J/A+AS/122/9 CCD UBVRI Photometry of 4 open clusters (Sagar+ 1997) ================================================================================ Multicolour deep CCD photometric study of the moderately young southern open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087 Sagar R., Cannon R.D. =1997A&AS..122....9S (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Clusters, open ; Photometry, UBVRI Keywords: HR diagram - stars: evolution - open clusters and associations: individual: NGC 3228, NGC 4103, NGC 5662, NGC 6087 Abstract: CCD observations in the U, B, V, R and I passbands have been used to generate colour-colour and deep colour-magnitude diagrams for the young open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087. The sample consists of about 2000 stars reaching down to V=20mag. The interstellar extinction across the face of the imaged cluster regions seems to be uniform with average values of E(B-V)=0.31, 0.34 and 0.22mag for NGC 4103, NGC 5662 and NGC 6087 respectively. The distances to the clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087 have been estimated as 0.5+/-0.05, 2.0+/-0.3, 0.8+/-0.1 and 1.0+/-0.1kpc respectively, while the corresponding ages estimated from the theoretical stellar evolutionary isochrones fitted to the bright proper motion cluster members are ~100, 30, 80 and 65Myr respectively. Present data are consistent with the membership of the Cepheid variable V Cen to NGC 5662 and of S Norm to NGC 6087. Heavy contamination by foreground and background field stars has unfortunately made it impossible to reach definite conclusions about the faint luminosity function, and the data do not reach faint enough limits to investigate pre-main sequence stars. Objects: ------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------ 10 21.8 -51 43 NGC 3228 = C 1019-514 12 06.7 -61 15 NGC 4103 = C 1204-609 14 35.2 -56 33 NGC 5662 = C 1431-563 16 18.9 -57 54 NGC 6087 = C 1614-577 ------------------------------------------ File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table6 55 408 Relative positions and UBVRI mag in NGC 3228 table7 62 288 Relative positions and UBVRI mag in NGC 4103 table8 80 502 Relative positions and UBVRI mag in NGC 5662 table9a 56 418 Relative positions and UBVRI mag in Region 1 of NGC 6087 table9b 63 381 Relative positions and UBVRI mag in Regions 2 and 3 of NGC 6087 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table6 table7 table8 table9b -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 2- 4 I3 --- SeqNum Sequential star number 5- 12 F8.2 pix Xpos X position 13- 20 F8.2 pix Ypos Y position 21- 27 F7.2 mag Vmag V magnitude 28- 34 F7.2 mag U-B ? U-B colour index 35- 41 F7.2 mag B-V ? B-V colour index 42- 48 F7.2 mag V-R ? V-R colour index 49- 55 F7.2 mag V-I ? V-I colour index 56- 80 A25 --- Name Other identifications (1) -------------------------------------------------------------------------------- Note (1): Prefixes are: W: Wesselink, 1969MNRAS.146..329W MV: Moffat & Vogt, 1973A&AS...10..135M H: Haug, 1978A&AS...34..417H K: King, 1980, J. Proc. R. Soc. N.S.W. 113, 7 C: Claria et al., 1991MNRAS.249..193C L: Landoldt, 1964ApJS....8..329L -------------------------------------------------------------------------------- Byte-by-byte Description of file: table9a -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 2- 4 I3 --- SeqNum Sequential star number 5- 12 F8.2 pix Xpos X position 13- 20 F8.2 pix Ypos Y position 21- 27 F7.2 mag Vmag V magnitude 28- 34 F7.2 mag U-B ? U-B colour index 35- 41 F7.2 mag B-V ? B-V colour index 42- 48 F7.2 mag V-I V-I colour index 49- 80 A32 --- Name Other identifications (1) -------------------------------------------------------------------------------- Note (1): L: Landoldt (1964ApJS....8..329L) -------------------------------------------------------------------------------- Acknowledgements: Ram Sagar References: Claria et al. 1991, MNRAS 249, 193 =1991MNRAS.249..193C Haug 1978, A&AS 34, 417 =1978A&AS...34..417H King 1980, J. Proc. R. Soc. N.S.W. 113, 7 (= Sydney Obs. Papers No. 87) Landoldt 1964, ApJS 8, 329 =1964ApJS....8..329L Moffat & Vogt 1973, A&AS 10, 135 =1973A&AS...10..135M Wesselink 1969, MNRAS 146, 329 =1969MNRAS.146..329W ================================================================================ (End) Patricia Bauer [CDS] 24-Jul-1996