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Post Info TOPIC: NGC 4833


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Posts: 131433
Date:
Caldwell 105
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NGC 4833 (also ESO 65-SC4, Caldwell 105 and Melotte 115) is a magnitude +8.4 globular cluster located 21,200 light-years away in the constellation Musca.

The galaxy was discovered by French astronomer Nicholas Louis de Lacaille using a 1.27 cm (0.5 inch) refractor in South Africa, on the 17th March 1752.

Right Ascension 12h 59m 34.98s, Declination Dec -70° 52' 27"

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Posts: 131433
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NGC 4833
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Title: New SX Phoenicis Variables in the Globular Cluster NGC 4833
Authors: Andrew N. Darragh, Brian W. Murphy

We report the discovery of 6 SX Phoenicis stars in the southern globular cluster NGC 4833. Images were obtained from January through June 2011 with the Southeastern Association for Research in Astronomy 0.6 meter telescope located at Cerro Tololo Interamerican Observatory. The image subtraction method of Alard & Lupton (1998)was used to search for variable stars in the cluster. We confirmed 17 previously catalogued variables by Demers & Wehlau(1977). In addition to the previously known variables we have identified 10 new variables. Of the total number of confirmed variables in our 10x10 arcminČ field, we classified 10 RRab variables, with a mean period of 0.69591 days, 7 RRc, with a mean period of 0.39555 days, 2 possible RRe variables with a mean period of 0.30950 days, a W Ursae Majoris contact binary, an Algol-type binary, and the 6 SX Phoenicis stars with a mean period of 0.05847 days. The periods, relative numbers of RRab and RRc variables, and Bailey diagram are indicative of the cluster being of the Oosterhoff type II. We present the phased-light curves, periods of previously known variables and the periods and classifications of the newly discovered variables, and their location on the colour-magnitude diagram.

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