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TOPIC: NGC 6253

Blobrana

L

Posts: 131433

Date: Nov 9 17:35 2016

ESO 180-SC2	Permalink

Title: White Dwarfs in the Metal-Rich Open Cluster NGC 6253 Author: Elizabeth J. Jeffery, Fabiola Campos, Alejandra Romero, S.O. Kepler We have obtained 53 images with the g filter and 19 images with the i filter, each with 600-second exposures of the super metal rich open cluster NGC 6253 with the Gemini-South telescope to create deep images of the cluster to observe the cluster white dwarfs for the first time. We will analyze the white dwarf luminosity function to measure the cluster's white dwarf age, search for any anomalous features (as has been seen in the similarly metal rich cluster NGC 6791), and constrain the initial-final mass relation at high metallicities. We present an update on these observations and our program to study the formation of white dwarfs in super high metallicity environments. Read more (293kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Nov 9 17:32 2016

Melotte 156	Permalink

NGC 6253 (also known as ESO 180-SC2, Cr 321, Mel 156 and OCL 972) is a magnitude +10.2 open cluster located 4,925 light-years away in the constellation Ara. The cluster was discovered by Scottish astronomer James Dunlop using a homemade 9-foot 22.86 cm (9 inch) f/12 speculum Newtonian reflector at Paramatta, New South Wales, Australia, on the 14th May 1826. John Herschel described it in an observation using a 18-inch reflector telescope as "a small triangular cluster, 2' diameter, stars of 13th magnitude" Right Ascension 16h 59m 6.1s, Declination -52° 42' 57" __________________

Blobrana

L

Posts: 131433

Date: Sep 30 02:19 2012

NGC 6253	Permalink

Title: Lithium Abundances of the Super-Metal-Rich Open Cluster NGC 6253 Authors: Jeffrey D. Cummings, Constantine P. Deliyannis, Barbara Anthony-Twarog, Bruce Twarog, Ryan M. Maderak High-resolution CTIO 4-m/HYDRA spectroscopy of the super-metal-rich open cluster NGC 6253 ([Fe/H]=+0.43±0.01) has been used to study the stellar lithium (Li) abundances near the cluster's turnoff. NGC 6253 greatly expands the range of [Fe/H] for clusters that have a Li abundance analysis. This is important for studying the complicated effects of, and potential correlations with, stellar Fe abundance on surface Li abundance. Comparisons to the younger and less-metal-rich Hyades and to the similarly-aged but solar-metallicity M67 show that NGC 6253's Li abundances are qualitatively consistent with the prediction, from Standard Stellar Evolution Theory, that higher-metallicity stars have a greater Li depletion. Comparison with M67 provides evidence that the more-metal-rich NGC 6253 had a higher initial Li, which is consistent with expectations from models of Galactic Li production. NGC 6253 is also compared to the intermediate-aged NGC 3680, NGC 752, and IC 4651 open clusters. Comparison of the Li-gap positions in all six clusters shows: a) the gap's position in Teff is independent of metallicity, but b) higher-metallicity clusters have their gaps in higher-mass stars. In addition, the Li gap's position is shown not to evolve with age, which provides an important constraint for the non-standard depletion mechanisms that may create the Li gap. Read more (96kb, PDF) __________________

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