Star clusters of the Large Magellanic Cloud - CCD photometry of NGC 1831

Abstract

view Abstract Citations (48) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Stars Clusters of the Large Magellanic Cloud: CCD Photometry of NGC 1831 Vallenari, A. ; Chiosi, C. ; Bertelli, G. ; Meylan, G. ; Ortolani, S. Abstract NGC 1831 is a populous, luminous star cluster located in the northern part of the Large Magellanic Cloud. In this paper, we present new Johnson BV-CCD photometry of 1800 stars in the cluster and 300 stars in a nearby field. Particular care is paid to estimate the errors in the data caused by uncertainties in the photometry and by crowding, and to isolate the portion of the cluster suffering from the least degree of incompleteness. The color-magnitude diagram (CMD) shows a well-defined main-sequence band terminating at about V= 18.10, a red giant clump centered at about half of a magnitude below the termination of the main-sequence band and spanning the color range 0.8 <= (B- V)<= 0.9, a sprinkle of stars of the same luminosity but of bluer color scattered toward the main-sequence band, and finally a scarce population of bright red stars. The metallicity, color excess, and distance modulus are derived from literature. The metallicity is assumed to be the mean value from several independent estimates, that is Z = 0.008. The color excess is E_B-V_= 0.05. The adopted distance modulus is (m-M)_0_= 18.5. The CMD and luminosity function (LF) of the main-sequence stars are examined with the aid of two different evolutionary schemes for intermediate mass stars, that is those with the classical extension of the convective regions and those allowing for the occurrence of convective overshoot. With the above metallicity, color excess, and distance modulus, the age of NGC 1831 is about 3.5 x 10^8^ yr with classical models and 5.5 X 10^8^ yr with overshoot models. The analysis of the sole CMD does not allow us to discriminate between the two evolutionary schemes, whereas looking simultaneously at the CMD and LF this is possible. Models with convective overshoot are able to simultaneously fit the morphology of the CMD and the slope of the LF, whereas classical models fail. Finally, the effects of unresolved stars, either true binaries or blended objects, are discussed to some extent. The existence of this type of stars in the CMD and LF does not alter the above conclusions. Publication: The Astronomical Journal Pub Date: September 1992 DOI: 10.1086/116300 Bibcode: 1992AJ....104.1100V Keywords: Astronomical Photometry; Charge Coupled Devices; Color-Magnitude Diagram; Magellanic Clouds; Star Clusters; Stellar Luminosity; Error Analysis; Main Sequence Stars; Stellar Magnitude; Astrophysics; MAGELLANIC CLOUDS; OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: NGC 1831 full text sources ADS | data products SIMBAD (2) NED (2)