Browsing by Author "Lahteenmaki, Anne"
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- 28-40 GHz variability and polarimetry of bright compact sources in the QUIJOTE cosmological fields
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-04) Perrott, Yvette C.; Lopez-Caniego, Marcos; Genova-Santos, Ricardo T.; Rubino-Martin, Jose Alberto; Ashdown, Mark; Herranz, Diego; Lahteenmaki, Anne; Lasenby, Anthony N.; Lopez-Caraballo, Carlos H.; Poidevin, Frederick; Tornikoski, MerjaWe observed 51 sources in the Q-U-I JOint TEnerife (QUIJOTE) cosmological fields that were brighter than 1 Jy at 30 GHz in the Planck Point Source Catalogue (version 1), with the Very Large Array at 28-40 GHz, in order to characterize their high-radio-frequency variability and polarization properties. We find a roughly lognormal distribution of polarization fractions with a median of 2 per cent, in agreement with previous studies, and a median rotation measure (RM) of ≈1110 rad m-2 with one outlier up to ≈64 000 rad m-2, which is among the highest RMs measured in quasar cores. We find hints of a correlation between the total intensity flux density and median polarization fraction. We find 59 per cent of sources are variable in total intensity, and 100 per cent in polarization at 3σ level, with no apparent correlation between total intensity variability and polarization variability. This indicates that it will be difficult to model these sources without simultaneous polarimetric monitoring observations and they will need to be masked for cosmological analysis. - Cosmological Evolution of Quasar Radio Emission in the View of Multifractality
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-03-10) Belete, A. Bewketu; Femmam, Smain; Tornikoski, Merja; Lahteenmaki, Anne; Tammi, Joni; Leao, I. C.; Martins, B. L. Canto; De Medeiros, J. R.Variations in scaling behavior in the flux and emissions of distant astronomical sources with respect to their cosmic time are important phenomena that can provide valuable information about the dynamics within the sources and their cosmological evolution with time. Different studies have been applying linear analysis to understand and model quasars' light curves. Here, we study the multifractal behavior of selected quasars' radio emissions in their observed frame (at 22 and 37 GHz bands) and their rest frame. To this end, we apply the wavelet transform-based multifractal analysis formalism called wavelet transform modulus maxima. In addition, we verify whether the autoregressive integrated moving average (ARIMA) models fit our data. In our work, we observe strong multifractal behavior for all the sources. Additionally, we find that the degree of multifractality is strongly similar for each source and significantly different between sources at 22 and 37 GHz. This similarity implies that the two frequencies have the same radiation region and mechanism, whereas the difference indicates that the sources have intrinsically different dynamics. Furthermore, we show that the degree of multifractality is the same in the observed and rest frames of the quasars, i.e., multifractality is an intrinsic property of radio quasars. Finally, we show that the ARIMA models fit the 3C 345 quasar at 22 GHz and partially fit most of the time series, with the exception of the 3C 273 and 3C 279 quasars at 37 GHz, for which the models are found to be inadequate. - The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(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.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. - Interactions between the Jet and Disk Wind in Nearby Radio-intermediate Quasar III Zw 2
