J/A+AS/137/233 UBVI imaging photometry of NGC 6231 (Baume+, 1999)
UBVI imaging photometry of NGC 6231
Baume G., Vazquez R.A., Feinstein A.
<Astron. Astrophys. Suppl. Ser. 137, 233 (1999)>
=1999A&AS..137..233B 1999A&AS..137..233B (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, UBVRI ; Clusters, open
Keywords: cluster: open - individual: Cr 272 -
stars: luminosity function, mass function - HR diagram
Description:
CCD UBVI photometry in the field of the open cluster NGC 6231 was
obtained for 1060 stars down to V=19mag. Memberships, reddening,
distance and age of this cluster were investigated. Its lower sequence
displays a notorious bend at V=13.5mag 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 10Myr is obtained. The luminosity and mass functions
were found to be flat for -7.5<Mv<1.5 and for 3 to 80M☉
respectively.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
16 54 12 -41 48.0 NGC 6231 = C 1650-417
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 64 1050 CCD photometric observations in NGC 6231
table1.tex 111 793 LaTeX version of Table 1
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- Seq Sequence number
9- 14 F6.1 pix Xpos X position (1)
17- 22 F6.1 pix Ypos Y position (1)
26- 30 F5.2 mag Vmag V magnitude
31- 32 A2 --- u_Vmag [: ] Uncertainty flag on Vmag (2)
34- 38 F5.2 mag B-V B-V colour index
39- 40 A2 --- u_B-V [: ] Uncertainty flag on B-V (2)
42- 46 F5.2 mag U-B ? U-B colour index
47- 48 A2 --- u_U-B [: ] Uncertainty flag on V-R (2)
50- 54 F5.2 mag V-I ? V-I colour index
55- 56 A2 --- u_V-I [: ] Uncertainty flag on V-I (2)
58- 61 A4 --- Rem Remarks (3)
--------------------------------------------------------------------------------
Note (1): 1 pix = 0.45".
X increases from East to West, Y increases from South to North
Note (2): (:) errors from 0.10 to 0.20
(::) errors larger than 0.20
Note (3): lm: likely member
nm: non member
pm: probable member
1: suspected variable in view of the photometric differences between
our data and the Perry et al. (1991A&AS...90..195P 1991A&AS...90..195P, PHC) ones.
ΔV in relation to PHC V mag are:
# 13 = -0.16
# 38 = -0.18 (Also probable β Cep according to PHC)
# 41 = 0.13
# 69 = -0.17
# 72 = -0.12
# 148 = -0.12
# 153 = -0.15
# 166 = -0.16 (Also probable variable according to PHC)
# 169 = -0.11
2: variable star according to Balona & Laney (1995MNRAS.276..627B 1995MNRAS.276..627B)
3: variable according to Feinstein & Ferrer (1968PASP...80..410F 1968PASP...80..410F)
and Raboud et al. (1997, Cat. J/A+A/325/167)
4: β Cep according to Balona & Laney (1995MNRAS.276..627B 1995MNRAS.276..627B)
--------------------------------------------------------------------------------
Acknowledgements: Gustavo L. Baume
(End) Gustavo L. Baume [Observ. Astron. La Plata] 01-Jun-1999