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J/AJ/119/2274   JK Photometry of globular clusters M15 & M56   (Ivanov+, 2000)
Extending the red giant branch versus metallicity calibration toward
metal-poor systems: near-infrared photometry of the galactic globular clusters
M56 and M15
      Ivanov V.D., Borissova J., Alonso-Herrero A., Russeva T.
     <Astron. J. 119, 2274 (2000)>
     =2000AJ....119.2274I
ADC_Keywords: Clusters, globular ; HR diagrams ; Photometry, infrared

Keywords: color-magnitude diagrams - globular clusters: individual (Liller 1,
          M15, M56, NGC 6553, NGC 7099) - stars: Population II

Abstract:
    Infrared JKs-band photometry of the Galactic globular clusters M15
    and, for the first time, M56 is presented. We estimate the reddening
    [E(B-V) = 0.18 {=/-} 0.08 mag] and distance modulus [(m - M)V =
    15.43 ± 0.30 mag] toward the poorly studied globular cluster M56.
    We combine our data with observations of other clusters from the
    literature (12 in total) to extend the [Fe/H] versus red giant branch
    (RGB) slope relation toward metal-poor clusters.

Description:
    We obtained JKs imaging of M56 and M15 using a 256 X 256 NICMOS3
    array at the 2.3 m Bok Telescope of the University of Arizona on Kitt
    Peak, with a plate scale of 0.6" pixel-1, under photometric conditions
    on 1998 November 5. The average seeing during the observations was
    1.0" - 1.2". The observational strategy consisted of taking cluster
    images interleaved with sky images 6' - 7' away from the targets.
Objects:
    -----------------------------------------
       RA   (2000)   DE      Designation(s)
    -----------------------------------------
    21 29 58.4   +12 10 01   M15 = NGC 7078
    19 16 35.5   +30 11 04   M56 = NGC 6779
    -----------------------------------------

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table2.dat        58     1459   Photometry of globular clusters M15 and M56


See also:
  J/A+A/303/468 : Spectrospcopy, IR-photom. in globular clusters (Minniti, 1995)
  J/A+A/331/70 : JKVI photometry of NGC 6553 stars (Guarnieri+ 1998)
  J/AJ/109/1131 : JHK Photometry in Metal Rich Globulars. (Kuchinski+ 1995)
  J/AJ/110/2844 : JHK photometry of globular clusters. III. (Kuchinski+ 1995)
  J/AJ/109/1154 : JHK Photometry of Liller 1 (Frogel+ 1995)


Byte-by-byte Description of file: table2.dat

   Bytes Format Units   Label     Explanations

   1-  3  A3    ---     Cluster   Cluster name
   6- 10  I5    ---     Number    Object number in Cluster (1)
  13- 18  F6.2  pix     Xpix      CCD X coordinate relative to cluster center
  21- 26  F6.2  pix     Ypix      CCD Y coordinate relative to cluster center
  30- 34  F5.2  mag     Kmag      The Ks filter magnitude
                                   (Persson et al. 1998AJ....116.2475P)
  38- 42  F5.2  mag     (J-K)     The (J-Ks) color
  46- 50  F5.2  mag     e_Kmag    DAOPHOT errors for Kmag
  54- 58  F5.2  mag     EJMag     DAOPHOT errors for the J filter

Note (1): Numbers larger than 10,000 are composed of the numbers from
          Clement 2000 plus 10,000 for cross-identification.


History:
    From AJ electronic edition.

References:
   Clement, C. M. 2000, in preparation
(End)                                          Greg Schwarz [AAS]    23-May-2000