Astrophysics and Space Science

, 363:228 | Cite as

The broad-band spectrum of the narrow-line Seyfert 1 NGC 4748: from UV to hard X-ray

  • A. A. VasylenkoEmail author
Original Article


We report the results obtained by a broad-band (0.5–500 keV) data analysis of narrow-line Seyfert 1 galaxy NGC 4748 observed with an XMM-Newton/PN, INTEGRAL/ISGRI and SWIFT/BAT telescopes. This galaxy has a soft X-ray excess that is typical for the class of narrow-line Seyfert 1. The question of the origin of soft excess in such objects is still unclear. We tested and compared two spectral models for the soft X-ray spectra based on the different physical scenarios. The first one is based on the Done and Nayakshin model of two-phase accretion disc in a vertical direction, which includes two reflection zones with different ionization levels. According to this model, we found that a highly ionized reflection has the value of ionization \(\xi \sim 3000~\mbox{erg}\,\mbox{s}^{-1}\,\mbox{cm}\) and is mostly responsible for the soft excess. This reflection becomes comparable with a low ionized one (\(\xi \sim 30~\mbox{erg}\,\mbox{s}^{-1}\,\mbox{cm}\)) in moderate X-ray range. However, this model requires also an additional component at soft energies with \(kT\sim 300\) eV. The second model is an energetically self-consistent model and assumes that a soft excess arises from optically thick thermal Comptonization of the disc emission. Combination of the UV (from XMM/Optical monitor) and X-ray data in the latter model allowed us to determine a mass of the central black hole of \(6.9\times 10^{6}M_{\odot }\) and Eddington ratio \(\log_{L/L_{Edd}}\simeq -0.57\). Also, we were not able to rule out one of competing models using only X-ray spectra of NGC 4748.


Accretion Active galaxies Individual NGC 4748 galaxies Nuclei X ray Seyfert 



This paper is based on the observations obtained by XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, and data provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NASA.

The author is grateful to Dr. Kryshtal O.N. and Dr. Fedorova E.V. for the useful discussion, Dr. Vavilova I.B. for helpful remarks and Dr. Chichuan Jin for his kind instructions on the correct use of optxagnf model. The author also thanks Torbaniuk O. and Dr. Pakuliak L. for technical assistance. The author is grateful to the anonymous referee for the helpful constructive comments and suggestions.


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Authors and Affiliations

  1. 1.Main Astronomical ObservatoryNational Academy of Sciences of UkraineKyivUkraine

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