University of Leicester
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Deep CHANDRA monitoring observations of NGC 4649. I. Catalog of source properties

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journal contribution
posted on 2016-05-18, 10:47 authored by B. Luo, G. Fabbiano, J. Strader, D.-W. Kim, J. P. Brodie, T. Fragos, J. S. Gallagher, Andrew King, A. Zezas
We present the X-ray source catalog for the Chandra monitoring observations of the elliptical galaxy, NGC 4649. The galaxy has been observed with Chandra ACIS-S3 in six separate pointings, reaching a total exposure of 299 ks. There are 501 X-ray sources detected in the 0.3-8.0 keV band in the merged observation or in one of the six individual observations; 399 sources are located within the D25 ellipse. The observed 0.3-8.0 keV luminosities of these 501 sources range from 9.3 × 1036 erg s–1 to 5.4 × 1039 erg s–1. The 90% detection completeness limit within the D25 ellipse is 5.5 × 1037 erg s–1. Based on the surface density of background active galactic nuclei (AGNs) and detection completeness, we expect ≈45 background AGNs among the catalog sources (≈15 within the D25 ellipse). There are nine sources with luminosities greater than 1039 erg s–1, which are candidates for ultraluminous X-ray sources. The nuclear source of NGC 4649 is a low-luminosity AGN, with an intrinsic 2.0-8.0 keV X-ray luminosity of 1.5 × 1038 erg s–1. The X-ray colors suggest that the majority of the catalog sources are low-mass X-ray binaries (LMXBs). We find that 164 of the 501 X-ray sources show long-term variability, indicating that they are accreting compact objects. We discover four transient candidates and another four potential transients. We also identify 173 X-ray sources (141 within the D25 ellipse) that are associated with globular clusters (GCs) based on Hubble Space Telescope and ground-based data; these LMXBs tend to be hosted by red GCs. Although NGC 4649 has a much larger population of X-ray sources than the structurally similar early-type galaxies, NGC 3379 and NGC 4278, the X-ray source properties are comparable in all three systems.



Astrophysical Journal Supplement Series, 2013, 204 (2).

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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