Resolving the mystery of X-ray-faint elliptical galaxies: Chandra X-ray observations of NGC 4697

Chandra observations of the X-ray-faint elliptical galaxy NGC 4697 resolve much of the X-ray emission (61% within one effective radius) into similar t o 80 point sources, of which most are low-mass X-ray binaries (LMXBs). Thes e LMXBs provide the bulk of the hard emission and much of the soft emission as well. Of the remaining unresolved emission, it is likely that about hal f is from fainter LMXBs, while the other half (similar to 23% of the total emission) is from interstellar gas. Three of the resolved sources are super soft sources. In the outer regions of NGC 4697, eight of the LMXBs (about 2 5%) are coincident with candidate globular clusters, indicating that globul ars have a high probability of containing X-ray binaries compared with the normal stellar population. The X-ray luminosities (0.3-10 keV) of the resol ved LMXBs 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 roughly the Eddington luminosity of an 1.4 M-. neutron sta r (NS); this knee might be useful as a distance indicator. The highest lumi nosity source has the Eddington luminosity of an similar to 20 M-. black ho le (BH). The presence of this large population of NS and massive BH stellar remnants in this elliptical galaxy shows that it (or its progenitors) once contained a large population of massive main-sequence stars.