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1. A Two-Week $IXPE$ Monitoring Campaign on Mrk 421

Author: Maksym, W. Peter, Liodakis, Ioannis, Saade, M. Lynne, Kim, Dawoon E., Middei, Riccardo, Di Gesu, Laura, Kiehlmann, Sebastian, Matzeu, Gabriele, Agudo, Iván, Marscher, Alan P., Ehlert, Steven R., Jorstad, Svetlana G., Kaaret, Philip, Marshall, Herman L., Pacciani, Luigi, Perri, Matteo, Puccetti, Simonetta, Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Escudero, Juan, Agís-González, Beatriz, Husillos, César, Morcuende, Daniel, Otero-Santos, Jorge, Sota, Alfredo, Piirola, Vilppu, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, McCall, Callum, Jermak, Helen E., Steele, Iain A., Borman, George A., Grishina, Tatiana S., Hagen-Thorn, Vladimir A., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Shishkina, Ekaterina V., Troitskiy, Ivan S., Troitskaya, Yulia V., Vasilyev, Andrey A., Zhovtan, Alexey V., Myserlis, Ioannis, Gurwell, Mark, Keating, Garrett, Rao, Ramprasad, Pauley, Colt, Angelakis, Emmanouil, Kraus, Alexander, Berdyugin, Andrei V., Kagitani, Masato, Kravtsov, Vadim, Poutanen, Juri, Sakanoi, Takeshi, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Song, Chanwoo, Blinov, Dmitry, Shablovinskaya, Elena, Antonelli, Lucio Angelo, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccoló, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Negro, Michela, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel Lawrence, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the first dense X-ray polarization monitoring campaign on the blazar Mrk 421. Our observations were accompanied by an even denser radio and optical polarization campaign. We find significant short-timescale variability in both X-ray polarization degree and angle, including a $\sim90^\circ$ angle rotation about the jet axis. We attribute this to random variations of the magnetic field, consistent with the presence of turbulence but also unlikely to be explained by turbulence alone. At the same time, the degree of lower-energy polarization is significantly lower and shows no more than mild variability. Our campaign provides further evidence for a scenario in which energy-stratified shock-acceleration of relativistic electrons, combined with a turbulent magnetic field, is responsible for optical to X-ray synchrotron emission in blazar jets., Comment: 23 pages, including 8 pages of appendices. 12 figures, 3 tables. Submitted to ApJ
Published: 2024

2. X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023

Author: Chen, Chien-Ting J., Liodakis, Ioannis, Middei, Riccardo, Kim, Dawoon E., Di Gesu, Laura, Di Marco, Alessandro, Ehlert, Steven R., Errando, Manel, Negro, Michela, Jorstad, Svetlana G., Marscher, Alan P., Wu, Kinwah, Agudo, Iván, Poutanen, Juri, Mizuno, Tsunefumi, Kouch, Pouya M., Lindfors, Elina, Borman, George A., Grishina, Tatiana S., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Troitsky, Ivan S., Troitskaya, Yulia V., Vasilyev, Andrey A., Zhovtan, Alexey V., Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Escudero, Juan, Agís-González, Beatriz, Husillos, César, Santos, Jorge Otero, Sota, Alfredo, Piirola, Vilppu, Myserlis, Ioannis, Angelakis, Emmanouil, Kraus, Alexander, Gurwell, Mark, Keating, Garrett, Rao, Ramprasad, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Song, Chanwoo, Berdyugin, Andrei V., Kagitani, Masato, Kravtsov, Vadim, Nitindala, Anagha P., Sakanoi, Takeshi, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Nakaoka, Tatsuya, Akitaya, Hiroshi, Casadio, Carolina, Sievers, Albrecht, Antonelli, Lucio Angelo, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccoló, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marshall, Herman L., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel Lawrence, Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: 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 Polarimetry Explorer (IXPE) with six 100-ks observations spanning from 2022 March to 2023 April. Each IXPE observation was accompanied by simultaneous X-ray data from NuSTAR, Swift/XRT, and/or XMM-Newton. Complementary optical-infrared polarization measurements were also available in the B, V, R, I, and J bands, as were radio polarization measurements from 4.85 GHz to 225.5 GHz. Among the first five IXPE observations, we did not find significant variability in the X-ray polarization degree and angle with IXPE. However, the most recent sixth observation found an elevated polarization degree at $>3\sigma$ above the average of the other five observations. The optical and radio measurements show no apparent correlations with the X-ray polarization properties. Throughout the six IXPE observations, the X-ray polarization degree remained higher than, or similar to, the R-band optical polarization degree, which remained higher than the radio value. This is consistent with the energy-stratified shock scenario proposed to explain the first two IXPE observations, in which the polarized X-ray, optical, and radio emission arises from different regions., Comment: Accepted for publication in ApJ
Published: 2024

3. Combined Fit of Spectrum and Composition for FR0 Radio Galaxy Emitted Ultra-High-Energy Cosmic Rays with Resulting Secondary Photons and Neutrinos

Author: Lundquist, Jon Paul, Vorobiov, Serguei, Merten, Lukas, Reimer, Anita, Boughelilba, Margot, Da Vela, Paolo, Tavecchio, Fabrizio, Bonnoli, Giacomo, and Righi, Chiara
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: This study comprehensively investigates the gamma-ray dim population of Fanaroff-Riley Type 0 (FR0) radio galaxies as potentially significant sources of ultra-high-energy cosmic rays (UHECRs, E $>$ 10$^{18}$ eV) detected on Earth. While individual FR0 luminosities are relatively low compared to the more powerful Fanaroff-Riley Type 1 and Type 2 galaxies, FR0s are substantially more prevalent in the local universe, outnumbering the more energetic galaxies by a factor of $\sim$5 within a redshift of z $\leq$ 0.05. Employing CRPropa3 simulations, we estimate the mass composition and energy spectra of UHECRs originating from FR0 galaxies for energies above 10$^{18.6}$ eV. This estimation fits data from the Pierre Auger Observatory (Auger) using three extensive air shower models; both constant and energy-dependent observed elemental fractions are considered. The simulation integrates an isotropic distribution of FR0 galaxies, extrapolated from observed characteristics, with UHECR propagation in the intergalactic medium, incorporating various plausible configurations of extragalactic magnetic fields, both random and structured. We then compare the resulting emission spectral indices, rigidity cutoffs, and elemental fractions with recent Auger results. In total, 25 combined energy spectrum and mass composition fits are considered. Beyond the cosmic ray fluxes emitted by FR0 galaxies, this study predicts the secondary photon and neutrino fluxes from UHECR interactions with intergalactic cosmic photon backgrounds. The multi-messenger approach, encompassing observational data and theoretical models, helps elucidate the contribution of low luminosity FR0 radio galaxies to the total cosmic ray energy density., Comment: To be submitted to The Astrophysical Journal. 22 pages, 16 figures, 6 tables
Published: 2024

4. Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations

Author: Liodakis, Ioannis, Kiehlmann, Sebastian, Marscher, Alan P., Zhang, Haocheng, Blinov, Dmitry, Jorstad, Svetlana G., Agudo, Iván, Benítez, Erika, Berdyugin, Andrei, Bonnoli, Giacomo, Casadio, Carolina, Chen, Chien-Ting, Chen, Wen-Ping, Ehlert, Steven R., Escudero, Juan, Grishina, Tatiana S., Hiriart, David, Hsu, Angela, Imazawa, Ryo, Jermak, Helen E., Jose, Jincen, Kaaret, Philip, Kopatskaya, Evgenia N., Lalchand, Bhavana, Larionova, Elena G., Lindfors, Elina, López, José M., McCall, Callum, Morozova, Daria A., Palaiologou, Efthymios, Pandey, Shivangi, Poutanen, Juri, Rakshit, Suvendu, Reig, Pablo, Sasada, Mahito, Savchenko, Sergey S., Shablovinskaya, Elena, Neha, Sharma, Shrestha, Manisha, Steele, Iain A., Troitskiy, Ivan S., Troitskaya, Yulia V., Uemura, Makoto, Vasilyev, Andrey A., Weaver, Zachary, Wiersema, Klaas, and Weisskopf, Martin C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models are still missing. Here we report on the first attempt to produce continuous, >24 hour polarization light curves of blazars using telescopes distributed across the globe and the rotation of the Earth to avoid the rising Sun. Our campaign involved 16 telescopes in Asia, Europe, and North America. We observed BL Lacertae and CGRaBS J0211+1051 for a combined 685 telescope hours. We find large variations in the polarization degree and angle for both sources in sub-hour timescales as well as a ~180 degree rotation of the polarization angle in CGRaBS J0211+1051 in less than two days. We compared our high-cadence observations to Particle-In-Cell magnetic reconnection and turbulent plasma simulations. We find that although the state of the art simulation frameworks can produce a large fraction of the polarization properties, they do not account for the entirety of the observed polarization behavior in blazar jets., Comment: 20 pages, 15 figures, 2 tables, accepted for publication in A&A. The data used in the paper are available here: https://doi.org/10.7910/DVN/IETSXS
Published: 2024
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5. IXPE observation of PKS 2155-304 reveals the most highly polarized blazar

Author: Kouch, Pouya M., Liodakis, Ioannis, Middei, Riccardo, Kim, Dawoon E., Tavecchio, Fabrizio, Marscher, Alan P., Marshall, Herman L., Ehlert, Steven R., Di Gesu, Laura, Jorstad, Svetlana G., Agudo, Iván, Madejski, Grzegorz M., Romani, Roger W., Errando, Manel, Lindfors, Elina, Nilsson, Kari, Toppari, Ella, Potter, Stephen B., Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, McCall, Callum, Jermak, Helen E., Steele, Iain A., Myserlis, Ioannis, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Angelakis, Emmanouil, Kraus, Alexander, Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Escudero, Juan, Agís-González, Beatriz, Husillos, César, Morcuende, Daniel, Otero-Santos, Jorge, Sota, Alfredo, Bachev, Rumen, Antonelli, Lucio Angelo, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Negro, Michela, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel Lawrence, Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155$-$304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We observed the source between Oct 27 and Nov 7, 2023. We also conducted an extensive contemporaneous multiwavelength (MW) campaign. We find that during the first half ($T_1$) of the IXPE pointing, the source exhibited the highest X-ray polarization degree detected for an HSP blazar thus far, (30.7$\pm$2.0)%, which dropped to (15.3$\pm$2.1)% during the second half ($T_2$). The X-ray polarization angle remained stable during the IXPE pointing at 129.4$^\circ$$\pm$1.8$^\circ$ and 125.4$^\circ$$\pm$3.9$^\circ$ during $T_1$ and $T_2$, respectively. Meanwhile, the optical polarization degree remained stable during the IXPE pointing, with average host-galaxy-corrected values of (4.3$\pm$0.7)% and (3.8$\pm$0.9)% during the $T_1$ and $T_2$, respectively. During the IXPE pointing, the optical polarization angle changed achromatically from $\sim$140$^\circ$ to $\sim$90$^\circ$ and back to $\sim$130$^\circ$. Despite several attempts, we only detected (99.7% conf.) the radio polarization once (during $T_2$, at 225.5 GHz): with degree (1.7$\pm$0.4)% and angle 112.5$^\circ$$\pm$5.5$^\circ$. The direction of the broad pc-scale jet is rather ambiguous and has been found to point to the east and south at different epochs; however, on larger scales (> 1.5 pc) the jet points toward the southeast ($\sim$135$^\circ$), similar to all of the MW polarization angles. Moreover, the X-ray to optical polarization degree ratios of $\sim$7 and $\sim$4 during $T_1$ and $T_2$, respectively, are similar to previous IXPE results for several HSP blazars. These findings, combined with the lack of correlation of temporal variability between the MW polarization properties, agree with an energy-stratified shock-acceleration scenario in HSP blazars., Comment: 17 pages, 10 figures, 4 tables, Accepted for publication in A&A
Published: 2024
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6. IOP4, the Interactive Optical Photo-Polarimetric Python Pipeline

Author: Pedrosa, Juan Escudero, Agudo, Ivan, Morcuende, Daniel, Otero-Santos, Jorge, Bonnoli, Giacomo, Piirola, Vilppu, Husillos, César, Bernardos, Mabel, López-Coto, Rubén, Sota, Alfredo, Casanova, Víctor, Aceituno, Francisco, and Santos-Sanz, Pablo
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: IOP4 is a pipeline to perform photometry and polarimetry analysis of optical data from Calar Alto (CAHA) and Sierra Nevada (OSN) observatories. IOP4 implements Object Relational Mapping (ORM) to seamlessly integrate all information about the reduction and results in a database which can be used to query and plot results, flag data and inspect the reduction process in an integrated fashion with the whole pipeline. It also ships with an already built-in web interface which can be used out of the box to browse the database and supervise all pipeline processes. It is built to ease debugging and inspection of data. Reduction from five different instruments are already implemented: RoperT90, AndorT90 and DIPOL (at OSN 0.9m telescope), AndorT150 (OSN 1.5m telescope) and CAFOS (CAHA 2.2m telescope). IOP4's modular design allows for easy integration of new observatories and instruments, and its results have already featured in several high-impact refereed publications. In this paper we describe the implementation and characteristics of IOP4., Comment: Submitted April 23, 2024
Published: 2024

7. The flaring activity of blazar AO 0235+164 during year 2021

Author: Pedrosa, Juan Escudero, Agudo, Iván, Moritz, Till, Marscher, Alan P., Jorstad, Svetlana, Tramacere, Andrea, Casadio, Carolina, Thum, Clemens, Myserlis, Ioannis, Sievers, Albrecht, Otero-Santos, Jorge, Morcuende, Daniel, López-Coto, Rubén, D'Ammando, Filippo, Bonnoli, Giacomo, Gurwell, Mark, Gómez, José Luis, Rao, Ramprasad, and Keating, Garrett
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. The blazar AO 0235+164, located at redshift $z=0.94$, has displayed interesting and repeating flaring activity in the past, the latest episodes occurring in 2008 and 2015. In 2020, the source brightened again, starting a new flaring episode that peaked in 2021. Aims. We study the origin and properties of the 2021 flare in relation to previous studies and the historical behavior of the source, in particular to the 2008 and 2015 flaring episodes. Methods. We analyze the multi-wavelength photo-polarimetric evolution of the source. From Very Long Baseline Array images, we derive the kinematic parameters of new components associated with the 2021 flare. We use this information to constrain a model for the spectral energy distribution of the emission during the flaring period. We propose an analytical geometric model to test whether the observed wobbling of the jet is consistent with precession. Results. We report the appearance of two new components that are ejected in a different direction than previously, confirming the wobbling of the jet. We find that the direction of ejection is consistent with that of a precessing jet.The derived period independently agrees with the values commonly found in the literature. Modeling of the spectral energy distribution further confirm that the differences between flares can be attributed to geometrical effects., Comment: Accepted 15 May 2024
Published: 2024
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8. Detection of X-ray Polarization from the Blazar 1ES 1959+650 with the Imaging X-ray Polarimetry Explorer

