Browsing by Author "Mukherjee, R."

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    A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands
    (IOP, 2024-01) Pope, I.; Mori, K.; Abdelmaguid, M.; Gelfand, J. D.; Reynolds, S. P.; Safi-Harb, S.; Hailey, C. J.; An, H.; (NuSTAR Collaboration); Bangale, P.; Batista, P.; Benbow, W.; Buckley, J. H.; Capasso, M.; Christiansen, J. L.; Chromey, A. J.; Falcone, A.; Feng, Q.; Finley, J. P.; Foote, G. M.; Gallagher, G.; Hanlon, W. F.; Hanna, D.; Hervet, O.; Holder, J.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kieda, D.; Kleiner, T. K.; Korzoun, N.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McGrath, C. E.; Mooney, C. L.; Moriarty, P.; Mukherjee, R.; O'Brien, S.; Ong, R. A.; Park, N.; Patel, S. R.; Pfrang, K.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Roache, E.; Sadeh, I.; Saha, L.; Sembroski, G. H.; Tak, D.; Tucci, J. V.; Weinstein, A.; Williams, D. A.; Woo, J.; (VERITAS Collaboration); Physics, School of Science
    G106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" and "tail") regions in the radio band. A discovery of very-high-energy gamma-ray emission (Eγ > 100 GeV) followed by the recent detection of ultrahigh-energy gamma-ray emission (Eγ > 100 TeV) from the tail region suggests that G106.3+2.7 is a PeVatron candidate. We present a comprehensive multiwavelength study of the Boomerang PWN (100'' around PSR J2229+6114) using archival radio and Chandra data obtained two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi-LAT and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with Γ = 1.52 ± 0.06 up to 20 keV. Contrary to the previous radio study by Kothes et al., we prefer a much lower PWN B-field (B ∼ 3 μG) and larger distance (d ∼ 8 kpc) based on (1) the nonvarying X-ray flux over the last two decades, (2) the energy-dependent X-ray size of the PWN resulting from synchrotron burn-off, and (3) the multiwavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock ∼1000 yr ago. In this case, the head region should be formed by GeV–TeV electrons injected earlier by the pulsar propagating into the low-density environment.
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    A VERITAS/Breakthrough Listen Search for Optical Technosignatures
    (IOP, 2023-09) Acharyya, A.; Adams, C. B.; Archer, A.; Bangale, P.; Batista, P.; Benbow, W.; Brill, A.; Capasso, M.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Foote, G. M.; Fortson, L.; Furniss, A.; Griffin, S.; Hanlon, W.; Hanna, D.; Hervet, O.; Hinrichs, C. E.; Hoang, J.; Holder, J.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kherlakian, M.; Kieda, D.; Kleiner, T. K.; Korzoun, N.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; McGrath, C. E.; Millard, M. J.; Miller, H. R.; Millis, J.; Mooney, C. L.; Moriarty, P.; Mukherjee, R.; O'Brien, S.; Ong, R. A.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Ryan, J. L.; Sadeh, I.; Saha, L.; Santander, M.; Sembroski, G. H.; Shang, R.; Tak, D.; Talluri, A. K.; Tucci, J. V.; Vazquez, N.; Williams, D. A.; Wong, S. L.; Woo, J.; VERITAS Collaboration; DeBoer, D.; Isaacson, H.; de Pater, I.; Price, D. C.; Siemion, A.; Physics, School of Science
    The Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for "technosignatures": artificial transmitters of extraterrestrial origin from beyond our solar system. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) Collaboration joined this program in 2018 and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds in duration detectable over interstellar distances. We report here on the analysis and results of dedicated VERITAS observations of Breakthrough Listen targets conducted in 2019 and 2020 and of archival VERITAS data collected since 2012. Thirty hours of dedicated observations of 136 targets and 249 archival observations of 140 targets were analyzed and did not reveal any signals consistent with a technosignature. The results are used to place limits on the fraction of stars hosting transmitting civilizations. We also discuss the minimum pulse sensitivity of our observations and present VERITAS observations of CALIOP: a space-based pulsed laser on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations. The detection of these pulses with VERITAS, using the analysis techniques developed for our technosignature search, allows a test of our analysis efficiency and serves as an important proof of principle.
