
is within 5 km/s from the cluster velocity
- - photometry
- The criterion is positive (+) is the star is on the red giant
branch, negative (-) if it is too red, and undefined (?) if
the star lies within the Hertzsprung gap. It may be a binary.
- the source of the radial velocity
- C: Coravel scanners
- G: Griffin's scanners
- L: CfA spectrographs
- V: Victoria instrument
- the available photometric data.
- UBV photoelectric or CCD
- UBV photographic
- Geneva system
- DDO system
- Washington system
- RI data, either Johnson, or Kron, or Cousins
- Eggen's uvby system
- UBViyz system
- Wing system
- The classification types from the evolutionary status or membership
- A: star on the Asymptotic giant branch
- B: star on the first ascending giant Branch
- C: star in the Clump
- D: possible Double star, within the Hertzsprung gap
- S: yellow or red Supergiant
- F: Field star (non-member)
- the indication of binarity "B" according to the radial velocity observations
- the V magnitude and B-V colour index
- the spectral type