Author: Errando, Manel, Liodakis, Ioannis, Marscher, Alan P., Marshall, Herman L., Middei, Riccardo, Negro, Michela, Peirson, Abel Lawrence, Perri, Matteo, Puccetti, Simonetta, Rabinowitz, Pazit L., Agudo, Iván, Jorstad, Svetlana G., Savchenko, Sergey S., Blinov, Dmitry, Bourbah, Ioakeim G., Kiehlmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Aceituno, Francisco José, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Víctor, Agís-González, Beatriz, Husillos, César, Marchini, Alessandro, Sota, Alfredo, Kouch, Pouya M., Lindfors, Elina, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Ingram, Adam, Massaro, Francesco, Antonelli, Lucio Angelo, Bonino, Raffaella, Cavazzuti, Elisabetta, Chen, Chien-Ting, Cibrario, Nicolò, Ciprini, Stefano, De Rosa, Alessandra, Di Gesu, Laura, Di Pierro, Federico, Donnarumma, Immacolata, Ehlert, Steven R., Fenu, Francesco, Gau, Ephraim, Karas, Vladimir, Kim, Dawoon E., Krawczynski, Henric, Laurenti, Marco, Lisalda, Lindsey, López-Coto, Rubén, Madejski, Grzegorz, Marin, Frédéric, Marinucci, Andrea, Mitsuishi, Ikuyuki, Muleri, Fabio, Pacciani, Luigi, Paggi, Alessandro, Petrucci, Pierre-Olivier, Cavero, Nicole Rodriguez, Romani, Roger W., Tavecchio, Fabrizio, Tugliani, Stefano, Wu, Kinwah, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Costa, Enrico, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Matt, Giorgio, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Observations of linear polarization in the 2-8 keV energy range with the Imaging X-ray Polarimetry Explorer (IXPE) explore the magnetic field geometry and dynamics of the regions generating non-thermal radiation in relativistic jets of blazars. These jets, particularly in blazars whose spectral energy distribution peaks at X-ray energies, emit X-rays via synchrotron radiation from high-energy particles within the jet. IXPE observations of the X-ray selected BL Lac-type blazar 1ES 1959+650 in 2022 May 3-4 showed a significant linear polarization degree of $\Pi_\mathrm{x} = 8.0\% \pm 2.3\%$ at an electric-vector position angle $\psi_\mathrm{x} = 123^\circ \pm 8^\circ$. However, in 2022 June 9-12, only an upper limit of $\Pi_\mathrm{x} \leq 5.1\%$ could be derived (at the 99% confidence level). The degree of optical polarization at that time $\Pi_\mathrm{O} \sim 5\%$ is comparable to the X-ray measurement. We investigate possible scenarios for these findings, including temporal and geometrical depolarization effects. Unlike some other X-ray selected BL Lac objects, there is no significant chromatic dependence of the measured polarization in 1ES 1959+650, and its low X-ray polarization may be attributed to turbulence in the jet flow with dynamical timescales shorter than 1 day., Comment: 16 pages, 4 figures, accepted for publication in The Astrophysical Journal
Published: 2024
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9. The Repeating Flaring Activity of Blazar AO 0235+164

Author: Pedrosa, Juan Escudero, Agudo, Iván, Tramacere, Andrea, Marscher, Alan P., Jorstad, Svetlana, Weaver, Z. R., Casadio, Carolina, Thum, Clemens, Myserlis, Ioannis, Fuentes, Antonio, Traianou, Efthalia, Kim, Jae-Young, Kramer, Joana, López-Coto, Rubén, D'Ammando, Filippo, Bernardos, M., Bonnoli, Giacomo, Blinov, Dmitriy A., Borman, G. A., Grishina, T. S., Hagen-Thorn, V. A., Kopatskaya, E. N., Larionova, E. G., Larionov, V. M., Larionova, L. V., Morozova, D. A., Savchenko, S. S., Troitskiy, I. S., Troitskaya, Y. V., and Vasilyev, A. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone several sharp multi-spectral-range flaring episodes during the last decades. In particular, the episodes peaking in 2008 and 2015, that received extensive multi-wavelength coverage, exhibited interesting behavior. Aims. We study the actual origin of these two observed flares by constraining the properties of the observed photo-polarimetric variability, those of the broad-band spectral energy-distribution and the observed time-evolution behavior of the source as seen by ultra-high resolution total-flux and polarimetric Very-long-baseline interferometry (VLBI) imaging. Methods. The analysis of VLBI images allows us to constrain kinematic and geometrical parameters of the 7 mm jet. We use the Discrete Correlation Function to compute the statistical correlation and the delays between emission at different spectral ranges. Multi-epoch modeling of the spectral energy distributions allows us to propose specific models of emission; in particular for the unusual spectral features observed in this source in the X-ray region of the spectrum during strong multi spectral-range flares. Results. We find that these X-ray spectral features can be explained by an emission component originating in a separate particle distribution than the one responsible for the two standard blazar bumps. This is in agreement with the results of our correlation analysis that do not find a strong correlation between the X-rays and the remaining spectral ranges. We find that both external Compton dominated and synchrotron self-Compton dominated models can explain the observed spectral energy distributions. However, synchrotron self-Compton models are strongly favored by the delays and geometrical parameters inferred from the observations.
Published: 2023
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10. Observations of Low and Intermediate Spectral Peak Blazars with the Imaging X-ray Polarimetry Explorer

Author: Marshall, Herman L., Liodakis, Ioannis, Marscher, Alan P., Di Lalla, Niccolo, Jorstad, Svetlana G., Kim, Dawoon E., Middei, Riccardo, Negro, Michela, Omodei, Nicola, Peirson, Abel L., Perri, Matteo, Puccetti, Simonetta, Agudo, Ivan, Bonnoli, Giacomo, Berdyugin, Andrei V., Cavazzuti, Elisabetta, Cavero, Nicole Rodriguez, Donnarumma, Immacolata, Di Gesu, Laura, Jormanainen, Jenni, Krawczynski, Henric, Lindfors, Elina, Marin, Frederic, Massaro, Francesco, Pacciani, Luigi, Poutanen, Juri, Tavecchio, Fabrizio, Kouch, Pouya M., Aceituno, Francisco Jose, Bernardos, Maria I., Casanova, Victor, Garcia-Comas, Maya, Agis-Gonzalez, Beatriz, Husillos, Cesar, Marchini, Alessandro, Sota, Alfredo, Blinov, Dmitry, Bourbah, Ioakeim G., Kielhmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Borman, George A., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Vasilyev, Andrey A., Zhovtan, Alexey V., Casadio, Carolina, Escudero, Juan, Kramer, Joana, Myserlis, Ioannis, Trainou, Efthalia, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Masiero, Joseph R., Mawet, Dimitri, Millar-Blanchaer, Maxwell A., Panopoulou, Georgia V., Tinyanont, Samaporn, Kagitani, Masato, Kravtsov, Vadim, Sakanoi, Takeshi, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolo, Capitanio, Fiamma, Castellano, Simone, Chen, Chen-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Marco, Alessandro, Doroshenko, Victor, Dovvciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., ODell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: 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, 3C 279, 3C 454.3, and S5 0716+714. For none of these objects was IXPE able to detect X-ray polarization at the 3$\sigma$ level. However, we placed upper limits on the polarization degree at $\sim$10-30\%. The undetected polarizations favor models where the X-ray band is dominated by unpolarized photons upscattered by relativistic electrons in the jets of blazars, although hadronic models are not completely eliminated. We discuss the X-ray polarization upper limits in the context of our contemporaneous multiwavelength polarization campaigns., Comment: 19 pages, 10 figures, 6 tables; submitted to the Astrophysical Journal
Published: 2023

