Deep Chandra Monitoring Observations of NGC 4649. I. Catalog of Source Properties
Abstract
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.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- February 2013
- DOI:
- 10.1088/0067-0049/204/2/14
- arXiv:
- arXiv:1211.2804
- Bibcode:
- 2013ApJS..204...14L
- Keywords:
-
- galaxies: active;
- galaxies: individual: NGC 4649;
- globular clusters: general;
- X-rays: binaries;
- X-rays: galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 14 pages, 12 figures, 10 tables. ApJS in press. Full tables available in the published version or upon request