We investigate the cores of fossil galaxy groups and clusters (`fossil
systems') using archival Chandra data for a sample of 17 fossil systems. We
determined the cool-core fraction for fossils via three observable diagnostics,
the central cooling time, cuspiness, and concentration parameter. We quantified
the dynamical state of the fossils by the X-ray peak/brightest cluster galaxy
(BCG), and the X-ray peak/emission weighted centre separations. We studied the
X-ray emission coincident with the BCG to detect the presence of potential
thermal coronae. A deprojection analysis was performed for z < 0.05 fossils to
obtain cooling time and entropy profiles, and to resolve subtle temperature
structures. We investigated the Lx-T relation for fossils from the 400d
catalogue to see if the scaling relation deviates from that of other groups.
Most fossils are identified as cool-core objects via at least two cool-core
diagnostics. All fossils have their dominant elliptical galaxy within 50 kpc of
the X-ray peak, and most also have the emission weighted centre within that
distance. We do not see clear indications of a X-ray corona associated with the
BCG unlike that has been observed for some other objects. Fossils do not have
universal temperature profiles, with some low-temperature objects lacking
features that are expected for ostensibly relaxed objects with a cool-core. The
entropy profiles of the z < 0.05 fossil systems can be well-described by a
power law model, albeit with indices smaller than 1. The 400d fossils Lx-T
relation shows indications of an elevated normalisation with respect to other
groups, which seems to persist even after factoring in selection effects.Comment: Accepted for publication in Astronomy and Astrophysic
