Chandra Observations of the X-ray Point Source Population in NGC 4636

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dc.creatorPosson-Brown, Jennifer
dc.creatorRaychaudhury, Somak
dc.creatorForman, William
dc.creatorDonnelly, R. Hank
dc.creatorJones, Christine
dc.date2006-05-12
dc.date2009-01-27
dc.date.accessioned2026-07-07T13:05:07Z
dc.date.available2026-07-07T13:05:07Z
dc.descriptionWe present the X-ray point source population in the nearby Virgo elliptical galaxy NGC 4636 from 3 Chandra/ACIS observations, totaling 193 ks, taken over 3 years. Using wavelet decomposition, we detect 318 point sources. Here, we use a subset of the 277 sources with >10 net cts (>1.2E37 erg/s, 0.5-2 keV, >1.5 arcmin of center). Between 1.5-6 arcmin from the center, 25% are likely background sources (AGN) and the rest are LMXBs within the galaxy, while at >6 arcmin, background sources dominate. We present a color-color diagram based on ratios of X-ray flux, which yields a tighter source distribution, and shows a large population of sources which are likely LMXBs and black hole candidates. We explore short and long-term variability (over time-scales of 1 day to 3 yr): 54 sources (24%) in the common ACIS fields show significant variability between observations. Of these, 37 are detected with >10 net counts only once and thus may be "transient". About 10% of sources in each observation show significant short-term variability. The cumulative luminosity function for the point sources can be represented as a power-law of slope 1.14. Between 1.5-6 arcmin of the center, 48 of the 129 X-ray point sources (37%) with >10 net counts are matched with optical globular cluster (GC) candidates (matches could be as high as 50% since many of the optical sources are AGN). 70% of matched sources are associated with the redder GC candidates, those that are thought to have near-solar metal abundance. The fraction of GC candidates matched with point sources decreases with decreasing GC luminosity. The X-ray luminosities of the matched point sources are not correlated with the luminosity or color of the host GC candidates. Finally, we estimate an upper limit of 4.5E37 erg/s to the current X-ray luminosity of the historical supernova SN1939A.
dc.descriptionAccepted for publication in the Astrophysical Journal; 19 pages, 15 figures, 3 tables. Version with full quality figures can be obtained at http://hea-www.harvard.edu/~jpbrown/ngc4636_astroph.pdf
dc.identifierhttps://arxiv.org/abs/astro-ph/0605308
dc.identifierhttp://arxiv.org/abs/astro-ph/0605308
dc.identifierAstrophys.J.695:1094-1110,2009
dc.identifierdoi:10.1088/0004-637X/695/2/1094
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/227393
dc.subjectAstrophysics
dc.titleChandra Observations of the X-ray Point Source Population in NGC 4636
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