Swift Observations of the highly X-ray variable Narrow Line Seyfert 1 galaxy RX J0148.3-2758

Abstract

We report on Swift observations of the Narrow-Line Seyfert 1 galaxy (NLS1) RX J0148.3--2758. It was observed for 41.6 ks in 2005 May and for 15.8 ks in 2005 December. On short as well as on long timescales RX J0148.3--2758 is a highly variable source. It doubles its X-ray flux within 18-25 ks. The observation of 2005 December 09, which had a flux 4 times lower than during the 2005 May observations, shows a significant hardening of the X-ray hardness ratio compared with the 2005-May and 2005-December 20/21 observations. A detailed analysis of the X-ray spectra shows that we actually observe two spectral changes in RX J0148.3-2758: First a decrease of the soft X-ray component between 2005 May and December 09, which is most likely due to an increase of the intrinsic absorber column, and second a decrease of the hard X-ray flux in the December 20/21 observations. The soft X-ray spectral slope ${\alpha }_{\mathrm{X},\mathrm{soft}}$=2.58${}_{-0.12}^{+0.15}$ during the high state in 2005 May agrees well with that measured by ROSAT (\axs=2.54\plm0.82). In contrast to the strong X-ray variability, the analysis of the Swift UVOT photometry from December 2005 of RX J0148.3--2758 shows no significant variability in any of the 6 UVOT filters. From the simultaneous X-ray and UV observations in 2005 December we measured the X-ray loudness alpha-ox varies between alpha-ox=1.5 and 1.8. Our Swift observations of RX J0148.3-2758 demonstrate the great potential the multi-wavelength observatory Swift has for AGN science. (shortened)

19 pages; accepted for publication the Astronomical Journal

References in corpus (12)

• Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships
• Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data
• Extreme X-ray spectral variability in the Seyfert 2 Galaxy NGC 1365
• Soft X-ray and Ultraviolet Emission Relations in Optically Selected AGN Samples
• An Unveiling Event in the Type 2 AGN NGC4388: A Challenge for a Parsec Scale Absorber
• The Swift/BAT High Latitude Survey: First Results
• Investigating the nature of narrow-line Seyfert 1 galaxies with high-energy spectral complexity
• Resolving the large scale spectral variability of the luminous Seyfert 1 galaxy 1H 0419-577: Evidence for a new emission component and absorption by cold dense matter
• The Locus of Highly Accreting AGNs on the M_BH--sigma Plane: Selections, Limitations, and Implications
• The Largest Blueshifts of [O III] emission line in Two Narrow-Line Quasars
• Black hole growth by accretion
• Chandra Observations of the NLS1 RX J2217.9-5941

Cited by in corpus (4)

• The Simultaneous Optical-to-X-ray Spectral Energy Distribution of Soft X-ray Selected AGN observed by Swift
• X-ray spectral variability in PG1535+547: the changing-look of a 'soft X-ray weak' AGN
• First detection of hard X-ray photons in the soft X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: The X-ray photon distribution observed by Swift
• An Update on the X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: Swift observations of UV variability and persistence of X-ray faintness