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Astron. Astrophys. 341, L13-L16 (1999)


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Letter to the Editor

Ultraluminous IRAS galaxy 10026+4347

X.-Y. Xia 1,4, S. Mao 2,4, H. Wu 3,4, Z. Zheng 3,4, Th. Boller 5, Z.-G. Deng 6,4 and Z.-L. Zou 3,4

1 Department of Physics, Tianjin Normal University, 300074 Tianjin, P.R. China
2 Max-Planck-Institut für Astrophysik Karl-Schwarzschchild-Strasse 1, D-85740 Garching, Germany
3 Beijing Astronomical Observatory, Chinese Academy of Sciences, 100080 Beijing, P.R. China
4 Beijing Astrophysics Center (BAC) *, 100871 Beijing, P.R. China
5 Max-Planck-Institut für Extraterrestrische Physik, Karl-Schwarzschild-Strasse 1, D-85740 Garching bei München, Germany
6 Department of Physics, Graduate School, Chinese Academy of Sciences, 100039 Beijing, P.R. China

Received 17 September 1998 / Accepted 8 November 1998

Abstract

We study optical and X-ray properties of the ultraluminous IRAS galaxy 10026+4347. This galaxy is a narrow-line QSO with very strong FeII emission. Three optical spectra were taken over two years. The full widths at half maximum (FWHMs) of the emission lines are constant whereas the third spectrum seems to show a continuum change. Intermediate-band photometry also shows a small (0.1 mag) but significant decrease in flux. HST WFPC2 images suggest that this object is a post-merger galaxy. The source is X-ray luminous ([FORMULA]) with a very soft X-ray spectrum (photon index [FORMULA]). The X-ray luminosity exhibits variabilities of a factor of [FORMULA] over four years and a factor of two within two days. During these X-ray flux changes, the X-ray spectral shapes are consistent with no variation. All the optical and X-ray properties resemble those of narrow-line Seyfert 1 galaxies (NLS1), except that the FWHM of [FORMULA] is about 2500 [FORMULA], larger than that for most NLS1s. We discuss the implications of our results on models of NLS1s.

Key words: galaxies: active – galaxies: interactions – quasars: emission lines – galaxies: Seyfert – galaxies: nuclei

* BAC is jointly sponsored by the Chinese Academy of Sciences and Peking University

Send offprint requests to: X.-Y. Xia

© European Southern Observatory (ESO) 1999

Online publication: November 26, 1998

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