Publications (98)
Radio jet emission from GeV-emitting narrow-line Seyfert 1 galaxies
E. Angelakis, L. Fuhrmann, N. Marchili +9
We studied the radio emission from four radio-loud and gamma-ray-loud narrow-line Seyfert 1 galaxies. The goal was to investigate whether a relativistic jet is operating at the sou…
Radio spectra of intermediate-luminosity broad-line radio galaxies
E. Angelakis, M. Kadler, K. Lewis +3
Within the context of investigating possible differences between the mechanisms at play in Radio Loud AGN and those in Radio Quiet ones, we study the spectral characteristics of a…
Location of Gamma-ray emission and magnetic field strengths in OJ 287
J. A. Hodgson, T. P. Krichbaum, A. P. Marscher +19
The Gamma-ray BL Lac object OJ 287 is known to exhibit inner-parsec "jet-wobbling", high degrees of variability at all wavelengths and quasi-stationary features including an appare…
Detecting the Elusive Blazar Counter-Jets
I. Liodakis, V. Pavlidou, E. Angelakis
Detection of blazar pc scale counter-jets is difficult, but it can provide invaluable insight into the relativistic effects, radiative processes and the complex mechanisms of jet p…
Early-time polarized optical light curve of GRB 131030A
O. G. King, D. Blinov, D. Giannios +23
We report the polarized optical light curve of a gamma-ray burst afterglow obtained using the RoboPol instrument. Observations began 655 seconds after the initial burst of gamma-ra…
MAGIC gamma-ray and multifrequency observations of flat spectrum radio quasar PKS 1510-089 in early 2012
MAGIC Collaboration, J. AleksiÄ, S. Ansoldi +218
Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs). MAGIC observed FSRQ…
Multiwavelength survey of a sample of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies
L. Foschini, M. Berton, A. Caccianiga +27
We report on a multiwavelength survey of a sample of 42 flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s). This is the largest known sample of this type of active g…
The July 2010 outburst of the NLS1 PMN J0948+0022
L. Foschini, G. Ghisellini, L. Maraschi +23
We report about the multiwavelength campaign on the Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z = 0.5846) performed in 2010 July-September and triggered by high activity…
Optical polarization map of the Polaris Flare with RoboPol
G. V. Panopoulou, K. Tassis, D. Blinov +26
The stages before the formation of stars in molecular clouds are poorly understood. Insights can be gained by studying the properties of quiescent clouds, such as their magnetic fi…
SBS 0846+513: a new gamma-ray emitting Narrow-Line Seyfert 1 galaxy
F. D'Ammando, M. Orienti, J. Finke +11
We report Fermi-LAT observations of the radio-loud AGN SBS 0846+513 (z=0.5835), optically classified as a Narrow-Line Seyfert 1 galaxy, together with new and archival radio-to-X-ra…
The Broadband Spectral Energy Distribution of the MOJAVE Sample
C. S. Chang, E. Ros, M. Kadler +6
We are constructing the broadband SED catalog of the MOJAVE sample from the radio to the gamma-ray band using MOJAVE, Swift UVOT/XRT/BAT, and Fermi/LAT data, in order to understand…
Two active states of the narrow-line gamma-ray-loud AGN GB 1310+487
K. V. Sokolovsky, F. K. Schinzel, Y. T. Tanaka +49
Previously unremarkable, the extragalactic radio source GB 1310+487 showed a gamma-ray flare on 2009 November 18, reaching a daily flux of ~10^-6 photons/cm^2/s at energies E>100 M…
Multi-frequency linear and circular radio polarization monitoring of jet emission elements in blazars
I. Myserlis, E. Angelakis, L. Fuhrmann +5
Radio emission in blazars -- the aligned subset of Active Galactic Nuclei (AGN) -- is produced by synchrotron electrons moving relativistically in their jet's magnetic field. Under…
On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
E. Angelakis, L. Fuhrmann, I. Nestoras +9
The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of {\em Fermi} blazars. The current study is…
First NuSTAR Observations of Mrk 501 within a Radio to TeV Multi-Instrument Campaign
A. Furniss, K. Noda, S. Boggs +273
