Narrow-line Seyfert 1 galaxies at hard X-rays★

Panessa, F.; Rosa, A. De; Bassani, L.; Bazzano, A.; Bird, A. J.; Landi, R.; Malizia, A.; Miniutti, G.; Molina, M.; Ubertini, P.

doi:10.1111/j.1365-2966.2011.19268.x

Cited by 68 publications

(68 citation statements)

References 108 publications

(190 reference statements)

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“…Most of these distinctive properties of NLS1s have been interpreted in the context of relatively small black hole masses undergoing rapid evolution, powered by higher accretion rates than their broad line equivalent (Peterson et al 2000). The average hard X-ray photon index of the NLS1 in our sample is indeed slightly larger than for the rest of the Seyfert class ( Γ NLS1 = 2.2 ± 0.1, Γ Sey1 = 2.01 ± 0.02), as also derived from INTEGRAL observations on 14 NLS1s (Ricci et al 2011b;Panessa et al 2011). On the other hand, the average variability amplitude is consistent with what is observed for broad line Seyfert 1 ( S V NLS1 = 15 ± 3%).…”

Section: Variability Of the Different Agn Classessupporting

confidence: 49%

Long-term variability of AGN at hard X-rays

Soldi¹,

Beckmann²,

Baumgartner³

et al. 2014

A&A

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Aims. Variability at all observed wavelengths is a distinctive property of active galactic nuclei (AGN). Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by absorption along the line of sight. Characterizing the intrinsic hard X-ray variability of a large AGN sample and comparing it to the results obtained at lower X-ray energies can significantly contribute to our understanding of the mechanisms underlying the high-energy radiation. Methods. Swift/BAT provides us with the unique opportunity to follow, on time scales of days to years and with regular sampling, the 14-195 keV emission of the largest AGN sample available up to date for this kind of investigation. As a continuation of an early work using the first 9 months of BAT data, we study the amplitude of the variations and their dependence on subclass and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. Results. About 80% of the AGN in the sample are found to exhibit significant variability on month-to-year time scales. In particular, radio loud sources are the most variable, and Seyfert 1.5−2 galaxies are slightly more variable than Seyfert 1, while absorbed and unabsorbed objects show similar timing properties. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes in the absorption column density. In general, the variations in the 14-24 and 35-100 keV bands are correlated well, suggesting a common origin to the variability across the BAT energy band. However, radio quiet AGN display on average 10% larger variations at 14-24 keV than at 35-100 keV, and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on a time scale of a month. In addition, sources with harder spectra are found to be more variable than softer ones, unlike what it is observed below 10 keV. These properties are generally consistent with a variable, in flux and shape, power law continuum, pivoting at energies > ∼ 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at hard X-rays are comparable to those at lower energies, with at least some of the differences possibly ascribable to components contributing differently in the two energy domains (e.g., reflection, absorption).

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Section: Variability Of the Different Agn Classessupporting

confidence: 49%

Long-term variability of AGN at hard X-rays

Soldi¹,

Beckmann²,

Baumgartner³

et al. 2014

A&A

View full text Add to dashboard Cite

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“…LEDA 023094, which is its optical counterpart with magnitude B = 15.5 and redshift of 0.027, displays optical features typical of NLS1 (see Section 3). These sources are rare among hard X-ray selected objects since their fraction is only 5% among all AGN and 10% among type 1 Seyferts (Panessa et al 2011). A possible interpretation for the peculiar observational properties of NLS1 is that these systems are accreting close to their Eddington limit, implying that, compared to typical Seyfert 1 galaxies, they should host black holes with smaller masses (M BH ≤ 10 7 M ⊙ ).…”

Section: Peculiar Sources and Discussionmentioning

confidence: 99%

“…PBC J0814.4+0421, the only NLS1 in the sample, is absorbed, but this is not unusual, as the presence of strong, partial and/or stratified absorption is one of the two competing models used to explain the complex X-ray spectra of this class of AGN (Panessa et al 2011).…”

