334 citations · 1.6k across the 24 of their papers we have counts for
24 papers
Extreme outflow velocities and weak UV emission lines indicate quasars shedding their dust cocoons
Guozhen Ma, Stefan J. Geier, Johan P. U. Fynbo +11
The recently discovered low-ionisation broad absorption line (LoBAL) quasar GQ 13092904 is unusual due to its very broad, highly blueshifted absorption troughs and an absence of…
X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023
Chien-Ting J. Chen, Ioannis Liodakis, Riccardo Middei +143
We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Pola…
Evidence of jet activity from the secondary black hole in the OJ287 binary system
Mauri J. Valtonen, Staszek Zola, Alok C. Gupta +29
We report the study of a huge optical intraday flare on November 12, 2021, at 2 am UT, in the blazar OJ287. In the binary black hole model it is associated with an impact of the se…
Observations of Low and Intermediate Spectral Peak Blazars with the Imaging X-ray Polarimetry Explorer
Herman L. Marshall, Ioannis Liodakis, Alan P. Marscher +145
We present X-ray polarimetry observations from the Imaging X-ray Polarimetry Explorer (IXPE) of three low spectral peak and one intermediate spectral peak blazars, namely 3C 273, 3…
Discovery of magnetic fields in five DC white dwarfs
Andrei V. Berdyugin, Vilppu Piirola, Stefano Bagnulo +2
About half of white dwarfs (WDs) evolve to the DC state as they cool; the others become DQ or (temporarily?) DZ WDs. The recent magnetic survey of the local 20 pc volume has establ…
X-ray Polarization Observations of BL Lacertae
Riccardo Middei, Ioannis Liodakis, Matteo Perri +143
Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus the Synchrotron emission to be resp…
Polarized Blazar X-rays imply particle acceleration in shocks
Ioannis Liodakis, Alan P. Marscher, Iván Agudo +125
Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to $\sim 1…
Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1
Henric Krawczynski, Fabio Muleri, Michal Dovčiak +111
A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a po…
Highly sensitive search for magnetic fields in white dwarfs using broad-band circular polarimetry
Andrei V. Berdyugin, Vilppu Piirola, Stefano Bagnulo +2
Circular polarisation measurements of white dwarfs of various ages and spectral types are useful to understand the origin and evolution of the magnetic field in degenerate stars. I…
Black hole spin-orbit misalignment in the X-ray binary MAXI J1820+070
Juri Poutanen, Alexandra Veledina, Andrei V. Berdyugin +10
The observational signatures of black holes in x-ray binary systems depend on their masses, spins, accretion rate and the misalignment angle between the black hole spin and the orb…
A luminous and isolated gamma-ray flare from the blazar B2 1215+30
VERITAS Collaboration, A. U. Abeysekara, S. Archambault +84
B2 1215+30 is a BL Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes, and subsequently confirmed by the VERITAS observatory with…
Optical and Radio variability of the Northern VHE gamma-ray emitting BL Lac objects
E. J. Lindfors, T. Hovatta, K. Nilsson +9
We compare the variability properties of very high energy gamma-ray emitting BL Lac objects in the optical and radio bands. We use the variability information to distinguish multip…
Primary black hole spin in OJ287 as determined by the General Relativity centenary flare
M. J. Valtonen, S. Zola, S. Ciprini +87
OJ287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts which are predictable in a binary black hole model. The model predicted a majo…
Precursor flares in OJ 287
P. Pihajoki, M. Valtonen, S. Zola +19
We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain th…
The structure and emission model of the relativistic jet in the quasar 3C 279 inferred from radio to high-energy gamma-ray observations in 2008-2010
M. Hayashida, G. M. Madejski, K. Nalewajko +90
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Tel…
Upsilon Andromedae b in polarized light: New constraints on the planet size, density and albedo
S. V. Berdyugina, A. V. Berdyugin, V. Piirola
Polarimetry is a novel tool to detect and characterize exoplanets and their atmospheres. Polarized scattered light from the non-transiting hot Jupiter ~And~b is measured…
The brightest gamma-ray flaring blazar in the sky: AGILE and multi-wavelength observations of 3C 454.3 during November 2010
S. Vercellone, E. Striani, V. Vittorini +84
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one gamma-ray flare per year, be…
The first Fermi multifrequency campaign on BL Lacertae: characterizing the low-activity state of the eponymous blazar
A. A. Abdo
We report on observations of BL Lacertae during the first 18 months of Fermi-LAT science operations and present results from a 48-day multifrequency coordinated campaign from 2008…
GJ 841B - The Second DQ White Dwarf with Polarized CH Molecular Bands
Tommi Vornanen, Svetlana Berdyugina, Andrei Berdyugin +1
We report a discovery of the circularly polarized CH and molecular bands in the spectrum of the DQ white dwarf GJ 841B. This is only the second such obje…
A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279
LAT Collaboration, members of the 3C 279 multi-band campaign
It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet po…
Variability and stability in blazar jets on time scales of years: Optical polarization monitoring of OJ287 in 2005-2009
C. Villforth, K. Nilsson, J. Heidt +45
(Abridged) OJ287 is a BL Lac object that has shown double-peaked bursts at regular intervals of ~12 yr during the last ~40 yr. We analyse optical photopolarimetric monitoring data…
WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008. Unveiling different emission components
C. M. Raiteri, M. Villata, A. Capetti +8
In 2007-2008 we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite, to stud…
The correlated optical and radio variability of BL Lacertae. WEBT data analysis 1994-2005
M. Villata, C. M. Raiteri, V. M. Larionov +2
Since 1997, BL Lacertae has undergone a phase of high optical activity, with the occurrence of several prominent outbursts. Starting from 1999, the Whole Earth Blazar Telescope (WE…
The WEBT Campaign on the Intermediate BL Lac Object 3C66A in 2007-2008
M. Boettcher, K. Fultz
Prompted by a high optical state in September 2007, the Whole Earth Blazar Telescope (WEBT) consortium organized an intensive optical, near-IR (JHK) and radio observing campaign on…