Browsing by Author "Pilia, Maura"

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Investigating the Mini and Giant Radio Flare Episodes of Cygnus X-3
(2020-12-29) Egron, Elise; Pellizzoni, Alberto; Righini, Simona; Giroletti, Marcello; Koljonen, Karri; Pottschmidt, Katja; Trushkin, Sergei; Lobina, Jessica; Pilia, Maura; Wilms, Joern; Corbel, Stéphane; Grinberg, Victoria; Loru, Sara; Trois, Alessio; Rodriguez, Jérome; Lähteenmäki, A.; Tornikoski, M.; Enestam, Sissi; Järvelä, E.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The microquasar Cygnus X-3 underwent a giant radio flare in 2017 April, reaching a maximum flux of ∼16.5 Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6, and 24.1 GHz, parallel to the Metsähovi radio telescope at 37 GHz, from 2017 April 4 to 11. We observe a spectral steepening from α = 0.2 to 0.5 (with S ν ∝ ν α) within 6 hr of the epoch of the flare's peak maximum, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of Cyg X-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994, 1995, 2002, and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phase φ ∼ 0.5 (orbital inferior conjunction). On the other hand, the light curves of the mini-flares observed at 15-22 GHz peak at φ ∼, except for the 2016 light curve, which is shifted 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state).
IXPE observation of PKS 2155-304 reveals the most highly polarized blazar
(2024-09-01) 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, Chi Yung; 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; Zane, Silvia
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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 (T1) of the IXPE pointing, the source exhibited the highest X-ray polarization degree detected for an HSP blazar thus far, (30.7 ± 2.0)%; this dropped to (15.3 ± 2.1)% during the second half (T2). The X-ray polarization angle remained stable during the IXPE pointing at 129.4 '±1.8 and 125.4 '±3.9 during T1 and T2, respectively. Meanwhile, the optical polarization degree remained stable during the IXPE pointing, with average host-galaxy-corrected values of (4.3 ± 0.7)% and (3.8 ± 0.9)% during the T1 and T2, respectively. During the IXPE pointing, the optical polarization angle changed achromatically from 140 to 90 and back to 130. Despite several attempts, we only detected (99.7% conf.) the radio polarization once (during T2, at 225.5 GHz): with degree (1.7 ± 0.4)% and angle 112.5 '±5.5. 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 ( 135), similarly to all of the MW polarization angles. Moreover, the X-ray-to-optical polarization degree ratios of 7 and 4 during T1 and T2, 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.