The multiwavelength variability of 3C 273

Soldi, S.; Türler, M.; Paltani, S.; Aller, H. D.; Aller, M. F.; Burki, G.; Chernyakova, M.; Lähteenmäki, A.; McHardy, I. M.; Robson, E. I.; Staubert, R.; Tornikoski, M.; Walter, R.; Courvoisier, T. J. L.

doi:10.1051/0004-6361:200809947

Cited by 144 publications

(173 citation statements)

References 59 publications

(97 reference statements)

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“…The flatter spectra observed in radio-loud AGNs are usually attributed to an enhanced X-ray emission from the jet component. Note however that variability analysis in 3C 273 has shown no correlation between X-ray emission and radiomm emission from the jet (Soldi et al 2008). On the other hand, a connection between radio-loudness and black hole mass has also been observed.…”

Section: The γ − M Bh Relation and The Radio-loudness Dichotomymentioning

confidence: 95%

X-ray power law spectra in active galactic nuclei

Ishibashi

Courvoisier

2010

A&A

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X-ray spectra of active galactic nuclei (AGN) are usually described as power law spectra, characterized by the spectral slope α or photon index Γ. Here we discuss the X-ray spectral properties within the framework of clumpy accretion flows, and estimate the power law slope as a function of the source parameters. We expect harder spectra in massive objects than in less massive sources, and steeper spectra in higher accretion rate systems. The predicted values of the photon index cover the range of spectral slopes typically observed in Seyfert galaxies and quasars. The overall trends are consistent with observations, and may account for the positive correlation of the photon index with Eddington ratio (and the possible anticorrelation with black hole mass) observed in different AGN samples. Spectral properties are also closely related to variability properties. We obtain that shorter characteristic time scales are associated with steeper spectra. This agrees with the observed "spectral-timing" correlation.

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Section: The γ − M Bh Relation and The Radio-loudness Dichotomymentioning

confidence: 95%

X-ray power law spectra in active galactic nuclei

Ishibashi

Courvoisier

2010

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“…The blazar 3C 273 is characterised by a strong radio emission from mm-to cm-wavelengths (Soldi et al 2008). It has been suggested that this radio emission is caused by synchrotron emission of relativistic electrons in the jet, which could emit up to infrared (IR) frequencies (McHardy et al 1999;Soldi et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…It has been suggested that this radio emission is caused by synchrotron emission of relativistic electrons in the jet, which could emit up to infrared (IR) frequencies (McHardy et al 1999;Soldi et al 2008). Türler et al (1999) found that the sub-mm to radio flaring Master student at the Argelander Institut für Astronomie (AIfA) -University of Bonn.…”

Section: Introductionmentioning

confidence: 99%

“…Two possible components have been suggested to explain the complex optical/UV spectrum. One rapidly variable component might stem from the accretion disk (Shields 1978;Soldi et al 2008) or illumination by an X-ray source (Ross & Fabian 1993) or a hot corona (Haardt et al 1994). The second component seems to be related to synchrotron emission from the jet (Paltani et al 1998).…”

Section: Introductionmentioning

confidence: 99%

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Exploring the nature of the broadband variability in the flat spectrum radio quasar 3C 273

Chidiac

Rani

Krichbaum

et al. 2016

A&A

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The detailed investigation of the broadband flux variability in the blazar 3C 273 allowed us to probe the location and size of emission regions and their physical conditions. We conducted correlation studies of the flaring activity in 3C 273, which was observed for the period between 2008 and 2012. The observed broadband variations were investigated using the structure function and the discrete correlation function methods. Starting from the commonly used power spectral density (PSD) analysis at X-ray frequencies, we extended our investigation to characterise the nature of variability at radio, optical, and γ-ray frequencies. The PSD analysis showed that the optical and infrared light-curve slopes are consistent with the slope of white-noise processes, while the PSD slopes at radio, X-ray, and γ-ray energies are consistent with red-noise processes. We found that the estimated fractional variability amplitudes strongly depend on the observed frequency. The flux variations at γ-ray and mm-radio bands are found to be significantly correlated. Using the estimated time lag of (110 ± 27) days between γ-ray and radio light-curves, where γ-ray variations lead the radio bands, we constrained the location of the γ-ray emission region at a de-projected distance of 1.2 ± 0.9 pc from the jet apex. Flux variations at X-ray bands were found to have a significant correlation with variations at both radio and γ-ray energies. The correlation between X-ray and γ-ray light curves indicates two possible time lags, which suggests that two components are responsible for the X-ray emission. A negative time lag of −(50 ± 20) days, where the X-rays are leading the emission, suggests that X-rays are emitted closer to the jet apex from a compact region (0.02-0.05 pc in size), most likely from the corona at a distance of (0.5 ± 0.4) pc from the jet apex. A positive time lag of (110 ± 20) days (γ-rays are leading the emission) suggests a jet-base origin of the other X-ray component at ∼4 to 5 pc from the jet apex. The flux variations at radio frequencies were found to be well correlated with each other such that the variations at higher frequencies are leading the lower frequencies, which is expected from the standard shock-in-jet model.

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“…In the softer X-ray domain ( < ∼ 10 keV), extensive variability studies have been carried out, especially in the recent years thanks to the numerous monitoring campaigns with RXTE and XMM-Newton, covering time scales from hours to years. Many important results have been obtained with these observations, such as the complex correlation of the X-rays with the emission at other wavelengths (e.g., McHardy et al 2007;Soldi et al 2008;Bell et al 2011;Mehdipour et al 2011;Chatterjee et al 2011), in particular, in the optical-UV band (e.g., Shemmer et al 2003;Uttley 2005;Arévalo et al 2008b;Breedt et alA&A 563, A57 (2014) between variability properties and black hole mass (e.g., Czerny et al 2001;Lu & Yu 2001;Uttley et al 2002;Papadakis 2004) and accretion rate (McHardy et al 2006;Körding et al 2007). See McHardy (2010) for a review of X-ray variability and its scaling from stellar to super-massive black holes.…”

Section: Introductionmentioning

confidence: 99%

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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The multiwavelength variability of 3C 273

Cited by 144 publications

References 59 publications

X-ray power law spectra in active galactic nuclei

X-ray power law spectra in active galactic nuclei

Exploring the nature of the broadband variability in the flat spectrum radio quasar 3C 273

Long-term variability of AGN at hard X-rays

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