BVRI main-sequence photometry of the globular cluster M 4.
Abstract
BV and RI photographic photometry is presented of 1421 and 189 stars in the intermediate metallicity globular cluster M4 (NGC 6121). The investigation includes the first results of RI main-sequence photometry of a globular cluster. The use of longer wavelengths and longer color baselines provides the potential for improved isochrone fittings and emphasizes the need for calculations of RI synthetic isochrones for comparison with observations. The position of the main sequence turnoff was found to lie at V = 16.6 and B - V = 0.80. A comparison of the present BV observations with CCD data from the literature showed excellent agreement between the two fiducial main sequences. For the cluster a distance modulus of 21.52 was derived, and reddening was determined to be near 0.44. The properties of the color magnitude and color-color diagrams in the longer wavelength bands are discussed in detail. A fold-out map is provided which shows the positions of the stars.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- September 1984
- DOI:
- 10.1086/190975
- Bibcode:
- 1984ApJS...56...19A
- Keywords:
-
- Astronomical Photometry;
- Globular Clusters;
- Main Sequence Stars;
- Stellar Color;
- Stellar Evolution;
- Stellar Magnitude;
- Astrometry;
- Astronomical Maps;
- Color-Color Diagram;
- Hertzsprung-Russell Diagram;
- Interstellar Extinction;
- Stellar Composition;
- Ubv Spectra;
- Astronomy