A Chandra ACIS S3 observation of the X-ray faint elliptical galaxy NGC 4697 resolves much of the X-ray emission (61% of the counts from within one effective radius) into 90 point sources, of which ∼80 are low mass X-ray binaries (LMXBs) associated with this galaxy. The dominance of LMXBs indicates that X-ray faint early-type galaxies have lost much of their interstellar gas. On the other hand, a modest portion of the X-ray emission from NGC 4697 is due to hot gas. Of the unresolved emission, it is likely that about half is from fainter unresolved LMXBs, while the other half (∼23% of the total count rate) is from interstellar gas. The X-ray emitting gas in NGC 4697 has a rather low temperature (kT = 0.29 keV). The emission from the gas is very extended, with a much flatter surface brightness profile than the optical light, and has an irregular, L-shaped morphology. The physical state of the hot gas is uncertain; the X-ray luminosity and extended surface brightness are inconsistent with a global supersonic wind, a partial wind, or a global cooling inflow. The gas may be undergoing subsonic inflation, rotationally induced outflow, or ram pressure stripping. X-ray spectra of the resolved sources and diffuse emission show that the soft X-ray spectral component, found in this and other X-ray faint ellipticals with ROSAT, is due to interstellar gas. The cumulative LMXB spectrum is well-fit by thermal bremsstrahlung at kT = 8.1 keV, without a significant soft component.NGC 4697 has a central X-ray source with a luminosity of L X = 8 × 10 38 ergs s −1 , which may be due to an AGN and/or one or more LMXBs. At most, the massive black hole at the center of this galaxy is radiating at a very small fraction (≤ 4 × 10 −8 ) of its Eddington luminosity.Three of the resolved sources in NGC 4697 are supersoft sources. In the outer regions of NGC 4697, seven of the LMXBs (about 20%) are coincident with candidate globular clusters, which indicates that globulars have a high probability of containing X-ray binaries compared to the normal stellar population. We suggest that all of the LMXBs may have been formed in globulars. The X-ray-to-optical luminosity ratio for the LMXBs in NGC 4697 is L X (LMXB, 0.3-10 keV)/L B = 8.1 × 10 29 ergs s −1 L −1 B⊙ , which is about 35% higher than the value for the bulge of M31. Other comparisons suggest that there are significant variations (factor of 2) in the LMXB X-ray-to-optical ratios of early-type galaxies and spiral bulges. The X-ray luminosity function of NGC 4697 is also flatter than that found for the bulge of M31. The X-ray luminosities (0.3-10 keV) of the resolved LMXBs range from ∼5×10 37 to ∼2.5×10 39 ergs s −1 . The luminosity function of the LMXBs has a "knee" at 3.2 × 10 38 ergs s −1 , which is approximately the Eddington luminosity of a 1.4 M ⊙ neutron star (NS). This knee appears to be a characteristic feature of the LMXB population of early-type galaxies, and we argue that it separates black hole and NS binaries. This characteristic luminosity could be used as a distance estimator....

We have investigated the X-ray spectral properties of a collection of low-mass X-ray binaries (LMXBs) within a sample of 15 nearby early-type galaxies using proprietary and archival data from the Chandra X-ray Observatory. We find that the spectrum of the sum of the sources in a given galaxy is remarkably similar from galaxy to galaxy when only sources with X-ray luminosities less than 10 39 ergs s −1 (0.3-10 keV) are considered. Fitting these lower luminosity sources in all galaxies simultaneously with a power law model led to a best-fit power law exponent of Γ = 1.56 ± 0.02 (90% confidence), and using a thermal bremsstrahlung model yielded kT brem = 7.3 ± 0.3 keV. This is the tightest constraint to date on the spectral properties of LMXBs in external galaxies. The spectral properties of the LMXBs do not vary with galactic radius out to three effective radii. There is also no apparent difference in the spectral properties of LMXBs that reside within globular clusters and those that do not. We demonstrate how the uniformity of the spectral properties of LMXBs can lead to more accurate determinations of the temperature and metallicity of the hot gas in galaxies that have comparable amounts of X-ray emission from hot gas and LMXBs.Although few in number in any given galaxy, sources with luminosities of 1 − 2 × 10 39 ergs s −1 are present in 10 of the galaxies. The spectra of these luminous sources are softer than the spectra of the rest of the sources, and are consistent with the spectra of Galactic black hole X-ray binary candidates when they are in their very high state. The spatial distribution of these sources is much flatter than the optical light distribution, suggesting that a significant portion of them must reside within globular clusters. The simplest explanation of these sources is that they are ∼ 10 − 15 M ⊙ black holes accreting near their Eddington limit. The spectra of these sources are very different than those of ultraluminous X-ray sources (ULXs) that have been found within spiral galaxies, suggesting that the two populations of X-ray luminous objects have different formation mechanisms. The number of sources with apparent luminosities above 2 × 10 39 ergs s −1 when determined using the distance of the galaxy is equal to the number of expected background AGN and thus appear to not be associated with the galaxy, indicating that very luminous sources are absent or very rare in early-type galaxies. The lack of ULXs within elliptical galaxies strengthens the argument that ULXs are associated with recent star formation.

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