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The radio source FIRST J102347.6+003841 was presented as the firstradio-selected cataclysmic. In the discovery paper, Bond et al. (2002) show aspectrum consistent with a magnetic AM Her-type system and a light curve withrapid, irregular flickering. In contrast, Woudt, Warner, and Pretorius (2004)found a smoothly-varying light curve with a period near 4.75 h and one minimumper orbit, indicating a dramatic change. We present time-resolved spectrashowing a superficially normal, mid-G type photosphere, with no detectableemission lines. The absorption-line radial velocity varies sinusoidally, withsemi-amplitude 268 +- 4 km/s, on the orbital period, which is refined to0.198094(2) d. At this orbital period the secondary's spectral type isatypically early, suggesting an unusual evolutionary history. We also obtainedBVI photometry around the orbit. The light curve resembles that given by Woudtet al., and the color modulation is consistent with a heating effect. A simpleillumination model matches the observations strikingly well with a Roche-lobefilling secondary near 5650 kelvin being illuminated by a primary giving outaround 2 solar luminosities. The modest amplitude of the observed modulationconstrains the orbital inclination to be less than about 55 deg, unless thegravity darkening is artificially reduced. The resulting primary star mass isabove the Chandrasekhar limit (assuming conventional gravity darkening). Weexamine the possibility that the compact object in this system is not a whitedwarf, in which case this is not actually a cataclysmic variable. On closeexamination, FIRST J102347.6+003841 defies easy classification.Comment: 24 pages, 5 postscript and two JPG figures; Astronomical Journal,  accepte

Is FIRST J102347.6+003841 Really a Cataclysmic Binary?