Chandra X-ray observations of the X-ray faint elliptical galaxy NGC 4697

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 eff ective radius) into 90 point sources, of which similar to 80 are low-mass X -ray binaries (LMXBs) associated with this galaxy. The dominance of LMXBs i ndicates that X-ray faint early-type galaxies have lost much of their inter stellar 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 (similar to 23% of the total count rate) is from interstellar gas. The X-ray-emittin g gas in NGC 4697 has a rather low temperature (kT = 0.29 keV). The emissio n from the gas is very extended, with a much flatter surface brightness pro file 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 exten ded surface brightness are inconsistent with a global supersonic wind, a pa rtial wind, or a global cooling inflow. The gas may be undergoing subsonic inflation, rotationally induced outflow, or ram pressure stripping. X-ray s pectra of the resolved sources and diffuse emission show that the soft X-ra y 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 ted by thermal bremsstrahlung at kT = 8.1 keV, without a significant soft c omponent. NGC 4697 has a central X-ray source with a luminosity of L-X = 8 x 10(38) e rgs s(-1), which may be due to an active galactic nucleus and/or one or mor e LMXBs. At most, the massive black hole (BH) at the center of this galaxy is radiating at a very small fraction (less than or equal to4 x 10(-8)) of its Eddington luminosity. Three of the resolved sources in NGC 4697 are supersoft sources. In the out er regions of NGC 4697, seven of the LMXBs (about 20%) are coincident with candidate globular clusters, which indicates that globulars have a high pro bability of containing X-ray binaries compared to the normal stellar popula tion. We suggest that all of the LMXBs may have been formed in globulars. T he X-ray to optical luminosity ratio for the LMXBs in NGC 4697 is L-X(LMXB, 0.3-10 keV)/L-B = 8.1 X 10(29) ergs s(-1) L-B.(-1), which is about 35% hig her than the value for the bulge of M31. Other comparisons suggest that the re are significant variations (factor of greater than or similar to2) in th e LMXB X-ray-to-optical ratios of early-type galaxies and spiral bulges. Th e 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 LMXB s range from similar to5 x 10(37) to similar to2.5 X 10(39) ergs s(-1). The luminosity function of the LMXBs has a "knee" at 3.2 X 10(38) ergs s(-1), which is approximately the Eddington luminosity of a 1.4 M. neutron star (N S). This knee appears to be a characteristic feature of the LMXB population of early-type galaxies, and we argue that it separates BH and NS binaries. This characteristic luminosity could be used as a distance estimator. If t hey are Eddington limited, the brightest LMXBs contain fairly massive accre ting BHs. The presence of this large population of NS and massive BH stella r remnants in this elliptical galaxy shows that it (or its progenitors) onc e contained a large population of massive main-sequence stars.