WIYN Open Cluster Study LXXIX. M48 (NGC 2548) I. Radial Velocities,
  Rotational Velocities, and Metallicities of Stars in the Open Cluster M48
  (NGC 2548)
  WIYN/Hydra spectra (R $\sim$ 13,500, signal-to-noise pixel$^{-1}$ = 50-1000)
of a 400 $\unicode{x212B}$ region around Li 6708 $\unicode{x212B}$ are used to
determine radial and rotational velocities for 287 photometrically selected
candidate members of the open cluster M48. The sample ranges from turnoff A
stars to late-K dwarfs and eight giants. We combine our $V_{\rm{RAD}}$
measurements and power spectrum analysis with parallax and proper motion data
from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as
single cluster members, 11 as binary members, 16 as members of uncertain
multiplicity, 56 as single nonmembers, 28 as single "likely" nonmembers, two as
single "likely" members, one as a binary "likely" member, five as binary
nonmembers, 10 as "likely" members of uncertain multiplicity, three as
nonmembers of uncertain multiplicity, and three as "likely" nonmembers of
uncertain multiplicity. From a subsample of 95 single members, we derive
$V_{\rm{RAD}}$ = 8.512 $\pm$ 0.087 km s$^{-1}$ ($\sigma_{\mu}$, and $\sigma$ =
0.848 km s$^{-1}$). Using 16 isolated Fe I lines for a subsample of 99 single
members (that have $\sigma_{T_{\rm{eff}}}$ $<$ 75 K (from 10 colors from
$UBVRI$), $v$ sin $i$ $<$ 25 km s$^{-1}$, and well-behaved Fe I lines),
[Fe/H]$_{\rm{M48}}$ = -0.063 $\pm$ 0.007 dex ($\sigma_{\mu}$). [Fe/H] is
independent of $T_{\rm{eff}}$ over an unprecedentedly large range of 2500 K.
The minimum cluster binary fraction is 11%-21%. M48 exhibits a clear but modest
broadening of the main-sequence turnoff, and there is no correlation between
color and $v$ sin $i$.
