Bruck 88 : a young star cluster with an old age resemblance in the outskirts of the Small Magellanic Cloud

A.E. PIATTI

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 445 p. 2302 - 2312

0035-8711

We present spectroscopic and photometric results for the Small Magellanic Cloud (SMC) cluster Bruck,88.From the comparison of the cluster integrated spectrum  with template cluster spectra we found that the Milky Way globular cluster template spectra  are the ones which best resemble it. However, the extracted cluster colour magnitude diagram  reveals that Bruck,88 is a young cluster (log($t$) = 8.1 $pm$ 0.1).The derived cluster age is compatible with the presence of a Bright Red Giant (BRG) star located $sim$ 2.6 arcsec in the sky from the cluster centre. We serendipitously observed HW,33, a star cluster located $approx$ 3 arcmin to the south-east from Bruck,88. We obtained for the cluster the same age than Bruck,88  and surprisingly, a BRG star located within the cluster radius also appears to be compatible with the cluster age. We estimated the MK type of the BRG star in the Bruck,88 field to be in the range G9,II/Ib ? K1,III. By combining the spectrum of a star within this MK type range  with a 100-150 Myr template cluster integrated spectrum, we found that a proportion 85/15 in the sense BRG/template results in a spectrum which best resembles that of Bruck,88. This result confirms that a BRG star dominates the cluster integrated spectrum, so that it causes the globular cluster appearance of its integrated light.