We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 1 April and 10 August 2013, including the first detailed characterization of the s…
Zooming towards the Event Horizon - mm-VLBI today and tomorrow
T. P. Krichbaum, A. Roy, J. Wagner +21
Global VLBI imaging at millimeter and sub-millimeter wavelength overcomes the opacity barrier of synchrotron self-absorption in AGN and opens the direct view into sub-pc scale regi…
The Time-Dependent Distribution of Optical Polarization Angle Changes in Blazars
S. Kiehlmann, D. Blinov, I. Liodakis +17
At optical wavelengths, blazar Electric Vector Position Angle (EVPA) rotations linked with gamma-ray activity have been the subject of intense interest and systematic investigation…
Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71: II. A search for intra-day variability at millimetre wavelengths with the IRAM 30 m telescope
I. Agudo, T. P. Krichbaum, H. Ungerechts +12
We report on a densely time sampled polarimetric flux density monitoring of the BL Lac object S5 0716+71 at 86 GHz and 229 GHz with the IRAM 30 m telescope within a coordinated bro…
Unusual Flaring Activity in the Blazar PKS 1424-418 during 2008-2011
S. Buson, F. Longo, S. Larsson +24
Context. Blazars are a subset of active galactic nuclei (AGN) with jets that are oriented along our line of sight. Variability and spectral energy distribution (SED) studies are cr…
Calibrating the power of relativistic jets
L. Foschini, M. L. Lister, T. Hovatta +12
There are several methods to calculate the radiative and kinetic power of relativistic jets, but their results can differ by one or two orders of magnitude. Therefore, it is necess…
F-GAMMA: Variability Doppler factors of blazars from multiwavelength monitoring
I. Liodakis, N. Marchili, E. Angelakis +8
Recent population studies have shown that the variability Doppler factors can adequately describe blazars as a population. We use the flux density variations found within the exten…
Multiwavelength monitoring of the enigmatic Narrow-Line Seyfert 1 PMN J0948+0022 in March-July 2009
LAT Collaboration, E. Angelakis, C. Bailyn +39
Following the recent discovery of gamma rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z=0.5846), we started a multiwavelength campaign from radio to gamma r…
Optical polarization of high-energy BL Lac objects
T. Hovatta, E. Lindfors, D. Blinov +9
We investigate the optical polarization properties of high-energy BL Lac objects using data from the RoboPol blazar monitoring program and the Nordic Optical Telescope. We wish to…
The RoboPol Pipeline and Control System
O. G. King, D. Blinov, A. N. Ramaprakash +26
We describe the data reduction pipeline and control system for the RoboPol project. The RoboPol project is monitoring the optical -band magnitude and linear polarization of a la…
Unification and physical interpretation of the radio spectra variability patterns in Fermi blazars and jet emission from NLSy1s
E. Angelakis, L. Fuhrmann, I. Nestoras +10
The F-GAMMA program is among the most comprehensive programs that aim at understanding the physics in active galactic nuclei through the multi-frequency monitoring of Fermi blazars…
Search for AGN counterparts of unidentified Fermi-LAT sources with optical polarimetry: Demonstration of the technique
N. Mandarakas, D. Blinov, I. Liodakis +12
The third Fermi-LAT catalog (3FGL) presented the data of the first four years of observations from the Fermi Gamma-ray Space Telescope mission. There are 3034 sources, 1010 of whic…
Time-correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission
W. Max-Moerbeck, T. Hovatta, J. L. Richards +12
In order to determine the location of the gamma-ray emission site in blazars, we investigate the time-domain relationship between their radio and gamma-ray emission. Light-curves f…
Detection of the distant quasar OP 313 with the first Large-Sized Telescope of CTAO
K. Abe, S. Abe, J. Abhir +412
In December 2023, the Large-Sized Telescope prototype (LST-1) detected for the first time VHE -ray emission from the FSRQ OP~313 becoming the furthest blazar ever observed at V…
