The Unusual Spectral Energy Distribution of LBQS 0102-2713

We have studied the spectral energy distribution of the quasar LBQS 0102-2713. The available multiwavelength data in the observers frame are one optical spectrum between 3200 and 7400 Å, seven Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra between 1700 and 2300 Å, one GALEX NUV flux density and a K_S magnitude obtained from NASA/IPAC Extragalactic Database, and three public ROSAT PSPC pointed observations in the 0.1-2.4 keV energy band. The α_ox values obtained from the HST FOS, the optical spectrum, and the ROSAT observations are -2.3 and -2.2, respectively, comparable to broad absorption line (BAL) quasars. The 2500 Å luminosity density is about a factor of 10 higher compared to the mean of the most luminous Sloan Digital Sky Survey quasars. The 2 keV νL _ν value is lower by about a factor of 10 compared to the radio-loud quasars shown in Figure 10 of Richards et al. LBQS 0102-2713 exhibits one of the steepest soft X-ray photon indices obtained so far. For a simple power-law fit with leaving the N_H free in the fit, we obtain a photon index of Γ = 6.0 ± 1.3. Fixing the N_H value to the Galactic value, the photon index still remains steep with a value of about 3.5. We argue that LBQS 0102-2713 is similar to BAL quasars with respect to their UV brightness and 2 keV X-ray weakness. However, the absorption by neutral matter is significantly lower compared to BAL quasars. The X-ray weakness is most probably not due intrinsically X-ray weakness based on the UV line strengths which are comparable to the line strength values reported in quasar composites. If the X-ray weakness will be confirmed in future observations, LBQS 0102-2713 might be indicative for a new class of quasars with an unusual combination in their UV, X-ray, and N_H properties.