The Hercules cluster in X-rays with $XMM$-$Newton$ and $Chandra$
  We present a detailed X-ray study of the central subcluster of the nearby
($z$ $\sim$0.0368) Hercules cluster (Abell 2151) identified as A2151C that
shows a bimodal structure. A bright clump of hot gas with X-ray emission
extending to radius $r$ $\sim$304 kpc and $L_X =
3.03_{-0.04}^{+0.02}\times10^{43}$ erg s$^{-1}$ in the 0.4$-$7.0 keV energy
range is seen as a fairly regular subclump towards the west (A2151C(B)). An
irregular, fainter and cooler subclump with radius $r$ $\sim$364 kpc is seen
towards the east (A2151C(F)) and has $L_X=1.13\pm{0.02}\times10^{43}$ erg
s$^{-1}$ in the 0.4$-$7.0 keV energy band. The average temperature and
elemental abundance of A2151C(B) are $2.01\pm{0.05}$ keV and $0.43\pm{0.05}$
Z$_{\odot}$ respectively, while these values are $1.17\pm{0.04}$ keV and
$0.13\pm{0.02}$ Z$_{\odot}$ for A2151C(F). Low temperature (${1.55}\pm{0.07}$
keV) and a short cooling time ($\sim$0.81 Gyr) within the central 15 arcsec
region confirm the presence of a cool core in A2151C(B). We identify several
compact groups of galaxies within A2151C(F). We find that A2151C(F) is a
distinct galaxy group in the process of formation and likely not a ram-pressure
stripped part of the eastern subcluster in Hercules (A2151E). X-ray emission
from A2151C shows a region of overlap between A2151C(B) and A2151C(F) but
without any enhancement of temperature or entropy in the two-dimensional (2D)
projected thermodynamic maps that could have indicated an interaction due to
merger between the two subclumps.
