A new narrow-line Seyfert 1 galaxy: RX J1236.9+2656

Abstract

We report identification of a narrow-line Seyfert 1 galaxy RX J1236.9+2656. X-ray emission from the NLS1 galaxy undergoes long-term variability with 0.1-2.0 keV flux changing by a factor of ∼ 2 within ∼3. The ROSAT PSPC spectrum of RX J1236.9+2656 is well represented by a power-law of Γ_x=3.7^+0.5_−0.3 absorbed by matter in our own Galaxy (N_H=1.33×10²⁰ cm⁻²). Intrinsic soft X-ray luminosity of the NLS1 galaxy is estimated to be ∼ 1.5×10¹³ erg s⁻¹ in the energy band of 0.1-2.0keV. The optical spectrum of RX J1236.9+2656 is typical of NLS1 galaxies and shows narrow Balmer emission lines (1100 km s⁻¹ < FWHM < 1700 km s⁻¹) of Hβ, Hα, and forbidden lines of [O III] and [N II]. Fe II multiplets, usually present in optical spectra of NLS1 galaxies, are also detected in RX J1236.9+2656.