<i>BeppoSAX</i> spectral survey of BL Lacs – New spectra  and results

Beckmann, V.; Wolter, A.; Celotti, A.; Costamante, L.; Ghisellini, G.; Maccacaro, T.; Tagliaferri, G.

doi:10.1051/0004-6361:20011752

Cited by 53 publications

(55 citation statements)

References 30 publications

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“…Beckmann et al 2002). This suggests that there may be commonality in the location of the acceleration region even for jets of vastly different scales.…”

Section: A Jet-disk Model For the Non-thermal X-ray/radio Continuummentioning

confidence: 99%

The X‐Ray–faint Emission of the Supermassive Nuclear Black Hole of IC 1459

Fabbiano

Elvis

Markoff

et al. 2003

ApJ

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Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (L X =8×10 40 erg s −1 , 0.3-8 keV), unabsorbed nuclear X-ray source, with a slope Γ = 1.88±0.09, and no strong Fe-K line at 6.4 keV (EW<382 eV). This describes a normal AGN X-ray spectrum, but lies at 3×10 −7 below the Eddington limit. The SED of the IC 1459 nucleus is extremely radio loud compared to normal radio-loud quasars. The nucleus is surrounded by hot ISM (kT∼0.5-0.6 keV) with an average density of 0.3 cm −3 , within the central ∼180 pc radius, which is comparable to the gravitational capture radius, r A ∼140 pc. We estimate that for a standard AGN efficiency of 10%, the Bondi accretion would correspond to a luminosity of ∼6×10 44 erg s −1 , nearly four orders of magnitude higher than L X . ADAF solutions can explain the X-ray spectrum, but not the high radio/X-ray ratio. A jet model fits the radio-100µm and X-ray spectra well. The total power in this jet is ∼10% of L Bondi , implying that accretion close to the Bondi rate is needed.

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“…Beckmann et al 2002). This suggests that there may be commonality in the location of the acceleration region even for jets of vastly different scales.…”

Section: A Jet-disk Model For the Non-thermal X-ray/radio Continuummentioning

confidence: 99%

The X‐Ray–faint Emission of the Supermassive Nuclear Black Hole of IC 1459

Fabbiano

Elvis

Markoff

et al. 2003

ApJ

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“…They confirmed the ROSAT findings, namely, a strong anticorrelation between X and peak for HBLs and no correlation for LBLs, with an initial increase in X going from LBLs to HBLs (see Padovani et al 2001 for details). Figure 8 shows an updated version of the X -peak plot for BL Lac objects from Padovani et al (2001), including the HBLs studied by Beckmann et al (2002). We have also included in this plot our sources, represented by filled circles.…”

Section: No 2 2002mentioning

confidence: 99%

“…The location of the broadband peaks also suggests a different origin for the X-ray emission of the two classes, namely, an extension of the synchrotron emission likely responsible for the lower energy continuum in HBLs, which typically display steep (energy index X $ 1:5) X-ray spectra, and inverse Compton emission in LBLs, which have harder ( X $ 1) spectra Urry et al 1996;Padovani & Giommi 1996). Beppo-SAX observations of BL Lac objects are confirming this picture (Wolter et al 1998;Padovani et al 2001;Beckmann et al 2002).…”

Section: Introductionmentioning

confidence: 96%

BeppoSAXObservations of Synchrotron X‐Ray Emission from Radio Quasars

Padovani

Costamante

Ghisellini

et al. 2002

ApJ

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We present new BeppoSAX Low Energy Concentrator Spectrometer (LECS), Medium Energy Concentrator Spectrometer (MECS), and Phoswich Detector System (PDS) observations of four flat-spectrum radio quasars (FSRQs) having effective spectral indices ro and ox typical of high-energy peaked BL Lac objects. Our sources have X-ray-to-radio flux ratios on average $70 times larger than '' classical '' FSRQs and lie at the extreme end of the FSRQ X-ray-to-radio flux ratio distribution. The collected data cover the energy range 0.1-10 keV (observer's frame), reaching $100 keV for one object. The BeppoSAX band in one of our sources, RGB J1629+4008, is dominated by synchrotron emission peaking at $2 Â 10 16 Hz, as also shown by its steep (energy index X $ 1:5) spectrum. This makes this object the first known FSRQ whose X-ray emission is not due to inverse Compton radiation. Two other sources display a flat BeppoSAX spectrum ( X $ 0:7), with weak indications of steepening at low X-ray energies. The combination of BeppoSAX and ROSAT observations, (nonsimultaneous) multifrequency data, and a synchrotron inverse Compton model suggests synchrotron peak frequencies %10 15 Hz, although a better coverage of their spectral energy distributions is needed to provide firmer values. If confirmed, these values would be typical of '' intermediate '' BL Lac objects for which the synchrotron and inverse Compton components overlap in the BeppoSAX band. Our sources, although firmly in the radio-loud regime, have powers more typical of high-energy peaked BL Lac objects than of FSRQs, and indeed their radio powers put them near the low-luminosity end of the FSRQ luminosity function. We discuss this in terms of an anticorrelation between synchrotron peak frequency and total power, based on physical arguments, and also as possibly due to a selection effect.

