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11 results on '"Sokolovsky, K. V."'

1. Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron: IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature.

Author

Pötzl, F. M., Lobanov, A. P., Ros, E., Gómez, J. L., Bruni, G., Bach, U., Fuentes, A., Gurvits, L. I., Jauncey, D. L., Kovalev, Y. Y., Kravchenko, E. V., Lisakov, M. M., Savolainen, T., Sokolovsky, K. V., and Zensus, J. A.

Subjects
INVERSE Compton scattering, ASTROPHYSICAL jets, BRIGHTNESS temperature, MAGNETIC structure, MAGNETIC fields, RADIO jets (Astrophysics), ACTIVE galactic nuclei
Abstract

Context. Supermassive black holes in the centres of radio-loud active galactic nuclei (AGN) can produce collimated relativistic outflows (jets). Magnetic fields are thought to play a key role in the formation and collimation of these jets, but the details are much debated. Aims. We study the innermost jet morphology and magnetic field strength in the AGN 3C 345 with an unprecedented resolution using images obtained within the framework of the key science programme on AGN polarisation of the Space VLBI mission RadioAstron. Methods. We observed the flat spectrum radio quasar 3C 345 at 1.6 GHz on 2016 March 30 with RadioAstron and 18 ground-based radio telescopes in full polarisation mode. Results. Our images, in both total intensity and linear polarisation, reveal a complex jet structure at 300 μas angular resolution, corresponding to a projected linear scale of about 2 pc or a few thousand gravitational radii. We identify the synchrotron self-absorbed core at the jet base and find the brightest feature in the jet 1.5 mas downstream of the core. Several polarised components appear in the Space VLBI images that cannot be seen from ground array-only images. Except for the core, the electric vector position angles follow the local jet direction, suggesting a magnetic field perpendicular to the jet. This indicates the presence of plane perpendicular shocks in these regions. Additionally, we infer a minimum brightness temperature at the largest (u, v)-distances of 1.1 × 1012 K in the source frame, which is above the inverse Compton limit and an order of magnitude larger than the equipartition value. This indicates locally efficient injection or re-acceleration of particles in the jet to counter the inverse Compton cooling or the geometry of the jet creates significant changes in the Doppler factor, which has to be > 11 to explain the high brightness temperatures. [ABSTRACT FROM AUTHOR]

Published
2021
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2. The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

