scholarly journals Long-Term Optical Behavior of BL Lac Objects

1994 ◽  
Vol 159 ◽  
pp. 394-394
Author(s):  
S. Kikuchi
Keyword(s):  
Time Scale ◽  
Shock Model ◽  
Bl Lac Objects ◽  
Optical Photometry ◽  
Preferred Direction ◽  
Bl Lac ◽  
Direction Of Polarization ◽  
Optical Behavior

On the basis of results of optical photometry and polarimetry of OJ287 and Mrk421 since 1981, we find two states of activities for both objects. In OJ287, a color-magnitude relation which is consistent with the standard jet-shock model is seen after the outburst in 1983, while before 1982 the optical colors were almost constant. In Mrk421, the colors became redder in 1985–87, and the change of the preferred direction of polarization was associated on smaller time scale in 1987.

scholarly journals Characterizing the γ-ray long-term variability of PKS 2155−304 with H.E.S.S. and Fermi-LAT

2017 ◽  
Vol 598 ◽  
pp. A39 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Flicker Noise ◽  
High Energy ◽  
Long Term Results ◽  
Noise Power ◽  
Quiescent State ◽  
Physical Processes ◽  
Bl Lac Objects ◽  
Power Spectral ◽  
Bl Lac

Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To this end, the long-term variability of the BL Lac object PKS 2155−304 is analyzed in the high (HE, 100 MeV < E < 300 GeV) and very high energy (VHE, E > 200 GeV) γ-ray domain. Over the course of ~9 yr of H.E.S.S. observations the VHE light curve in the quiescent state is consistent with a log-normal behavior. The VHE variability in this state is well described by flicker noise (power-spectral-density index βVHE = 1.10+0.10-0.13) on timescales larger than one day. An analysis of ~5.5 yr of HE Fermi-LAT data gives consistent results (βHE = 1.20+0.21-0.23, on timescales larger than 10 days) compatible with the VHE findings. The HE and VHE power spectral densities show a scale invariance across the probed time ranges. A direct linear correlation between the VHE and HE fluxes could neither be excluded nor firmly established. These long-term-variability properties are discussed and compared to the red noise behavior (β ~ 2) seen on shorter timescales during VHE-flaring states. The difference in power spectral noise behavior at VHE energies during quiescent and flaring states provides evidence that these states are influenced by different physical processes, while the compatibility of the HE and VHE long-term results is suggestive of a common physical link as it might be introduced by an underlying jet-disk connection.

VERITAS OBSERVATIONS OF RELATIVISTIC OUTFLOWS IN LOW- AND INTERMEDIATE-FREQUENCY-PEAKED BL LAC OBJECTS

2014 ◽  
Vol 28 ◽  
pp. 1460178
Author(s):  
◽  
HEIKE PROKOPH
Keyword(s):  
Gamma Ray ◽  
Intermediate Frequency ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Bl Lacs ◽  
Gamma Ray Telescopes ◽  
Very High

The majority of blazars detected at very high energies (VHE; E > 100 GeV) are high-frequency-peaked BL Lac objects (HBLs). Low- and intermediate-frequency-peaked BL Lacs (LBLs/IBLs with synchrotron-peak frequencies in the infrared and optical regime) are generally more powerful, more luminous, and have a richer jet environment than HBLs. However, only a handful of these IBL and LBLs have been detected by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array has been monitoring five known VHE LBLs/IBLs since 2009: 3C 66A, W Comae, PKS 1424+240, S5 0716+714 and BL Lacertae, with typical exposures of 5-10 hours per year. The results of these long-term observations are presented, including a bright, subhour-scale VHE flare of BL Lacertae in June 2011, the first low-state detections of 3C 66A and W Comae, and the detection and characterization of the IBL B2 1215+30.

scholarly journals A CCD survey of BL Lac objects

1986 ◽  
Vol 119 ◽  
pp. 125-126
Author(s):  
Helmut Kuhr ◽  
Josef Fried
Keyword(s):  
Optical Spectroscopy ◽  
Max Planck ◽  
Complete Sample ◽  
Bl Lac Objects ◽  
Ccd Imaging ◽  
Bl Lac ◽  
5 Ghz ◽  
Spectroscopy Optical

A long term project was started at the Max-Planck-Institut fur Astronomie, Heidelberg, to study a complete sample of 46 northern and southern BL Lac objects with flux densities exceeding 1 Jy at 5 GHz using optical spectroscopy, optical polarimetry, and direct deep CCD imaging.