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-02-01) Wang, Ailing; An, Tao; Guo, Shaoguang; Mohan, Prashanth; Chamani, Wara; Baan, Willem A.; Hovatta, Talvikki; Falcke, Heino; Galvin, Tim J.; Hurley-Walker, Natasha; Jaiswal, Sumit; Lahteenmaki, Anne; Lao, Baoqiang; Lv, Weijia; Tornikoski, Merja; Zhang, YingkangDisk winds and jets are ubiquitous in active galactic nuclei (AGN), and how these two components interact remains an open question. We study the radio properties of the radio-intermediate quasar III Zw 2. We detect two jet knots, J1 and J2, on parsec scales that move at a mildly apparent superluminal speed of 1.35c. Two gamma-ray flares were detected in III Zw 2 in 2009-2010, corresponding to the primary radio flare in late 2009 and the secondary radio flare in early 2010. The primary 2009 flare was found to be associated with the ejection of J2. The secondary 2010 flare occurred at a distance of similar to 0.3 pc from the central engine, probably resulting from the collision of the jet with the accretion disk wind. The variability characteristics of III Zw 2 (periodic radio flares, unstable periodicity, multiple quasiperiodic signals and the possible harmonic relations between them) can be explained by the global instabilities of the accretion disk. These instabilities originating from the outer part of the warped disk propagate inward and can lead to modulation of the accretion rate and consequent jet ejection. At the same time, the wobbling of the outer disk may also lead to oscillations of the boundary between the disk wind and the jet tunnel, resulting in changes in the jet-wind collision site. Object III Zw 2 is one of the few cases observed with jet-wind interactions, and the study in this paper is of general interest for gaining insight into the dynamic processes in the nuclear regions of AGN. - Magnetic field strengths of the synchrotron self-absorption region in the jet of CTA 102 during radio flares
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-02) Kim, Sang-Hyun; Lee, Sang-Sung; Lee, Jee Won; Hodgson, Jeffrey A.; Kang, Sincheol; Algaba, Juan-Carlos; Kim, Jae-Young; Hodges, Mark; Agudo, Ivan; Fuentes, Antonio; Escudero, Juan; Myserlis, Ioannis; Traianou, Efthalia; Lahteenmaki, Anne; Tornikoski, Merja; Tammi, Joni; Ramakrishnan, Venkatessh; Jarvela, EmiliaCTA 102 is a blazar implying that its relativistic jet points towards Earth and emits synchrotron radiation produced by energetic particles gyrating in the magnetic field. This study aims to figure out the physical origins of radio flares in the jet, including the connection between the magnetic field and the radio flares. The data set in the range of 2.6-343.5 GHz was collected over a period of ∼5.5 yr (2012 November 20-2018 September 23). During the data collection period, seven flares at 15 GHz with a range of the variability time-scale of roughly 76-227 d were detected. The quasi-simultaneous radio data were used to investigate the synchrotron spectrum of the source. We found that the synchrotron radiation is self-absorbed. The turnover frequency and the peak flux density of the synchrotron self-absorption (SSA) spectra are in the ranges of ∼42-172 GHz and ∼0.9-10.2 Jy, respectively. From the SSA spectra, we derived the SSA magnetic field strengths to be ∼9.20, ∼12.28, and ∼50.97 mG on 2013 December 24, 2014 February 28, and 2018 January 13, respectively. We also derived the equipartition magnetic field strengths to be in the range of ∼24-109 mG. The equipartition magnetic field strengths are larger than the SSA magnetic field strengths in most cases, which indicates that particle energy mainly dominates in the jet. Our results suggest that the flares in the jet of CTA 102 originated due to particle acceleration. We propose the possible mechanisms of particle acceleration. - Multiwavelength behaviour of the blazar 3C 279: decade-long study from γ-ray to radio
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020-03-01) Larionov, V. M.; Jorstad, S. G.; Marscher, A. P.; Villata, M.; Raiteri, C. M.; Smith, P. S.; Agudo, Ivan; Savchenko, S. S.; Morozova, D. A.; Acosta-Pulido, J. A.; Aller, M. F.; Aller, H. D.; Andreeva, T. S.; Arkharov, A. A.; Bachev, R.; Bonnoli, G.; Borman, G. A.; Bozhilov, V.; Calcidese, P.; Carnerero, M.; Carosati, D.; Casadio, C.; Chen, W-P; Damljanovic, G.; Dementyev, A.; Di Paola, A.; Frasca, A.; Fuentes, A.; Gomez, J. L.; Gonzalez-Morales, P.; Giunta, A.; Grishina, T. S.; Gurwell, M. A.; Hagen-Thorn, V. A.; Hovatta, Talvikki; Ibryamov, S.; Joshi, M.; Kiehlmann, S.; Kim, J-Y; Kimeridze, Givi N.; Kopatskaya, E. N.; Kovalev, Yu A.; Kovalev, Y.; Kurtanidze, O. M.; Kurtanidze, Sofia