Author

Ackermann, M., Ajello, M., Atwood, W. B., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Becerra, Gonzalez J., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Britto, R. J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Carpenter, B., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen-Tanugi, J., Cominsky, L. R., Conrad, J., Cutini, S., D’Abrusco, R., D’Ammando, F., de, Angelis A., Desiante, R., Digel, S. W., Di, Venere L., Drell, P. S., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Finke, J., Focke, W. B., Franckowiak, A., Fuhrmann, L., Furniss, A. K., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Hewitt, J. W., Hill, A. B., Horan, D., Johannesson, G., Johnson, A. S., Johnson, W. N., Krauss, F., Kuss, M., La, Mura G., Larsson, S., Latronico, L., Leto, C., Li, J., Li, L., Longo, F., Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Madejski, G. M., Mayer, M., Mazziotta, M. N., McEnery, J. E., Michelson, P. F., Moiseev, A. A., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nuss, E., Ojha, R., Omodei, N., Orienti, M., Orlando, E., Paggi, A., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Romani, R. W., Salvetti, D., Schaal, M., Schinzel, F. K., Schulz, A., Sgro, C., Siskind, E. J., Sokolovsky, K. V., Spada, F., Spandre, G., Spinelli, P., Stawarz, Lukasz, Suson, D. J., Thayer, J. G., Thayer, J. B., Tibaldo, L., Torres, D. F., Torresi, E., Tosti, G., Troja, E., Vianello, G., Winer, B. L., Wood, K. S., Zimmer, S., Fukazawa, Yasushi, Itoh, Ryosuke, Kataoka, Jun, Kawano, Takafumi, Mizuno, Tsunefumi, Ohno, Masanori, Ohsugi, Takashi, Takahashi, Hiromitsu, Takahashi, Tadayuki, Tanaka, Yasuyuki, Uchiyama, Yasunobu, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Fermi-LAT, Ackermann M, Ajello M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Gonzalez JB, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bnino R, Bottagini E, Brandt TJ, Bregeon J, Britto RJ, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caragiulo M, Caraveo PA, Careenter B, Casandjian JM, Cavazzuti E, Cecchi C, Charles E, Chekhtman A, Cheung CC, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, D'Abrusco R, DAmmando F, de Angelis A, Desiante R, Digel SW, Di Venere L, Drell PS, FAvuzzi C, Fegan SJ, Ferrara EC, Finke J, Focke WB, Franckowiak A, Fuhrmann L, Fukazawa Y, Furniss AK, Fusco P, Gargano E, Gasparrini D, Giglietto N, Giommi P, Giordano E, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guiriec S, Hewitt JW, Hill AB, Horan D, Itoh R, Johannesson G, Johnson AS, Johnson WN, Kataoka J, Kawano T, Krauss F, Kuss M, La Mura G, Larsson S, Latronico L, Leto C, Li J, Li L, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Mayer M, Mazziotta MN, McEnery JE, Michelson PF, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nuss E, Ohno M, Oxsugi T, Ojha R, Omdei N, Orienti M, Orlando E, Paggi A, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Raino S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Romani RW, Salvetti D, Schaal M, Schinzel FK, Schulz A, Sgro C, Siskind EJ, Sokolovsky KV, Spada F, Spandre G, Spinelli P, Stawarz L, Suson DJ, Takahashi H, Takahashi T, Tanaka Y, Thayer JG, Thayer JB, Tibaldo L, Torres DF, Torresi E, Tosti G, Troja E, Uchiyama Y, Vianello G, Winer BL, Wood KS, Zimmer S, ITA, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Ackermann, M., Ajello, M., Atwood, W. B., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Britto, R. J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Carpenter, B., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen Tanugi, J., Cominsky, L. R., Conrad, J., Cutini, S., D'Abrusco, R., D'Ammando, F., Angelis, A. De, Desiante, R., Digel, S. W., Di Venere, L., Drell, P. S., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Finke, J., Focke, W. B., Franckowiak, A., Fuhrmann, L., Fukazawa, Y., Furniss, A. K., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Hewitt, J. W., Hill, A. B., Horan, D., Itoh, R., Jóhannesson, G., Johnson, A. S., Johnson, W. N., Kataoka, J., Kawano, T., Krauss, F., Kuss, M., La Mura, G., Larsson, S., Latronico, L., Leto, C., Li, J., Li, L., Longo, Francesco, Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Madejski, G. M., Mayer, M., Mazziotta, M. N., Mcenery, J. E., Michelson, P. F., Mizuno, T., Moiseev, A. A., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nuss, E., Ohno, M., Ohsugi, T., Ojha, R., Omodei, N., Orienti, M., Orlando, E., Paggi, A., Paneque, D., Perkins, J. S., Pesce Rollins, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Romani, R. W., Salvetti, D., Schaal, M., Schinzel, F. K., Schulz, A., Sgrò, C., Siskind, E. J., Sokolovsky, K. V., Spada, F., Spandre, G., Spinelli, P., Stawarz, L., Suson, D. J., Takahashi, H., Takahashi, T., Tanaka, Y., Thayer, J. G., Thayer, J. B., Tibaldo, L., Torres, D. F., Torresi, E., Tosti, G., Troja, E., Uchiyama, Y., Vianello, G., Winer, B. L., Wood, K. S., and Zimmer, S.