11. Chasing Gravitational Waves with the Cherenkov Telescope Array

Author: Green, Jarred Gershon, Carosi, Alessandro, Nava, Lara, Patricelli, Barbara, Schüssler, Fabian, Seglar-Arroyo, Monica, Consortium, Cta, Abe, Kazuki, Abe, Shotaro, Acharyya, Atreya, Adam, Remi, Aguasca-Cabot, Arnau, Agudo, Ivan, Alfaro, Jorge, Alvarez-Crespo, Nuria, Batista, Rafael Alves, Amans, Jean-Philippe, Amato, Elena, Ambrosino, Filippo, Angüner, Ekrem Oguzhan, Antonelli, Lucio Angelo, Aramo, Carla, Arcaro, Cornelia, Arrabito, Luisa, Asano, Katsuaki, Aschersleben, Jann, Ashkar, Halim, Stuani, Luiz Augusto, Baack, Dominik, Backes, Michael, Balazs, Csaba, Balbo, Matteo, Larriva, Andres Baquero, Martins, Victor Barbosa, de Almeida, Ulisses Barres, Barrio, Juan Abel, Bastieri, Denis, Batista, Pedro Ivo, Batković, Ivana, Batzofin, Rowan William, Baxter, Joshua Ryo, Beck, Geoffrey, Tjus, Julia Becker, Beiske, Lukas, Belardinelli, Daniele, Benbow, Wystan, Bernardini, Elisa, Medrano, Juan Bernete, Bernlöhr, Konrad, Berti, Alessio, Beshley, Vasyl, Bhattacharjee, Pooja, Bhattacharyya, Saptashwa, Bi, Baiyang, Biederbeck, Noah, Biland, Adrian, Bissaldi, Elisabetta, Blanch, Oscar, Blazek, Jiri, Boisson, Catherine, Bolmont, Julien, Bonnoli, Giacomo, Bordas, Pol, Bošnjak, Željka, Bradascio, Federica, Braiding, Catherine, Bronzini, Ettore, Brose, Robert, Brown, Anthony M., Brun, Francois, Brunelli, Giulia, Bulgarelli, Andrea, Burelli, Irene, Burmistrov, Leonid, Burton, Michael, Bylund, Tomas, Calisse, Paolo Gherardo, Campoy-Ordaz, Anna, Cantlay, Brandon Khan, Capalbi, Milvia, Caproni, Anderson, Capuzzo-Dolcetta, Roberto, Carlile, Colin, Caroff, Sami, Carosi, Roberto, Carrasco, Marie-Sophie, Cascone, Enrico, Cassol, Franca, Castrejon, Noelia, Catalani, Fernando, Cerasole, Davide, Cerruti, Matteo, Chaty, Sylvain, Chen, Andrew W, Chernyakova, Maria, Chiavassa, Andrea, Chudoba, Jiří, Araujo, Carlos Henrique Coimbra, Conforti, Vito, Conte, Francesco, Contreras, Jose Luis, Cossou, Christophe, Costa, Alessandro, Costantini, Heide, Cristofari, Pierre, Cuevas, Omar, Curtis-Ginsberg, Zachary, D'Amico, Giacomo, D'Ammando, Filippo, Dadina, Mauro, Dalchenko, Mykhailo, David, Ludovic, Davids, Isak Delberth, Dazzi, Francesco, De Angelis, Alessandro, de Lavergne, Mathieu de Bony, De Caprio, Vincenzo, De Cesare, Giovanni, Pino, Elisabete M. de Gouveia Dal, De Lotto, Barbara, de Lucia, Mario, de Menezes, Raniere, de Naurois, Mathieu, Wilhelmi, Emma de Oña, De Simone, Nicola, de Souza, Vitor, Del Peral, Luis, del Valle, Maria Victoria, Delagnes, Eric, Giler, Andres Gabriel Delgado, Delgado, Carlos, Dell'aiera, Michael, Della Ceca, Roberto, Della Valle, Massimo, Della Volpe, Domenico, Depaoli, Davide, Dettlaff, Antonios, Di Girolamo, Tristano, Di Piano, Ambra, Di Pierro, Federico, Di Tria, Riccardo, Di Venere, Leonardo, Díaz-Bahamondes, Christian, Dib, Claudio, Diebold, Sebastian, Dima, Razvan, Dinesh, Adithiya, Djannati-Ataï, Arache, Djuvsland, Julia Isabel, Dominguez, Alberto, Dominik, Rune Michael, Donini, Alice, Dorner, Daniela, Dörner, Julien, Doro, Michele, Anjos, Rita de Cassia dos, Dournaux, Jean-Laurent, Dravins, Dainis, Duangchan, Chaimongkol, Dubos, Coline, Ducci, Lozenzo, Dwarkadas, Vikram V., Ebr, Jan, Eckner, Christopher, Egberts, Kathrin, Einecke, Sabrina, Elsässer, Dominik, Emery, Gabriel, Godoy, Miguel Escobar, Escudero, Juan, Esposito, Paolo, Falceta-Gonçalves, Diego, Ramazani, Vandad Fallah, Faure, Alice, Fedorova, Elena, Fegan, Stephen, Feijen, Kirsty, Feng, Qi, Ferrand, Gilles, Ferrarotto, Fabio, Fiandrini, Emanuele, Fiasson, Armand, Fioretti, Valentina, Foffano, Luca, Guiteras, Lluis Font, Fontaine, Gerard, Fröse, Stefan, Fukami, Satoshi, Fukui, Yasuo, Funk, Stefan, Gaggero, Daniele, Galanti, Giorgio, Galaz, Gaspar, Gallant, Yves A., Gallozzi, Stefano, Gammaldi, Viviana, Gasbarra, Claudio, Gaug, Markus, Ghalumyan, Arsen, Gianotti, Fulvio, Giarrusso, Marina, Giglietto, Nicola, Giordano, Francesco, Giuliani, Andrea, Glicenstein, Jean-Francois, Glombitza, Jonas, Goldoni, Paolo, González, José Mauricio, González, Maria Magdalena, Coelho, Jaziel Goulart, Granot, Jonathan, Grasso, Dario, Haro, Roger Grau, Green, David, Greenshaw, Tim, Grolleron, Guillaume, Grube, Jeff, Gueta, Orel, Gunji, Shuichi, Hadasch, Daniela, Hamal, Petr, Hanlon, William, Hara, Satoshi, Harvey, Violet M., Hashiyama, Kazuaki, Hassan, Tarek, Heller, Matthieu, Cadena, Sergio Hernández, Hie, Jonathan, Hiroshima, Nagisa, Hnatyk, Bohdan, Hnatyk, Roman, Hoffmann, Dirk, Hofmann, Werner, Holler, Markus, Horan, Deirdre, Horvath, Pavel, Hovatta, Talvikki, Hrupec, Dario, Hussain, Saqib, Iarlori, Marco, Inada, Tomohiro, Incardona, Federico, Inome, Yusuke, Inoue, Susumu, Iocco, Fabio, Ishio, Kazuma, Jamrozy, Marek, Janecek, Petr, Jankowsky, Felix, Jarnot, Christian, Jean, Pierre, Martínez, Irene Jiménez, Jin, Weidong, Jocou, Laurent, Juramy-Gilles, Claire, Jurysek, Jakub, KALEKIN, Oleg, Kantzas, Dimitrios, Karas, Vladimir, Kaufmann, Sarah, Kerszberg, Daniel, Khelifi, Bruno, Kieda, David B, Kleiner, Tobias Kai, Kluźniak, Włodzimierz, Kobayashi, Yukiho, Kohri, Kazunori, Komin, Nukri, Kornecki, Paula, Kosack, Karl, Kubo, Hidetoshi, Kushida, Junko, La Barbera, Antonino, La Palombara, Nicola, Lainez, Maria, Lamastra, Alessandra, Lapington, Jon S, Lazarevic, Sanja, Lazendic-Galloway, Jasmina, Leach, Steven, Lemoine-Goumard, Marianne, Lenain, Jean-Philippe, Leto, Giuseppe, Leuschner, Fabian, Lindfors, Elina, Linhoff, Maximilian, Liodakis, Ioannis, Loïc, Lozach, Lombardi, Saverio, Longo, Francesco, López-Coto, Rubén, López-Moya, Marcos, López-Oramas, Alicia, Loporchio, Serena, Bahilo, Julio Lozano, Luque-Escamilla, Pedro L., Macias, Oscar, Maier, Gernot, Majumdar, Pratik, Malyshev, Denys, Malyshev, Dmitry, Mandat, Dusan, Manicò, Giulio, Marinos, Peter David, Markoff, Sera, Márquez, Isabel, Marquez, Patricia, Marsella, Giovanni, Martí, Josep, Martin, Pierrick, Martínez, Gustavo Augusto, Martínez, Manel, Martinez, Oibar, Marty, Christophe, Mas-Aguilar, Alvaro, Mastropietro, Michele, Maurin, Gilles, Max-Moerbeck, Walter, Mazin, Daniel, Melkumyan, David, Menchiari, Stefano, Mestre, Enrique, Meunier, Jean-Luc, Meyer, Dominique M. -A., Miceli, Davide, Michailidis, Miltiadis, Michałowski, Jerzy, Miener, Tjark, Miranda, Jose Miguel, Mitchell, Alison, Mizote, Masaya, Mizuno, Tsunefumi, Moderski, Rafal, Mohrmann, Lars, Molero, Miguel, Molfese, Cesare, Molina, Edgar, Montaruli, Teresa, Moralejo, Abelardo, Morcuende, Daniel, Morik, Katharina, Morselli, Aldo, Moulin, Emmanuel, Zamanillo, Victor Moya, Mukherjee, Reshmi, Munari, Kevin, Muraczewski, Adam, Muraishi, Hiroshi, Nakamori, Takeshi, Nayak, Amrit, Nemmen, Rodrigo, Nickel, Lukas, Niemiec, Jacek, Nieto, Daniel, Rosillo, Mireia Nievas, Nikołajuk, Marek, Nishijima, Kyoshi, Noda, Koji, Nosek, Dalibor, Novosyadlyj, Bohdan, Novotný, Vladimír, Nozaki, Seiya, O'Brien, Paul, Ohishi, Michiko, Ohtani, Yoshiki, Okumura, Akira, Olive, Jean-François, Olmi, Barbara, Ong, Rene A., Orienti, Monica, Orito, Reiko, Orlandini, Mauro, Orlando, Elena, Ostrowski, Michal, Otte, Nepomuk, Oya, Igor, Pagano, Isabella, Pagliaro, Antonio, Palatiello, Michele, Panebianco, Gabriele, Paredes, Josep M., Parmiggiani, Nicolò, Patel, Sonal Ramesh, Pavlović, Dijana, Pe'er, Asaf, Pech, Miroslav, Pecimotika, Mario, Peresano, Michele, Pérez-Romero, Judit, Peron, Giada, Persic, Massimo, Petrucci, Pierre-Olivier, Petruk, Oleh, Pfeifle, Felix, Pintore, Fabio, Pirola, Giorgio, Pittori, Carlotta, Plard, Cyann, Podobnik, Franjo, Pohl, Martin, Pons, Estelle, Prandini, Elisa, Prast, Julie, Principe, Giacomo, Priyadarshi, Chaitanya, Produit, Nicolas, Prokhorov, Dmitry, Pueschel, Elisa, Pühlhofer, Gerd, Pumo, Maria Letizia, Punch, Michael, Quirrenbach, Andreas, Raino, Silvia, Randazzo, Nunzio, Rando, Riccardo, Ravel, Thierry, Razzaque, Soebur, Regeard, Maxime, Reichherzer, Patrick, Reimer, Anita, Reimer, Olaf, Reisenegger, Andreas, Reposeur, Thierry, Reville, Brian, Rhode, Wolfgang, Ribó, Marc, Richtler, Tom, Rieger, Frank, Roache, Emmet, Fernandez, Gonzalo Rodriguez, Frías, Maria Dolores Rodríguez, Rodríguez-Vázquez, Juan José, Romano, Patrizia, Romeo, Giuseppe, Rosado, Jaime, Rowell, Gavin P, Rudak, Bronislaw, Ruiter, Ashley J., Rulten, Cameron Boyd, Russo, Federico, Sadeh, Iftach, Saha, Lab, Saito, Takayuki, Sakurai, Shunsuke, Salzmann, Heiko, Sanchez, David, Sanchez-Conde, Miguel, Sangiorgi, Pierluca, Sano, Hidetoshi, Santander, Marcos, Santangelo, Andrea, Santos-Lima, Reinaldo, Sanuy, Andreu, Šarić, Toni, Sarkar, Arkadipta, Sarkar, Subir, Saturni, Francesco Gabriele, Savchenko, Volodymyr, Scherer, Andres, Schipani, Pietro, Schleicher, Bernd, Schovanek, Petr, Schubert, Jan Lukas, Schwanke, Ullrich, Schwefer, Georg, Scuderi, Salvatore, Arroyo, Monica Seglar, Seitenzahl, Ivo, Sergijenko, Olga, Sguera, Vito, Shang, Ruo-Yu, Sharma, Pooja, Sidibe, Guereguin Der Sylvestre, Sidoli, Lara, Siejkowski, Hubert, Siqueira, Clarissa, Sizun, Patrick, Sliusar, Vitalii, Slowikowska, Agnieszka, Sol, Helene, Specovius, Andreas, Spencer, Samuel Timothy, Spiga, Daniele, Stamerra, Antonio, Stanič, Samo, Starecki, Tomasz, Starling, Rhaana, Steppa, Constantin, Stolarczyk, Thierry, Strišković, Jelena, Strzys, Marcel C., Suda, Yusuke, Suomijarvi, Tiina, Tak, Donggeun, Takahashi, Mitsunari, Takeishi, Ryuji, Tam, Pak-Hin Thomas, Tanaka, Shuta J, Tanaka, Takaaki, Terauchi, Kenta, Testa, Vincenzo, Tibaldo, Luigi, Tibolla, Omar, Torradeflot, Francesc, Torres, Diego F., Torresi, Eleonora, Tothill, Nick, Toussenel, Francois, Touzard, Victoria, Tramacere, Andrea, Travnicek, Petr, Tripodo, Giovanni, Truzzi, Stefano, Tsiahina, Adellain, Tutone, Antonio, Vacula, Martin, Vallage, Bertrand, Vallania, Piero, Vallés, Ramon, van Eldik, Christopher, van Scherpenberg, Juliane, Vandenbroucke, Justin, Vassiliev, Vladimir, Venault, Philippe, Ventura, Sofia, Vercellone, Stefano, Verna, Gaia, Viana, Aion, Viaux, Nicolás, Vigliano, Alessandro, Vignatti, Jonatan, Vigorito, Carlo francesco, Vitale, Vincenzo, Vodeb, Veronika, Voisin, Vincent, Vorobiov, Serguei, Voutsinas, Georgios Gerasimos, Vovk, Ievgen, Waegebaert, Vincent, Wagner, Stefan Joachim, Walter, Roland, Ward, Martin, Wechakama, Maneenate, White, Richard, Wierzcholska, Alicja, Will, Martin, Williams, David A., Wohlleben, Frederik, Wolter, Anna, Yamamoto, Tokonatsu, Yamazaki, Ryo, Yang, Lili, Yoshida, Tatsuo, Yoshikoshi, Takanori, Zacharias, Michael, Sanchez, Ricardo Zanmar, Zavrtanik, Danilo, Zavrtanik, Marko, Zdziarski, Andrzej A., Zech, Andreas, Zhdanov, Valery I., Ziȩtara, Krzysztof, Živec, Miha, and Zuriaga-Puig, Jaume
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very-high-energy (VHE, > 100GeV) photons which have yet to be detected in coincidence with a gravitational wave signal. The Cherenkov Telescope Array (CTA) is a next-generation VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity and ability to slew anywhere on the sky within a few tens of seconds. New observing modes and follow-up strategies are being developed for CTA to rapidly cover localization areas of gravitational wave events that are typically larger than the CTA field of view. This work will evaluate and provide estimations on the expected number of of gravitational wave events that will be observable with CTA, considering both on- and off-axis emission. In addition, we will present and discuss the prospects of potential follow-up strategies with CTA., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023), 2023 (arXiv:2309.08219)
Published: 2023

12. Magnetic Field Properties inside the Jet of Mrk 421: Multiwavelength Polarimetry Including the Imaging X-ray Polarimetry Explorer

Author: Kim, Dawoon E., Di Gesu, Laura, Liodakis, Ioannis, Marscher, Alan P., Jorstad, Svetlana G., Midde, Riccardo, Marshall, Herman L., Pacciani, Luigi, Agudo, Iván, Tavecchio, Fabrizio, Cibrario, Nicolò, Tugliani, Stefano, Bonino, Raffaella, Negro, Michela, Puccetti, Simonetta, Tombesi, Francesco, Costa, Enrico, Donnarumma, Immacolata, Soffitta, Paolo, Mizuno, Tsunefumi, Fukazawa, Yasushi, Kawabata, Koji S., Nakaoka, Tatsuya, Uemura, Makoto, Imazawa, Ryo, Sasada, Mahito, Akitaya, Hiroshi, Aceituno, Francisco Josè, Bonnoli, Giacomo, Casanova, Vìctor, Myserlis, Ioannis, Sievers, Albrecht, Angelakis, Emmanouil, Kraus, Alexander, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Kang, Sincheol, Kim, Sang-Hyun, Lee, Sang-Sung, Agìs-Gonzàlez, Beatriz, Sota, Alfredo, Escudero, Juan, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Kouch, Pouya M., Lindfors, Elina, Bourbah, Ioakeim G., Kiehlmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Savchenko, Sergey S., Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Swartz, Doug, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements on 2022 December 6-8. We detected X-ray polarization of Mrk 421 with a degree of $\Pi_{\rm X}$=14$\pm$1$\%$ and an electric-vector position angle $\psi_{\rm X}$=107$\pm$3$^{\circ}$ in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in $\psi_{\rm X}$. During 7 months from the first IXPE pointing of Mrk 421 in 2022 May, $\psi_{\rm X}$ varied across the range of 0$^{\circ}$ to 180$^{\circ}$, while $\Pi_{\rm X}$ maintained similar values within $\sim$10-15$\%$. Furthermore, a swing in $\psi_{\rm X}$ in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that the X-ray polarization degree was generally $\sim$2-3 times greater than that at longer wavelengths, while the polarization angle fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that rotation of $\psi$ occurred in the opposite direction with respect to the rotation of $\psi_{\rm X}$ over longer timescales at similar epochs. The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. The accompanying spectral variation during the $\psi_{\rm X}$ rotation can be explained by a fluctuation in the physical conditions, e.g., in the energy distribution of relativistic electrons. The opposite rotation direction of $\psi$ between the X-ray and longer-wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths., Comment: 17 pages, 13 figures, 4 tables; Accepted for publication in A&A
Published: 2023
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13. X-ray Polarization of the BL Lac Type Blazar 1ES 0229+200

Author: Ehlert, Steven R., Liodakis, Ioannis, Middei, Riccardo, Marscher, Alan P., Tavecchio, Fabrizio, Agudo, Iván, Kouch, Pouya M., Lindfors, Elina, Nilsson, Kari, Myserlis, Ioannis, Gurwell, Mark, Rao, Ramprasad, Aceituno, Francisco Jose, Bonnoli, Giacomo, Casanova, Victor, Agiz-Gonzalez, Beatriz, Escudero, Juan, Santos, Jorge Otero, Sota, Alfredo, Angelakis, Emmanouil, Kraus, Alexander, Keating, Garrett K., Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marshall, Herman L., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Negro, Michela, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present polarization measurements in the $2-8 \thinspace \mathrm{keV}$ band from blazar 1ES 0229+200, the first extreme high synchrotron peaked source to be observed by the Imaging X-ray Polarimetry Explorer (IXPE). Combining two exposures separated by about two weeks, we find the degree of polarization to be $\Pi_{X} = 17.9 \pm 2.8 \%$ at an electric-vector position angle $\psi_X = 25.0 \pm 4.6^{\circ}$ using a spectropolarimetric fit from joint IXPE and XMM-Newton observations. There is no evidence for the polarization degree or angle varying significantly with energy or time on both short time scales (hours) or longer time scales (days). The contemporaneous polarization degree at optical wavelengths was $>$7$\times$ lower, making 1ES 0229+200 the most strongly chromatic blazar yet observed. This high X-ray polarization compared to the optical provides further support that X-ray emission in high-peaked blazars originates in shock-accelerated, energy-stratified electron populations, but is in tension with many recent modeling efforts attempting to reproduce the spectral energy distribution of 1ES 0229+200 which attribute the extremely high energy synchrotron and Compton peaks to Fermi acceleration in the vicinity of strongly turbulent magnetic fields., Comment: 17 Pages, 6 Figures, Resubmitted to ApJ after addressing referee comments
Published: 2023

