The UV spectrum of the narrow-line Seyfert 1 galaxy, REJ1034+396

Abstract

We present UV spectroscopy of RE1034+396, taken with the Faint Object Spectrograph on the Hubble Space Telescope. With a spectral resolution of ~1-2A FWHM and a typical S/N of ~15 per diode, this is one of the first detailed UV spectra of an object in the narrow-line Seyfert 1 (NLS1) class. The spectrum probes the physics and kinematics of the high-ionization and coronal line gas, and the strength and form of the big blue bump component in the UV. We detect many emission lines, including Lyman alpha, CIV1549, HeII1640, CIII]1909 and MgII2798. We also identify a feature at 2647A (in the rest-frame) with highly-ionized iron [FeXI]2649; a line of the same species ([FeXI]7892) has also been seen in the optical spectrum. The velocity widths of the UV lines are relatively narrow (FWHM<2000 km/s) and similar to those of the optical lines, which suggests that all line emission in REJ1034+396, ie. including that of high- and low-ionization species and the forbidden lines, may be dominated by an intermediate-velocity (FWHM~1000 km/s), intermediate-density (log Ne~7.5 cm-3) region of gas. The slope of the UV continuum (alpha~0.9) is soft (ie. red) relative to quasars and the UV-to-soft X-ray flux ratio is unusually low implying that the big blue bump component is very weak in the UV. The present epoch UV to soft X-ray continuum is consistent with earlier data, demonstrating that this extreme big blue bump component is also very stable, unlike many other NLS1s which show extreme patterns of variability.