Study of LINER sources with broad H(alpha) emission. X-ray properties
  and comparision to luminous AGN and X-ray binaries
  We study the X-ray properties of LINER sources with definite detection of a
broad H(alpha) emission line in their optical spectra, LINER 1s from Ho et al.
sample. These objects preferentially harbor a low luminosity active nucleus at
the center and show small or no intrinsic absorption (<10^(22) cm^(-1)). We
analyzed all available X-ray archived XMM-Newton and Chandra observations of 13
LINER 1s satisfying the above criterion in a systematic homogeneous way. We
looked for any correlations between the X-ray properties and the intrinsic
parameters of our sample of LINER 1s. An absorbed power-law gave a good fit to
the spectra of 9 out of the 13 sources. A thermal component and an absorbed
power-law were required in the remaining 4 sources. We found a photon index
between 1.3\pm0.2 for the hardest source and 2.4^(+0.2)_(-0.3) for the softest
one with a mean value of 1.9\pm0.2 and a dispersion sigma=0.3. The thermal
component had a mean temperature kT~0.6 keV. Significant short (hours to days)
time-scale variability is not common in the present sample and was observed in
only 2 sources (NGC 3226 and NGC 4278). Three other sources indicate a possible
variability with a low K-S test probability (2%-4%) that the nuclear emission
originates from a constant source. Significant variability on months to years
time-scales is detected in 7 out of the 9 sources observed more than once. No
significant Fe K(alpha) emission line at 6.4 keV was detected and upper limits
were derived for the 4 sources with a high enough signal to noise ratio around
6 keV. Finally, we established, for the first time for a sample of LINER 1s,
that the photon index is significantly anticorrelated to L_(2-10 keV)/L_(Edd).
This anticorrelation is similar to the one seen in XRBs in their low/hard state
where a radiatively inefficient accretion flow is thought to be responsible for
the X-ray emitted energy.
