Browsing by Author "Gunji, Shuichi"
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Item A Space-based All-sky MeV γ-ray Survey with the Electron Tracking Compton Camera(2019-07) Hamaguchi, Kenji; Tanimori, Toru; Takada, Atsushi; Beacom, John F.; Gunji, Shuichi; Mori, Masaki; Nakamori, Takeshi; Shrader, Chris R.; Smith, David M.; Tamagawa, Toru; Tsurutani, Bruce T.Thematic Activity/Project/state of the Profession Consideration Area: A sensitive survey of the MeV γ-ray sky is needed to understand important astrophysical problems such as γ-ray bursts in the early universe, progenitors of Type Ia supernovae, and the nature of dark matter. However, the study has not progressed remarkably since the limited survey by COMPTEL onboard CGRO in the 1990s. Tanimori et al. have developed a Compton camera that tracks the trajectory of each recoil electron in addition to the information obtained by the conventional Compton cameras, leading to superior imaging. This Electron Tracking Compton Camera (ETCC) facilitates accurate reconstruction of the incoming direction of each MeV photon from a wide sky at ∼degree angular resolution and with minimized particle background using trajectory information. The latest ETCC model, SMILE-2+, made successful astronomical observations during a day balloon flight in 2018 April and detected diffuse continuum and 511 keV annihilation line emission from the Galactic Center region at a high significance in ∼2.5 hours. We believe that MeV observations from space with upgraded ETCCs will dramatically improve our knowledge of the MeV universe. We advocate for a space-based all-sky survey mission with multiple ETCCs onboard and detail its expected benefits.Item X-Ray Polarization of the Black Hole X-Ray Binary 4U 1630–47 Challenges the Standard Thin Accretion Disk Scenario(AAS, 2024-03-20) Ratheesh, Ajay; Dovčiak, Michal; Krawczynski, Henric; Podgorný, Jakub; Marra, Lorenzo; Veledina, Alexandra; Suleimanov, Valery F.; Cavero, Nicole Rodriguez; Steiner, James F.; Svoboda, Jiří; Marinucci, Andrea; Bianchi, Stefano; Negro, Michela; Matt, Giorgio; Tombesi, Francesco; Poutanen, Juri; Ingram, Adam; Taverna, Roberto; West, Andrew; Karas, Vladimir; Ursini, Francesco; Soffitta, Paolo; Capitanio, Fiamma; Viscolo, Domenico; Manfreda, Alberto; Muleri, Fabio; Parra, Maxime; Beheshtipour, Banafsheh; Chun, Sohee; Cibrario, Nicolò; Lalla, Niccolò Di; Fabiani, Sergio; Hu, Kun; Kaaret, Philip; Loktev, Vladislav; Mikušincová, Romana; Mizuno, Tsunefumi; Omodei, Nicola; Petrucci, Pierre-Olivier; Puccetti, Simonetta; Rankin, John; Zane, Silvia; Zhang, Sixuan; Agudo, Iván; Antonelli, Lucio A.; Bachetti, Matteo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolò; Castellano, Simone; Cavazzuti, Elisabetta; Chen, Chien-Ting; Ciprini, Stefano; Costa, Enrico; Rosa, Alessandra De; Monte, Ettore Del; Gesu, Laura Di; Marco, Alessandro Di; Donnarumma, Immacolata; Doroshenko, Victor; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Jorstad, Svetlana G.; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Monaca, Fabio La; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Marin, Frédéric; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Mitsuishi, Ikuyuki; Ng, Stephen C.-Y.; O’Dell, Stephen L.; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Pilia, Maura; Possenti, Andrea; Ramsey, Brian D.; Roberts, Oliver J.; Romani, Roger W.; Sgrò, Carmelo; Slane, Patrick; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Weisskopf, Martin C.; Wu, Kinwah; Xie, FeiA large energy-dependent X-ray polarization degree is detected by the Imaging X-ray Polarimetry Explorer (IXPE) in the high-soft emission state of the black hole X-ray binary 4U 1630–47. The highly significant detection (at ≈50σ confidence level) of an unexpectedly high polarization, rising from ~6% at 2 keV to ~10% at 8 keV, cannot be easily reconciled with standard models of thin accretion disks. In this work, we compare the predictions of different theoretical models with the IXPE data and conclude that the observed polarization properties are compatible with a scenario in which matter accretes onto the black hole through a thin disk covered by a partially ionized atmosphere flowing away at mildly relativistic velocities.