Subjects
Nuclear and High Energy Physics, BL Lacertae objects: general, galaxies: active, galaxies: jets, gamma rays: galaxies, Astronomy and Astrophysics, Space and Planetary Science, Active galactic nucleus, BL Lacertae objects: general, galaxies: active, galaxies: jets, gamma rays: galaxies, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, jets [galaxies], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, law.invention, Telescope, law, Nuclear Experiment, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), general [BL Lacertae objects], jet [galaxies], active [galaxies], galaxies [gamma rays], ddc:520, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fermi Gamma-ray Space Telescope
Abstract

The astrophysical journal 810(1), 14 - (2015). doi:10.1088/0004-637X/810/1/14, The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV with a Test Statistic greater than 25, between 2008 August 4 and 2012 July 31. The 3LAC includes 1591 AGNs located at high Galactic latitudes ($| b| \gt 10^\circ $), a 71% increase over the second catalog based on 2 years of data. There are 28 duplicate associations, thus 1563 of the 2192 high-latitude gamma-ray sources of the 3FGL catalog are AGNs. Most of them (98%) are blazars. About half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. Based on their gamma-ray spectral properties, these sources are evenly split between flat-spectrum radio quasars (FSRQs) and BL Lacs. The most abundant detected BL Lacs are of the high-synchrotron-peaked (HSP) type. About 50% of the BL Lacs have no measured redshifts. A few new rare outliers (HSP-FSRQs and high-luminosity HSP BL Lacs) are reported. The general properties of the 3LAC sample confirm previous findings from earlier catalogs. The fraction of 3LAC blazars in the total population of blazars listed in BZCAT remains non-negligible even at the faint ends of the BZCAT-blazar radio, optical, and X-ray flux distributions, which hints that even the faintest known blazars could eventually shine in gamma-rays at LAT-detection levels. The energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs., Published by Univ.11032, Chicago, Ill. [u.a.]

Published
2015
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3. RadioAstron gravitational redshift experiment: status update

Author

Litvinov, D.A., Bach, U., Bartel, N., Belousov, K.G., Bietenholz, M., Biriukov, A.V., Cimo, G, Duev, D. A., Gurvits, L., Gusev, A.V., Haas, R, Kauts, V.L., Kanevsky, B.Z., Kovalenko, A.V., Kronschnabl, G, Kulagin, V.V., Lindqvist, Maria, Molera Calves, G, Neidhardt, A., Plotz, C., Pogrebenko, S. V., Porayko, N.K., Rudenko, V.N., Sokolovsky, K. V., Smirnov, A.I., Stepanyants, V.A., Yang, J., Zakhvatkin, M.V., Bianchi, M., Jantzen, R.T., and Ruffini, R.

Subjects
radio continuum: galaxies, quasars: individual (3C273), techniques: interferometric, galaxies: active, Astrophysics::Earth and Planetary Astrophysics, galaxies: jets
Abstract

A test of a cornerstone of general relativity, the gravitational redshift effect, is currently being conducted with the RadioAstron spacecraft, which is on a highly eccentric orbit around Earth. Using ground radio telescopes to record the spacecraft signal, synchronized to its ultra-stable on-board H-maser, we can probe the varying flow of time on board with unprecedented accuracy. The observations performed so far, currently being analyzed, have already allowed us to measure the effect with a relative accuracy of 4 × 10−4 . We expect to reach 2.5×10−5 with additional observations in 2016, an improvement of almost a magnitude over the 40-year old result of the GP-A mission.

Published
2016

4. Opacity, variability, and kinematics of AGN jets.

Author

Kutkin, A M, Pashchenko, I N, Sokolovsky, K V, Kovalev, Y Y, Aller, M F, and Aller, H D

Subjects
VERY long baseline interferometry, LOUDNESS, ACTIVE galactic nuclei, KINEMATICS, SHORTWAVE radio, KRIGING
Abstract