The F-GAMMA program: multi-wavelength AGN studies in the Fermi-GST era
E. Angelakis, L. Fuhrmann, I. Nestoras +4
The F -GAMMA program is a coordinated effort of several observing facilities to understand the AGN/blazar phenomenon via a multi-frequency monitoring approach, especially in the er…
Reconciling inverse-Compton Doppler factors with variability Doppler factors in blazar jets
I. Liodakis, A. Zezas, E. Angelakis +2
Blazar population models have shown that the inverse-Compton and variability Doppler factor estimates yield consistent results at the population level for flat spectrum radio quasa…
Inner jet kinematics and the viewing angle towards the γ-ray narrow-line Seyfert 1 galaxy 1H 0323+342
L. Fuhrmann, V. Karamanavis, S. Komossa +9
Near-Eddington accretion rates onto low-mass black holes are thought to be a prime driver of the multi-wavelength properties of the narrow-line Seyfert 1 (NLS1) population of activ…
Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71, III. Rapid and correlated flux density variability from radio to sub-mm bands
L. Fuhrmann, T. P. Krichbaum, A. Witzel +22
The BL Lac object S5 0716+71 was observed in a global multi-frequency campaign to search for rapid and correlated flux density variability and signatures of an inverse-Compton (IC)…
Rapid and correlated variability of blazar S5 0716+71 from radio- to sub-mm bands
L. Fuhrmann, T. P. Krichbaum, A. Witzel +9
The BL Lac object S5 0716+71 was target of a coordinated and global multi-frequency campaign to search for rapid and correlated variability and signatures of the inverse-Compton ca…
Radio and gamma-ray follow-up of the exceptionally high activity state of PKS 1510-089 in 2011
M. Orienti, S. Koyama, F. D'Ammando +24
We investigate the radio and gamma-ray variability of the flat spectrum radio quasar PKS 1510-089 in the time range between 2010 November and 2012 January. In this period the sourc…
Basic properties of Narrow-Line Seyfert 1 Galaxies with Relativistic Jets
L. Foschini, E. Angelakis, G. Bonnoli +25
We present the preliminary results of a survey performed with Swift to observe a sample of radio-loud Narrow-Line Seyfert 1 Galaxies (RLNLS1s). Optical-to-X-ray data from Swift are…
Monitoring the radio spectra of selected blazars in the Fermi-GST era. The Effelsberg 100 m telescope covering the cm band
E. Angelakis, L. Fuhrmann, N. Marchili +2
The analysis of the spectral energy distribution variability at frequencies from radio to TeV is a powerful tool in the investigation of the dynamics, the physics and the structure…
The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
MAGIC Collaboration, J. AleksiÄ, S. Ansoldi +270
We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE…
RoboPol: A four-channel optical imaging polarimeter
A. N. Ramaprakash, C. V. Rajarshi, H. K. Das +30
We present the design and performance of RoboPol, a four-channel optical polarimeter operating at the Skinakas Observatory in Crete, Greece. RoboPol is capable of measuring both re…
Simultaneous Radio to (Sub-) mm-Monitoring of Variability and Spectral Shape Evolution of potential GLAST Blazars
L. Fuhrmann, J. A. Zensus, T. P. Krichbaum +2
The Large Area Telescope (LAT) instrument onboard GLAST offers a tremendous opportunity for future blazar studies. In order to fully benefit from its capabilities and to maximize t…
RoboPol: AGN polarimetric monitoring data
D. Blinov, S. Kiehlmann, V. Pavlidou +29
We present uniformly reprocessed and re-calibrated data from the RoboPol programme of optopolarimetric monitoring of active galactic nuclei (AGN), covering observations between 201…
The RoboPol sample of optical polarimetric standards
D. Blinov, S. Maharana, F. Bouzelou +34
Optical polarimeters are typically calibrated using measurements of stars with known and stable polarization parameters. However, there is a lack of such stars available across the…
Using evolutionary algorithms to model relativistic jets: Application to NGC 1052
C. M. Fromm, Z. Younsi, A. Bazcko +9
High-resolution Very-Long-Baseline Interferometry observations of NGC 1052 show a two sided jet with several regions of enhanced emission and a clear emission gap between the two j…
Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources
Planck Collaboration, J. Aatrokoski, P. A. R. Ade +246
Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact S…
Fermi/LAT discovery of gamma-ray emission from a relativistic jet in the narrow-line Seyfert 1 quasar PMN J0948+0022
L. Foschini, G. Ghisellini, L. Maraschi +2
We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope of high-energy gamma-ray emission from the peculiar quasar PMN J0948+0022 (z=0…
RoboPol: Connection between optical polarization plane rotations and gamma-ray flares in blazars
D. Blinov, V. Pavlidou, I. Papadakis +21
We use results of our 3 year polarimetric monitoring program to investigate the previously suggested connection between rotations of the polarization plane in the optical emission…
F-GAMMA: Multi-frequency radio monitoring of Fermi blazars. The 2.64 to 43 GHz Effelsberg light curves from 2007-2015
E. Angelakis, L. Fuhrmann, I. Myserlis +7
The advent of the Fermi-GST with its unprecedented capability to monitor the entire 4 pi sky within less than 2-3 hours, introduced new standard in time domain gamma-ray astronomy.…
Multi-frequency measurements of the NVSS foreground sources in the Cosmic Background Imager fields. I. Data release
E. Angelakis, A. Kraus, A. C. S. Readhead +5
We present the results of the flux density measurements at 4.85 GHz and 10.45 GHz of a sample of 5998 NVSS radio sources with the Effelsberg 100 m telescope. The initial motivation…
Planck early results XIV: ERCSC validation and extreme radio sources
Planck Collaboration, P. A. R. Ade, N. Aghanim +206
Planck's all sky surveys at 30-857 GHz provide an unprecedented opportunity to follow the radio spectra of a large sample of extragalactic sources to frequencies 2-20 times higher…
The Simultaneous Low State Spectral Energy Distribution of 1ES 2344+514 from Radio to Very High Energies
MAGIC Collaboration, J. AleksiÄ, L. A. Antonelli +191
[Abridged] Context. To construct and interpret the spectral energy distribution (SED) of BL Lacertae objects, simultaneous broad-band observations are mandatory. Aims. We present t…
Radio to gamma-ray variability study of blazar S5 0716+714
B. Rani, T. P. Krichbaum, L. Fuhrmann +34
We present the results of a series of radio, optical, X-ray and gamma-ray observations of the BL Lac object S50716+714 carried out between April 2007 and January 2011. The multi-fr…
The first gamma-ray outburst of a Narrow-Line Seyfert 1 Galaxy: the case of PMN J0948+0022 in July 2010
L. Foschini, G. Ghisellini, Y. Y. Kovalev +24
We report on a multiwavelength campaign on the radio-loud Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z=0.5846) performed in 2010 July-September and triggered by a high-ene…
15 GHz Monitoring of Gamma-ray Blazars with the OVRO 40 Meter Telescope in Support of Fermi
J. L. Richards, W. Max-Moerbeck, V. Pavlidou +11
We present results from the first two years of our fast-cadence 15 GHz gamma-ray blazar monitoring program, part of the F-GAMMA radio monitoring project. Our sample includes the 11…
Radio and gamma-ray loud narrow-line Seyfert 1 galaxies in the spotlight
V. Karamanavis, E. Angelakis, S. Komossa +3
Narrow-line Seyfert 1 (NLS1) galaxies provide us with unique insights into the drivers of AGN activity under extreme conditions. Given their low black hole (BH) masses and near-Edd…
Multifrequency Studies of the Peculiar Quasar 4C +21.35 During the 2010 Flaring Activity
M. Ackermann, M. Ajello, A. Allafort +288
The discovery of rapidly variable Very High Energy (VHE; E > 100 GeV) gamma-ray emission from 4C +21.35 (PKS 1222+216) by MAGIC on 2010 June 17, triggered by the high activity dete…
Broad-band properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies
L. Foschini, M. Berton, A. Caccianiga +27
We report about recent updates of broad-band properties of radio-loud narrow-line Seyfert 1 galaxies.
