2020AJ....159..220S

WIYN/Hydra spectra (R ∼ 13,500, signal-to-noise pixel^–1 = 50-1000) of a 400 Å region around Li 6708 Å 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_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_RAD = 8.512 ± 0.087 km s^–1 (σ_µ, and σ = 0.848 km s^–1). Using 16 isolated Fe I lines for a subsample of 99 single members (that have σ_Teff_< 75 K (from 10 colors from UBVRI), v sin i < 25 km s^–1, and well-behaved Fe I lines), [Fe/H]_M48 = -0.063 ± 0.007 dex (σ_µ). [Fe/H] is independent of T_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.