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J/AJ/116/1757       M30 UBV photometry                  (Guhathakurta+, 1998)
Globular cluster photometry with the Hubble Space Telescope.
VII. Color gradients and blue stragglers in the central region of M30 from
Wide Field Planetary Camera 2 observations.
      Guhathakurta P., Webster Z.T., Yanny B., Schneider D.P., Bahcall J.N.
      <Astron. J. 116, 1757 (1998)>
      =1998AJ....116.1757G
ADC_Keywords: Clusters, globular ; Stars, blue ; Photometry, UBV

Mission_Name: HST

Keywords: blue stragglers - color-magnitude diagrams -
          globular clusters: individual: M 30, NGC 7099 - stars: evolution -
          stars: luminosity function, mass function

Abstract:
    We present F555W (V), F439W (B), and F336W (U) photometry of 9507
    stars in the central 2' of the dense, post-core-collapse cluster M30
    (NGC 7099) derived from Hubble Space Telescope Wide Field Planetary
    Camera 2 images. These data are used to study the mix of stellar
    populations in the central region of the cluster. Forty-eight blue
    straggler stars are identified; they are found to be strongly
    concentrated toward the cluster center. The specific frequency of blue
    stragglers, FBSS=N(BSS)/N(V<VHB+2), is 0.25±0.05 in the inner
    region of M30 (r<20"), significantly higher than the frequency found
    in other clusters: FBSS=0.05-0.15. The shape of M30's blue straggler
    luminosity function resembles the prediction of the collisional
    formation model, and is inconsistent with the binary merger model of
    Bailyn & Pinsonneault (1995ApJ...439..705B). An unusually blue star
    (B=18.6, B-V=-0.97), possibly a cataclysmic variable based on its
    color, is found about 1.2" from the crowded cluster center; the
    photometric uncertainty for this star is large, however, because of
    the presence of a very close neighbor. Bright red giant stars (B<16.6)
    appear to be depleted by a factor of 2-3 in the inner r<10" relative
    to fainter giants, subgiants, and main-sequence turnoff stars (95%
    significance). We confirm that there is a radial gradient in the color
    of the overall cluster light, going from B-V∼0.82 at r∼1' to B-V∼0.45
    in the central 10". The central depletion of the bright red giants is
    responsible for about half of the observed color gradient; the rest of
    the gradient is caused by the relative underabundance of faint red
    main-sequence stars near the cluster center (presumably a result of
    mass segregation). The luminosity function of M30's evolved stars does
    not match the luminosity function shape derived from standard stellar
    evolutionary models: the ratio of the number of bright giants to the
    number of turnoff stars in the cluster is 30% higher than predicted by
    the model (3.8σ effect), roughly independent of red giant
    brightness over the range MV=-2 to +2.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat        44     9940   M 30 stellar photometry and astrometry


See also:
   J/AJ/107/1745 : HST UVI photometry of M15. II. (Yanny+, 1994)
   J/AJ/108/1786 : Blue stragglers + variable stars in M3 (Guhathakurta+, 1994)
    J/AJ/113/669 : Stars in M13 core (Cohen+ 1997)


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

   Bytes Format Units   Label     Explanations

   1-  4  I4    ---     GWY       Identification number (1)
   6- 11  F6.2  arcsec  oRA       Relative right ascension to star 3611 (J2000) (2)
  13- 18  F6.2  arcsec  oDE       Relative declination to star 3611 (J2000) (2)
  20- 25  F6.2  arcsec  r         Projected distance from the cluster centroid (3)
  27- 31  F5.2  mag     Vmag      V magnitude
  33- 37  F5.2  mag     B-V       B-V colour index
  39- 43  F5.2  mag     U-V       ? U-V colour index

Note (1): Cl* NGC 7099 GWY NNNN in Simbad

Note (2): Star 3611 position: RA=21h40min22.402s, DE=-23°10'42.42" (J2000.0)

Note (3): Cluster centroid position:
            RA=21h40min22.24s, DE=-23°10'50.0" (J2000.0)


History: Copied from ftp ku.sns.ias.edu


References:
   Guhathakurta et al., Paper I.       1992AJ....104.1790G
   Yanny et al., Paper II.             1994AJ....107.1745Y, Cat. J/AJ/107/1745
   Guhathakurta et al., Paper III.     1994AJ....108.1786G, Cat. J/AJ/108/1786
   Yanny et al., Paper IV.             1994ApJ...435L..59Y
   Guhathakurta et al., Paper V.       1996AJ....111..267G
   Cohen et al., Paper VI.             1997AJ....113..669C, Cat. J/AJ/113/669
(End)                                          Patricia Bauer [CDS]  09-Nov-1998