14. IXPE and multi-wavelength observations of blazar PG 1553+113 reveal an orphan optical polarization swing

Author: Middei, Riccardo, Perri, Matteo, Puccetti, Simonetta, Liodakis, Ioannis, Di Gesu, Laura, Marscher, Alan P., Cavero, Nicole Rodriguez, Tavecchio, Fabrizio, Donnarumma, Immacolata, Laurenti, Marco, Jorstad, Svetlana G., Agudo, Iván, Marshall, Herman L., Pacciani, Luigi, Kim, Dawoon E., Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Agís-González, Beatriz, Sota, Alfredo, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Sievers, Albrecht, Kouch, Pouya M., Lindfors, Elina, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Angelakis, Emmanouil, Kraus, Alexander, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, García, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Negro, Michela, Ng, Chi-Yung, O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The lower energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553+113, a high-synchrotron-peak blazar observed by the Imaging X-ray Polarimetry Explorer (IXPE). We detect an X-ray polarization degree of $(10\pm2)\%$ along an electric-vector position angle of $\psi_X=86^{\circ}\pm8^{\circ}$. At the same time, the radio and optical polarization degrees are lower by a factor of $\sim$3. During our IXPE pointing, we observed the first orphan optical polarization swing of the IXPE era, as the optical angle of PG 1553+113 underwent a smooth monotonic rotation by about 125$^\circ$, with a rate of $\sim$17 degrees per day. We do not find evidence of a similar rotation in either radio or X-rays, which suggests that the X-ray and optically emitting regions are separate or, at most, partially co-spatial. Our spectro-polarimetric results provide further evidence that the steady-state X-ray emission in blazars originates in a shock-accelerated and energy-stratified electron population., Comment: Accepted for pubblication in The Astrophysical Journal Letters. 3 Figures, 13 pages
Published: 2023

15. X-ray Polarization of BL Lacertae in Outburst

Author: Peirson, Abel L., Negro, Michela, Liodakis, Ioannis, Middei, Riccardo, Kim, Dawoon E., Marscher, Alan P., Marshall, Herman L., Pacciani, Luigi, Romani, Roger W., Wu, Kinwah, Di Marco, Alessandro, Di Lalla, Niccolo, Omodei, Nicola, Jorstad, Svetlana G., Agudo, Ivan, Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco Jose, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Victor, Garcia-Comas, Maya, Agis-Gonzalez, Beatriz, Husillos, Cesar, Marchini, Alessandro, Sota, Alfredo, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Sievers, Albrecht, Gurwell, Mark, Rao, Ramprasad, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Kang, Sincheol, Kim, Sang-Hyun, Lee, Sang-Sung, Angelakis, Emmanouil, Kraus, Alexander, Cibrario, Nicolo, Donnarumma, Immacolata, Poutanen, Juri, Tavecchio, Fabrizio, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolo, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Doroshenko, Victor, Dovciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Madejski, Grzegorz, Maldera, Simone, Manfreda, Alberto, Marin, Frederic, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We report the first $> 99\%$ confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/$\gamma$-ray outburst, a 287 ksec observation (2022 November 27-30) was taken using the Imaging X-ray Polarimetry Explorer ({\it IXPE}), together with contemporaneous multiwavelength observations from the Neil Gehrels {\it Swift} observatory and {\it XMM-Newton} in soft X-rays (0.3--10~keV), {\it NuSTAR} in hard X-rays (3--70~keV), and optical polarization from the Calar Alto, and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the {\it IXPE} energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find $>99\%$ confidence X-ray polarization $\Pi_{2-4{\rm keV}} = 21.7^{+5.6}_{-7.9}\%$ and electric vector polarization angle $\psi_{2-4{\rm keV}} = -28.7 \pm 8.7^{\circ}$ in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous {\it IXPE} BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs., Comment: Accepted to ApJL. 16 pages, 8 figures
Published: 2023
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16. Discovery of X-ray polarization angle rotation in active galaxy Mrk 421

Author: Di Gesu, Laura, Marshall, Herman L., Ehlert, Steven R., Kim, Dawoon E., Donnarumma, Immacolata, Tavecchio, Fabrizio, Liodakis, Ioannis, Kiehlmann, Sebastian, Agudo, Iván, Jorstad, Svetlana G., Muleri, Fabio, Marscher, Alan P., Puccetti, Simonetta, Middei, Riccardo, Perri, Matteo, Pacciani, Luigi, Negro, Michela, Romani, Roger W., Di Marco, Alessandro, Blinov, Dmitry, Bourbah, Ioakeim G., Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Gurwell, Mark, Rao, Ramprasad, Keating, Garrett, Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco Josè, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Vìctor, Garcìa-Comas, Maya, Agìs-Gonzàlez, Beatriz, Husillos, Cèsar, Marchini, Alessandro, Sota, Alfredo, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Savchenko, Sergey S., Vasilyev, Andrey A., Gòmez, Josè L., Antonelli, Lucio A., Barnouin, Thibault, Bonino, Raffaella, Cavazzuti, Elisabetta, Costamante, Luigi, Chen, Chien-Ting, Cibrario, Nicolò, De Rosa, Alessandra, Di Pierro, Federico, Errando, Manel, Kaaret, Philip, Karas, Vladimir, Krawczynski, Henric, Lisalda, Lindsey, Madejski, Grzegorz, Malacaria, Christian, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, O'Dell, Stephen L., Paggi, Alessandro, Peirson, Abel L., Petrucci, Pierre-Olivier, Ramsey, Brian D., Tennant, Allyn F., Wu, Kinwah, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, Del Monte, Ettore, Di Lalla, Niccolò, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Ng, C. -Y., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The magnetic field conditions in astrophysical relativistic jets can be probed by multiwavelength polarimetry, which has been recently extended to X-rays. For example, one can track how the magnetic field changes in the flow of the radiating particles by observing rotations of the electric vector position angle $\Psi$. Here we report the discovery of a $\Psi_{\mathrm x}$ rotation in the X-ray band in the blazar Mrk 421 at an average flux state. Across the 5 days of Imaging X-ray Polarimetry Explorer (IXPE) observations of 4-6 and 7-9 June 2022, $\Psi_{\mathrm x}$ rotated in total by $\geq360^\circ$. Over the two respective date ranges, we find constant, within uncertainties, rotation rates ($80 \pm 9$ and $91 \pm 8 ^\circ/\rm day$) and polarization degrees ($\Pi_{\mathrm x}=10\%\pm1\%$). Simulations of a random walk of the polarization vector indicate that it is unlikely that such rotation(s) are produced by a stochastic process. The X-ray emitting site does not completely overlap the radio/infrared/optical emission sites, as no similar rotation of $\Psi$ was observed in quasi-simultaneous data at longer wavelengths. We propose that the observed rotation was caused by a helical magnetic structure in the jet, illuminated in the X-rays by a localized shock propagating along this helix. The optically emitting region likely lies in a sheath surrounding an inner spine where the X-ray radiation is released.
Published: 2023

17. X-ray Polarization Observations of BL Lacertae

Author: Middei, Riccardo, Liodakis, Ioannis, Perri, Matteo, Puccetti, Simonetta, Cavazzuti, Elisabetta, Di Gesu, Laura, Ehlert, Steven R., Madejski, Grzegorz, Marscher, Alan P., Marshall, Herman L., Muleri, Fabio, Negro, Michela, Jorstad, Svetlana G., Agís-González, Beatriz, Agudo, Iván, Bonnoli, Giacomo, Bernardos, Maria I., Casanova, Víctor, García-Comas, Maya, Husillos, César, Marchini, Alessandro, Sota, Alfredo, Kouch, Pouya M., Borman, George A., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Vasilyev, Andrey A., Zhovtan, Alexey V., Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Hales, Antonio, Kameno, Seiji, Kneissl, Ruediger, Messias, Hugo, Nagai, Hiroshi, Blinov, Dmitry, Bourbah, Ioakeim G., Kiehlmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Masiero, Joseph R., Mawet, Dimitri, Millar-Blanchaer, Maxwell A., Panopoulou, Georgia V., Tinyanont, Samaporn, Berdyugin, Andrei V., Kagitani, Masato, Kravtsov, Vadim, Sakanoi, Takeshi, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Gurwell, Mark, Rao, Ramprasad, Di Lalla, Niccoló, Cibrario, Nicoló, Donnarumma, Immacolata, Kim, Dawoon E., Omodei, Nicola, Pacciani, Luigi, Poutanen, Juri, Tavecchio, Fabrizio, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: 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 responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae performed with the Imaging X-ray Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization degree $\Pi_X<$12.6\% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac., Comment: 17 pages, 5 figures, accepted for publication in ApJL
Published: 2022
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18. Observability of the very-high-energy emission from GRB 221009A

Author: Galanti, Giorgio, Nava, Lara, Roncadelli, Marco, Tavecchio, Fabrizio, and Bonnoli, Giacomo
Subjects: Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Abstract: The LHAASO Collaboration detected the gamma ray burst GRB 221009A at energies above $500 \, {\rm GeV}$ with a tail extending up to $18 \, \rm TeV$, whose spectral analysis has presently been performed up to $7 \, \rm TeV$ for the lower energy instrument LHAASO-WCDA only, with no indication of a cutoff. Soon thereafter, Carpet-2 at Baksan Neutrino Observatory reported the observation of an air shower consistent with being caused by a photon of energy $251 \, {\rm TeV}$ from the same GRB. Given the source redshift $z=0.151$, the expected attenuation due to the extragalactic background light is very severe so that these detections have proven very hard to explain. In this Letter, we show that the existence of axion-like-particles (ALPs) with mass $m_a \simeq (10^{-11}-10^{-7}) \, {\rm eV}$ and two-photon coupling $g_{a \gamma \gamma} \simeq (3-5) \times 10^{-12} \, {\rm GeV}^{- 1}$ strongly reduce the optical depth of TeV photons, thus explaining the observations. Our ALPs meet all available constraints, are consistent with two previous hints at their existence and are good candidates for cold dark matter. Moreover, we show that Lorentz Invariance Violation (LIV) can explain the Carpet-2 result but not the LHAASO observations., Comment: 22 pages, 13 figures, This version matches the published paper: Phys. Rev. Lett. 131, 251001 (2023)
Published: 2022
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19. Polarized Blazar X-rays imply particle acceleration in shocks

Author: Liodakis, Ioannis, Marscher, Alan P., Agudo, Iván, Berdyugin, Andrei V., Bernardos, Maria I., Bonnoli, Giacomo, Borman, George A., Casadio, Carolina, Casanova, Víctor, Cavazzuti, Elisabetta, Cavero, Nicole Rodriguez, Di Gesu, Laura, Di Lalla, Niccoló, Donnarumma, Immacolata, Ehlert, Steven R., Errando, Manel, Escudero, Juan, García-Comas, Maya, Agís-González, Beatriz, Husillos, César, Jormanainen, Jenni, Jorstad, Svetlana G., Kagitani, Masato, Kopatskaya, Evgenia N., Kravtsov, Vadim, Krawczynski, Henric, Lindfors, Elina, Larionova, Elena G., Madejski, Grzegorz M., Marin, Frédéric, Marchini, Alessandro, Marshall, Herman L., Morozova, Daria A., Massaro, Francesco, Masiero, Joseph R., Mawet, Dimitri, Middei, Riccardo, Millar-Blanchaer, Maxwell A., Myserlis, Ioannis, Negro, Michela, Nilsson, Kari, O'Dell, Stephen L., Omodei, Nicola, Pacciani, Luigi, Paggi, Alessandro, Panopoulou, Georgia V., Peirson, Abel L., Perri, Matteo, Petrucci, Pierre-Olivier, Poutanen, Juri, Puccetti, Simonetta, Romani, Roger W., Sakanoi, Takeshi, Savchenko, Sergey S., Sota, Alfredo, Tavecchio, Fabrizio, Tinyanont, Samaporn, Vasilyev, Andrey A., Weaver, Zachary R., Zhovtan, Alexey V., Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Ng, Stephen C. -Y., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: 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 $\sim 1$ TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization - the only range available until now - probe extended regions of the jet containing particles that left the acceleration site days to years earlier (Jorstad et al., 2005; Marin et al., 2018; Blinov et al., 2021), and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian~501 (Mrk~501). We measure an X-ray linear polarization degree $\Pi_X \sim10\%$, a factor of $\sim2$ higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration, and also implies that the plasma becomes increasingly turbulent with distance from the shock., Comment: 34 pages, 4 figures, 4 tables
Published: 2022
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20. Discovery of X-ray polarization angle rotation in the jet from blazar Mrk 421

Author: Di Gesu, Laura, Marshall, Herman L., Ehlert, Steven R., Kim, Dawoon E., Donnarumma, Immacolata, Tavecchio, Fabrizio, Liodakis, Ioannis, Kiehlmann, Sebastian, Agudo, Iván, Jorstad, Svetlana G., Muleri, Fabio, Marscher, Alan P., Puccetti, Simonetta, Middei, Riccardo, Perri, Matteo, Pacciani, Luigi, Negro, Michela, Romani, Roger W., Di Marco, Alessandro, Blinov, Dmitry, Bourbah, Ioakeim G., Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Gurwell, Mark A., Rao, Ramprasad, Keating, Garrett K., Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco José, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Víctor, García-Comas, Maya, Agís-González, Beatriz, Husillos, César, Marchini, Alessandro, Sota, Alfredo, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Savchenko, Sergey S., Vasilyev, Andrey A., Gómez, José L., Antonelli, Lucio A., Barnouin, Thibault, Bonino, Raffaella, Cavazzuti, Elisabetta, Costamante, Luigi, Chen, Chien-Ting, Cibrario, Nicolò, De Rosa, Alessandra, Di Pierro, Federico, Errando, Manel, Kaaret, Philip, Karas, Vladimir, Krawczynski, Henric, Lisalda, Lindsey, Madejski, Grzegorz, Malacaria, Christian, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, O’Dell, Stephen L., Paggi, Alessandro, Peirson, Abel L., Petrucci, Pierre-Olivier, Ramsey, Brian D., Tennant, Allyn F., Wu, Kinwah, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, Del Monte, Ettore, Di Lalla, Niccolò, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Ng, C.-Y., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Published: 2023
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21. FR-0 jetted active galaxies: extending the zoo of candidate sites for UHECR acceleration

