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Stellar Population Synthesis of Bright X-ray Point Sources in NGC 1399

Author Affiliations

  • 1Department of Physics, University of Calicut, Kerala, INDIA

Res. J. Recent Sci., Volume 3, Issue (ISC-2013), Pages 86-88, (2014)


We present the stellar population synthesis (SPS) of X-ray point sources in NGC 1399 with an aim to investigate the dependence of X-ray characteristics on the dynamical properties of the sources. Our sample includes 22 bright X-ray sources (Lx ≥1038 erg/sec) in NGC 1399, of which two are ultra-luminous X-ray sources (ULXs). Using the SPS code of Bruzual and Charlot 2003 (BC03) and magnitudes in four Hubble space telescope (HST) filters, we estimate the possible ages and masses of these sources. We find that their X-ray luminosities are anti-correlated with the derived stellar masses excepting the two ULXs, the Spearman’s rank correlation coefficient being -0.62 with a significance greater than 99%. As the optical counterparts are definitely multiple sources (most likely globular clusters), the strong trend exhibited by X-ray sources suggests the possibility of existence of multiple sources for the production of X-rays as well. Further, SPS also shows that the brighter X-ray sources are in general older. This analysis also suggests that the energy production mechanism in ULXs may be different from other non- ULX sources in our sample, as they are not following the correlation.


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