Synchrotron self-absorption in active galactic nuclei (AGN) jets manifests itself as a time delay between flares observed at high and low radio frequencies. It is also responsible for the observing frequency-dependent change in size and position of the apparent base of the jet, aka the core shift effect, detected with very long baseline interferometry (VLBI). We measure the time delays and the core shifts in 11 radio-loud AGN to estimate the speed of their jets without relying on multi-epoch VLBI kinematics analysis. The 15–8 GHz total flux density time lags are obtained using Gaussian process regression, the core shift values are measured using VLBI observations and adopted from the literature. A strong correlation is found between the apparent core shift and the observed time delay. Our estimate of the jet speed is higher than the apparent speed of the fastest VLBI components by the median coefficient of 1.4. The coefficient ranges for individual sources from 0.5 to 20. We derive Doppler factors, Lorentz factors, and viewing angles of the jets, as well as the corresponding de-projected distance from the jet base to the core. The results support evidence for acceleration of the jets with bulk motion Lorentz factor Γ ∝  R 0.52±0.03 on de-projected scales R of 0.5–500 parsecs. [ABSTRACT FROM AUTHOR]

Published
2019
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5. The extreme blazar AO 0235+164 as seen by extensive ground and space radio observations.

Author

Kutkin, A. M., Pashchenko, I. N., Lisakov, M. M., Voytsik, P. A., Sokolovsky, K. V., Kovalev, Y. Y., Lobanov, A. P., Ipatov, A. V., Aller, M. F., Aller, H. D., Lahteenmaki, A., Tornikoski, M., and Gurvits, L. I.

Subjects
BL Lacertae objects, ASTRONOMICAL observations, OPACITY (Optics), GAUSSIAN processes, VERY long baseline interferometry
Abstract

Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra-compact blazar AO0235+164 with RadioAstron ground-space radio interferometer, multifrequency VLBA, EVN, and single-dish radio observations. We employ visibility modelling and image stacking for deriving structure and kinematics of the source, and use Gaussian process regression to find the relative multiband time delays of the flares. The multifrequency core size and time lags support prevailing synchrotron self-absorption. The intrinsic brightness temperature of the core derived from ground-based very long baseline interferometry (VLBI) is close to the equipartition regime value. In the same time, there is evidence for ultra-compact features of the size of less than 10 μas in the source, which might be responsible for the extreme apparent brightness temperatures of up to 1014 K as measured by RadioAstron. In 2007-2016 the VLBI components in the source at 43 GHz are found predominantly in two directions, suggesting a bend of the outflow from southern to northern direction. The apparent opening angle of the jet seen in the stacked image at 43 GHz is two times wider than that at 15 GHz, indicating a collimation of the flow within the central 1.5 mas. We estimate the Lorentz factor Γ = 14, the Doppler factor δ = 21, and the viewing angle θ = 1.7° of the apparent jet base, derive the gradients of magnetic field strength and electron density in the outflow, and the distance between jet apex and the core at each frequency. [ABSTRACT FROM AUTHOR]

Published
2018
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6. Parsec-scale Faraday rotation and polarization of 20 active galactic nuclei jets.

Author

Kravchenko, E. V., Kovalev, Y. Y., and Sokolovsky, K. V.

Subjects
GALACTIC nuclei, FARADAY effect, OPTICAL polarization, WAVELENGTHS, JETS (Nuclear physics), MAGNETIC fields
Abstract

We perform polarimetry analysis of 20 active galactic nuclei jets using the very long baseline array at 1.4, 1.6, 2.2, 2.4, 4.6, 5.0, 8.1, 8.4 and 15.4 GHz. The study allowed us to investigate linearly polarized properties of the jets at parsec scales: distribution of the Faraday rotation measure (RM) and fractional polarization along the jets, Faraday effects and structure of Faraday-corrected polarization images. Wavelength dependence of the fractional polarization and polarization angle is consistent with external Faraday rotation, while some sources show internal rotation. The RM changes along the jets, systematically increasing its value towards synchrotron self-absorbed cores at shorter wavelengths. The highest core RM reaches 16 900 rad m-2 in the source rest frame for the quasar 0952+179, suggesting the presence of highly magnetized, dense media in these regions. The typical RM of transparent jet regions has values of an order of a hundred rad m-2. Significant transverse RM gradients are observed in seven sources. The magnetic field in the Faraday screen has no preferred orientation, and is observed to be random or regular from source to source. Half of the sources show evidence for the helical magnetic fields in their rotating magneto-ionic media. At the same time jets themselves contain large-scale, ordered magnetic fields and tend to align its direction with the jet flow. The observed variety of polarized signatures can be explained by a model of spine-sheath jet structure. [ABSTRACT FROM AUTHOR]

Published
2017
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7. Polarization angle swings in blazars: The case of 3C 279.

Author

Kiehlmann, S., Savolainen, T., Jorstad, S. G., Sokolovsky, K. V., Schinzel, F. K., Marscher, A. P., Larionov, V. M., Agudo, I., Akitaya, H., Benítez, E., Berdyugin, A., Blinov, D. A., Bochkarev, N. G., Borman, G. A., Burenkov, A. N., Casadio, C., Doroshenko, V. T., Efimova, N. V., Fukazawa, Y., and Gömez, J. L.

Subjects
POLARIZATION (Nuclear physics), BL Lacertae objects, ACTIVE galaxies, ELECTROMAGNETIC waves, ASTROPHYSICAL radiation, MAGNETIC fields, QUASARS
Abstract

Context. Over the past few years, on several occasions, large, continuous rotations of the electric vector position angle (EVPA) of linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy γ-ray flares and they have attracted considerable attention, since they could allow us to probe the magnetic field structure in the γ-ray emitting region of the jet. The flat-spectrum radio quasar 3C 279 is one of the most prominent examples showing this behaviour. Aims. Our goal is to study the observed EVPA rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability. Methods. We have combined multiple data sets of R-band photometry and optical polarimetry measurements of 3C 279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008-2012. Several large EVPA rotations are identified in the data. We introduce a quantitative measure for the EVPA curve smoothness, which is then used to test a set of simple random walk polarization variability models against the data. Results. 3C 279 shows different polarization variation characteristics during an optical low-flux state and a flaring state. The polarization variation during the flaring state, especially the smooth ~360° rotation of the EVPA in mid-2011, is not consistent with the tested stochastic processes. Conclusions. We conclude that, during the two different optical flux states, two different processes govern polarization variation, which is possibly a stochastic process during the low-brightness state and a deterministic process during the flaring activity. [ABSTRACT FROM AUTHOR]

Published
2016
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8. Very Long Baseline polarimetry and the γ-ray connection in Markarian 421 during the broadband campaign in 2011.

Author

Giroletti, M., Lico, R., Orienti, M., D'Ammando, F., Blasi, M. G., Kino, M., Sokolovsky, K. V., Kovalev, Y. Y., Paneque, D., Piner, B. G., Gómez, J. L., Casadio, C., Cotton, W., Edwards, P. G., Fuhrmann, L., Krichbaum, T. P., Marscher, A. P., and Jorstad, S.

Subjects
LIGHT curves, TOPOLOGY, ACTIVE galaxies, ASTROPHYSICS, ASTRONOMY
Abstract

Conte×t. This is the third paper in a series devoted to the analysis of the multiwavelength data from a campaign on the nearby (z = 0.03) TeV blazar Mrk 421 during 2011. Aims. We investigate the structure of the high angular resolution polarization, the magnetic topology, the total intensity light curve, the γ-ray flu×, and the photon inde×. We describe how they evolve and how they are connected. Methods. We analyzed data in polarized intensity obtained with the Very Long Baseline Array (VLBA) at twelve epochs (one observation per month from January to December 2011) at 15, 24, and 43 GHz. For the absolute orientation of the electric vector position angles (EVPA) we used the D-terms method; we also confirm its accuracy. We also used γ-ray data from the Fermi Large Area Telescope on weekly time bins throughout 2011. Results. The source shows polarized emission, and its properties vary with time, frequency, and location along the jet. The core mean polarization fraction is generally between 1% and 2%, with a 4% peak at 43 GHz in March; the polarization angle is variable, mainly at 15 GHz, where it changes frequently, and less so at 43 GHz, where it oscillates in the range 114°-173°∘. The jet polarization properties are more stable, with a fractional polarization of around 16% and a polarization angle nearly perpendicular to the jet a×is. The average flu× and photon inde× at γ-ray energies are (17.4 ± 0.5) ×10-8 ph cm-2 s-1 and Γ = 1.77 ± 0.02. The γ-ray light curve shows variability, with a main peak of (38 ± 11) × 10-8 ph cm-2 s-1 at the beginning of March and two later peaks centered on September 8 and November 13. The first γ-ray peak appears to be associated with the peak in the core polarized emission at 43 GHz, as well as with the total intensity light curve. A discrete correlation function analysis yields a correlation coefficient of 0.54 at zero delay, with a significance level >99.7%. Conclusions. With this multifrequency study, we accurately determine the polarization properties of Mrk 421, both in the core and in the jet region. The radio and γ-ray light curves are correlated. The observed EVPA variability at 15 GHz is partly due to opacity and partly to a variable Faraday rotation effect. To e×plain the residual variability of the intrinsic polarization angle and the low degree of polarization in the core region, we invoke a blend of variable cross-polarized subcomponents with different polarization properties within the beam. [ABSTRACT FROM AUTHOR]