Author: Merten, Lukas, Boughelilba, Margot, Reimer, Anita, Da Vela, Paolo, Vorobiov, Serguei, Tavecchio, Fabrizio, Bonnoli, Giacomo, Lundquist, Jon Paul, and Righi, Chiara
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Fanaroff-Riley (FR) 0 radio galaxies form a low-luminosity extension to the well-established ultra-high-energy cosmic-ray (UHECR) candidate accelerators FR-1 and FR-2 galaxies. Their much higher number density -- up to a factor five times more numerous than FR-1 with $z\leq 0.05$ -- makes them good candidate sources for an isotropic contribution to the observed UHECR flux. Here, the acceleration and survival of UHECR in prevailing conditions of the FR-0 environment are discussed. First, an average spectral energy distribution (SED) is compiled based on the \textit{FR0CAT}. These photon fields, composed of a jet and a host galaxy component, form a minimal target photon field for the UHECR, which will suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. The two most promising acceleration scenarios based on Fermi-I order and gradual shear acceleration are discussed as well as different escape scenarios. When an efficient acceleration mechanism precedes gradual shear acceleration, e.g., Fermi-I or others, FR-0 galaxies are likely UHECR accelerators. Gradual shear acceleration requires a jet Lorentz factor of $\Gamma>1.6$, to be faster than the corresponding escape. In less optimistic models, a contribution to the cosmic-ray flux between the knee and ankle is expected to be relatively independent of the realized turbulence and acceleration., Comment: 8 pages, 4 figures, 2 tables, ICRC 2021
Published: 2021

22. Scrutinizing FR 0 Radio Galaxies as Ultra-High-Energy Cosmic Ray Source Candidates

Author: Merten, Lukas, Boughelilba, Margot, Reimer, Anita, Da Vela, Paolo, Vorobiov, Serguei, Tavecchio, Fabrizio, Bonnoli, Giacomo, Lundquist, Jon Paul, and Righi, Chiara
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Fanaroff-Riley (FR) 0 radio galaxies compose a new class of radio galaxies, which are usually weaker but much more numerous than the well-established class of FR 1 and FR 2 galaxies. The latter classes have been proposed as sources of the ultra-high-energy cosmic rays (UHECRs) with energies reaching up to ${\sim}10^{20}$ eV. Based on this conjecture, the possibility of UHECR acceleration and survival in an FR 0 source environment is examined in this work. In doing so, an average spectral energy distribution (SED) based on data from the FR 0 catalog (FR0CAT) is compiled. The resulting photon fields are used as targets for UHECRs, which suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. Multiple mechanisms are discussed to assess the UHECR acceleration probability, including Fermi-I order and gradual shear accelerations, and particle escape from the source region. This work shows that in a hybrid scenario, combining Fermi and shear accelerations, FR 0 galaxies can contribute to the observed UHECR flux, as long as $\Gamma_\mathrm{j}\gtrsim 1.6$, where shear acceleration starts to dominate over escape. Even in less optimistic scenarios, FR 0s can be expected to contribute to the cosmic-ray flux between the knee and the ankle. Our results are relatively robust with respect to the realized magnetic turbulence model and the speed of the accelerating shocks., Comment: 19 pages, 16 figures, 4 tables, accepted in Astroparticle Physics
Published: 2021
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23. MAGIC eyes to the extreme: testing the blazar emission models on EHBLs

Author: Prandini, Elisa, Arcaro, Cornelia, Ramazani, Vandad Fallah, Asano, Katsuaki, Bonnoli, Giacomo, Cerruti, Matteo, D'Ammando, Filippo, Foffano, Luca, and Tavecchio, Fabrizio
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: Extreme high-energy peaked BL Lac objects (EHBLs) are blazars whose synchrotron emission peaks at exceptionally high energies, above few keV, in the hard X-ray regime. So far, only a handful of those objects has been detected at very high energy (VHE, E > 100 GeV) gamma rays by Imaging Atmospheric Cherenkov Telescopes. Very remarkably, VHE observations of some of these blazars (like 1ES 0229+200) have provided evidence of a VHE gamma-ray emission extending to several TeV, which is difficult to explain with standard, one-zone synchrotron self-Compton models usually applied to BL Lac objects. The MAGIC collaboration coordinated a multi-year, multi-wavelength observational campaign on ten targets. The MAGIC telescopes detected VHE gamma rays from four EHBLs. In this paper we focus on the source 1ES 1426+426 and its X-ray and VHE gamma-ray properties. The results of different models (synchrotron self-Compton, spine-layer, hadronic) reproducing the broadband spectral energy distribution are also presented., Comment: Proceedings of the 36th International Cosmic Ray Conference (ICRC2019), July 24th-August 1st, 2019. Madison, WI, U.S.A
Published: 2019

24. The PDS 110 observing campaign - photometric and spectroscopic observations reveal eclipses are aperiodic

Author: Osborn, Hugh P., Kenworthy, Matthew, Rodriguez, Joseph E., de Mooij, Ernst J. W., Kennedy, Grant M., Relles, Howard, Gomez, Edward, Hippke, Michael, Banfi, Massimo, Barbieri, Lorenzo, Becker, Igor, Benni, Paul, Berlind, Perry, Bieryla, Allyson, Bonnoli, Giacomo, Boussier, Hubert, Brincat, Stephen, Briol, John, Burleigh, Matthew, Butterley, Tim, Calkins, Michael L., Chote, Paul, Ciceri, Simona, Deldem, Marc, Dhillon, Vik S., Dose, Eric, Dubois, Frank, Dvorak, Shawn, Esquerdo, Gilbert A., Evans, Daniel, Berangez, Stephane Ferratfiat Dagot, Fossey, Stephen, Güenther, Maximilian N., Hall, John, Hambsch, Josch, Casas, Enrique Herrero, Hills, Kevin, James, Robert, Kafka, Stella, Killestein, Thomas L., Kotnik, Clifford, Latham, David W., Lemay, Damien, Lewin, Pablo, Littlefair, Stuart, Lopresti, Claudio, Mallonn, Matthias, Mancini, Luigi, Marchini, Alessandro, McCormac, James J., Murawski, Gabriel, Myers, Gordon, Papini, Ricardo, Popov, Velimir, Quadri, Ulisse, Quinn, Samuel N., Raynard, Liam, Rizzuti, Luca, Roa, James, Robertson, Jeff, Salvaggio, Fabio, Scholz, Alexander, Sfair, Rafael, Smith, Alexis M. S., Southworth, John, Tan, TG, Vanaverbeke, Sigfried, Waagen, Elizabeth O., Watson, Christopher, West, Richard, Wheatley, P. J., Wilson, Richard W., Winter, Othon C., and Zhou, George
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: PDS 110 is a young disk-hosting star in the Orion OB1A association. Two dimming events of similar depth and duration were seen in 2008 (WASP) and 2011 (KELT), consistent with an object in a closed periodic orbit. In this paper we present data from a ground-based observing campaign designed to measure the star both photometrically and spectroscopically during the time of predicted eclipse in September 2017. Despite high-quality photometry, the predicted eclipse did not occur, although coherent structure is present suggesting variable amounts of stellar flux or dust obscuration. We also searched for RV oscillations caused by any hypothetical companion and can rule out close binaries to 0.1 $M_\odot$. A search of Sonneberg plate archive data also enabled us to extend the photometric baseline of this star back more than 50 years, and similarly does not re-detect any deep eclipses. Taken together, they suggest that the eclipses seen in WASP and KELT photometry were due to aperiodic events. It would seem that PDS 110 undergoes stochastic dimmings that are shallower and shorter-duration than those of UX Ori variables, but may have a similar mechanism., Comment: Accepted to MNRAS; 12 pages, 7 figures; Supplementary photometric data in zipped latex source as all_photometry.csv
Published: 2019
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25. The flaring activity of blazar AO 0235+164 in 2021

Author: Escudero Pedrosa, Juan, primary, Agudo, Iván, additional, Moritz, Till, additional, Alan Marscher, P., additional, Jorstad, Svetlana, additional, Tramacere, Andrea, additional, Casadio, Carolina, additional, Thum, Clemens, additional, Myserlis, Ioannis, additional, Sievers, Albrecht, additional, Otero-Santos, Jorge, additional, Morcuende, Daniel, additional, López-Coto, Rubén, additional, D'Ammando, Filippo, additional, Bonnoli, Giacomo, additional, Gurwell, Mark, additional, Luis Gómez, José, additional, Rao, Ramprasad, additional, and Keating, Garrett, additional
Published: 2024
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26. A facility to evaluate the focusing performance of mirrors for Cherenkov Telescopes

Author: Canestrari, Rodolfo, Giro, Enrico, Bonnoli, Giacomo, Farisato, Giancarlo, Lessio, Luigi, Rodeghiero, Gabriele, Spiga, Rossella, Toso, Giorgio, and Pareschi, Giovanni
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: Cherenkov Telescopes are equipped with optical dishes of large diameter -- in general based on segmented mirrors -- with typical angular resolution of a few arc-minutes. To evaluate the mirror's quality specific metrological systems are required that possibly take into account the environmental conditions in which typically these telescopes operate (in open air without dome protection). For this purpose a new facility for the characterization of mirrors has been developed at the labs of the Osservatorio Astronomico di Brera of the Italian National Institute of Astrophysics. The facility allows the precise measurement of the radius of curvature and the distribution of the concentred light in terms of focused and scattered components and it works in open air. In this paper we describe the facility and report some examples of its measuring capabilities., Comment: 24 pages, 12 figures, 1 table, accepted for publication on September 26th 2015 in Nuclear Instruments and Methods in Physics Research Section A (NIM-A)
Published: 2015
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27. An emerging population of BL Lacs with extreme properties: towards a class of EBL and cosmic magnetic field probes?

Author: Bonnoli, Giacomo, Tavecchio, Fabrizio, Ghisellini, Gabriele, and Sbarrato, Tullia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: High energy observations of extreme BL Lac objects, such as 1ES 0229+200 or 1ES 0347-121, recently focused interest both for blazar and jet physics and for the implication on the extragalactic background light and intergalactic magnetic field estimate. However, the number of these extreme highly peaked BL Lac objects (EHBL) is still rather small. Aiming at increase their number, we selected a group of EHBL candidates starting from the BL Lac sample of Plotkin et al. (2011), considering those undetected (or only barely detected) by the Large Area Telescope onboard Fermi and characterized by a high X-ray vs. radio flux ratio. We assembled the multi-wavelength spectral energy distribution of the resulting 9 sources, profiting of publicly available archival observations performed by the Swift, Galex and Fermi satellites, confirming their nature. Through a simple one-zone synchrotron self-Compton model we estimate the expected VHE flux, finding that in the majority of cases it is within the reach of present generation of Cherenkov arrays or of the forthcoming Cherenkov Telescope Array (CTA)., Comment: 12 pages, 5 figures, accepted for publication in MNRAS
Published: 2015
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28. Investigation of Multi-Messenger Properties of FR0 Radio Galaxy Emitted Ultra-High Energy Cosmic Rays

Author: Lundquist, Jon Paul, primary, Merten, Lukas, additional, Vorobiov, Serguei, additional, Boughelilba, Margot, additional, Reimer, Anita, additional, Da Vela, Paolo, additional, Tavecchio, Fabrizio, additional, Bonnoli, Giacomo, additional, and Righi, Chiara, additional
Published: 2024
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29. Magnetic field properties inside the jet of Mrk 421

Author: Kim, Dawoon E., primary, Di Gesu, Laura, additional, Liodakis, Ioannis, additional, Marscher, Alan P., additional, Jorstad, Svetlana G., additional, Middei, Riccardo, additional, Marshall, Herman L., additional, Pacciani, Luigi, additional, Agudo, Iván, additional, Tavecchio, Fabrizio, additional, Cibrario, Nicoló, additional, Tugliani, Stefano, additional, Bonino, Raffaella, additional, Negro, Michela, additional, Puccetti, Simonetta, additional, Tombesi, Francesco, additional, Costa, Enrico, additional, Donnarumma, Immacolata, additional, Soffitta, Paolo, additional, Mizuno, Tsunefumi, additional, Fukazawa, Yasushi, additional, Kawabata, Koji S., additional, Nakaoka, Tatsuya, additional, Uemura, Makoto, additional, Imazawa, Ryo, additional, Sasada, Mahito, additional, Akitaya, Hiroshi, additional, Josè Aceituno, Francisco, additional, Bonnoli, Giacomo, additional, Casanova, Vìctor, additional, Myserlis, Ioannis, additional, Sievers, Albrecht, additional, Angelakis, Emmanouil, additional, Kraus, Alexander, additional, Yeon Cheong, Whee, additional, Jeong, Hyeon-Woo, additional, Kang, Sincheol, additional, Kim, Sang-Hyun, additional, Lee, Sang-Sung, additional, Agìs-Gonzàlez, Beatriz, additional, Sota, Alfredo, additional, Escudero, Juan, additional, Gurwell, Mark, additional, Keating, Garrett K., additional, Rao, Ramprasad, additional, Kouch, Pouya M., additional, Lindfors, Elina, additional, Bourbah, Ioakeim G., additional, Kiehlmann, Sebastian, additional, Kontopodis, Evangelos, additional, Mandarakas, Nikos, additional, Romanopoulos, Stylianos, additional, Skalidis, Raphael, additional, Vervelaki, Anna, additional, Savchenko, Sergey S., additional, Antonelli, Lucio A., additional, Bachetti, Matteo, additional, Baldini, Luca, additional, Baumgartner, Wayne H., additional, Bellazzini, Ronaldo, additional, Bianchi, Stefano, additional, Bongiorno, Stephen D., additional, Brez, Alessandro, additional, Bucciantini, Niccoló, additional, Capitanio, Fiamma, additional, Castellano, Simone, additional, Cavazzuti, Elisabetta, additional, Chen, Chien-Ting, additional, Ciprini, Stefano, additional, De Rosa, Alessandra, additional, Del Monte, Ettore, additional, Di Lalla, Niccoló, additional, Di Marco, Alessandro, additional, Doroshenko, Victor, additional, Dovčiak, Michal, additional, Ehlert, Steven R., additional, Enoto, Teruaki, additional, Evangelista, Yuri, additional, Fabiani, Sergio, additional, Ferrazzoli, Riccardo, additional, Garcia, Javier A., additional, Gunji, Shuichi, additional, Hayashida, Kiyoshi, additional, Heyl, Jeremy, additional, Iwakiri, Wataru, additional, Kaaret, Philip, additional, Karas, Vladimir, additional, Kislat, Fabian, additional, Kitaguchi, Takao, additional, Kolodziejczak, Jeffery J., additional, Krawczynski, Henric, additional, La Monaca, Fabio, additional, Latronico, Luca, additional, Maldera, Simone, additional, Manfreda, Alberto, additional, Marin, Frédéric, additional, Marinucci, Andrea, additional, Massaro, Francesco, additional, Matt, Giorgio, additional, Mitsuishi, Ikuyuki, additional, Muleri, Fabio, additional, Ng, C.-Y., additional, O’Dell, Stephen L., additional, Omodei, Nicola, additional, Oppedisano, Chiara, additional, Papitto, Alessandro, additional, Pavlov, George G., additional, Peirson, Abel L., additional, Perri, Matteo, additional, Pesce-Rollins, Melissa, additional, Petrucci, Pierre-Olivier, additional, Pilia, Maura, additional, Possenti, Andrea, additional, Poutanen, Juri, additional, Ramsey, Brian D., additional, Rankin, John, additional, Ratheesh, Ajay, additional, Roberts, Oliver, additional, Romani, Roger W., additional, Sgró, Carmelo, additional, Slane, Patrick, additional, Spandre, Gloria, additional, Swartz, Doug, additional, Tamagawa, Toru, additional, Taverna, Roberto, additional, Tawara, Yuzuru, additional, Tennant, Allyn F., additional, Thomas, Nicholas E., additional, Trois, Alessio, additional, Tsygankov, Sergey S., additional, Turolla, Roberto, additional, Vink, Jacco, additional, Weisskopf, Martin C., additional, Wu, Kinwah, additional, Xie, Fei, additional, and Zane, Silvia, additional
Published: 2024
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30. Observability of the Very-High-Energy Emission from GRB 221009A