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“…According to the classification scheme of Padovani & Giommi (1995), 1ES 0414+009 belongs to the class of high-frequency-peaked BL Lac (HBLs), objects with a synchrotron-emission peak located at UV/soft-X-ray frequencies, or equivalently, sources for which the X-ray emission is dominated by synchrotron radiation. There are several archival measurements of the spectral properties of 1ES 0414+009 in X-rays taken using ASCA (Kubo et al 1998), ROSAT (Brinkmann et al 1995), and BeppoSAX (Beckmann et al 2002). Observations with EXOSAT (Giommi et al 1990;Sambruna et al 1994) showed evidence of temporal variability and strong spectral variations, at times having an X-ray photon index of Γ X < 2.…”

Section: Introductionmentioning

confidence: 99%

Discovery of hard-spectrumγ-ray emission from the BL Lacertae object 1ES 0414+009

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

A&A

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Context. 1ES 0414+009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-highenergy (VHE, E > 100 GeV) γ-rays due to its high X-ray and radio flux. Aims. Observations in the VHE γ-ray band and across the electromagnetic spectrum can provide insights into the origin of highly energetic particles present in the source and the radiation processes at work. Because of the distance of the source, the γ-ray spectrum might provide further limits on the level of the extragalactic background light (EBL). Methods. We report observations made between October 2005 and December 2009 with H.E.S.S., an array of four imaging atmospheric Cherenkov telescopes. Observations at high energies (HE, 100 MeV-100 GeV) with the Fermi-LAT instrument in the first 20 months of its operation are also reported. To complete the multi-wavelength picture, archival UV and X-ray observations with the Swift satellite and optical observations with the ATOM telescope are also used. Results. Based on the observations with H.E.S.S., 1ES 0414+009 is detected for the first time in the VHE band. An excess of 224 events is measured, corresponding to a significance of 7.8σ. The photon spectrum of the source is well described by a power law, with photon index of Γ VHE = 3.45 ± 0.25 stat ± 0.20 syst . The integral flux above 200 GeV is (1.88 ± 0.20 stat ± 0.38 syst ) ×10 −12 cm −2 s −1 . Observations with the Fermi-LAT in the first 20 months of operation show a flux between 200 MeV and 100 GeV of (2.3 ± 0.2 stat ) × 10 −9 erg cm −2 s −1 , and a spectrum well described by a power-law function with a photon index Γ HE = 1.85 ± 0.18. Swift/XRT observations show an X-ray flux between 2 and 10 keV of (0.8−1) × 10 −11 erg cm −2 s −1 , and a steep spectrum Γ X = (2.2−2.3). Combining X-ray with optical-UV data, a fit with a log-parabolic function locates the synchrotron peak around 0.1 keV. Conclusions. Although the GeV-TeV observations do not provide better constraints on the EBL than previously obtained, they confirm a low density of the EBL, close to the lower limits from galaxy counts. The absorption-corrected HE and VHE γ-ray spectra are both hard and have similar spectral indices (≈1.86), indicating no significant change of slope between the HE and VHE γ-ray bands, and locating the γ-ray peak in the SED above 1-2 TeV. As for other TeV BL Lac objects with the γ-ray peak at such high energies and a large separation between the two SED humps, this average broad-band SED represents a challenge for simple one-zone synchrotron self-Compton models, requiring a high Doppler factor and very low B-field.

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BeppoSAX spectral survey of BL Lacs – New spectra and results

Cited by 53 publications

References 30 publications

The X‐Ray–faint Emission of the Supermassive Nuclear Black Hole of IC 1459

The X‐Ray–faint Emission of the Supermassive Nuclear Black Hole of IC 1459

BeppoSAXObservations of Synchrotron X‐Ray Emission from Radio Quasars

Discovery of hard-spectrumγ-ray emission from the BL Lacertae object 1ES 0414+009

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