BVR CCD photometry on NGC 1777

We present photographic (B and V) and CCD (B, V, and R) photometry of stars in the remote LMC cluster NGC 1777, and integrated UBV photometry of the inner part of the cluster. A comparison of the results from the two techniques reveals large (~0.20m) systematic differences which we attribute to the difficulty of faint photometry. The photographic calibration depended on images produced by a Racine wedge, while the CCD calibration was accomplished in a manner analogous to photoelectric photometry. The stellar photometry provides a C-M diagram to V=21.5 which includes an evolved main sequence and a well-populated giant branch. A variety of methods, including comparisons of the observations to two sets of isochrones, allows us to estimate the cluster age as 0.9+/-0.2x10^9^ years. However we are only able to estimate the metallicity ([Fe/H]) crudely as -0.7+/-0.5. The C-M diagrams of the field in three regions near NGC 1777 indicate the presence of stars in the age range 1x10^9^ to >=3x10^9^ years, although we are unable to discern whether a mixture of two or more distinct populations or a continuous distribution of field-star ages is responsible for this spread.

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Creator Mateo M.; Hodge P.
Publisher CDS
Publication Year 2000
OpenAccess true
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Resource Type Dataset; AstroObjects
Discipline Astrophysics and Astronomy; Galactic and extragalactic Astronomy; Natural Sciences; Observational Astronomy; Physics; Stellar Astronomy