Author: Galanti, Giorgio, primary, Nava, Lara, additional, Roncadelli, Marco, additional, Tavecchio, Fabrizio, additional, and Bonnoli, Giacomo, additional
Published: 2023
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31. X-Ray Polarization of the BL Lacertae Type Blazar 1ES 0229+200

Author: Ehlert, Steven R., primary, Liodakis, Ioannis, additional, Middei, Riccardo, additional, Marscher, Alan P., additional, Tavecchio, Fabrizio, additional, Agudo, Iván, additional, Kouch, Pouya M., additional, Lindfors, Elina, additional, Nilsson, Kari, additional, Myserlis, Ioannis, additional, Gurwell, Mark, additional, Rao, Ramprasad, additional, Aceituno, Francisco José, additional, Bonnoli, Giacomo, additional, Casanova, Víctor, additional, Agís-González, Beatriz, additional, Escudero, Juan, additional, Husillos, César, additional, Otero Santos, Jorge, additional, Sota, Alfredo, additional, Angelakis, Emmanouil, additional, Kraus, Alexander, additional, Keating, Garrett K., additional, Antonelli, Lucio A., additional, Bachetti, Matteo, additional, Baldini, Luca, additional, Baumgartner, Wayne H., additional, Bellazzini, Ronaldo, additional, Bianchi, Stefano, additional, Bongiorno, Stephen D., additional, Bonino, Raffaella, additional, Brez, Alessandro, additional, Bucciantini, Niccoló, additional, Capitanio, Fiamma, additional, Castellano, Simone, additional, Cavazzuti, Elisabetta, additional, Chen, Chien-Ting, additional, Ciprini, Stefano, additional, Costa, Enrico, additional, De Rosa, Alessandra, additional, Del Monte, Ettore, additional, Di Gesu, Laura, additional, Di Lalla, Niccoló, additional, Di Marco, Alessandro, additional, Donnarumma, Immacolata, additional, Doroshenko, Victor, additional, Dovčiak, Michal, additional, Enoto, Teruaki, additional, Evangelista, Yuri, additional, Fabiani, Sergio, additional, Ferrazzoli, Riccardo, additional, Garcia, Javier A., additional, Gunji, Shuichi, additional, Hayashida, Kiyoshi, additional, Heyl, Jeremy, additional, Iwakiri, Wataru, additional, Jorstad, Svetlana G., additional, Kaaret, Philip, additional, Karas, Vladimir, additional, Kislat, Fabian, additional, Kitaguchi, Takao, additional, Kolodziejczak, Jeffery J., additional, Krawczynski, Henric, additional, La Monaca, Fabio, additional, Latronico, Luca, additional, Maldera, Simone, additional, Manfreda, Alberto, additional, Marin, Frédéric, additional, Marinucci, Andrea, additional, Marshall, Herman L., additional, Massaro, Francesco, additional, Matt, Giorgio, additional, Mitsuishi, Ikuyuki, additional, Mizuno, Tsunefumi, additional, Muleri, Fabio, additional, Negro, Michela, additional, Ng, C.-Y., additional, O’Dell, Stephen L., additional, Omodei, Nicola, additional, Oppedisano, Chiara, additional, Papitto, Alessandro, additional, Pavlov, George G., additional, Peirson, Abel L., additional, Perri, Matteo, additional, Pesce-Rollins, Melissa, additional, Petrucci, Pierre-Olivier, additional, Pilia, Maura, additional, Possenti, Andrea, additional, Poutanen, Juri, additional, Puccetti, Simonetta, additional, Ramsey, Brian D., additional, Rankin, John, additional, Ratheesh, Ajay, additional, Roberts, Oliver J., additional, Romani, Roger W., additional, Sgró, Carmelo, additional, Slane, Patrick, additional, Soffitta, Paolo, additional, Spandre, Gloria, additional, Swartz, Douglas A., additional, Tamagawa, Toru, additional, Taverna, Roberto, additional, Tawara, Yuzuru, additional, Tennant, Allyn F., additional, Thomas, Nicholas E., additional, Tombesi, Francesco, additional, Trois, Alessio, additional, Tsygankov, Sergey S., additional, Turolla, Roberto, additional, Vink, Jacco, additional, Weisskopf, Martin C., additional, Wu, Kinwah, additional, Xie, Fei, additional, and Zane, Silvia, additional
Published: 2023
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32. Hints for an axion-like particle from PKS 1222+216?

Author: Galanti, Giorgio, Roncadelli, Marco, Tavecchio, Fabrizio, and Bonnoli, Giacomo
Subjects: Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Abstract: Flat spectrum radio quasars (FSRQs) are a particular class of blazars rich of optical/ultraviolet photons inside the broad line region (BLR), necessarily implying a huge optical depth for $\gamma$ rays above 20 GeV. As a consequence, photons with energy above such a threshold should not be emitted. However, photons in the energy range 70 - 400 GeV have been observed by MAGIC from the FSRQ PKS 1222+216. Several astrophysical explanations exist in the literature, but they are all ad hoc, namely devised only for that specific purpose. We show that such a surprising discovery can be explained within standard blazar models by adding the new possibility that photons oscillate into axion-like particles (ALPs) and vice-versa inside the source. Through the photon-ALP oscillation mechanism a sizable fraction of very-high energy (VHE) photons can escape absorption from the BLR in a similar fashion as they largely avoid absorption from the extragalactic background light (EBL) in the intergalactic space. Actually, we show that not only are VHE photon indeed emitted, but also that their spectral energy distribution (SED) is such that they lie on the same Compton peak to which also lower energy photons simultaneously detected by Fermi/LAT belong., Comment: 6 pages, 1 figure. Proceeding of "Science with the New Generation of High Energy Gamma-ray experiments", 10th Workshop, Lisbon - Portugal, 4-6 June 2014 (to be published in the Proceedings)
Published: 2014

33. Very-high-energy quasars hint at ALPs

Author: Roncadelli, Marco, Galanti, Giorgio, Tavecchio, Fabrizio, and Bonnoli, Giacomo
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics, High Energy Physics - Phenomenology
Abstract: One of the mysteries of very-high-energy (VHE) astrophysics is the observation of flat spectrum radio quasars (FSRQs) above about 30 GeV, because at those energies their broad line region should prevent photons produced by the central engine to escape. Although a few astrophysical explanations have been put forward, they are totally ad hoc. We show that a natural explanation emerges within the conventional models of FSRQs provided that photon-ALP oscillations take place inside the source for the model parameters within an allowed range., Comment: 4 pages, 3 figures. Proceeding of the workshop "9th Patras Workshop on Axions, WIMPs and WISPs", 24 - 28 June 2013, Schloss Waldhausen, Mainz, Germany (to be published in the Proceedings)
Published: 2013

34. Boosting the performance of the ASTRI SST-2M prototype: reflective and anti-reflective coatings

Author: Bonnoli, Giacomo, Canestrari, Rodolfo, Catalano, Osvaldo, Pareschi, Giovanni, Stringhetti, Luca, and Perri, Luca
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: ASTRI is a Flagship Project of the Italian Ministry of Education, University and Research, led by the Italian National Institute of Astrophysics, INAF. One of the main aims of the ASTRI Project is the design, construction and verification on-field of a dual mirror (2M) end-to-end prototype for the Small Size Telescope (SST) envisaged to become part of the Cherenkov Telescope Array. The ASTRI SST-2M prototype adopts the Schwarzschild-Couder design, and a camera based on SiPM (Silicon Photo Multiplier); it will be assembled at the INAF astronomical site of Serra La Nave on mount Etna (Catania, Italy) within mid 2014, and will start scientific validation phase soon after. The peculiarities of the optical design and of the SiPM bandpass pushed towards specifically optimized choices in terms of reflective coatings for both the primary and the secondary mirror. In particular, multi-layer dielectric coatings, capable of filtering out the large Night Sky Background contamination at wavelengths $\lambda \gtrsim 700$ nm have been developed and tested, as a solution for the primary mirrors. Due to the conformation of the ASTRI SST-2M camera, a reimaging system based on thin pyramidal light guides could be optionally integrated aiming to increase the fill factor. An anti-reflective coating optimized for a wide range of incident angles faraway from normality was specifically developed to enhance the UV-optical transparency of these elements. The issues, strategy, simulations and experimental results are thoroughly presented., Comment: 4 pages, 6 figures. In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All ASTRI contributions at arXiv:1307.4639
Published: 2013

35. Calibration of the ASTRI SST-2M Prototype using Muon Ring Images

Author: Strazzeri, Elisabetta, Bonnoli, Giacomo, Lombardi, Saverio, Maccarone, Maria Concetta, and Mineo, Teresa
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The study of ring images generated from high-energy muons is a very useful tool for the performance monitoring and calibration of any Imaging Atmosphere Cherenkov Telescope. Isolated muons travelling towards the telescope light collector system produce characteristic Cherenkov ring images in the focal plane camera. Since the geometry and the distribution of light deployed onto the camera can be easily reconstructed analytically for a muon of given energy and direction, muon rings are a powerful tool for monitoring the behaviour of crucial properties of an imaging telescope such as the point-spread-function and the overall light collection efficiency. In this contribution we present the possibility of using the analysis of muon ring images as calibrator for the ASTRI SST-2M prototype point spread function., Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All ASTRI contributions at arXiv:1307.4639
Published: 2013

36. Estimating the redshift of PKS 0447-439 through its GeV-TeV emission

Author: Prandini, Elisa, Bonnoli, Giacomo, and Tavecchio, Fabrizio
Subjects: Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. Blazars are radio-loud active galactic nuclei (AGN) with a jet pointing at small angles towards the observer. The overall emitted spectrum is typically non-thermal, and in some cases the emission and/or absorption lines are so faint as to prevent the determination of the redshift based on optical spectroscopy methods. PKS 0447-439 is a bright blazar recently detected at very high energy. The redshift of the source is still disputed: a recent spectral analysis reports only a lower limit of z > 1.246, which contradicts the previous measure of z = 0.205 reported in the literature. Aims. We aim to give a redshift estimate of the blazar PKS 0447-439 based on combined GeV (Fermi/LAT) and TeV (H.E.S.S.) observations. Methods. Taking into account the absorption of TeV photons by the interaction with the extragalactic background light (EBL), we applied the method we developed in a previous work to derive the redshift of PKS 0447-439. Moreover, we compiled the overall spectral energy distribution (SED) using optical-UV, soft X-ray, and -ray data, nearly simultaneous to the H.E.S.S. observations at TeV energies. Finally we modelled the spectral energy distribution (SED) within the framework of a homogeneous, leptonic synchrotron self-Compton (SSC) model. Results. Using the recent TeV spectrum measured by H.E.S.S. we obtain for PKS 0447-439 a redshift of zrec = 0.20 \pm 0.05, which is our estimate on the source distance. This value agrees very well with the value reported in the literature and confirms that our method can be successfully used to constrain blazars distances. Assuming this distance, the SED can be well fitted with the above mentioned model. The physical parameters that we find suggest a strongly matter-dominated jet. Conclusions. Our analysis confirms that the redshift of PKS 0447-439 is likely 0.2, and supports the result present in the literature., Comment: 5 pages, 3 figures. A&A in press
Published: 2011
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37. Monitoring of bright, nearby Active Galactic Nuclei with the MAGIC telescopes

Author: Wagner, Robert, Backes, Michael, Satalecka, Konstancja, Bonnoli, Giacomo, Doert, Marlene, Steinke, Burkhard, Strah, Nikola, Terzic, Tomislav, Tescaro, Diego, and Uellenbeck, Malwina
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Observations and detections of Active Galactic Nuclei (AGN) by Cherenkov telescopes are often triggered by information about high flux states in other wavelength bands. To overcome this bias, the VHE gamma-ray telescope MAGIC has conducted dedicated monitoring observations of nearby AGN since 2006. Three well established, TeV-bright blazars were selected to be observed regularly: Mrk 421, Mrk 501, and 1ES1959+650. The goals of these observations are to obtain an unbiased distribution of flux states shedding light on the duty cycle of AGN, to investigate potential spectral changes during periods of different source activity, and to correlate the results with multiwavelength observations. Also clues on a potential periodic behavior of the sources might be drawn from a study of the obtained lightcurves. By testing predictions of theoretical models, like, e.g., the correlation between the TeV flux level and the peak frequency predicted in SSC models, monitoring deepens our knowledge about the acceleration and emission processes in AGN. The status and results of the MAGIC AGN monitoring program will be presented., Comment: 4 pages, 3 figures, proceedings of the 32nd cosmic ray conference, Beijing 2011
Published: 2011
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38. TeV blazars and their distance

Author: Prandini, Elisa, Bonnoli, Giacomo, Maraschi, Laura, Mariotti, Mose', and Tavecchio, Fabrizio
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Recently, a new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed, with the underlying assumption that the Very High Energy (VHE) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the gamma-ray spectrum observed by Fermi/LAT. The constraints found are related to the real redshifts by a simple linear relation, that has been used to infer the unknown distance of blazars. The sample will be revised with the up-to-date spectra in both TeV and GeV bands, the method tested with the more recent EBL models and finally applied to the unknown distance blazars detected at VHE., Comment: Contribution to "Cosmic Radiation Fields: Sources in the early Universe", Desy, Germany, November 9-12, 2010; 6 pages, 3 figures (revised version)
Published: 2011