Published
2014
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9. Two active states of the narrow-line gamma-ray-loud AGN GB1310+487.

Author

Sokolovsky, K. V., Schinzel, F. K., Tanaka, Y. T., Abolmasov, P. K., Angelakis, E., Bulgarelli, A., Carrasco, L., Cenko, S. B., Cheung, C. C., Clubb, K. I., D'Ammando, F., Escande, L., Fegan, S. J., Filippenko, A. V., Finke, J. D., Fuhrmann, L., Fukazawa, Y., Hays, E., Healey, S. E., and Ikejiri, Y.

Subjects
*GAMMA rays, *PHOTONS, *EMISSION-line galaxies, *SPECTRAL energy distribution, *SYNCHROTRON radiation
Abstract

Context. Previously unremarkable, the extragalactic radio source GB 1310+487 showed a γ-ray flare on 2009 November 18, reaching a daily flux of ∼10−6 photons cm−2 s−1 at energies E > 100MeV and became one of the brightest GeV sources for about two weeks. Its optical spectrum shows strong forbidden-line emission while lacking broad permitted lines, which is not typical for a blazar. Instead, the spectrum resembles those of narrow emission-line galaxies. Aims. We investigate changes in the object’s radio-to-GeV spectral energy distribution (SED) during and after the prominent γ-ray flare with the aim of determining the nature of the object and of constraining the origin of the variable high-energy emission. Methods. The data collected by the Fermi and AGILE satellites at γ-ray energies; Swift at X-ray and ultraviolet (UV); the Kanata, NOT, and Keck telescopes at optical; OAGH and WISE at infrared (IR); and IRAM 30m, OVRO 40m, Effelsberg 100 m, RATAN-600, and VLBA at radio are analyzed together to trace the SED evolution on timescales of months. Results. The γ-ray/radio-loud narrow-line active galactic nucleus (AGN) is located at redshift z = 0.638. It shines through an unrelated foreground galaxy at z = 0.500. The AGN light is probably amplified by gravitational lensing. The AGN SED shows a two-humped structure typical of blazars and γ-ray-loud narrow-line Seyfert 1 galaxies, with the high-energy (inverse-Compton) emission dominating by more than an order of magnitude over the low-energy (synchrotron) emission during γ-ray flares. The difference between the two SED humps is smaller during the low-activity state. Fermi observations reveal a strong correlation between the γ-ray flux and spectral index, with the hardest spectrum observed during the brightest γ-ray state. The γ-ray flares occurred before and during a slow rising trend in the radio, but no direct association between γ-ray and radio flares could be established. Conclusions. If the γ-ray flux is a mixture of synchrotron self-Compton and external Compton emission, the observed GeV spectral variability may result from varying relative contributions of these two emission components. This explanation fits the observed changes in the overall IR to γ-ray SED. [ABSTRACT FROM AUTHOR]

Published
2014
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10. The TeV blazar Markarian 421 at the highest spatial resolution.

