Spectral Variability of BL Lac Objects

D’Amicis, R.; Nesci, R.; Massaro, E.; Maesano, M.; Montagni, F.; D’Alessio, F.

doi:10.1071/as01113

Cited by 23 publications

(27 citation statements)

References 9 publications

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“…Between the two BeppoSAX pointings the source remained substantially constant, with small (∼0.1 mag) variations. The energy spectral slope (F ν ∝ ν −α ) from our BVRI observations was 1.63 ± 0.06, a typical value for the source at this luminosity level (D'Amicis et al 2002). On the other hand, the spectral shape (and flux levels) is affected by the contribution of the host galaxy, and in Fig.…”

Section: Oq 530mentioning

confidence: 91%

The BL Lacertae objects OQ 530 and S5 0716+714

Tagliaferri

Ravasio

Ghisellini

et al. 2003

A&A

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Abstract. We present the results of the BeppoSAX observations of two BL Lacs, OQ 530 and S5 0716+714, as part of a ToO program for the simultaneous observation at radio, optical, X-ray and TeV energies. Both sources are detected in the LECS and MECS, with S5 0716+714 visible also in the PDS band, up to about ∼60 keV. The X-ray spectra of both sources are better fitted by a double power-law model, with a steep soft X-ray component flattening at harder energies, with breaks at 0.3 and 1.5 keV, respectively. The concave shape of the spectra in both objects is consistent with soft X-rays being produced by the synchrotron and harder X-rays by the inverse Compton processes. Also the X-ray variability properties confirm this scenario; in particular, for S5 0716+714 our observation shows variations by about a factor of 3 over one hour below ∼3 keV and no variability above. Their simultaneous broad-band energy spectral distributions can be successfully interpreted within the frame of a homogeneous synchrotron and inverse Compton model, including a possible contribution from an external source of seed photons with the different spectral states of S5 0716+714 being reproduced by changing the injected power. The resulting parameters are fully consistent with the two sources being intermediate objects within the "sequence" scenario proposed for blazars.

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Section: Oq 530mentioning

confidence: 91%

The BL Lacertae objects OQ 530 and S5 0716+714

Tagliaferri

Ravasio

Ghisellini

et al. 2003

A&A

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“…Massaro et al 1998;Ghosh et al 2000;Trèvese & Vagnetti 2002;Villata et al 2002;D'Amicis et al 2002;Vagnetti et al 2003;Gu et al 2006;Ramírez et al 2004;Wu et al 2011). These results often led to the interpretation that these are the only optical color variability behaviors that could arise.…”

Section: Previous Color Variability Studiesmentioning

confidence: 99%

A Consolidated Framework of the Color Variability in Blazars: Long-term Optical/Near-infrared Observations of 3C 279

Isler

Urry

Coppi

et al. 2017

ApJ

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We evaluate the optical/near-infrared (OIR) color variability of 3C 279 in both γ-ray flaring and non-flaring states over 7-year timescales using the Small and Medium Aperture Research Telescope System (SMARTS ) in Cerro Tololo, Chile and γ-ray fluxes obtained from the Fermi γ-ray Space Telescope. This observing strategy differs from previous blazar color variability studies in two key ways: 1) the reported color variability is assessed across optical through near-infrared wavelengths, and 2) the color variability is assessed over timescales significantly longer than an individual flare or ground-based observing season. We highlight 3C 279 because of its complex color variability, which is difficult to reconcile with the simple 'redder when brighter' behavior often associated with Flat Spectrum Radio Quasar (FSRQ) color variability. We suggest that the observed OIR color changes depend on a combination of the jet and disk emission. We parametrize this behavior in terms of a single variable, ζ m n , representing a smooth transition from disk-dominated, to a mixed contribution, to a jet-dominated system, which provides an explanation of the long-term OIR color variability in the same blazar over time. This suggests a general scheme that could apply to OIR color variability in other blazars.

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“…Investigations of spectral variability have also detected this general trend (D'Amicis et al 2002;Vagnetti et al 2003;Fiorucci et al 2004). From our investigations, the variations in the spectral index of 14 of 29 FSRQs indeed follow this trend.…”

Section: Discussionmentioning

confidence: 53%

The optical variability of flat-spectrum radio quasars in the SDSS stripe 82 region

2011

A&A

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Context. Although a bluer-when-brighter trend is commonly observed in blazars, the opposite trend of redder-when-brighter has also been found in some blazars. Aims. We investigate the frequency of the redder-when-brighter trend in flat-spectrum radio quasars (FSRQs). Methods. We investigate the optical variability of 29 FSRQs in the SDSS Stripe 82 region using SDSS DR7 released multi-epoch data covering about nine years. We determined the spectral index by fitting a powerlaw to SDSS ugriz photometric data, and explored the relationship between the spectral index and source brightness. Results. For all FSRQs studied, we detect variations in r band flux of overall amplitude between 0.24 mag and 3.46 mag in different sources. Fourteen of 29 FSRQs display a bluer-when-brighter trend. However, only one source exhibits a redder-when-brighter trend, which implies that this behavior is rare in our FSRQ sample. In this source, the thermal emission from the accretion disk may be responsible for the redder-when-brighter trend.

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Spectral Variability of BL Lac Objects

Cited by 23 publications

References 9 publications

The BL Lacertae objects OQ 530 and S5 0716+714

The BL Lacertae objects OQ 530 and S5 0716+714

A Consolidated Framework of the Color Variability in Blazars: Long-term Optical/Near-infrared Observations of 3C 279

The optical variability of flat-spectrum radio quasars in the SDSS stripe 82 region

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