  We present a new short-period brown dwarf candidate around the star TYC
1240-00945-1. This candidate was discovered in the first year of the
Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which
is part of the third phase of the Sloan Digital Sky Survey (SDSS-III), and we
designate the brown dwarf as MARVELS-1b. MARVELS uses the technique of
dispersed fixed-delay interferometery to simultaneously obtain radial velocity
measurements for 60 objects per field using a single, custom-built instrument
that is fiber fed from the SDSS 2.5-m telescope. From our 20 radial velocity
measurements spread over a ~370 d time baseline, we derive a Keplerian orbital
fit with semi-amplitude K=2.533+/-0.025 km/s, period P=5.8953+/-0.0004 d, and
eccentricity consistent with circular. Independent follow-up radial velocity
data confirm the orbit. Adopting a mass of 1.37+/-0.11 M_Sun for the slightly
evolved F9 host star, we infer that the companion has a minimum mass of
28.0+/-1.5 M_Jup, a semimajor axis 0.071+/-0.002 AU assuming an edge-on orbit,
and is probably tidally synchronized. We find no evidence for coherent
instrinsic variability of the host star at the period of the companion at
levels greater than a few millimagnitudes. The companion has an a priori
transit probability of ~14%. Although we find no evidence for transits, we
cannot definitively rule them out for companion radii ~<1 R_Jup.