The long-term optical behavior of BL Lac object S5 0716+714

2010 ◽  
Vol 53 (7) ◽  
pp. 1370-1374 ◽  
Author(s):  
BingKai Zhang ◽  
BenZhong Dai ◽  
Li Zhang ◽  
Zhen Cao
Keyword(s):  
Bl Lac ◽  
Optical Behavior

scholarly journals Long term γ-ray variability of blazars

2020 ◽  
Vol 634 ◽  
pp. A80 ◽  
Author(s):  
Bhoomika Rajput ◽  
C. S. Stalin ◽  
Suvendu Rakshit
Keyword(s):  
Time Scales ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
Bl Lac Objects ◽  
Spectrum Radio ◽  
Bl Lac ◽  
Bl Lacs

We used the data from the Fermi Gamma-ray Space Telescope to characterise the γ-ray flux variability of blazars on month-like time scales. Our sample consists of 1120 blazars of which 481 are flat spectrum radio quasars (FSRQs) and 639 are BL Lac objects (BL Lacs). We generated monthly binned light curves of our sample for a period of approximately nine years from 2008 August to 2017 December and quantified variability by using excess variance (Fvar). On month-like time scales, 371/481 FSRQs are variable (80%), while only about 50% (304/639) of BL Lacs are variable. This suggests that FSRQs are more variable than BL Lac objects. We find a mean Fvar of 0.55 ± 0.33 and 0.47 ± 0.29 for FSRQs and BL Lacs respectively. Large Fvar in FSRQs is also confirmed from the analysis of the ensemble structure function. By Dividing our sample of blazars based on the position of the synchrotron peak in their broad-band spectral energy distribution, we find that the low synchrotron peaked (LSP) sources have the largest mean Fvar value of 0.54 ± 0.32 while the intermediate synchrotron peaked (ISP) and high synchrotron peaked sources have mean Fvar values of 0.45 ± 0.25 and 0.47 ± 0.33 respectively. On month-like time scales, we find FSRQs to show a high duty cycle (DC) of variability of 66% relative to BL Lacs that show a DC of 36%. We find that both the Fvar and time scale of variability (τ) do not correlate with MBH. We note that Fvar is found to be weakly correlated with Doppler factor (δ) and τ is also weakly correlated with δ. Most of the sources in our sample have τ of the order of days, which might be related to processes in the jet. We find marginal difference in the distribution of τ between FSRQs and BL Lacs.

scholarly journals VHE BL Lacs through the MAGIC glasses

2014 ◽  
Vol 10 (S313) ◽  
pp. 64-69
Author(s):  
Josefa Becerra González ◽  
Keyword(s):  
Optical Emission ◽  
Theoretical Models ◽  
High Energy ◽  
Bl Lac Objects ◽  
Individual Object ◽  
Bl Lac ◽  
Multi Wavelength ◽  
Very High Energy ◽  
First Time

AbstractIn this contribution an overview of the latest results on the study of BL Lac objects with the MAGIC telescopes at the very high energy (VHE, E>100 GeV) gamma-rays is presented. Three new VHE sources were detected during 2014, two BL Lac objects and the gravitational lensed blazar S3 0218+357. MAGIC detected very fast intra-night variability from IC 310. This detection points to smaller emitting regions than the event horizon, this is hard to be explained in the framework of the current theoretical models. The long term multi wavelength (MWL) study of the BL Lac PKS 1424+240 shows correlation between the radio and optical emission, pointing to a common origin. The MWL SED is not well fitted by a one-zone synchrotron-self Compton (SSC) model, but a two-zone SSC model can explain both, the MWL light curve and the SED. Spectral curvature has been found in the observed VHE spectrum from PG 1553+113. This is the first time that spectral curvature compatible with the EBL absorption is found in an individual object.

Long-term optical variability of BL Lac objects

2005 ◽  
pp. 139-142
Author(s):  
Ewa Szuszkiewicz ◽  
Cesare Barbieri ◽  
Enrico Cappellaro ◽  
Giuliano Romano ◽  
Massimo Turatto
Keyword(s):  
Optical Variability ◽  
Bl Lac Objects ◽  
Bl Lac

scholarly journals Monitoring of BL Lac objects at 327 MHz

1986 ◽  
Vol 119 ◽  
pp. 171-172
Author(s):  
Hari Om Vats ◽  
S.S. Degaonkar ◽  
P.K. Manoharan ◽  
S. Ananthakrishnan
Keyword(s):  
Data Base ◽  
Radio Telescope ◽  
Time Scale ◽  
Preliminary Analysis ◽  
Bl Lac Objects ◽  
Bl Lac

The variable BL Lac objects OJ 287 and B2 (1308+326) have been observed using the Ooty Synthesis Radio Telescope (OSRT) at 327 MHz. Preliminary analysis of one of them, namely OJ 287 indicates that flux variations of ∼ 20% on a time scale of few hours to few days could be present, but this needs to be confirmed by a larger data base.

scholarly journals X-ray intensity variations in BL Lac sources H2155-304 and PKS 0548-322

1986 ◽  
Vol 119 ◽  
pp. 273-274
Author(s):  
P.C. Agrawal ◽  
K.P. Singh ◽  
G.R. Riegler
Keyword(s):  
Time Scale ◽  
Compact Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Bl Lacs ◽  
Einstein Observatory

The X-ray Observations of two BL Lac Objects H2155-304 and PKS 0548-322 made with HRI and MPC on the Einstein Observatory show intensity variations on time scale of hours in both the sources. X-ray spectra of the two BL Lacs are derived. Limits on the mass of the accreting compact objects are obtained from time scale and magnitude of variations. Implications of the results are briefly discussed.

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