RoboPol: optical polarization-plane rotations and flaring activity in blazars
D. Blinov, V. Pavlidou, I. E. Papadakis +26
We present measurements of rotations of the optical polarization of blazars during the second year of operation of RoboPol, a monitoring programme of an unbiased sample of gamma-ra…
Optical polarisation variability of radio loud narrow line Seyfert 1 galaxies. Search for long rotations of the polarisation plane
E. Angelakis, S. Kiehlmann, I. Myserlis +5
Narrow line Seyfert 1 galaxies (NLSy1s) constitute the AGN subclass associated with systematically smaller black hole masses. A few radio loud ones have been detected in MeV -- GeV…
Relativistic jets in Narrow-Line Seyfert 1
L. Foschini, E. Angelakis, G. Bonnoli +20
Narrow-Line Seyfert 1 (NLS1) class of active galactic nuclei (AGNs) is generally radio-quiet, but a small percent of them are radio-loud. The recent discovery by Fermi/LAT of high-…
Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013
M. BalokoviÄ, D. Paneque, G. Madejski +305
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, V…
Connection between inner jet kinematics and broadband flux variability in the BL Lac object S5 0716+714
B. Rani, T. P. Krichbaum, A. P. Marscher +5
We present a high-frequency very long baseline interferometry (VLBI) kinematical study of the BL Lac object S5 0716+714 over the time period of September 2008 to October 2010. The…
Optical polarisation variability of narrow line Seyfert 1 galaxies
E. Angelakis, S. Kiehlmann, I. Myserlis +6
We have monitored the R-band optical linear polarisation of ten jetted NLSy1 galaxies with the aim to quantify their variability and search for candidate long rotation of the polar…
The RoboPol optical polarization survey of gamma-ray - loud blazars
V. Pavlidou, E. Angelakis, I. Myserlis +23
We present first results from RoboPol, a novel-design optical polarimeter operating at the Skinakas Observatory in Crete. The data, taken during the May - June 2013 commissioning o…
Radio-to-gamma-ray Monitoring of the Narrow-Line Seyfert 1 Galaxy PMN J0948+0022 from 2008 to 2011
L. Foschini, E. Angelakis, L. Fuhrmann +39
We present more than three years of observations at different frequencies, from radio to high-energy gamma-rays, of the Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z=0.585)…
Assessing the Significance of Apparent Correlations Between Radio and Gamma-ray Blazar Fluxes
V. Pavlidou, J. L. Richards, W. Max-Moerbeck +13
Whether a correlation exists between the radio and gamma-ray flux densities of blazars is a long-standing question, and one that is difficult to answer confidently because of vario…
The F-GAMMA program: Multi-frequency study of Active Galactic Nuclei in the Fermi era. Program description and the first 2.5 years of monitoring
L. Fuhrmann, E. Angelakis, J. A. Zensus +15
To fully exploit the scientific potential of the Fermi mission, we initiated the F-GAMMA program. Between 2007 and 2015 it was the prime provider of complementary multi-frequency m…
What can the 2008/10 broadband flare of PKS 1502+106 tell us? Nuclear opacity, magnetic fields, and the location of gamma rays
V. Karamanavis, L. Fuhrmann, E. Angelakis +7
Context. The origin of blazar variability, seen from radio up to gamma rays, is still a heavily debated matter and broadband flares offer a unique testbed towards a better understa…
Simultaneous Planck, Swift, and Fermi observations of X-ray and gamma-ray selected blazars
P. Giommi, G. Polenta, A. Lahteenmaki +92
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands.…
High cadence, linear and circular polarization monitoring of OJ 287 - Helical magnetic field in a bent jet
I. Myserlis, S. Komossa, E. Angelakis +5
We present a multi-frequency, dense radio monitoring program of the blazar OJ287 using the 100m Effelsberg radio telescope. We analyze the evolution in total flux density, linear a…
Multiwavelength observations of the gamma-ray emitting narrow-line Seyfert 1 PMN J0948+0022 in 2011
F. D'Ammando, J. Larsson, M. Orienti +13
We report on radio-to-gamma-ray observations during 2011 May-September of PMN J0948+0022, the first narrow-line Seyfert 1 (NLSy1) galaxy detected in gamma-rays by Fermi-LAT. Strong…
RoboPol: First season rotations of optical polarization plane in blazars
D. Blinov, V. Pavlidou, I. Papadakis +25
We present first results on polarization swings in optical emission of blazars obtained by RoboPol, a monitoring program of an unbiased sample of gamma-ray bright blazars specially…
Multifrequency studies of the narrow-line Seyfert 1 galaxy SBS 0846+513
F. D'Ammando, M. Orienti, J. Finke +10
The narrow-line Seyfert 1 galaxy SBS 0846+513 was first detected by the Large Area Telescope (LAT) on-board Fermi in 2011 June-July when it underwent a period of flaring activity.…
RoboPol: Do optical polarization rotations occur in all blazars?
