Browsing by Author "Barres De Almeida, U."

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  • The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies
    (2020-02-20) Abeysekara, A. U.; Benbow, W.; Bird, R.; Brill, A.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Christiansen, J. L.; Chromey, A. J.; Daniel, M. K.; Dumm, J.; Falcone, A.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Galante, N.; Gent, A.; Gillanders, G. H.; Giuri, C.; Gueta, O.; Hassan, T.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Moriarty, P.; Mukherjee, R.; Nelson, T.; Nieto, D.; Nievas Rosillo, M.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pichel, A.; Pohl, M.; Prado, R. R.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Stevenson, B.; Sushch, I.; Tyler, J.; Vassiliev, V. V.; Wakely, S. P.; Weinstein, A.; Wells, R. M.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Baack, D.; Babić, A.; Banerjee, B.; Barres De Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli, G.; Busetto, G.; Carosi, R.; Ceribella, G.; Chai, Y.; Cikota, S.; Colak, S. M.; Colin, U.; Colombo, E.; Contreras, J. L.; Cortina, Juan; Covino, S.; D'Elia, V.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Delfino, M.; Delgado, J.; Di Pierro, F.; Do Souto Espiñera, E.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Fernández-Barral, A.; Ferrara, G.; Fidalgo, D.; Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; Gallozzi, S.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Godinović, N.; Green, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Herrera, J.; Hoang, J.; Hrupec, D.; Inoue, S.; Ishio, K.; Iwamura, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Machado De Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Masuda, S.; Mazin, D.; Miceli, D.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Niedzwiecki, A.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Nöthe, M.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Penil, P.; Peresano, M.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Satalecka, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Somero, A.; Stamerra, A.; Strom, D.; Strzys, M.; Sun, S.; Surić, T.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Alba, N.; Tsujimoto, S.; Van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Will, Martin; Zarić, D.; Aller, H. D.; Aller, M. F.; Carini, M. T.; Horan, D.; Jordan, B.; Jorstad, S. G.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lahteenmaki, Anne; Larionov, V. M.; Larionova, E. G.; Madejski, G.; Marscher, A. P.; Max-Moerbeck, W.; Moody, J. Ward; Morozova, D. A.; Nikolashvili, M. G.; Raiteri, C. M.; Readhead, A. C.S.; Richards, J. L.; Sadun, A. C.; Sakamoto, T.; Sigua, L. A.; Smith, P. S.; Talvikki, H.; Tammi, Joni; Tornikoski, Merja; Troitsky, I. S.; Villata, M.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ∼27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsahovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ∼25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ⪆ 33) and the size of the emission region (δ-1RB≲ 3.8 × 1013cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model.
  • Insights into the emission of the blazar 1ES 1011+496 through unprecedented broadband observations during 2011 and 2012
    (2016) Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Arcaro, C.; Babic, A.; Bangale, P.; Barres De Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; De Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Vogler, P.; Will, M.; Zanin, R.; Buson, S.; D'Ammando, F.; Lähteenmäki, A.; Hovatta, T.; Kovalev, Y. Y.; Lister, M. L.; Max-Moerbeck, W.; Mundell, C.; Pushkarev, A. B.; Rastorgueva-Foi, E.; Readhead, A. C S; Richards, J. L.; Tammi, J.; Sanchez, D. A.; Tornikoski, M.; Savolainen, Tuomas; Steele, I.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Context. 1ES 1011+496 (z = 0:212) was discovered in very high-energy (VHE, E > 100 GeV) γ rays with MAGIC in 2007. The absence of simultaneous data at lower energies led to an incomplete characterization of the broadband spectral energy distribution (SED). Aims. We study the source properties and the emission mechanisms, probing whether a simple one-zone synchrotron self-Compton (SSC) scenario is able to explain the observed broadband spectrum. Methods. We analyzed data in the range from VHE to radio data from 2011 and 2012 collected by MAGIC, Fermi-LAT, Swift, KVA, OVRO, and Metsähovi in addition to optical polarimetry data and radio maps from the Liverpool Telescope and MOJAVE. Results. The VHE spectrum was fit with a simple power law with a photon index of 3:69 ± 0:22 and a flux above 150 GeV of (1:46 ± 0:16) × 10-11 ph cm-2 s-1. The source 1ES 1011+496 was found to be in a generally quiescent state at all observed wavelengths, showing only moderate variability from radio to X-rays. A low degree of polarization of less than 10% was measured in optical, while some bright features polarized up to 60% were observed in the radio jet. A similar trend in the rotation of the electric vector position angle was found in optical and radio. The radio maps indicated a superluminal motion of 1.8±0.4 c, which is the highest speed statistically significant measured so far in a high-frequency-peaked BL Lac. Conclusions. For the first time, the high-energy bump in the broadband SED of 1ES 1011+496 could be fully characterized from 0.1 GeV to 1 TeV, which permitted a more reliable interpretation within the one-zone SSC scenario. The polarimetry data suggest that at least part of the optical emission has its origin in some of the bright radio features, while the low polarization in optical might be due to the contribution of parts of the radio jet with different orientations of the magnetic field with respect to the optical emission.
