Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chandra Observations of the X-ray Point Source Population in NGC 4636   We 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.

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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci