Spectral Slope Variability of BL Lacertae Objects in the Optical Band

Vagnetti, F.; Trèvese, D.; Nesci, R.

doi:10.1086/374889

Cited by 88 publications

(112 citation statements)

References 21 publications

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“…Although they used UBV magnitudes collected from many instruments, only 4 of the 16 blazars in common have remarkable differences in the spectral slope. More recently, Vagnetti et al (2003) analyzed the spectral slope variability of 8 BL Lacs in the BVR c I c bands. Our results for 7 common blazars are in perfect agreement within typical standard deviations.…”

Section: Figmentioning

confidence: 99%

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The continuum spectral features of blazars in the optical region

Fiorucci

Ciprini

Tosti

2004

A&A

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Abstract. Many quasi-simultaneous optical observations of 37 blazars were obtained at the Perugia University Observatory over the last ten years. In this paper we analyze the dereddened spectral flux distribution in the optical frequency range, and we compare our results with the overall spectral energy distribution (SED). The implications for existing models of the objects are briefly discussed. In particular, we show how the LBLs have a spectral slope α 1.5, as expected from Synchrotron SelfCompton models, while the optical emission of HBLs and FSRQs is probably contaminated by other components. Moreover, we show evidence of how the spectral index vs. flux plot exhibits a characteristic loop-like pattern that is probably due to changes in the injection of accelerated particles.

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Section: Figmentioning

confidence: 99%

“…Obviously this is partially due to statistical fluctuations (see Fig. 1 in Vagnetti et al 2003, where the signal-to-noise is generally higher). However, it is statistically impossible to explain all the fluctuations invoking only the noise: too many variations exceed 4-5 cumulative standard deviations.…”

Section: Spectral Slope Variabilitymentioning

confidence: 99%

The continuum spectral features of blazars in the optical region

Fiorucci

Ciprini

Tosti

2004

A&A

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“…On the subject of blazars, there are many papers exploring the relationship between the spectrum and brightness (Edelson et al 1990;Trevese & Vagnetti 2002;Vagnetti et al 2003;Dai et al 2009;Poon et al 2009;Yuan et al 2015;Yuan & Fan 2015). Stevens & Gear (1999) analyzed the distributions of α ro and α rx (r, o, x, represents radio band, optical band and X-ray band, respectively), and obtained a correlation between the two spectral indices.…”

Section: Introductionmentioning

confidence: 99%

Optical monitoring of BL Lac object S5 0716+714 and FSRQ 3C 273 from 2000 to 2014

Yuan

Fan

Tao

et al. 2017

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Context. Using the 1.56 m telescope at the Shanghai Observatory (ShAO), China, we monitored two sources, BL Lac object S5 0716+714 and flat spectrum radio quasar (FSRQ) 3C 273. For S5 0716+714, we report 4969 sets of CCD (Charge-coupled Device) photometrical optical observations (1369 for V band, 1861 for R band and 1739 for I band) in the monitoring time from Results. The two sources both show IDV properties for S5 0716+714. The timescales are in the range from 17.3 min to 4.82 h; for 3C 273, the timescale is ∆T = 35.6 min. Based on the periodic analysis methods, we find the periods P V = 24.24 ± 1.09 days, P R = 24.12 ± 0.76 days, P I = 24.82 ± 0.73 days for S5 0716+714, and P = 12.99 ± 0.72, 21.76 ± 1.45 yr for 3C 273. The two sources displayed the "bluer-when-brighter" spectral evolution properties. Conclusions. S5 0716+714 and 3C 273 are frequently studied objects. The violent optical variability and IDV may come from the jet. Gaussian fitting can be used to analyze IDVs. The relations between brightness (flux density) and spectrum are strongly influenced by the frequency.

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“…Nevertheless, the observation of micro-variability on a timescale of hours in FSRQs, which is considered to be a strong discriminator between accretion disks and relativistic jet models of these sources, is also a logical way of exploring the structure and physical conditions near the nucleus. Although monitoring campaigns have been performed at all wavelengths for a limited number of objects, the many parameters involved in physical models of emission mechanisms have not been tightly constrained (Vagnetti et al 2003). Thus, there is a need to collect data over relatively long observing periods to monitor multiband variability limited to the optical range.…”

Section: Introductionmentioning

confidence: 99%

Multi-colour optical variability of the blazar 3C 454.3 in 2007–2010

Zhai

Zheng

Wei

2011

A&A

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Context. We present our optical multiband (B and R) observations of the blazar 3C 454.3, which were acquired over 30 nights from August 2007 to December 2010. Aims. We analyse our data to study the optical emission variability properties of 3C 454.3. Methods. The observations were carried out using both the 1 m EOS Telescope (EST) and the 0.8 m Tsinghua-NAOC Telescope (TNT) simultaneously in most nights at the Xinglong Observatory of National Astronomical Observatories, Chinese Academy of Sciences (NAOC). Both telescopes are equipped with the same type of Princeton Instrument CCD and standard Johnson-Cousin UBVRI filters. To reach a similar signal-to-noise ratio (S/N) in different bands with the same exposure time, observations using the larger diameter EST were carried out with B-band filter, while those of the smaller diameter TNT were carried out with R-band filter. Any time differences between the two telescopes were corrected using GPS. The typical sampling rate was one data point per minute, which is the highest time-resolution so far. Results. A multi-peak outburst was observed during November-December 2007, in addition to a later outburst during October 27-November 1, 2010. The brightest magnitudes for 3C 454.3 during our observations were B = 13.77 mag and R = 12.69 mag at JD = 2 454 436.0952 (December 1, 2007). One of the most striking events was detected on December 1, 2007, when a flux increase of about 0.67 mag occurred in 3.2 h. A colour analysis shows that the colour variability processes are apparently complex. A bluer-when-brighter trend, a redder-when-brighter trend (generally in faint states), and no significant colour variance were all detected during the outburst of November-December 2007. Furthermore, the kind of "saturation" effect in the B − R trend is not visible in the bright state (R < 14) during August 12-14, 2007. These trends may be due to the interactive contribution from the accretion disc and the jet components. Meanwhile, intra-night variability in B and R bands was found to be correlated, without any time delay exceeding one minute.

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Spectral Slope Variability of BL Lacertae Objects in the Optical Band

Cited by 88 publications

References 21 publications

The continuum spectral features of blazars in the optical region

The continuum spectral features of blazars in the optical region

Optical monitoring of BL Lac object S5 0716+714 and FSRQ 3C 273 from 2000 to 2014

Multi-colour optical variability of the blazar 3C 454.3 in 2007–2010

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