Optical and X-ray characteristics of a newly discovered narrow-line quasi-stellar object: RX J1334.2+3759

Abstract

We report the discovery of a narrow-line quasi-stellar object (NLQSO) RX J1334.213759 with a steep soft X-ray spectrum. Soft X-ray emission from the NLQSO is highly variable. Changes in the intensity by a factor of ~2 have been detected in the ROSAT Position Sensitive Proportional Counter (PSPC) observations of RX J1334.2+3759 on time-scales of ~20 000-40 000 s. Rapid variability events have also been observed from RX J1334.2+3759. The most extreme variable event has ΔL/Δt=1:95±1:02. 10⁴² erg s⁻² corresponding to a change in the intensity by a factor of ~4 within ≲400 s. The PSPC spectra of the NLQSO can be well represented by a power law of photon index Γ_X ∼3:8, modified by an absorbing column local to the source (ΔN_H~3:3×10²⁰ cm⁻²) over and above that caused by our own Galaxy (N_H=7:9×10¹⁹ cm⁻²). The intrinsic soft X-ray luminosity of RX J1334.2+3759 is estimated to be ∼ 2:2×10⁴⁴ erg s⁻¹ in the energy band of 0:1-2:0 keV. The optical spectrum of RX J1334.2+3759 is typical of the narrow-line Seyfert 1 (NLS1) galaxies showing strong Balmer Hβ, Hα, and forbidden line of [O III]λ5007. Fe II multiplets, usually present in the optical spectra of NLS1 galaxies, are also detected from RX J1334.2+3759. Decomposition of the Hβ and Hα line profiles shows the presence of narrow [full width at half-maximum (FWHM) ~880 kms⁻¹] and broad (FWHM ~2850 km s⁻¹) components in the spectrum of RX J1334.2+3759. The narrow-line region of RX J1334.2+3759 appears to be significantly different from those of normal Seyfert galaxies. A possible explanation for the observed properties of the narrow-line region and the broad-line region is suggested in terms of density enhancements.