Multi-wavelength observations of the BL Lac object Fermi J1544-0649: One year after its awakening

Multi-wavelength search for quasi-periodic oscillations in BL Lac 4FGL J0112.1+2245

Astrophysics and Space Science ◽

10.1007/s10509-021-04039-w ◽

2022 ◽

Vol 367 (1) ◽

Author(s):

Y. L. Gong ◽

T. F. Yi ◽

X. Yang ◽

H. Z. Li ◽

X. Chang ◽

...

Keyword(s):

Periodic Oscillations ◽

Bl Lac ◽

Multi Wavelength

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Establishing a particle distribution for multi-wavelength emission from BL Lac objects

Astrophysics and Space Science ◽

10.1007/s10509-020-03864-9 ◽

2020 ◽

Vol 365 (9) ◽

Author(s):

X. X. Xie ◽

K. R. Zhu ◽

S. J. Kang ◽

Y. G. Zheng

Keyword(s):

Particle Distribution ◽

Bl Lac Objects ◽

Bl Lac ◽

Multi Wavelength ◽

Wavelength Emission

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Multi-wavelength polarization VLBI observations of two BL Lac objects

10.22323/1.036.0027 ◽

2007 ◽

Author(s):

Vladislavs Bezrukovs ◽

Denise Gabuzda

Keyword(s):

Bl Lac Objects ◽

Vlbi Observations ◽

Bl Lac ◽

Multi Wavelength

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Technical Note: One year of Raman-lidar measurements in Gual Pahari EUCAARI site close to New Delhi in India – Seasonal characteristics of the aerosol vertical structure

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-4513-2012 ◽

2012 ◽

Vol 12 (10) ◽

pp. 4513-4524 ◽

Cited By ~ 46

Author(s):

M. Komppula ◽

T. Mielonen ◽

A. Arola ◽

K. Korhonen ◽

H. Lihavainen ◽

...

Keyword(s):

Technical Note ◽

New Delhi ◽

Aerosol Layer ◽

Raman Lidar ◽

Extinction Coefficients ◽

Seasonal Characteristics ◽

Lidar Measurements ◽

Multi Wavelength ◽

Lidar Ratio ◽

One Year

Abstract. One year of multi-wavelength (3 backscatter + 2 extinction + 1 depolarization) Raman lidar measurements at Gual Pahari, close to New Delhi, were analysed. The data was split into four seasons: spring (March–May), summer (June–August), autumn (September–November) and winter (December–February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1–3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm−1 sr−1 and 142 Mm−1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared to other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Ångström exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.

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Modelling the Multifrequency SED of AGN Candidates among the Unidentied EGRET and Fermi Gamma-Ray Sources

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2014.01.0163 ◽

2014 ◽

Vol 1 (1) ◽

pp. 163-169

Author(s):

Pieter J. Meintjes ◽

Pheneas Nkundabakura ◽

Brian Van Soelen ◽

Alida Odendaal

Keyword(s):

Gamma Ray ◽

Radio Galaxy ◽

Radio Galaxies ◽

Galactic Latitude ◽

Large Telescope ◽

High Galactic Latitude ◽

New Class ◽

Multi Wavelength ◽

One Year

Of the 271 sources in the 3rd EGRET catalogue, 131 were reported as unidentied, i.e. not associated with any particular class of point source in the sky. Since the largest fraction of the EGRET sources were extragalactic, a sample of 13 extragalactic unidentied sources have been selected for multi-wavelength follow-up studies. Five of the selected EGRET sources coincide with gamma-ray flux enhancements seen in the Fermi-LAT data after one year of operation. In this article, we report the multi-wavelength properties of, among others, the 5 sources detected by Fermi-LAT from our sample of high galactic latitude unidentied EGRET sources. Recent spectroscopic observations with the Southern African Large Telescope (SALT) conrmed one of the unidentied EGRET sources as a possible Seyfert 2 galaxy, or alternatively, a narrow line radio galaxy. The detected gamma-ray emission (E<sub>γ</sub> > 30 MeV) of the 5 coinciding EGRET/Fermi-LAT sources are tted with external Compton and Synchrotron Self Compton (SSC) models to investigate the energetics required to produce the EGRET/Fermi gamma-ray flux. In all the models the inclination angle of the jet with respect to the observer is jet 60, between those of Seyfert 1 and Seyfert 2/radio galaxies. These results confirm the possibility of Seyfert and radio galaxies sources are constituting a new class of gamma-ray source in the energy range E<sub>γ</sub> > 30 MeV.

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Energy Distribution and Variability of BL LAC Objects. The Cases of PKS 2155–304 and 3C 66A.

Symposium - International Astronomical Union ◽

10.1017/s0074180900038560 ◽

1983 ◽

Vol 104 ◽

pp. 39-40

Author(s):

L. Maraschi ◽

D. Maccagni ◽

E. G. Tanzi ◽

M. Tarenghi ◽

A. Treves

Keyword(s):

Energy Distribution ◽

Power Law ◽

Maximum Amplitude ◽

X Rays ◽

Bl Lac Objects ◽

X Ray ◽

International Ultraviolet Explorer ◽

Bl Lac ◽

One Year ◽

Ultraviolet Observations

PKS 2155–304 was repeatedly observed in 1979 and 1980 with the International Ultraviolet Explorer. Variations up to a factor of 2 in one year and by 20% in a day are found. The maximum amplitude of variation in X-rays is similar but the timescales are much shorter (a factor of 2 in one day; Urry and Mushotzky, 1982). In all cases the 1200–3100 A continuum is well fitted by a power law with frequency spectral index αUV between −0.7±0.03 and −0.9±0.03. Optical and ultraviolet observations taken within one day show different spectral slopes (Fig. 1). Separate power law fits in the two bands yield αopt = −0.46±0.01 and αUV = −0.80±0.02. The observations by Urry and Mushotzky indicate that the energy distribution steepens further in the soft X-ray region.

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One year of Raman-lidar measurements in Gual Pahari EUCAARI site close to New Delhi in India: seasonal characteristics of the aerosol vertical structure

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-31123-2010 ◽

2010 ◽

Vol 10 (12) ◽

pp. 31123-31151 ◽

Cited By ~ 8

Author(s):

M. Komppula ◽

T. Mielonen ◽

A. Arola ◽

K. Korhonen ◽

H. Lihavainen ◽

...

Keyword(s):

New Delhi ◽

Aerosol Layer ◽

Raman Lidar ◽

Extinction Coefficients ◽

Seasonal Characteristics ◽

Four Seasons ◽

Lidar Measurements ◽

Multi Wavelength ◽

Lidar Ratio ◽

One Year

Abstract. One year of multi-wavelength (3+2) Raman lidar measurements at Gual Pahari, close to Delhi, were analysed. The data was split into four seasons: spring (March–May), summer (June–August), autumn (September–November) and winter (December–February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1–3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm−1 sr−1 and 142 Mm−1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared with other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Ångström exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.

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VHE BL Lacs through the MAGIC glasses

Proceedings of the International Astronomical Union ◽

10.1017/s174392131500188x ◽

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.

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