THE SIMULTANEOUS OPTICAL-TO-X-RAY SPECTRAL ENERGY DISTRIBUTION OF SOFT X-RAY SELECTED ACTIVE GALACTIC NUCLEI OBSERVED BY SWIFT

By D. Grupe, S. Komossa, K. Leighly, K. Page. 2010

159 citations recorded by the source corpus.

We report Swift observations of a sample of 92 bright soft X-ray selected active galactic nuclei (AGNs). This sample represents the largest number of AGNs observed to study the spectral energy distribution (SED) of AGNs with simultaneous optical/UV and X-ray data. The principal motivation of this study is to understand the SEDs of AGNs in the optical/UV to X-ray regime and to provide bolometric corrections which are important in determining the Eddington ratio L/LEdd. In particular, we rigorously explore the dependence of the UV–EUV contribution to the bolometric correction on the assumed EUV spectral shape. We find strong correlations of the spectral slopes αX and αUV with L/LEdd. Although narrow-line Seyfert 1 galaxies (NLS1s) have steeper αX and higher L/LEdd than broad-line Seyfert 1 galaxies (BLS1s), their optical/UV to X-ray spectral slopes αox and optical/UV slopes αUV are very similar. The mean SED of NLS1s shows that in general this type of AGNs appears to be fainter in the UV and at hard X-ray energies than BLS1s. We find a strong correlation between αX and αUV for AGNs with X-ray spectral slopes αX<1.6. For AGNs with steeper X-ray spectra, both this relation and the relation between αX and L/LEdd break down. At αX≈1.6, L/LEdd reaches unity. We note an offset in the αUV–L/LEdd relation between NLS1s and BLS1s. We argue that αUV is a good estimator of L/LEdd and suggest that αUV can be used to estimate L/LEdd in high-redshift QSOs. Although NLS1s appear to be highly variable in X-rays, they only vary marginally in the UV.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/46252d2ab9b7227eaad4228ab8aff1f6342985ae

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In Astronomy and Astrophysics

1. E. Berger
2. Raffaella Margutti
3. S. Komossa
4. M. Nicholl
5. Ryan Chornock
6. J. Guillochon
7. M. Lister
8. Y. Kovalev

In Nuclear and High Energy Physics

1. M. Lister
2. Y. Kovalev
3. E. Berger
4. Luigi Foschini
5. E. Lusso
6. G. Risaliti
7. M. Nicholl
8. J. Guillochon

Citations in the corpus

• Properties of flat-spectrum radio-loud Narrow-Line Seyfert 1 Galaxies (2014, methodology): “This spectral index can be compared with the values of 0.79 (median 0.61) for BLS1, and 0.85 (median 0.65) for NLS1 in the Grupe et al. (2010) sample, also based onSwift/UVOT observations.”
• A HUBBLE DIAGRAM FOR QUASARS (2015, methodology): “…(SDSS) second quasar catalog with XMM-Newton observations (Young et al. 2010), (3) a sample of 545 object from the COSMOS–XMM-Newton survey (Lusso et al. 2010), and (4) a sample of 200 quasars with UV and X-ray observations from the Swift observatory (Grupe et al. 2010; Vagnetti et al. 2010).”
• PS16dtm: A Tidal Disruption Event in a Narrow-line Seyfert 1 Galaxy (2017, background): “…on timescales as short as days (Boller et al. 1993, 1996; Edelson et al. 2002) and that this variability is typically correlated with UV/optical variability (Uttley 2006; Grupe et al. 2010), it is significant that a long-term X-ray low state is contemporaneous with a bright UV/optical transient.”