  We present results of a 37 ks observation of CL 0016+16 with the XMM-Newton
EPIC instrument. Within 1.5 arcmin of the cluster centre we measure a gas
temperature of kT = 9.13^{+0.24}_{-0.22} keV and an abundance of
0.22^{+0.04}_{-0.03} times the solar value (1 sigma uncertainties). This
significant improvement over previous measurements has allowed us to revise the
estimate of the Hubble constant based on CL 0016+16 to 68 +/- 8 km s^{-1}
Mpc^{-1} (random error only), close to the value from the Hubble Space
Telescope distance-scale project. The total gravitating mass within a radius of
248 kpc of the cluster centre is in good agreement with that found from
gravitational lensing over the same region, supporting the assumption of
isothermal gas in hydrostatic equilibrium. The gas mass fraction of 0.13 +/-
0.02 is in remarkable agreement with that given by cosmological parameters for
the Universe as a whole, suggesting that CL 0016+16 is a fair sample of the
matter content of the Universe. While there is no spectral or spatial evidence
to suggest a cooling flow in CL 0016+16, we find an asymmetrical central X-ray
structure which may have a harder spectrum than the cluster as a whole, and be
evidence for some merger activity, in addition to a previously reported
asymmetry to the west of the cluster. The nearest companion cluster to CL
0016+16 is measured to have a gas temperature of kT = 3.8^{+0.3}_{-0.3} keV and
an abundance of 0.6^{+0.3}_{-0.2} times the solar value (1 sigma
uncertainties). We also present spectral data for the companion quasar whose
spectrum was confused with CL 0016+16 in previous ASCA data.

Astrophysics