Section: X-ray Versus Optical Classification and Absorptionmentioning

confidence: 99%

Accurate classification of 28 objects detected in the 39 months Palermo Swift/BAT hard X-ray catalogue

Parisi¹

2012

Proceedings of the Extreme and Variable High Energy Sky — PoS(Extremesky 2011)

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Through an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we have obtained optical spectroscopy for 29 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 39 months Palermo catalogue. All these objects have also observations taken with Swift/XRT or XMM-EPIC which not only allow us to pinpoint their optical counterpart, but also to study their X-ray spectral properties (column density, power law photon index and F2−10 keV flux). We find that 28 sources in our sample are AGN; 7 are classified as type 1 while 21 are of type 2; the remaining object is a galactic cataclysmic variable. Among our type 1 AGN, we find 5 objects of intermediate Seyfert type (1.2-1.9) and one Narrow Line Seyfert 1 galaxy; for 4 out of 7 sources, we have been able to estimate the central black hole mass. Three of the type 2 AGN of our sample display optical features typical of the LINER class and one is a likely Compton thick AGN. All galaxies classified in this work are relatively nearby objects since their redshifts lie in the range 0.008-0.075; the only galactic object found lies at an estimated distance of 90 pc. We have also investigated the optical versus X-ray emission ratio of the galaxies of our sample to test the AGN unified model. For them, we have also compared the X-ray absorption (due to gas) with the optical reddening (due to dust): we find that for most of our sources, specifically those of type 1.9-2.0 the former is higher than the latter confirming early results by Maiolino et al. (2001); this is possibly due to the properties of dust in the circumnuclear obscuring torus of the AGN.

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“…This class of sources is characterized by relatively narrow permitted lines (below 2000 km s −1 for NLS1, below 4000 km s −1 for bright type A quasars); the permitted lines have Lorentzian profiles, strong Fe II emission, relatively small optical variability, but with occasional flares, relatively large X-ray variability, and their X-ray spectra are dominated by strong soft X-ray excess, followed by a steep hard X-ray power law (Boller et al 1996;Brandt et al 1997;Leighly Leighly1999;Wang & Netzer 2003;Gallo 2006;Panessa et al 2011;Marziani et al 2013;Ai et al 2013). These properties are probably connected with the accretion at the levels close to the Eddington ratio (e.g., Pounds et al 1995;Mineshige et al 2000;Grupe 2004;Collin et al 2006).…”

Section: Nature Of the Blr In Type A Quasarsmentioning

confidence: 99%

SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II component

Hryniewicz

Czerny

Pych

et al. 2014

A&A

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Context. The Mg II line is of extreme importance in intermediate redshift quasars since it allows us to measure the black hole mass in these sources and to use these sources as probes of the distribution of dark energy in the Universe, as a complementary tool to SN Ia. Aims. Reliable use of Mg II requires a good understanding of all the systematic effects involved in the measurement of the line properties, including the contamination by Fe II UV emission. Methods. We performed three spectroscopic observations of a quasar LBQS 2113-4538 (z = 0.956) with the SALT telescope, separated in time by several months and we analyze in detail the mean spectrum and the variability in the spectral shape. Results. We show that even in our good-quality spectra the Mg II doublet is well fit by a single Lorentzian shape. We tested several models of the Fe II pseudo-continuum and showed that one of them well represents all the data. The amplitudes of both components vary in time, but the shapes do not change significantly. The measured line width of LBQS 2113-4538 identifies this object as a class A quasar. The upper limit of 3% for the contribution of the narrow line region (NLR) to Mg II may suggest that the separation of the broad line region and NLR disappears in this class of objects.

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Narrow-line Seyfert 1 galaxies at hard X-rays★

Cited by 68 publications

References 108 publications

Long-term variability of AGN at hard X-rays

Long-term variability of AGN at hard X-rays

Accurate classification of 28 objects detected in the 39 months Palermo Swift/BAT hard X-ray catalogue

SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II component

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