BeppoSAX observations of 1-Jy BL Lacertae objects -- II

Padovani, P.; Costamante, L.; Giommi, P.; Ghisellini, G.; Celotti, A.; Wolter, A.

doi:10.1111/j.1365-2966.2004.07313.x

Cited by 23 publications

(20 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Data acquired by BeppoSAX on January 28, 1999 were reported by Padovani et al (2004). They found extra-absorption and both spectral index and flux consistent with the values derived by Madejski et al (1996) for the ASCA data.…”

Section: Previous X-ray Observations By Other Satellitessupporting

confidence: 66%

See 1 more Smart Citation

X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view

Raiteri

Villata

Kadler

et al. 2006

A&A

View full text Add to dashboard Cite

We analyse five observations of the BL Lac object AO 0235+16 performed with the Chandra and XMM-Newton satellites during the years 2000-2005. In the February 2002 observation the source is found in a bright state and presents a steep X-ray spectrum, while in all the other epochs it is faint and the spectrum is hard. The soft X-ray spectrum appears to be strongly absorbed, likely by the intervening system at z = 0.524, which also absorbs the optical-UV radiation. We find that models that consider spectral curvature are superior to single power law ones in fitting the X-ray spectrum. In particular, we favour a double power law model, which agrees with the assumption of a superposition of two different components in the X-ray domain. Both in the Chandra and in one of the XMM-Newton observations, a tentative detection of the redshifted Fe Kα emission line may suggest its origin from the inner part of an accretion disc. Thermal emission from this accretion disc might explain the UV-soft-X-ray bump that appears in the spectral energy distributions, when the X-ray spectra are complemented with the optical-UV data from the Optical Monitor onboard XMM-Newton. More likely, the bump can be interpreted in terms of an additional synchrotron component emitted from an inner region of the jet with respect to that where the lower-energy emission comes from. An inspection of the X-ray light curves reveals that intraday variability occurs only when the source is in a bright state.

show abstract

Section: Previous X-ray Observations By Other Satellitessupporting

confidence: 66%

“…a (1) Worral & Wilkes (1990); (2) Ghosh & Soundararajaperumal (1995); (3) Madejski et al (1996); (4) Comastri et al (1997); (5) Webb et al (2000); (6) Junkkarinen et al (2004); (7) Padovani et al (2004). b F 2 keV .…”

Section: Introductionunclassified

X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view

Raiteri

Villata

Kadler

et al. 2006

A&A

View full text Add to dashboard Cite

show abstract

“…As for the ROSAT spectrum, Madejski et al (1996) suggested that in a bright state the peak of the synchrotron component may shift to higher energies, and thus the synchrotron radiation would dominate in the soft X-ray region. This interpretation was also followed by Padovani et al (2004), when fitting the ROSAT spectrum with the homogeneous, one-zone model of Ghisellini et al (2002). However, this scenario is questioned by the contemporaneous optical data shown in Fig.…”

Section: Multiepoch Spectral Energy Distributionmentioning

confidence: 75%

Multifrequency variability of the blazar AO 0235+164

Raiteri¹,

Villata²,

Kadler

et al. 2006

A&A

View full text Add to dashboard Cite

Aims. A huge multiwavelength campaign targeting the blazar AO 0235+164 was organized by the Whole Earth Blazar Telescope (WEBT) in [2003][2004][2005] to study the variability properties of the source. Methods. Monitoring observations were carried out at cm and mm wavelengths, and in the near-IR and optical bands, while three pointings by the XMM-Newton satellite provided information on the X-ray and UV emission.Results. We present the data acquired during the second observing season, [2004][2005], by 27 radio-to-optical telescopes. The ∼2600 data points collected allow us to trace the low-energy behaviour of the source in detail, revealing an increased near-IR and optical activity with respect to the previous season. Increased variability is also found at the higher radio frequencies, down to ∼15 GHz, but not at the lower ones. While the X-ray (and optical) light curves obtained during the XMM-Newton pointings reveal no significant short-term variability, the simultaneous intraday radio observations with the 100 m telescope at Effelsberg show flux-density changes at 10.5 GHz, which are more likely due to a combination of intrinsic and extrinsic processes. Conclusions. The radio (and optical) outburst predicted to peak around February-March 2004 on the basis of the previously observed 5-6 yr quasi-periodicity did not occur. The analysis of the optical light curves reveals now a longer characteristic time scale of variability of ∼8 yr, which is also present in the radio data. The spectral energy distributions corresponding to the XMM-Newton observations performed during the WEBT campaign are compared with those pertaining to previous pointings of X-ray satellites. Bright, soft X-ray spectra can be described in terms of an extra component, which appears also when the source is faint through a hard UV spectrum and a curvature of the X-ray spectrum. Finally, there might be a correlation between the X-ray and optical bright states with a long time delay of about 5 yr, which would require a geometrical interpretation.

show abstract

“…also [5]). A rough order-of-magnitude estimate for the physical parameters in the emitting region may be obtained by fitting the multiwavelength SED with a homogeneous, one-zone synchrotron -inverse Compton model, suggesting viewing angles ∼ 2.9 • , magnetic field strengths ∼ 3.8 Gauss and bulk Lorentz factors ∼ 16 for the low state ( [28]). The analysis of the long-term variability in AO 0235+16 over a time range of ∼ 25 yr has revealed evidence for a (5.7 ± 0.5) yr periodicity in its radio lightcurves and a possible (2.95 ± 0.15) yr periodicity in its optical lightcurves, e.g.…”

Section: Application To Ao 0235+16mentioning

confidence: 99%

Periodic variability and binary black hole systems in blazars

Rieger¹

2005

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. We consider the periodic modulation of emission from jets in blazar-type sources. A differential Doppler boosting origin, associated with the helical motion of a radiating component, is analyzed for different periodic driving sources including orbital motion and jet precession in a binary black hole system (BBHS). We emphasize that for non-ballistic helical motion classical travel time effects can lead to strong shortening effects, such that the observed period may be a factor γ 2 b smaller than the underlying driving period, where γ b denotes the bulk Lorentz factor of the jet flow. The relevance of the above noted scenarios is discussed for the BL Lac object AO 0235+16.

show abstract

BeppoSAX observations of 1-Jy BL Lacertae objects -- II

Cited by 23 publications

References 42 publications

X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view

X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view

Multifrequency variability of the blazar AO 0235+164

Periodic variability and binary black hole systems in blazars

Contact Info

Product

Resources

About