| Issue |
Astron. Astrophys. Suppl. Ser.
Volume 137, Number 2, June I 1999
|
|
|---|---|---|
| Page(s) | 233 - 244 | |
| DOI | https://doi.org/10.1051/aas:1999245 | |
| Published online | 15 June 1999 | |
imaging photometry of NGC 6231
*,**
Observatorio Astronómico de La Plata, Paseo del Bosque s/n, 1900 La Plata and PROFOEG-CONICET, Argentina
Send offprint request to: gbaume@fcaglp.fcaglp.unlp.edu.ar
Received:
18
May
1998
Accepted:
4
February
1999
CCD UBVI photometry in the field of the open cluster NGC 6231 was
obtained for 1060 stars down to 
mag. Memberships, reddening,
distance and age of this cluster were investigated. Its lower sequence displays
a notorious bend at 
mag followed by a high number of faint stars
showing a large magnitude spread at constant colour. This distribution of stars
does not seem to be produced by a mere accumulation of field stars seen in the
direction of the cluster but by a real star excess in the zone. The evidence
suggests these stars are serious candidates to be cluster members caught in
their way towards the ZAMS. Fitting them with pre main sequence isochrones an age
spread of about 10 Myr is obtained. The luminosity and mass functions were found
to be flat for 
and from 3 to 80 
respectively.
Key words: cluster: open / individual: NGC 6231 / stars: luminosity function, mass function / HR diagram
© European Southern Observatory (ESO), 1999