  • Long-Term multi-wavelength study of 1ES 0647+250
    (2023-02-01) Acciari, V. A.; Aniello, T.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Arcaro, C.; Artero, M.; Asano, K.; Baack, D.; Babia, A.; Baquero, A.; Barres De Almeida, U.; Batkoviä, I.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Hovatta, T.; , MAGIC Collaboration
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Context. The BL Lac object 1ES 0647+250 is one of the few distant ?-ray emitting blazars detected at very high energies (VHEs; 100 GeV) during a non-flaring state. It was detected with the MAGIC telescopes during a period of low activity in the years 2009 2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with the highest VHE flux in the last epoch. An extensive multi-instrument data set was collected as part of several coordinated observing campaigns over these years. Aims. We aim to characterise the long-Term multi-band flux variability of 1ES 0647+250, as well as its broadband spectral energy distribution (SED) during four distinct activity states selected in four different epochs, in order to constrain the physical parameters of the blazar emission region under certain assumptions. Methods. We evaluated the variability and correlation of the emission in the different energy bands with the fractional variability and the Z-Transformed discrete correlation function, as well as its spectral evolution in X-rays and ? rays. Owing to the controversy in the redshift measurements of 1ES 0647+250 reported in the literature, we also estimated its distance in an indirect manner through a comparison of the GeV and TeV spectra from simultaneous observations with Fermi-LAT and MAGIC during the strongest flaring activity detected to date. Moreover, we interpret the SEDs from the four distinct activity states within the framework of one-component and two-component leptonic models, proposing specific scenarios that are able to reproduce the available multi-instrument data. Results. We find significant long-Term variability, especially in X-rays and VHE ? rays. Furthermore, significant (3 4I) correlations were found between the radio, optical, and high-energy (HE) ?-ray fluxes, with the radio emission delayed by about 400 days with respect to the optical and ?-ray bands. The spectral analysis reveals a harder-when-brighter trend during the non-flaring state in the X-ray domain. However, no clear patterns were observed for either the enhanced states or the HE (30 MeV < E < 100 GeV) and VHE ?-ray emission of the source. The indirect estimation of the redshift yielded a value of z = 0.45 ± 0.05, which is compatible with some of the values reported in the literature. The SEDs related to the low-Activity state and the three flaring states of 1ES 0647+250 can be described reasonably well with the both one-component and two-component leptonic scenarios. However, the long-Term correlations indicate the need for an additional radio-producing region located about 3.6 pc downstream from the gamma-ray producing region.
  • VHE gamma-ray detection of FSRQ QSO B1420+326 and modeling of its enhanced broadband state in 2020
    (2021-03-29) Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres De Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli, G.; Bošnjak, A.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Di Pierro, F.; Di Venere, L.; Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara, G.; Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; Garciá López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jormanainen, J.; Jouvin, L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Machado De Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Mender, S.; Micánović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Neustroev, V.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Albà, N.; Tosti, L.; Truzzi, S.; Tutone, A.; Van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Zarić, D.; Angioni, R.; D'Ammando, F.; Ciprini, S.; Cheung, C. C.; Orienti, M.; Pacciani, L.; Prajapati, P.; Kumar, P.; Ganesh, S.; Kurtenkov, A.; Marchini, A.; Carrasco, L.; Escobedo, G.; Porras, A.; Recillas, E.; Lähteenmäki, A.; Tornikoski, M.; Berton, M.; Tammi, J.; Vera, R. J.C.; Jorstad, S. G.; Marscher, A. P.; Weaver, Z. R.; Hart, M.; Hallum, M. K.; Larionov, V. M.; Borman, G. A.; Grishina, T. S.; Kopatskaya, E. N.; Larionova, E. G.; Nikiforova, A. A.; Morozova, D. A.; Savchenko, S. S.; Troitskaya, Yu V.; Troitsky, I. S.; Vasilyev, A. A.; Hodges, M.; Hovatta, T.; Kiehlmann, S.; Max-Moerbeck, W.; Readhead, A. C.S.; Reeves, R.; Pearson, T. J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Context. QSO B1420+326 is a blazar classified as a flat-spectrum radio quasar (FSRQ). At the beginning of the year 2020, it was found to be in an enhanced flux state and an extensive multiwavelength campaign allowed us to trace the evolution of the flare. Aims. We search for very high-energy (VHE) gamma-ray emission from QSO B1420+326 during this flaring state. We aim to characterize and model the broadband emission of the source over different phases of the flare. Methods. The source was observed with a number of instruments in radio, near-infrared, optical (including polarimetry and spectroscopy), ultraviolet, X-ray, and gamma-ray bands. We use dedicated optical spectroscopy results to estimate the accretion disk and the dust torus luminosity. We performed spectral energy distribution modeling in the framework of combined synchrotron-self-Compton and external Compton scenario in which the electron energy distribution is partially determined from acceleration and cooling processes. Results. During the enhanced state, the flux of both SED components of QSO B1420+326 drastically increased and the peaks were shifted to higher energies. Follow-up observations with the MAGIC telescopes led to the detection of VHE gamma-ray emission from this source, making it one of only a handful of FSRQs known in this energy range. Modeling allows us to constrain the evolution of the magnetic field and electron energy distribution in the emission region. The gamma-ray flare was accompanied by a rotation of the optical polarization vector during a low -polarization state. Also, a new superluminal radio knot contemporaneously appeared in the radio image of the jet. The optical spectroscopy shows a prominent FeII bump with flux evolving together with the continuum emission and a MgII line with varying equivalent width.