Author

Blasi, M. G., Lico, R., Giroletti, M., Orienti, M., Giovannini, G., Cotton, W., Edwards, P. G., Fuhrmann, L., Krichbaum, T. P., Kovalev, Y. Y., Jorstad, S., Marscher, A., Kino, M., Paneque, D., Perez-Torres, M. A., Piner, B. G., and Sokolovsky, K. V.

Subjects
ACTIVE galactic nuclei, ANGULAR distribution (Nuclear physics), ASTRONOMICAL observations, WAVELENGTHS, FLUX (Energy), BL Lacertae objects, JETS (Nuclear physics)
Abstract

Context. High-resolution radio observations allow us to directly image the innermost region of active galactic nuclei. The Very Long Baseline Array (VLBA) data analyzed in this paper were obtained during a multiwavelength (MWL) campaign, carried out in 2011, from radio to very high energy gamma rays, on the TeV blazar Markarian 421 (Mrk 421). Aims. Our aim was to obtain information on the jet structure in Mrk 421 during the MWL campaign at the highest possible angular resolution and with high temporal frequency observations, in order to compare structural and flux density evolution with higher energy variations. Methods. We consider data obtained with the VLBA at 43 GHz through two sets of observations: one is part of a dedicated multifrequency monitoring campaign, in which we observed Mrk 421 once a month from January to December 2011 at three frequencies; the other is extracted from the Boston University monitoring program, which observes 34 blazars at 43 GHz about once per month. We model-fit the data in the visibility plane, study the proper motion of jet components, the light curve, and the spectral index of the jet features. We compare the radio data with optical light curves obtained at the Steward Observatory, considering also the optical polarization information. Results. Mrk 421 has a bright nucleus and a one-sided jet extending towards the north-west for a few parsecs. The model-fits show that brightness distribution is well described using 6-7 circular Gaussian components, four of which are reliably identified at all epochs; all components are effectively stationary except for component D, at ∼0.4 mas from the core, whose motion is, however, subluminal. Analysis of the light curve shows two different states, with the source being brighter and more variable in the first half of 2011 than in the second half. The highest flux density is reached in February. A comparison with the optical data reveals an increase of the V magnitude and of the fractional polarization simultaneous with the enhancement of the radio activity. [ABSTRACT FROM AUTHOR]

Published
2013
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11. The first Fermi multifrequency campaign on BL Lacertae: characterizing the low-activity state of the eponymous blazar

