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J/AJ/120/333        UBVRI and Hα in NGC 6530           (Sung+, 2000)
UBVRI and Hα photometry of the young open cluster NGC 6530.
    Sung H., Chun M.-Y., Bessell M.S.
   <Astron. J. 120, 333 (2000)>
   =2000AJ....120..333S
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, UBVRI ;
              Photometry, H-alpha ;
Keywords: color-magnitude diagrams -
          open clusters and associations: individual (NGC 6530) -
          stars: early-type - stars: pre-main-sequence

Abstract:
    New UBVRI and Hα photometry has been obtained for the young open
    cluster NGC 6530 located 10' east of the Lagoon Nebula (M8). We found
    37 pre-main-sequence (PMS) stars with Hα emission and nine PMS
    candidates using the R-Hα color, a measure of Hα emission.
    From this new photometry we derived the cluster parameters
    (V0-MV=11.25±0.1mag and E(B-V)=0.35mag), typical age (1.5Myr),
    and an age spread of about 5Myr. We confirmed the presence of a small
    amount of differential reddening across the cluster. We also verified
    the abnormal reddening law for the cluster, especially for a heavily
    embedded O7 V star, Herschel 36. Comparisons were made for several PMS
    evolution models with regard to the resulting age distribution and the
    initial mass function.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat       144      887   Photometric data
table3.dat       114       37   PMS stars with Hα emission
table4.dat       114        9   PMS candidates with weak Hα emission
table5.dat        71       29   PMS stars and candidates from HST data


See also:
  J/AJ/116/1801 : IC 4996 CCD photometry (Delgado+, 1998)
  J/A+AS/123/63 : NGC 6530 multiwavelength photometry (van den Ancker+ 1997)


Byte-by-byte Description of file: table1.dat

   Bytes Format Units   Label   Explanations

   1-  3  I3    ---     SCB     [1/887]+ Running identification number in 
                                 NGC 6530 (Cl* NGC 6530 SCB NNNN in Simbad)
   5-  6  I2    h       RAh     Right Ascension (J2000)
   8-  9  I2    min     RAm     Right Ascension (J2000)
  11- 14  F4.1  s       RAs     Right Ascension (J2000)
      16  A1    ---     DE-     Declination (J2000)
  17- 18  I2    deg     DEd     Declination (J2000)
  20- 21  I2    arcmin  DEm     Declination (J2000)
  23- 26  F4.1  arcsec  DEs     Declination (J2000)
      28  I1    ---     Tab     [3-4]? Table number if object in tables 3 or 4
  30- 35  F6.3  mag     Vmag    The weighted mean V band magnitude
  37- 42  F6.3  mag     V-I     The weighted mean V-I color
  44- 49  F6.3  mag     B-V     The weighted mean B-V color
  51- 56  F6.3  mag     U-B     The weighted mean U-B color
  58- 63  F6.3  mag     R-Ha    ? The weighted mean (R-Hα filter) color
  66- 70  F5.3  mag     e_Vmag  Uncertainty in Vmag
  72- 76  F5.3  mag     e_V-I   Uncertainty in V-I
  78- 82  F5.3  mag     e_B-V   Uncertainty in B-V
  84- 88  F5.3  mag     e_U-B   Uncertainty in U-B
  90- 94  F5.3  mag     e_R-Ha  ? Uncertainty in R-Ha
  97- 98  I2    ---     o_Vmag  Number of observations for Vmag
 100-101  I2    ---     o_V-I   Number of observations for V-I
 103-104  I2    ---     o_B-V   Number of observations for B-V
 106-107  I2    ---     o_U-B   Number of observations for U-B
 109-110  I2    ---     o_R-Ha  Number of observations for R-Ha
 112-114  I3    ---     Walker  ? The Walker (1957ApJ...125..636W)
                                  identification number (NGC 6530 NNN in Simbad)
     115  A1    ---   f_Walker  Duplicity or uncertainty (?) flag for Walker
 117-120  F4.2  ---     Prob    [0,1]? Proper motion membership probability (1)
 122-128  A7    ---     SpType  ? Spectral type and luminosity class (2)
 130-144  A15   ---     Remark  Further remarks (2)

Note (1): Membership probability by van Altena & Jones (1972A&A....20..425V).

Note (2): Spectral types are mostly from Hiltner et al. (1965ApJ...141..183H)
           except for Herschel36 which is from Woolf (1961PASP...73..206W).


Byte-by-byte Description of file: table3.dat table4.dat

   Bytes Format Units   Label     Explanations

   1-  4  I4    ---     SCB       Sequential number
   6-  7  I2    h       RAh       Right ascension (J2000)
   9- 10  I2    min     RAm       Right ascension (J2000)
  12- 15  F4.1  s       RAs       Right ascension (J2000)
      17  A1    ---     DE-       Declination sign (J2000)
  18- 19  I2    deg     DEd       Declination (J2000)
  21- 22  I2    arcmin  DEm       Declination (J2000)
  24- 25  I2    arcsec  DEs       Declination (J2000)
  27- 32  F6.3  mag     Vmag      V magnitude
  34- 38  F5.3  mag     V-I       V-I colour index
  40- 44  F5.3  mag     B-V       B-V colour index
  46- 51  F6.3  mag     U-B       ? U-B colour index
  53- 58  F6.3  mag     R-Ha      R-Hα colour index
  60- 64  F5.3  mag     e_Vmag    rms uncertainty on Vmag
  66- 70  F5.3  mag     e_V-I     rms uncertainty on V-I
  72- 76  F5.3  mag     e_B-V     rms uncertainty on B-V
  78- 82  F5.3  mag     e_U-B     ? rms uncertainty on U-B
  84- 88  F5.3  mag     e_R-Ha    rms uncertainty on R-Ha
      90  I1    ---     o_Vmag    Number of observation for Vmag
      92  I1    ---     o_V-I     Number of observation for V-I
      94  I1    ---     o_B-V     Number of observation for B-V
      96  I1    ---     o_U-B     ? Number of observation for U-B
      98  I1    ---     o_R-Ha    Number of observation for R-Ha
 100-114  A15   ---     Rem       Remarks


Byte-by-byte Description of file: table5.dat

   Bytes Format Units   Label     Explanations

       1  A1    ---     PMS       [SC] S: PMS stars, C: PMS candidates
   3-  6  I4    ---     SCB       Sequential number
   8-  9  I2    h       RAh       Right ascension (J2000)
  11- 12  I2    min     RAm       Right ascension (J2000)
  14- 17  F4.1  s       RAs       Right ascension (J2000)
      19  A1    ---     DE-       Declination sign (J2000)
  20- 21  I2    deg     DEd       Declination (J2000)
  23- 24  I2    arcmin  DEm       Declination (J2000)
  26- 27  I2    arcsec  DEs       Declination (J2000)
  29- 34  F6.3  mag     Vmag      V magnitude
  36- 40  F5.3  mag     V-I       V-I colour index
  42- 47  F6.3  mag     Ha        Hα magnitude
  49- 53  F5.3  mag     e_Vmag    rms uncertainty on Vmag
  55- 59  F5.3  mag     e_V-I     rms uncertainty on V-I
  61- 65  F5.3  mag     e_Ha      rms uncertainty on Ha
      67  I1    ---     o_Vmag    Number of observation for V
      69  I1    ---     o_V-I     ? Number of observation for V-I
      71  I1    ---     o_Ha      Number of observation for Hα


History:
    From AJ electronic version
(End)                    Greg Schwarz [AAS], Patricia Bauer [CDS]    29-Aug-2000