SIMBAD references

A Chandra observation of the intermediate-luminosity (M_B=-20) elliptical galaxy NGC 3379 resolves 75% of the X-ray emission within the central 5 kpc into point sources. Spectral analysis of the remaining unresolved emission within the central 770 pc indicates that 90% of the emission probably arises from undetected point sources, while 10% arises from thermal emission from kT=0.6 keV gas. Assuming a uniform density distribution in the central region of the galaxy gives a gas mass of 5x10⁵ M_☉. Such a small amount of gas can be supplied by stellar mass loss in only 10⁷ yr. Thus, the gas must be accreting into the central supermassive black hole at a very low radiative efficiency as in the ADAF or RIAF models, or it is being expelled in a galactic wind driven by the same AGN feedback mechanism as that observed in cluster cooling flows. If the gas is being expelled in an AGN-driven wind, then the ratio of mechanical to radio power of the AGN must be 10⁴, which is comparable to that measured in cluster cooling flows that have recently been perturbed by radio outbursts. Only 8% of the detected point sources are coincident with globular cluster positions, which is significantly less than that found among other elliptical galaxies observed by Chandra. The low specific frequency of globular clusters and the small fraction of X-ray point sources associated with globular clusters in NGC 3379 is more similar to the properties of lenticular galaxies rather than elliptical galaxies.

The brightest point source in NGC 3379 is located 360 pc from the central AGN with a peak luminosity of 3.5x10³⁹ ergs/s, which places it in the class of ultraluminous X-ray point sources (ULXs). Analysis of an archival ROSAT HRI observation of NGC 3379 shows that this source was at a comparable luminosity 5 yr prior to the Chandra observation. The spectrum of the ULX is well described by a power-law model with Γ=1.6±0.1 and galactic absorption, similar to other ULXs observed by Chandra and XMM-Newton and to the low-hard state observed in Galactic black hole binaries. During the Chandra observation, the source intensity smoothly varies by a factor of 2 with the suggestion of an 8-10 hr period. No changes in hardness ratio are detected as the intensity of the source varies. While periodic behavior has recently been detected in several ULXs, all of these reside within spiral galaxies. The ULX in NGC 3379 is the only known ULX in an elliptical galaxy with a smoothly varying light curve suggestive of an eclipsing binary system.