O.; Lahteenmaki, Anne; Lazaro, C.; Larionova, L.; Larionova, E. G.; Leto, G.; Marchini, A.; Matsumoto, K.; Mihov, B.; Minev, M.; Mingaliev, M. G.; Mirzaqulov, D.; Dimitrova, R. V. Munoz; Myserlis, I.; Nikiforova, A. A.; Nikolashvili, M. G.; Nizhelsky, N. A.; Ovcharov, E.; Pressburger, L. D.; Rakhimov, I. A.; Righini, S.; Rizzi, N.; Sadakane, K.; Sadun, A. C.; Samal, M. R.; Sanchez, R. Z.; Semkov, E.; Sergeev, S. G.; Sigua, L. A.; Slavcheva-Mihova, L.; Sola, P.; Sotnikova, Yu; Strigachev, A.; Thum, C.; Traianou, Efthalia; Troitskaya, Yu; Troitsky, I. S.; Tsybulev, P. G.; Vasilyev, A. A.; Vince, O.; Weaver, Z. R.; Williamson, K. E.; Zhekanis, G.We report the results of decade-long (2008-2018) γ -ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, Fermi and Swift data, as well as polarimetric and spectroscopic data. The X-ray and γ -ray light curves correlate well, with no delay ≳ 3 h, implying general cospatiality of the emission regions. The γ -ray-optical flux-flux relation changes with activity state, ranging from a linear to amore complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz Very Long Baseline Array images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain γ -ray variability on very short time-scales. The MgII emission line flux in the 'blue' and 'red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands, we find progressive delays of the most prominent light-curve maxima with decreasing frequency, as expected from the frequency dependence of the τ= 1 surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at ∼5 GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet. - Planck 2013 results. III. LFI systematic uncertainties
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2014-11) Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Bernard, J. -P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J. -F.; Catalano, A.; Chamballu, A.; Chiang, L. -Y; Cristensen, P. R.; Church, S.; Olombi, S. C.; Colombo, L. P. L.; Crill, B. P.; Cruz, M.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rose, A.; de Zotti, G.; Delabrouillei, J.; Dick, J.; Dickinson, C.; Diego, J. M.; Lahteenmaki, Anne; , Planck CollaborationWe present the current estimate of instrumental and systematic effect uncertainties for the Planck-Low Frequency Instrument relevant to the first release of the Planck cosmological results. We give an overview of the main effects and of the tools and methods applied to assess residuals in maps and power spectra. We also present an overall budget of known systematic effect uncertainties, which are dominated by sidelobe straylight pick-up and imperfect calibration. However, even these two effects are at least two orders of magnitude weaker than the cosmic microwave background fluctuations as measured in terms of the angular temperature power spectrum. A residual signal above the noise level is present in the multipole range l <20, most notably at 30GHz, and is probably caused by residual Galactic straylight contamination. Current analysis aims to further reduce the level of spurious signals in the data and to improve the systematic effects modelling, in particular with respect to straylight and calibration uncertainties. - Revisiting Radio Variability of the Blazar 3C 454.3
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-12-01) Tripathi, Ashutosh; Gupta, Alok C.; Smith, Krista Lynne; Wiita, Paul J.; Aller, Margo F.; Volvach, Alexandr E.; Lahteenmaki, Anne; Aller, Hugh D.; Tornikoski, Merja; Volvach, Larisa N.We examine lengthy radio light curves of the flat spectrum radio galaxy 3C 454.3 for possible quasiperiodic oscillations (QPOs). The data used in this work were collected at five radio frequencies, 4.8, 8.0, 14.5, 22.0, and 37.0 GHz between 1979 and 2013 as observed at the University of Michigan Radio Astronomical Observatory, Crimean Astrophysical Observatory, and Aalto University Metsahovi Radio Observatory. We employ generalized Lomb-Scargle periodogram and weighted wavelet transform analyses to search for periodicities in these light curves. We confirm a QPO period of ∼2000 days to be at least 4σ significant using both methods at all five radio frequencies between 1979 and 2007, after which a strong flare changed the character of the light curve. We also find a ∼600 day period, which is at least 4σ significant, but only in the 22.0 and 37.0 GHz light curves. We briefly discuss physical mechanisms capable of producing such variations.