D. Blinov, V. Pavlidou, I. Papadakis +23
We present a new set of optical polarization plane rotations in blazars, observed during the third year of operation of RoboPol. The entire set of rotation events discovered during…
Global alignments of parsec-scale AGN radio jets and their polarization planes
D. Blinov, C. Casadio, N. Mandarakas +1
A number of works reported on the existence of a large scale alignment of the polarization plane of extragalactic sources as well as the alignment of radio-sources structural axes.…
The broadband emission properties of AGN jets
C. S. Chang, E. Ros, M. Kadler +7
The origin of the high-energy emission of blazars is still a matter of debate. To investigate the emission mechanism of extragalactic outflows and to pin down the location of the e…
Localizing the rays from blazar PKS 1502+106
Vassilis Karamanavis, L. Fuhrmann, T. P. Krichbaum +7
Blazars are among the most variable objects in the universe. They feature energetic jets of plasma that launch from the cores of these active galactic nuclei (AGN), triggering acti…
Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009
M. L. Ahnen, S. Ansoldi, L. A. Antonelli +290
We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1 which inc…
Fermi/LAT discovery of gamma-ray emission from a relativistic jet in the narrow-line quasar PMN J0948+0022
LAT Collaboration, A. A. Abdo, G. Ghisellini +3
We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope of high-energy gamma-ray emission from the peculiar quasar PMN J0948+0022 (z=0…
MAGIC and Multi-Wavelength Observations of Mrk 180 and 1ES 2344+514 in 2008
S. Rügamer, E. Angelakis, D. Bastieri +14
Simultaneous multi-wavelength (MW) campaigns are the most promising approaches to investigate the still unrevealed nature of blazars, active galactic nuclei which are variable on a…
Exploring the nature of broadband variability in the FSRQ 3C 273
C. Chidiac, B. Rani, T. P. Krichbaum +12
Detailed investigation of broadband flux variability in the blazar 3C 273 allows us to probe the location and size of emission regions and their physical conditions. We report the…
Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state
M. Ackermann, M. Ajello, J. Ballet +208
The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuou…
PKS 1502+106: A high-redshift Fermi blazar at extreme angular resolution. Structural dynamics with VLBI imaging up to 86 GHz
V. Karamanavis, L. Fuhrmann, T. P. Krichbaum +7
Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106 showing a rapid and strong gamma-ray outburst foll…
Properties of flat-spectrum radio-loud Narrow-Line Seyfert 1 Galaxies
L. Foschini, M. Berton, A. Caccianiga +27
We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources of this type and omitting th…
Scale invariant jets: from blazars to microquasars
I. Liodakis, V. Pavlidou, I. Papadakis +9
Black holes, anywhere in the stellar-mass to supermassive range, are often associated with relativistic jets. Models suggest that jet production may be a universal process common i…
Properties of the radio jet emission of four gamma-ray Narrow Line Seyfert 1 galaxies
E. Angelakis, L. Fuhrmann, I. Myserlis +8
The detection of gamma rays from a small number of Narrow Line Seyfert 1 galaxies by the LAT instrument onboard Fermi seriously challenged our understanding of AGN physics. Among t…
Quasi-simultaneous multi-frequency observations of inverted-spectrum GPS candidate sources
B. Vollmer, T. P. Krichbaum, E. Angelakis +1
Gigahertz-Peaked Spectrum (GPS) sources are probably the precursors of local radio galaxies.Existing GPS source samples are small (<200). It is necessary to extend the availabe sam…
