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J/ApJ/298/544        NGC 121 BR photometry (Stryker+ 1985)
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The main-sequence turnoff of the old SMC globular cluster NGC 121
      Stryker L.L., Da Costa G.S., Mould J.R.
     <Astrophys. J. 298, 544 (1985)>
     =1985ApJ...298..544S      (SIMBAD/NED BibCode)
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ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Photometry, CCD
Keywords: clusters: globular - galaxies: Magellanic Clouds - stars: abundances -
          stars: evolution

Abstract:
    The age of the SMC globular cluster NGC 121 is found from
    main-sequence isochrone fitting to be 12+/-2x10^9^yr if a distance
    modulus that assumes Mv=+0.6 for the field RR Lyrae variables near
    the cluster is used. If instead (m-M)o = 19.3, then the cluster age is
    9+/-2x10^9^yr. The cluster is known to contain both RR Lyrae
    variables and a marginal carbon star; comparison with theoretical
    models indicates no significant inconsistencies in this joint
    occurrence at either modulus. The color-magnitude diagram for the
    nearby field also shows a faint, blue main-sequence turnoff and, in
    contrast to previous Magellanic Cloud field studies, the field lacks
    any evidence for the existence of a significant intermediate-age
    component. A new look at the chemical evolution of the Small
    Magellanic Cloud suggests that, unlike the Galaxy, where the rate of
    enrichment has been steady after the initial phase, the enrichment in
    the SMC remained small for a long interval before increasing rapidly
    sometime in the last 1-2x10^9^yr.

Objects:
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       RA  (2000)  DE    Designation(s)
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      00 26.7    -71 31  NGC 121
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File Summary:
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  FileName      Lrecl  Records   Explanations
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ReadMe             80        .   This file
table1             40      242   Photometry in NGC 121
table2             42      300   Photometry in field
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Byte-by-byte Description of file: table1 table2
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   Bytes Format Units   Label     Explanations
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   1-  3  I3    ---     Star      Star identification number
   5-  8  F4.2  mag     B-R       B-R color index
  10- 14  F5.2  mag     Rmag      R magnitude
  16- 21  F6.2  pix     Xpos      X position (1)
  23- 28  F6.2  pix     Ypos      Y position (1)
  30- 34  F5.2  mag     DB-R      ? November 18-20 B-R color index difference
  36- 40  F5.2  mag     DRmag     ? November 18-20 R magnitude difference
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Note (1): Origin: southwest corner of fig. 1
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History: Prepared via OCR at CDS.
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(End)                       Marie-Jose Wagner, Patricia Bauer [CDS]  30-Sep-1996