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    Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A
    (IOP, 2023-09) Acharyya, A.; Adams, C. B.; Archer, A.; Bangale, P.; Bartkoske, J. T.; Batista, P.; Benbow, W.; Brill, A.; Buckley, J. H.; Christiansen, J. L.; Chromey, A. J.; Errando, M.; Falcone, A.; Feng, Q.; Foote, G. M.; Fortson, L.; Furniss, A.; Gallagher, G.; Hanlon, W.; Hanna, D.; Hervet, O.; Hinrichs, C. E.; Hoang, J.; Holder, J.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kherlakian, M.; Kieda, D.; Kleiner, T. K.; Korzoun, N.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; McGrath, C. E; Millard, M. J.; Millis, J.; Mooney, C. L.; Moriarty, P.; Mukherjee, R.; O’Brien, S.; Ong, R. A.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Sadeh, I.; Sadun, A. C.; Saha, L.; Santander, M.; Sembroski, G. H.; Shang, R.; Splettstoesser, M.; Talluri, A. Kaushik; Tucci, J. V.; Vassiliev, V. V.; Weinstein, A.; Williams, D. A.; Wong, S. L.; Woo, J.; The VERITAS Collaboration; Aharonian, F.; Aschersleben, J.; Backes, M.; Martins, V. Barbosa; Batzofin, R.; Becherini, Y.; Berge, D.; Bernlöhr, K.; Bi, B.; Böttcher, M.; Boisson, C.; Bolmont, J.; De Bony De Lavergne, M.; Borowska, J.; Bouyahiaoui, M.; Bradascio, F.; Breuhaus, M.; Brose, R.; Brun, F.; Bruno, B.; Bulik, T.; Burger-Scheidlin, C.; Caroff, S.; Casanova, S.; Cecil, R.; Celic, J.; Cerruti, M.; Chand, T.; Chandra, S.; Chen, A.; Chibueze, J.; Chibueze, O.; Cotter, G.; Dai, S.; Mbarubucyeye, J. Damascene; Djannati-Ataï, A.; Dmytriiev, A.; Doroshenko, V.; Einecke, S.; Ernenwein, J.-P.; De Clairfontaine, G. Fichet; Filipovic, M.; Fontaine, G.; Füßling, M.; Funk, S.; Gabici, S.; Ghafourizadeh, S.; Giavitto, G.; Glawion, D.; Glicenstein, J. F.; Goswami, P.; Grolleron, G.; Haerer, L.; Hinton, J. A.; Holch, T. L.; Holler, M.; Horns, D.; Jamrozy, M.; Jankowsky, F.; Joshi, V.; Jung-Richardt, I.; Kasai, E.; Katarzyński, K.; Khatoon, R.; Khélifi, B.; Klepser, S.; Kluźniak, W.; Kosack, K.; Kostunin, D.; Lang, R. G.; Le Stum, S.; Lemière, A.; Lenain, J.-P.; Leuschner, F.; Lohse, T.; Luashvili, A.; Lypova, I.; Mackey, J.; Malyshev, D.; Marandon, V.; Marchegiani, P.; Marcowith, A.; Martí-Devesa, G.; Marx, R.; Mitchell, A.; Moderski, R.; Mohrmann, L.; Montanari, A.; Moulin, E.; Murach, T.; Nakashima, K.; Niemiec, J.; Noel, A. Priyana; O’Brien, P.; Olivera-Nieto, L.; De Ona Wilhelmi, E.; Ostrowski, M.; Panny, S.; Panter, M.; Peron, G.; Prokhorov, D. A.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Reichherzer, P.; Reimer, A.; Reimer, O.; Ren, H.; Renaud, M.; Rieger, F.; Rudak, B.; Ruiz-Velasco, E.; Sahakian, V.; Santangelo, A.; Sasaki, M.; Schäfer, J.; Schüssler, F.; Schutte, H. M.; Schwanke, U.; Shapopi, J. N. S.; Specovius, A.; Spencer, S.; Stawarz, Ł.; Steenkamp, R.; Steinmassl, S.; Sushch, I.; Suzuki, H.; Takahashi, T.; Tanaka, T.; Terrier, R.; Van Eldik, C.; Vecchi, M.; Veh, J.; Venter, C.; Vink, J.; White, R.; Wierzcholska, A.; Wong, Yu Wun; Zacharias, M.; Zargaryan, D.; Zdziarski, A. A.; Zech, A.; Zouari, S.; Żywucka, N.; The H.E.S.S. Collaboration; Mori, K.; Physics, School of Science
    We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2fdg2 away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on 2021 December 8. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV γ-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ray flux. The X-ray data from Swift-XRT and NuSTAR characterize the transition between the low-energy and high-energy components of the broadband spectral energy distribution (SED), and the γ-ray data from Fermi-LAT, VERITAS, and H.E.S.S. require a spectral cutoff near 100 GeV. Both the X-ray and γ-ray measurements provide strong constraints on the leptonic and hadronic models. We analytically explore a synchrotron self-Compton model, an external Compton model, and a lepto-hadronic model. Models that are entirely based on internal photon fields face serious difficulties in matching the observed SED. The existence of an external photon field in the source would instead explain the observed γ-ray spectral cutoff in both the leptonic and lepto-hadronic models and allow a proton jet power that marginally agrees with the Eddington limit in the lepto-hadronic model. We show a numerical lepto-hadronic model with external target photons that reproduces the observed SED and is reasonably consistent with the neutrino event despite requiring a high jet power.
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    Multiwavelength Observations of the Blazar VER J0521+211 during an Elevated TeV Gamma-Ray State
    (IOP, 2022-06-27) Adams, C. B.; Batista, P.; Benbow, W.; Brill, A.; Brose , R.; Buckley, J. H.; Capasso, M.; Christiansen, J. L.; Errando, M.; Feng, Q.; Finley, J. P.; Foote, G. M.; Fortson, L.; Furniss, A.; Gallagher, G.; Gent, A.; Giuri, C.; Hanlon, W. F.; Hanna, D.; Hassan, T.; Hervet, O.; Holder, J.; Hona, B.; Hughes, G.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kieda, D.; Kleiner, T. K.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nievas-Rosillo, M.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Patel, S.; Patel, S. R.; Pfrang, K.; Pohl, M.; Prado, R. R.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Ryan, J. L.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shang, R.; Stevenson, B.; Tucci, J. V.; Vassiliev, V. V.; Wakely, S. P.; Weinstein, A.; Wells, R. M.; Williams, D. A.; Williamson, T. J.; (The VERITAS Collaboration); Acciari, V. A.; Aniello, T.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Arcaro, C.; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bökenkamp, H.; Bonnoli, G.; Bošnjak, Ž.; Burelli, I.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; Da Vela, P.; Dazzi, F.; De Angelis , A.; De Lotto, B.; Del Popolo, A.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Di Pierro, F.; Di Venere, L.; Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fariña, L.; Fattorini, A.; Font, L.; Fruck, C.; Fukami, S.; Fukazawa, Y.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Heckmann, L.; Herrera, J.; Hrupec, D.; Hütten, M.; Inada, T.; Iotov, R.; Ishio, K.; Iwamura, Y.; Jiménez Martínez, I.; Jormanainen, J.; Jouvin, L.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Linhoff, L.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Lorini, A.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Mariotti, M.; Martínez, M.; Mas Aguilar, A.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Mondal, H. A.; Moralejo, A.; Morcuenda, D.; Moreno, V.; Nakamori, T.; Nanci, C.; Nava, L.; Neustroev, V.; Nievas Rosillo, M.; Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredas, J. M.; Pavletić, L.; Peñil, P.; Persic, M.; Pihet, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka , K.; Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schmuckermaier, F.; Schubert, J. L.; Schweizer , T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strišković, J.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Takeishi, R.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Viale, I.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Wunderlich, C.; Yamamoto, T.; Zarić, D.; (The MAGIC Collaboration),; Physics, School of Science