Structural variability of 3C 111 on parsec scales
C. GroÃberger, M. Kadler, J. Wilms +15
We discuss the parsec-scale structural variability of the extragalactic jet 3C 111 related to a major radio flux density outburst in 2007. The data analyzed were taken within the s…
F-GAMMA: On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
E. Angelakis, L. Fuhrmann, I. Nestoras +10
The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars. In the current study we sho…
Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars
L. Fuhrmann, S. Larsson, J. Chiang +10
The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis betw…
AGN astrophysics via multi-frequency monitoring of gamma-ray blazars in the Fermi-GST era
E. Angelakis, L. Fuhrmann, J. A. Zensus +10
The F-GAMMA-project is the coordinated effort of several observatories to understand the AGN phenomenon and specifically blazars via multi-frequency monitoring in collaboration wit…
Multi-wavelength characterization of the blazar S5~0716+714 during an unprecedented outburst phase
MAGIC Collaboration, M. L. Ahnen, S. Ansoldi +187
The BL Lac object S5~0716+714, a highly variable blazar, underwent an impressive outburst in January 2015 (Phase A), followed by minor activity in February (Phase B). The MAGIC obs…
Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710
A. Akyuz, D. J. Thompson, D. Donato +7
Aims. The observation of gamma -ray flares from blazar 0836+710 in 2011, following a period of quiescence, offered an opportunity to study correlated activity at different waveleng…
APEX sub-mm monitoring of gamma-ray blazars
S. Larsson, L. Fuhrmann, A. Weiss +13
So far, no systematic long-term blazar monitoring programs and detailed variability studies exist at sub-mm wavelengths. Here, we present a new sub-mm blazar monitoring program usi…
Insights from the first flaring activity of a high-synchrotron-peaked blazar with X-ray polarization and VHE gamma rays
MAGIC Collaboration, K. Abe, S. Abe +250
We study a flaring activity of the HSP Mrk421 that was characterized from radio to very-high-energy (VHE; E TeV) gamma rays with MAGIC, Fermi-LAT, Swift, XMM-Newton and sever…
RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars
E. Angelakis, T. Hovatta, D. Blinov +25
We present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPol observing season. We investigate whether gamma- ray--loud and…
MAGIC and Multi-Wavelength Observations of three HBLs in 2008
S. Rügamer, E. Angelakis, D. Bastieri +9
The high-frequency peaked blazars and known TeV emitters 1ES 1011+496, Mrk 180 and 1ES 2344+514 have been observed in the course of multi-wavelength campaigns in 2008, covering the…
High-Energy Polarimetry - a new window to probe extreme physics in AGN jets
B. Rani, H. Zhang, S. D. Hunter +31
The constantly improving sensitivity of ground-based and space-borne observatories has made possible the detection of high-energy emission (X-rays and gamma-rays) from several thou…
The radio/gamma-ray connection in Active Galactic Nuclei in the era of the Fermi Large Area Telescope
M. Ackermann, M. Ajello, A. Allafort +144
We present a detailed statistical analysis of the correlation between radio and gamma-ray emission of the Active Galactic Nuclei (AGN) detected by Fermi during its first year of op…
Full-Stokes polarimetry with circularly polarized feeds - Sources with stable linear and circular polarization in the GHz regime
I. Myserlis, E. Angelakis, A. Kraus +8
We present a pipeline that allows recovering reliable information for all four Stokes parameters with high accuracy. Its novelty relies on the treatment of the instrumental effects…