A Sample-oriented catalogue of BL Lacertae objects

Padovani, P.; Giommi, P.

doi:10.1093/mnras/277.4.1477

Cited by 168 publications

(133 citation statements)

References 35 publications

Supporting

Mentioning

130

Contrasting

Order By: Relevance

“…The same selection criteria were applied to the BL Lac sample of Padovani & Giommi (1995) (nine additional targets). We have taken into account recent emission redshift measurements, including upper limits (Sbarufatti et al 2005(Sbarufatti et al , 2006.…”

Section: Target Selectionmentioning

confidence: 99%

See 1 more Smart Citation

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Bergeron

Boissé

Ménard

2010

A&A

View full text Add to dashboard Cite

In order to investigate the origin of the excess of strong Mg ii systems towards GRB afterglows as compared to QSO sightlines, we have measured the incidence of Mg ii absorbers towards a third class of objects: the blazars. This class includes the BL Lac object population for which a tentative excess of Mg ii systems had already been reported. We observed with FORS1 at the ESO-VLT 42 blazars with an emission redshift 0.8 < z em < 1.9, to which we added the three high z northern objects belonging to the 1 Jy BL Lac sample. We detect 32 Mg ii absorbers in the redshift range 0.35-1.45, leading to an excess in the incidence of Mg ii absorbers compared to that measured towards QSOs by a factor ∼2, detected at 3σ. The amplitude of the effect is similar to that found along GRB sightlines. Our analysis provides a new piece of evidence that the observed incidence of Mg ii absorbers might depend on the type of background source. In front of blazars, the excess is apparent for both "strong" (w r (2796) > 1.0 Å) and weaker (0.3 < w r (2796) < 1.0 Å) Mg ii systems. The dependence on velocity separation with respect to the background blazars indicates, at the ∼1.5σ level, a potential excess for β ≡ v/c ∼ 0.1. We show that biases involving dust extinction or gravitational amplification are not likely to notably affect the incidence of Mg ii systems towards blazars. Finally we discuss the physical conditions required for these absorbers to be gas entrained by the powerful blazar jets. More realistic numerical modelling of jet-ambient gas interaction is required to reach any firm conclusions as well as repeat observations at high spectral resolution of strong Mg ii absorbers towards blazars in both high and low states.

show abstract

Section: Target Selectionmentioning

confidence: 99%

“…Our sample comprises 35 BL Lacs, 7 FSRQs A51, page 2 of 13 Rector & Stocke (2001). PG In the BL Lac sample of Padovani & Giommi (1995) and not in RS. Pl In the BL Lac list kindly provided by R. Plotkin prior to publication.…”

Section: Target Selectionmentioning

confidence: 99%

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Bergeron

Boissé

Ménard

2010

A&A

View full text Add to dashboard Cite

show abstract

“…The ⋆ E-mail: aditi@aries.res.in spectral energy distribution (SED) of blazars display two welldefined broad spectral components (Mukherjee et al 1997;Weekes 2003). Based on the location of these peaks, we have low energy peaked blazars (LBLs) whose first component peaks in near-IR (NIR)/optical while the second component usually peaks at GeV energies and high energy peaked blazars (HBLs) where first peak is in UV/X-rays while the second peak at TeV energies (Padovani & Giommi 1995, Abdo et al 2010. During flaring state the peak is found to be shifted towards higher frequencies.…”

Section: Introductionmentioning

confidence: 99%

Multiband optical variability studies of BL Lacertae

Agarwal¹,

Gupta²

2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We monitored BL Lacertae for 13 nights in optical B, V, R, and I bands during October and November 2014 including quasi-simultaneous observations in V and R bands using two optical telescopes in India. We have studied multi-band optical flux variations, colour variation and spectral changes in this blazar. Source was found to be active during the whole monitoring period and showed significant intraday variability on 3 nights in V and R filters while displayed hints of variability on 6 other dates in R passband and on 2 nights in V filter. From the colour-magnitude analysis of the source we found that the spectra of the target gets flatter as it becomes brighter on intra-night timescale. Using discrete correlation technique, we found that intraday light curves in both V and R filters are almost consistent and well correlated with each other. We also generated spectral energy distribution (SED) of the target using the B, V, R, and I data sets for all 13 nights which could help us investigate the physical process responsible for the observed variations in BL Lacertae objects. We also discuss possible physical causes of the observed spectral variability.

show abstract

“…This component peaks at frequencies ranging from the IR to the X-ray band. The true position of this peak was proposed by Padovani & Giommi (1995) as an indicator in classifying sources; they define LBL (Low energy peaked BL Lac) to be objects with the first bump in the IR-to-optical band, and HBL (High energy peaked BL Lac) as those with SEDs peaking in the UV-X-ray band. According to the Synchrotron Self Compton (SSC) emission mechanism, the higher-frequency bump can be attributed to inverse Compton scattering of synchrotron photons by the same population of relativistic electrons that produce the synchrotron emission (Jones et al 1974;Ghisellini & Maraschi 1989).…”

Section: Introductionmentioning

confidence: 99%

Swift observations of the very intense flaring activity of Mrk 421 during 2006. I. Phenomenological picture of electron acceleration and predictions for MeV/GeV emission

Tramacere¹,

Giommi

Perri

et al. 2009

A&A

Self Cite

280

295

View full text Add to dashboard Cite

Aims. We present the results of a deep spectral analysis of all Swift observations of Mrk 421 between April 2006 and July 2006, when it reached its highest X-ray flux recorded until the end of 2006. The peak flux was about 85 milli-Crab in the 2.0-10.0 keV band, and the peak energy (E p ) of the spectral energy distribution (SED) was often at energies higher than 10 keV. We study trends between the spectral parameters, and the physical insights the parameters provide into the underlying acceleration and emission mechanisms. Methods. We performed a spectral analysis of Swift observations to investigate trends between the spectral parameters. We searched for acceleration and energetic features phenomenologically linked to the SSC model parameters, by predicting their effects in the γ-ray band, and in particular, the spectral shape expected in the Fermi Gamma-ray Space Telescope-LAT band. Results. We confirm that the X-ray spectrum is described well by a log-parabolic distribution close to E p , that the peak flux of the SED (S p ) is correlated with E p , and that E p is anti-correlated with the curvature parameter (b). The spectral evolution in the Hardness-ratio-flux plane shows both clockwise and counter-clockwise patterns. During the most energetic flares, the UV-to-soft-X-ray spectral shape requires an electron distribution spectral index of s 2.3. Conclusions. We demonstrate that the UV-to-X-ray emission from Mrk 421 is probably generated by a population of electrons that is actually curved, and has a low energy power-law tail. The observed spectral curvature is consistent with both stochastic acceleration or energy-dependent acceleration probability mechanisms, whereas the power-law slope of XRT-UVOT data is close to that inferred from the GRBs X-ray afterglow and in agreement with the universal first-order relativistic shock acceleration models. This scenario implies that magnetic turbulence may play a twofold role: spatial diffusion relevant to the first order process and momentum diffusion relevant to the second order process.

show abstract

A Sample-oriented catalogue of BL Lacertae objects

Cited by 168 publications

References 35 publications

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Multiband optical variability studies of BL Lacertae

Swift observations of the very intense flaring activity of Mrk 421 during 2006. I. Phenomenological picture of electron acceleration and predictions for MeV/GeV emission

Contact Info

Product

Resources

About