Author

Abdo, A. A., Ackermann, M., Ajello, M., Antolini, E., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bonamente, E., Borgland, A. W., Bregeon, J., Brez, A., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Cannon, A., Caraveo, P. A., Carrigan, S., Casandjian, J. M., Cecchi, C., Celik, O., Charles, E., Chekhtman, A., Cheung, C. C., Chiang, J., Ciprini, S., Claus, R., Cohen-Tanugi, J., Conrad, J., Costamante, L., Cutini, S., Dermer, C. D., de, Palma F., Donato, D., do, Couto e Silva E., Drell, P. S., Dubois, R., Escande, L., Favuzzi, C., Fegan, S. J., Finke, J., Focke, W. B., Fortin, P., Frailis, M., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Guiriec, S., Hadasch, D., Hays, E., Hughes, R. E., Johannesson, G., Johnson, A. S., Johnson, W. N., Knodlseder, J., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lee, S.-H., Llena, Garde M., Longo, F., Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Makeev, A., Mazziotta, M. N., McEnery, J. E., Mehault, J., Michelson, P. F., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nakamori, T., Naumann-Godo, M., Nishino, S., Nolan, P. L., Norris, J. P., Nuss, E., Omodei, N., Orlando, E., Ormes, J. F., Fukazawa, Y., Hayashida, M., Itoh, R., Kamae, T., Katagiri, H., Kataoka, J., Mizuno, T., Ohsugi, T., Okumura, Akira, Ozaki, Masanobu, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Théorique et Astroparticules (LPTA), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Fermi-LAT, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Abdo, A. A., Ackermann, M., Ajello, M., Antolini, E., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bonamente, E., Borgland, A. W., Bregeon, J., Brez, A., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Cannon, A., Caraveo, P. A., Carrigan, S., Casandjian, J. M., Cecchi, C., Celik, ., Charles, E., Chekhtman, A., Cheung, C. C., Chiang, J., Ciprini, S., Claus, R., Cohen Tanugi, J., Conrad, J., Costamante, L., Cutini, S., Dermer, C. D., Palma, F., Donato, D., E. d. C., Drell, P. S., Dubois, R., Escande, L., Favuzzi, C., Fegan, S. J., Finke, J., Focke, W. B., Fortin, P., Frailis, M., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Guiriec, S., Hadasch, D., Hayashida, M., Hays, E., Hughes, R. E., Itoh, R., Johannesson, G., Johnson, A. S., Johnson, W. N., Kamae, T., Katagiri, H., Kataoka, J., Kn\odlseder, J., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lee, S., Garde, M., Longo, Francesco, Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Makeev, A., Mazziotta, M. N., Mcenery, J. E., Mehault, J., Michelson, P. F., Mizuno, T., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nakamori, T., Naumann Godo, M., Nishino, S., Nolan, P. L., Norris, J. P., Nuss, E., Ohsugi, T., Okumura, A., Omodei, N., Orlando, E., Ormes, J. F., Ozaki, M., Paneque, D., Panetta, J. H., Parent, D., Pelassa, V., Pepe, M., Pesce Rollins, M., Piron, F., Porter, T. A., Rain\`o, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Ritz, S., Roth, M., Sadrozinski, H. F., Sanchez, D., Sander, A., Schinzel, F. K., Sgr\`o, C., Siskind, E. J., Smith, P. D., Sokolovsky, K. V., Spandre, G., Spinelli, P., Strickman, M. S., Suson, D. J., Takahashi, H., Tanaka, T., Thayer, J. B., Thayer, J. G., Thompson, D. J., Tibaldo, L., Torres, D. F., Tosti, G., Tramacere, A., Uehara, T., Usher, T. L., Vandenbroucke, J., Vasileiou, V., Vilchez, N., Vitale, V., Waite, A. P., Wallace, E., Wang, P., Winer, B. L., Wood, K. S., Yang, Z., Ylinen, T., Ziegler, M., Berdyugin, A., Boettcher, M., Carrami\~nana, A., Carrasco, L., La, E., Diltz, C., Hovatta, T., Kadenius, V., Kovalev, Y. Y., L\ahteenm\aki, A., Lindfors, E., Marscher, A. P., Nilsson, K., Pereira, D., Reinthal, R., Roustazadeh, P., Savolainen, T., Sillanp\a\a, A., Takalo, L. O., Tornikoski, M., Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Brightness, [PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Cosmology and Nongalactic Astrophysics (astro-ph.CO), [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, BL Lacertae objects: individual: BL Lacertae, 01 natural sciences, law.invention, 98.54.Cm Active and peculiar galaxies and related systems (including BL Lacertae objects, blazars, Seyfert galaxies, Markarian galaxies, and active galactic nuclei) 95.85.Pw &ggr;-ray 95.30.Gv Radiation mechanisms, polarization 98.62.En, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], law, 0103 physical sciences, gamma rays: galaxies, BL Lacertae objects: general, BL Lacertae objects: individual (BL Lacertae), galaxies: jets, radiation mechanisms: non-thermal, X-rays: galaxies, Egret, galaxie [gamma rays], Blazar, 010303 astronomy & astrophysics, individual: BL Lacertae [BL Lacertae objects], Physics, High Energy Astrophysical Phenomena (astro-ph.HE), biology, general [BL Lacertae objects], 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Low activity, Astronomy and Astrophysics, non-thermal [radiation mechanisms], biology.organism_classification, Synchrotron, galaxies [X-rays], jet [galaxies], Space and Planetary Science, Spectral energy distribution, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Fermi Gamma-ray Space Telescope
Abstract

著者人数: 181名, Accepted: 2010-12-30, 資料番号: SA1002984000

Published
2011

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