39. Blazars distance indications from Fermi and TeV data

Author: Prandini, Elisa, Bonnoli, Giacomo, Maraschi, Laura, Mariotti, Mose', and Tavecchio, Fabrizio
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: A new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes will be presented. The underlying assumption is that the Very High Energy (VHE) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the extrapolation of the gamma-ray spectrum observed by Fermi/LAT. Starting from the observed spectral data at VHE, the EBL-corrected spectra are derived as a function of the redshift z and fitted with power laws. Comparing the redshift dependent VHE slopes with the power law fits to the LAT data an upper limit to the source redshift can be derived. The method is applied to all TeV blazars detected by LAT with known distance and an empirical law describing the relation between the upper limits and the true redshifts is derived. This law can be used to estimate the distance of unknown redshift blazars: as an example, the distance of PKS 1424+240 is inferred., Comment: Contribution to SciNeGHE 2010, Trieste, Italy, September 2010; 4 pages, 2 figure
Published: 2011
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40. MAGIC observations of Mkn 421 in 2008, and related optical/X-ray/TeV MWL study

Author: Bonnoli, Giacomo, Hsu, Ching-Cheng, Goebel, Florian, Lindfors, Elina, Majumdar, Pratik, Satalecka, Konstancja, Stamerra, Antonio, Tavecchio, Fabrizio, and Wagner, Robert
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The HBL-type blazar Markarian 421 is one of the brightest TeV gamma-ray sources of the Northern sky. From December 2007 until June 2008 it was intensively observed in the VHE (E>100 GeV) band by the MAGIC gamma-ray telescope. The source showed intense and prolonged activity during the whole period. In some nights the integral flux rose up to 3.6 Crab units (E>200 GeV). Intra-night rapid flux variations were observed. We compared the optical (KVA) and X-ray (RXTE-ASM, Swift-XRT) data with the MAGIC VHE data, investigating the correlations between different energy bands., Comment: 4 pages,4figures, Contribution to the 31st ICRC, Lodz, Poland, July 2009
Published: 2009

41. Monitoring of Bright Blazars with MAGIC in the 2007/2008 Season

Author: Satalecka, Konstancja, Hsu, Ching-Cheng, Bernardini, Elisa, Bonnoli, Giacomo, Galante, Nicola, Goebel, Florian, Lindfors, Elina, Majumdar, Pratik, Stamerra, Antonio, and Wagner, Robert
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Because of the short duty-cycles and observation-time constraints, studies of bright TeV (E>100 GeV) blazars are mostly restricted to flaring episodes or rather short (days to few weeks) multiwavelength campaigns. At the same time, long-term studies of these objects are essential to gain a more complete understanding of the blazar phenomenon and to constrain theoretical models concerning jet physics. Only unbiased long-term studies are adequate for the determination of flaring state probabilities and for estimating the statistical significance of possible correlations between TeV flaring states and other wavebands or observables, such as neutrino events. Regular observations also provide triggers for multiwavelength ToO observations originating from the TeV waveband. These are particularly needed to identify and study orphan TeV flares, i.e. flares without counterparts in other wavebands. In 2007/8 the MAGIC telescope has monitored three TeV blazars on a regular basis: Mrk 501, Mrk 421, and 1ES 1959+650. We present preliminary results of these observations including the measured light curves and a correlation study for VHE gamma-rays and X-rays and VHE gamma-rays and optical R-band for Mrk 421., Comment: 10 pages, 7 figures, Proceedings of the SciNEGHE'08
Published: 2009
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42. Repeating flaring activity of the blazar AO 0235+164

Author: Escudero Pedrosa, Juan, primary, Agudo, Iván, additional, Tramacere, Andrea, additional, Alan Marscher, P., additional, Jorstad, Svetlana, additional, Weaver, Z.R., additional, Casadio, Carolina, additional, Thum, Clemens, additional, Myserlis, Ioannis, additional, Fuentes, Antonio, additional, Traianou, Efthalia, additional, Kim, Jae-Young, additional, Kramer, Joana, additional, López-Coto, Rubén, additional, D'Ammando, Filippo, additional, Bernardos, M., additional, Bonnoli, Giacomo, additional, Dmitriy Blinov, A., additional, Borman, G.A., additional, Grishina, T.S., additional, Hagen-Thorn, V.A., additional, Kopatskaya, E.N., additional, Larionova, E.G., additional, Larionov, V.M., additional, Larionova, L.V., additional, Morozova, D.A., additional, Savchenko, S.S., additional, Troitskiy, I.S., additional, Troitskaya, Y.V., additional, and Vasilyev, A.A., additional
Published: 2023
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43. The UHECR-FR0 Radio Galaxy Connection: A Multi-Messenger Study of Energy Spectra/Composition Emission and Extragalactic Magnetic Field Propagation

Author: Lundquist, Jon Paul, primary, Merten, Lukas, additional, Vorobiov, Serguei, additional, Boughelilba, Margot, additional, Reimer, Anita, additional, Da Vela, Paolo, additional, Tavecchio, Fabrizio, additional, Bonnoli, Giacomo, additional, and Righi, Chiara, additional
Published: 2023
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44. IXPE and Multiwavelength Observations of Blazar PG 1553+113 Reveal an Orphan Optical Polarization Swing

Author: Middei, Riccardo, primary, Perri, Matteo, additional, Puccetti, Simonetta, additional, Liodakis, Ioannis, additional, Di Gesu, Laura, additional, Marscher, Alan P., additional, Cavero, Nicole Rodriguez, additional, Tavecchio, Fabrizio, additional, Donnarumma, Immacolata, additional, Laurenti, Marco, additional, Jorstad, Svetlana G., additional, Agudo, Iván, additional, Marshall, Herman L., additional, Pacciani, Luigi, additional, Kim, Dawoon E., additional, Aceituno, Francisco José, additional, Bonnoli, Giacomo, additional, Casanova, Víctor, additional, Agís-González, Beatriz, additional, Sota, Alfredo, additional, Casadio, Carolina, additional, Escudero, Juan, additional, Myserlis, Ioannis, additional, Sievers, Albrecht, additional, Kouch, Pouya M., additional, Lindfors, Elina, additional, Gurwell, Mark, additional, Keating, Garrett K., additional, Rao, Ramprasad, additional, Kang, Sincheol, additional, Lee, Sang-Sung, additional, Kim, Sang-Hyun, additional, Cheong, Whee Yeon, additional, Jeong, Hyeon-Woo, additional, Angelakis, Emmanouil, additional, Kraus, Alexander, additional, Antonelli, Lucio A., additional, Bachetti, Matteo, additional, Baldini, Luca, additional, Baumgartner, Wayne H., additional, Bellazzini, Ronaldo, additional, Bianchi, Stefano, additional, Bongiorno, Stephen D., additional, Bonino, Raffaella, additional, Brez, Alessandro, additional, Bucciantini, Niccolò, additional, Capitanio, Fiamma, additional, Castellano, Simone, additional, Cavazzuti, Elisabetta, additional, Chen, Chien-Ting, additional, Ciprini, Stefano, additional, Costa, Enrico, additional, De Rosa, Alessandra, additional, Del Monte, Ettore, additional, Di Lalla, Niccolò, additional, Di Marco, Alessandro, additional, Doroshenko, Victor, additional, Dovčiak, Michal, additional, Ehlert, Steven R., additional, Enoto, Teruaki, additional, Evangelista, Yuri, additional, Fabiani, Sergio, additional, Ferrazzoli, Riccardo, additional, García, Javier A., additional, Gunji, Shuichi, additional, Hayashida, Kiyoshi, additional, Heyl, Jeremy, additional, Iwakiri, Wataru, additional, Kaaret, Philip, additional, Karas, Vladimir, additional, Kislat, Fabian, additional, Kitaguchi, Takao, additional, Kolodziejczak, Jeffery J., additional, Krawczynski, Henric, additional, La Monaca, Fabio, additional, Latronico, Luca, additional, Maldera, Simone, additional, Manfreda, Alberto, additional, Marin, Frédéric, additional, Marinucci, Andrea, additional, Massaro, Francesco, additional, Matt, Giorgio, additional, Mitsuishi, Ikuyuki, additional, Mizuno, Tsunefumi, additional, Muleri, Fabio, additional, Negro, Michela, additional, Ng, Chi-Yung, additional, O’Dell, Stephen L., additional, Omodei, Nicola, additional, Oppedisano, Chiara, additional, Papitto, Alessandro, additional, Pavlov, George G., additional, Peirson, Abel L., additional, Pesce-Rollins, Melissa, additional, Petrucci, Pierre-Olivier, additional, Pilia, Maura, additional, Possenti, Andrea, additional, Poutanen, Juri, additional, Ramsey, Brian D., additional, Rankin, John, additional, Ratheesh, Ajay, additional, Roberts, Oliver J., additional, Romani, Roger W., additional, Sgrò, Carmelo, additional, Slane, Patrick, additional, Soffitta, Paolo, additional, Spandre, Gloria, additional, Swartz, Douglas A., additional, Tamagawa, Toru, additional, Taverna, Roberto, additional, Tawara, Yuzuru, additional, Tennant, Allyn F., additional, Thomas, Nicholas E., additional, Tombesi, Francesco, additional, Trois, Alessio, additional, Tsygankov, Sergey S., additional, Turolla, Roberto, additional, Vink, Jacco, additional, Weisskopf, Martin C., additional, Wu, Kinwah, additional, Xie, Fei, additional, and Zane, Silvia, additional
Published: 2023
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45. X-Ray Polarization of BL Lacertae in Outburst

Author: Peirson, Abel L., primary, Negro, Michela, additional, Liodakis, Ioannis, additional, Middei, Riccardo, additional, Kim, Dawoon E., additional, Marscher, Alan P., additional, Marshall, Herman L., additional, Pacciani, Luigi, additional, Romani, Roger W., additional, Wu, Kinwah, additional, Di Marco, Alessandro, additional, Di Lalla, Niccoló, additional, Omodei, Nicola, additional, Jorstad, Svetlana G., additional, Agudo, Iván, additional, Kouch, Pouya M., additional, Lindfors, Elina, additional, Aceituno, Francisco José, additional, Bernardos, Maria I., additional, Bonnoli, Giacomo, additional, Casanova, Víctor, additional, García-Comas, Maya, additional, Agís-González, Beatriz, additional, Husillos, César, additional, Marchini, Alessandro, additional, Sota, Alfredo, additional, Casadio, Carolina, additional, Escudero, Juan, additional, Myserlis, Ioannis, additional, Sievers, Albrecht, additional, Gurwell, Mark, additional, Rao, Ramprasad, additional, Imazawa, Ryo, additional, Sasada, Mahito, additional, Fukazawa, Yasushi, additional, Kawabata, Koji S., additional, Uemura, Makoto, additional, Mizuno, Tsunefumi, additional, Nakaoka, Tatsuya, additional, Akitaya, Hiroshi, additional, Cheong, Yeon, additional, Jeong, Hyeon-Woo, additional, Kang, Sincheol, additional, Kim, Sang-Hyun, additional, Lee, Sang-Sung, additional, Angelakis, Emmanouil, additional, Kraus, Alexander, additional, Cibrario, Nicoló, additional, Donnarumma, Immacolata, additional, Poutanen, Juri, additional, Tavecchio, Fabrizio, additional, Antonelli, Lucio A., additional, Bachetti, Matteo, additional, Baldini, Luca, additional, Baumgartner, Wayne H., additional, Bellazzini, Ronaldo, additional, Bianchi, Stefano, additional, Bongiorno, Stephen D., additional, Bonino, Raffaella, additional, Brez, Alessandro, additional, Bucciantini, Niccoló, additional, Capitanio, Fiamma, additional, Castellano, Simone, additional, Cavazzuti, Elisabetta, additional, Chen, Chien-Ting, additional, Ciprini, Stefano, additional, Costa, Enrico, additional, De Rosa, Alessandra, additional, Del Monte, Ettore, additional, Di Gesu, Laura, additional, Doroshenko, Victor, additional, Dovčiak, Michal, additional, Ehlert, Steven R., additional, Enoto, Teruaki, additional, Evangelista, Yuri, additional, Fabiani, Sergio, additional, Ferrazzoli, Riccardo, additional, Garcia, Javier A., additional, Gunji, Shuichi, additional, Hayashida, Kiyoshi, additional, Heyl, Jeremy, additional, Iwakiri, Wataru, additional, Kaaret, Philip, additional, Karas, Vladimir, additional, Kitaguchi, Takao, additional, Kolodziejczak, Jeffery J., additional, Krawczynski, Henric, additional, La Monaca, Fabio, additional, Latronico, Luca, additional, Madejski, Grzegorz, additional, Maldera, Simone, additional, Manfreda, Alberto, additional, Marin, Frédéric, additional, Marinucci, Andrea, additional, Massaro, Francesco, additional, Matt, Giorgio, additional, Mitsuishi, Ikuyuki, additional, Muleri, Fabio, additional, Ng, C.-Y., additional, O’Dell, Stephen L., additional, Oppedisano, Chiara, additional, Papitto, Alessandro, additional, Pavlov, George G., additional, Perri, Matteo, additional, Pesce-Rollins, Melissa, additional, Petrucci, Pierre-Olivier, additional, Pilia, Maura, additional, Possenti, Andrea, additional, Puccetti, Simonetta, additional, Ramsey, Brian D., additional, Rankin, John, additional, Ratheesh, Ajay, additional, Roberts, Oliver J., additional, Sgró, Carmelo, additional, Slane, Patrick, additional, Soffitta, Paolo, additional, Spandre, Gloria, additional, Swartz, Douglas A., additional, Tamagawa, Toru, additional, Taverna, Roberto, additional, Tawara, Yuzuru, additional, Tennant, Allyn F., additional, Thomas, Nicholas E., additional, Tombesi, Francesco, additional, Trois, Alessio, additional, Tsygankov, Sergey, additional, Turolla, Roberto, additional, Vink, Jacco, additional, Weisskopf, Martin C., additional, Xie, Fei, additional, and Zane, Silvia, additional
Published: 2023
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46. A facility to evaluate the focusing performance of mirrors for Cherenkov Telescopes

Author: Canestrari, Rodolfo, Giro, Enrico, Bonnoli, Giacomo, Farisato, Giancarlo, Lessio, Luigi, Rodeghiero, Gabriele, Spiga, Rossella, Toso, Giorgio, and Pareschi, Giovanni
Published: 2016
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47. X-Ray Polarization Observations of BL Lacertae

