Spectral properties of XRBs in dusty early-type galaxies
  We present spectral properties of a total of 996 discrete X-ray sources
resolved in a sample of 23 dusty early-type galaxies selected from different
environments. The combined X-ray luminosity function of all the 996 sources
within the optical \D of the sample galaxies is well described by a broken
power law with a break at 2.71$\times$\te \lum and is close to the Eddington
limit for a 1.4\Msun neutron star. Out of the 996, about 63\p of the sources
have their X-ray luminosities in the range between few\tim\ts to 2.0 \tim \tn
\lum and are like normal LMXBs; about 15-20\p with luminosities $<$ few \tim
10$^{37}$ \lum are either super-soft or very-soft sources; while the remainder
represents ULXs, HMXBs or unrelated heavily absorbed harder sources. More XRBs
have been detected in the galaxies from isolated regions while those from rich
groups and clusters host very few sources. The X-ray color-color plot for these
sources has enabled us to classify them as SNRs, LMXBs, HMXBs and heavily
absorbed AGNs. The composite X-ray spectra of the resolved sources within \D
region of each of the galaxies are best represented by a power law with the
average photon spectral index close to 1.65. The contribution of the resolved
sources to the total X-ray luminosity of their host is found to vary greatly,
in the sense that, in galaxies like NGC 3379 the XRB contribution is about 81\p
while for NGC 5846 it is only 2\p. A correlation has been evidenced between the
cumulative X-ray luminosity of the resolved sources against the star formation
rate and the Ks band luminosity of the target galaxies indicating their
primordial origin.
