DOUBLE-PEAKED BALMER LINE EMISSION IN THE RADIO-QUIET AGN RX J1042+1212

We present optical and X-ray spectra of a radio-quiet, X-ray-selected AGN, RX J1042 + 1212 (z = 0.271). The H alpha and H beta emission line s are very broad (with full widths at half maximum of similar to 10000 km s(-1)) and have double-peaked profiles. Such features are rarely o bserved in AGN in general, but are even more unusual in radio-quiet ob jects. The analysis of the ROSAT PSPC data reveals a non-varying, unab sorbed spectrum with an energy spectral index alpha(x) = 1.2 and littl e or no emission from a soft X-ray excess. The slope of the optical sp ectrum is similar, alpha(opt) = 1.0, and is consistent with an extrapo lation of the X-ray spectrum, suggesting that the same power-law conti nuum may dominate throughout, and that the big blue bump component is relatively weak. We look for a link between these various properties, and investigate models of double-peaked Balmer line emission in AGN. A n accretion disc origin is unlikely in RX J1042 + 1212, as this model predicts that lines emitted by a disc should have a net gravitational redshift (both H alpha and H beta have a net blueshift). Emission from two broad-line regions, each gravitationally bound to one component o f a supermassive black hole binary, is a possibility If the two compon ents are similar in size and nature. Alternatively, the lines (or at l east the narrow peaks of the lines) may be produced by a double-sided jet or bipolar flow.