Author: Middei, Riccardo, primary, Liodakis, Ioannis, additional, Perri, Matteo, additional, Puccetti, Simonetta, additional, Cavazzuti, Elisabetta, additional, Di Gesu, Laura, additional, Ehlert, Steven R., additional, Madejski, Grzegorz, additional, Marscher, Alan P., additional, Marshall, Herman L., additional, Muleri, Fabio, additional, Negro, Michela, additional, Jorstad, Svetlana G., additional, Agís-González, Beatriz, additional, Agudo, Iván, additional, Bonnoli, Giacomo, additional, Bernardos, Maria I., additional, Casanova, Víctor, additional, García-Comas, Maya, additional, Husillos, César, additional, Marchini, Alessandro, additional, Sota, Alfredo, additional, Kouch, Pouya M., additional, Lindfors, Elina, additional, Borman, George A., additional, Kopatskaya, Evgenia N., additional, Larionova, Elena G., additional, Morozova, Daria A., additional, Savchenko, Sergey S., additional, Vasilyev, Andrey A., additional, Zhovtan, Alexey V., additional, Casadio, Carolina, additional, Escudero, Juan, additional, Myserlis, Ioannis, additional, Hales, Antonio, additional, Kameno, Seiji, additional, Kneissl, Ruediger, additional, Messias, Hugo, additional, Nagai, Hiroshi, additional, Blinov, Dmitry, additional, Bourbah, Ioakeim G., additional, Kiehlmann, Sebastian, additional, Kontopodis, Evangelos, additional, Mandarakas, Nikos, additional, Romanopoulos, Stylianos, additional, Skalidis, Raphael, additional, Vervelaki, Anna, additional, Masiero, Joseph R., additional, Mawet, Dimitri, additional, Millar-Blanchaer, Maxwell A., additional, Panopoulou, Georgia V., additional, Tinyanont, Samaporn, additional, Berdyugin, Andrei V., additional, Kagitani, Masato, additional, Kravtsov, Vadim, additional, Sakanoi, Takeshi, additional, Imazawa, Ryo, additional, Sasada, Mahito, additional, Fukazawa, Yasushi, additional, Kawabata, Koji S., additional, Uemura, Makoto, additional, Mizuno, Tsunefumi, additional, Nakaoka, Tatsuya, additional, Akitaya, Hiroshi, additional, Gurwell, Mark, additional, Rao, Ramprasad, additional, Lalla, Niccoló Di, additional, Cibrario, Nicoló, additional, Donnarumma, Immacolata, additional, Kim, Dawoon E., additional, Omodei, Nicola, additional, Pacciani, Luigi, additional, Poutanen, Juri, additional, Tavecchio, Fabrizio, additional, Antonelli, Lucio A., additional, Bachetti, Matteo, additional, Baldini, Luca, additional, Baumgartner, Wayne H., additional, Bellazzini, Ronaldo, additional, Bianchi, Stefano, additional, Bongiorno, Stephen D., additional, Bonino, Raffaella, additional, Brez, Alessandro, additional, Bucciantini, Niccoló, additional, Capitanio, Fiamma, additional, Castellano, Simone, additional, Ciprini, Stefano, additional, Costa, Enrico, additional, De Rosa, Alessandra, additional, Del Monte, Ettore, additional, Marco, Alessandro Di, additional, Doroshenko, Victor, additional, Dovčiak, Michal, additional, Enoto, Teruaki, additional, Evangelista, Yuri, additional, Fabiani, Sergio, additional, Ferrazzoli, Riccardo, additional, Garcia, Javier A., additional, Gunji, Shuichi, additional, Hayashida, Kiyoshi, additional, Heyl, Jeremy, additional, Iwakiri, Wataru, additional, Karas, Vladimir, additional, Kitaguchi, Takao, additional, Kolodziejczak, Jeffery J., additional, Krawczynski, Henric, additional, Monaca, Fabio La, additional, Latronico, Luca, additional, Maldera, Simone, additional, Manfreda, Alberto, additional, Marin, Frédéric, additional, Marinucci, Andrea, additional, Massaro, Francesco, additional, Matt, Giorgio, additional, Mitsuishi, Ikuyuki, additional, Ng, C.-Y., additional, O’Dell, Stephen L., additional, Oppedisano, Chiara, additional, Papitto, Alessandro, additional, Pavlov, George G., additional, Peirson, Abel L., additional, Pesce-Rollins, Melissa, additional, Petrucci, Pierre-Olivier, additional, Pilia, Maura, additional, Possenti, Andrea, additional, Ramsey, Brian D., additional, Rankin, John, additional, Ratheesh, Ajay, additional, Romani, Roger W., additional, Sgró, Carmelo, additional, Slane, Patrick, additional, Soffitta, Paolo, additional, Spandre, Gloria, additional, Tamagawa, Toru, additional, Taverna, Roberto, additional, Tawara, Yuzuru, additional, Tennant, Allyn F., additional, Thomas, Nicholas E., additional, Tombesi, Francesco, additional, Trois, Alessio, additional, Tsygankov, Sergey, additional, Turolla, Roberto, additional, Vink, Jacco, additional, Weisskopf, Martin C., additional, Wu, Kinwah, additional, Xie, Fei, additional, and Zane, Silvia, additional
Published: 2022
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48. Polarized blazar X-rays imply particle acceleration in shocks

Author: Liodakis, Ioannis, primary, Marscher, Alan P., additional, Agudo, Iván, additional, Berdyugin, Andrei V., additional, Bernardos, Maria I., additional, Bonnoli, Giacomo, additional, Borman, George A., additional, Casadio, Carolina, additional, Casanova, Vı́ctor, additional, Cavazzuti, Elisabetta, additional, Rodriguez Cavero, Nicole, additional, Di Gesu, Laura, additional, Di Lalla, Niccoló, additional, Donnarumma, Immacolata, additional, Ehlert, Steven R., additional, Errando, Manel, additional, Escudero, Juan, additional, Garcı́a-Comas, Maya, additional, Agı́s-González, Beatriz, additional, Husillos, César, additional, Jormanainen, Jenni, additional, Jorstad, Svetlana G., additional, Kagitani, Masato, additional, Kopatskaya, Evgenia N., additional, Kravtsov, Vadim, additional, Krawczynski, Henric, additional, Lindfors, Elina, additional, Larionova, Elena G., additional, Madejski, Grzegorz M., additional, Marin, Frédéric, additional, Marchini, Alessandro, additional, Marshall, Herman L., additional, Morozova, Daria A., additional, Massaro, Francesco, additional, Masiero, Joseph R., additional, Mawet, Dimitri, additional, Middei, Riccardo, additional, Millar-Blanchaer, Maxwell A., additional, Myserlis, Ioannis, additional, Negro, Michela, additional, Nilsson, Kari, additional, O’Dell, Stephen L., additional, Omodei, Nicola, additional, Pacciani, Luigi, additional, Paggi, Alessandro, additional, Panopoulou, Georgia V., additional, Peirson, Abel L., additional, Perri, Matteo, additional, Petrucci, Pierre-Olivier, additional, Poutanen, Juri, additional, Puccetti, Simonetta, additional, Romani, Roger W., additional, Sakanoi, Takeshi, additional, Savchenko, Sergey S., additional, Sota, Alfredo, additional, Tavecchio, Fabrizio, additional, Tinyanont, Samaporn, additional, Vasilyev, Andrey A., additional, Weaver, Zachary R., additional, Zhovtan, Alexey V., additional, Antonelli, Lucio A., additional, Bachetti, Matteo, additional, Baldini, Luca, additional, Baumgartner, Wayne H., additional, Bellazzini, Ronaldo, additional, Bianchi, Stefano, additional, Bongiorno, Stephen D., additional, Bonino, Raffaella, additional, Brez, Alessandro, additional, Bucciantini, Niccoló, additional, Capitanio, Fiamma, additional, Castellano, Simone, additional, Ciprini, Stefano, additional, Costa, Enrico, additional, De Rosa, Alessandra, additional, Del Monte, Ettore, additional, Di Marco, Alessandro, additional, Doroshenko, Victor, additional, Dovčiak, Michal, additional, Enoto, Teruaki, additional, Evangelista, Yuri, additional, Fabiani, Sergio, additional, Ferrazzoli, Riccardo, additional, Garcia, Javier A., additional, Gunji, Shuichi, additional, Hayashida, Kiyoshi, additional, Heyl, Jeremy, additional, Iwakiri, Wataru, additional, Karas, Vladimir, additional, Kitaguchi, Takao, additional, Kolodziejczak, Jeffery J., additional, La Monaca, Fabio, additional, Latronico, Luca, additional, Maldera, Simone, additional, Manfreda, Alberto, additional, Marinucci, Andrea, additional, Matt, Giorgio, additional, Mitsuishi, Ikuyuki, additional, Mizuno, Tsunefumi, additional, Muleri, Fabio, additional, Ng, Stephen C.-Y., additional, Oppedisano, Chiara, additional, Papitto, Alessandro, additional, Pavlov, George G., additional, Pesce-Rollins, Melissa, additional, Pilia, Maura, additional, Possenti, Andrea, additional, Ramsey, Brian D., additional, Rankin, John, additional, Ratheesh, Ajay, additional, Sgró, Carmelo, additional, Slane, Patrick, additional, Soffitta, Paolo, additional, Spandre, Gloria, additional, Tamagawa, Toru, additional, Taverna, Roberto, additional, Tawara, Yuzuru, additional, Tennant, Allyn F., additional, Thomas, Nicolas E., additional, Tombesi, Francesco, additional, Trois, Alessio, additional, Tsygankov, Sergey, additional, Turolla, Roberto, additional, Vink, Jacco, additional, Weisskopf, Martin C., additional, Wu, Kinwah, additional, Xie, Fei, additional, and Zane, Silvia, additional
Published: 2022
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49. The small-sized telescope of CTAO

Author: Tagliaferri, Gianpiero, primary, Antonelli, Angelo, additional, Arnesen, Tora, additional, Aschersleben, Jann, additional, Attina', Primo, additional, Balbo, Matteo, additional, Bang, Sunghyun, additional, Barcelo, Miquel, additional, Baryshev, Andrey, additional, Bellassai, Giancarlo, additional, Berge, David, additional, Bicknell, Chris, additional, Bigongiari, Ciro, additional, Bonnoli, Giacomo, additional, Bouley, Frederic, additional, Brown, Anthony, additional, Bulgarelli, Andrea, additional, Cappi, Massimo, additional, Caraveo, Patrizia, additional, Caschera, Salvatore, additional, Chadwick, Paula, additional, Conte, Francesco, additional, Cotter, Garret, additional, Cristofari, Pierre, additional, De Frondat, Fatima, additional, De Gouveia Dal Pino, Elisabete, additional, De Simone, Nico, additional, Depaoli, Davide, additional, Dournaux, Jean Laurent, additional, Duffy, Connor, additional, Einecke, Sabrina, additional, Fermino, Carlos E., additional, Funk, Stefan, additional, Gargano, Carmelo, additional, Giavitto, Gianluca, additional, Giuliani, Andrea, additional, Greenshaw, Tim, additional, Hinton, Jim, additional, Huet, Jean-Michel, additional, Iovenitti, Simone, additional, la Palombara, Nicola, additional, Lapington, Jon S., additional, Laporte, Philippe, additional, Leach, Steve, additional, Lessio, Luigi, additional, Leto, Giuseppe, additional, Lloyd, Sheridan J., additional, Lucarelli, Fabrizio, additional, Lombardi, Saverio, additional, Macchi, Alberto, additional, Martinetti, Eugenio, additional, Micciche', Antonio, additional, Millul, Rachele, additional, Mineo, Teresa, additional, Mitsunari, Takahashi, additional, Nayak, Amrit P., additional, Nicotra, Gaetano, additional, Okumura, Akira, additional, Pareschi, Giovanni, additional, Penno, Marek, additional, Prokoph, Heike, additional, Rebert, Emma, additional, Righi, Chiara, additional, Rulten, Cameron B., additional, Russo, Federico, additional, Sanchez, Ricardo Zanmar, additional, Saturni, Francesco G., additional, Schaefer, Johannes, additional, Schwab, Benni, additional, Scuderi, Salvatore, additional, Sironi, Giorgia, additional, Sliusar, Vitalii, additional, Sol, Helene, additional, Spencer, Samuel, additional, Stamerra, Antonio, additional, Tajima, Hiro, additional, tavecchio, Fabrizio, additional, Tosti, Gino, additional, Trois, Alessio, additional, Vecchi, Manuela, additional, Vercellone, Stefano, additional, Vink, Jacco, additional, Walter, Roland, additional, Watson, Jason, additional, White, Richard, additional, Zanin, Roberta, additional, Zampieri, Luca, additional, Zech, Andreas, additional, and Zink, Adrian, additional
Published: 2022
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50. Multiwavelength observations in 2019-2020 of a new very-high-energy gamma-ray emitter: the flat spectrum radio quasar QSO B1420+326

Author: Fermi Large Area Telescope Collaboration, D’Ammando, Filippo, Angioni, Roberto, Orienti, Monica, MAGIC Collaboration, Sitarek, Julian, Nozaki, Seiya, Lindfors, Elina, Bonnoli, Giacomo, Fallah Ramazani, Vandad, Jorstad, Svetlana, Arbet Engels, Axel, and Biland, Adrian
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: The flat-spectrum radio quasar QSO B1420+326 underwent an enhanced γ-ray flux state seen by Fermi-LAT at the turn of 2019/2020. Compared to the low state both the position and luminosity of the two spectral energy distribution peaks changed by at least two orders of magnitude. The high state resulted in the discovery of the very-high-energy (>100 GeV) γ-ray emission from the source by the MAGIC telescopes. The organized multiwavelength campaign allow us to trace the broadband emission of the source through different phases of the flaring activity. The source was observed by 20 instruments in radio, near-infrared, optical, ultra-violet, X-ray and γ-ray bands. We use dedicated optical spectroscopy results to estimate the accretion disc and the dust torus luminosity. The optical spectroscopy shows a prominent FeII bump with flux evolving together with the continuum emission and a MgII line with varying equivalent width. The γ-ray flare was accompanied by a rotation of the optical polarization vector and emission of a new superluminal radio knot. We model spectral energy distributions in different flare phases in the framework of combined synchrotron-self-Compton and external Compton scenario in which the shape of the electron energy distribution is determined from cooling processes. ISSN:1824-8039
Published: 2022

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