    We report on a long-lasting, elevated gamma-ray flux state from VER J0521+211 observed by VERITAS, MAGIC, and Fermi-LAT in 2013 and 2014. The peak integral flux above 200 GeV measured with the nightly binned light curve is (8.8 ± 0.4) × 10−7 photons m−2 s−1, or ∼37% of the Crab Nebula flux. Multiwavelength observations from X-ray, UV, and optical instruments are also presented. A moderate correlation between the X-ray and TeV gamma-ray fluxes was observed, and the X-ray spectrum appeared harder when the flux was higher. Using the gamma-ray spectrum and four models of the extragalactic background light (EBL), a conservative 95% confidence upper limit on the redshift of the source was found to be z ≤ 0.31. Unlike the gamma-ray and X-ray bands, the optical flux did not increase significantly during the studied period compared to the archival low-state flux. The spectral variability from optical to X-ray bands suggests that the synchrotron peak of the spectral energy distribution (SED) may become broader during flaring states, which can be adequately described with a one-zone synchrotron self-Compton model varying the high-energy end of the underlying particle spectrum. The synchrotron peak frequency of the SED and the radio morphology of the jet from the MOJAVE program are consistent with the source being an intermediate-frequency-peaked BL Lac object.
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    VERITAS and Fermi-LAT Constraints on the Gamma-Ray Emission from Superluminous Supernovae SN2015bn and SN2017egm
    (IOP, 2023) Acharyya, A.; Adams, C. B.; Bangale, P.; Benbow, W.; Buckley, J. H.; Capasso, M.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Foote, G. M.; Fortson, L.; Furniss, A.; Gallagher, G.; Gent, A.; Hanlon, W. F.; Hervet, O.; Holder, J.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kherlakian, M.; Kieda, D.; Kleiner, T. K.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; McGrath, C. E.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nievas-Rosillo, M.; O'Brien, S.; Ong, R. A.; Patel, S. R.; Pfrang, K.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Ryan, J. L.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shang, R.; Splettstoesser, M.; Tak, D.; Tucci, J. V.; Weinstein, A.; Williams, D. A.; VERITAS collaboration; Metzger, B. D.; Nicholl, M.; Vurm, I.; Physics, School of Science
    Superluminous supernovae (SLSNe) are a rare class of stellar explosions with luminosities ∼ 10–100 times greater than ordinary core-collapse supernovae. One popular model to explain the enhanced optical output of hydrogen-poor (Type I) SLSNe invokes energy injection from a rapidly spinning magnetar. A prediction in this case is that high-energy gamma-rays, generated in the wind nebula of the magnetar, could escape through the expanding supernova ejecta at late times (months or more after optical peak). This paper presents a search for gamma-ray emission in the broad energy band from 100 MeV to 30 TeV from two Type I SLSNe, SN2015bn, and SN2017egm, using observations from Fermi-LAT and VERITAS. Although no gamma-ray emission was detected from either source, the derived upper limits approach the putative magnetar's spin-down luminosity. Prospects are explored for detecting very-high-energy (VHE; 100 GeV–100 TeV) emission from SLSNe-I with existing and planned facilities such as VERITAS and CTA.
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    VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations
    (IOP, 2023-06) Acharyya, A.; Adams, C. B.; Archer, A.; Bangale, P.; Benbow, W.; Brill, A.; Christiansen, J. L.; Chromey, A. J.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Foote, G. M.; Fortson, L.; Furniss, A.; Gallagher, G.; Hanlon, W.; Hanna, D.; Hervet, O.; Hinrichs, C. E.; Hoang, J.; Holder, J.; Jin, W.; Johnson, M. N.; Kaaret, P.; Kertzman, M.; Kieda, D.; Kleiner, T. K.; Korzoun, N.; Krennrich, F.; Lang, M. J.; Lundy, M.; Maier, G.; McGrath, C. E.; Millard, M. J.; Millis, J.; Mooney, C. L.; Moriarty, P.; Mukherjee, R.; O'Brien, S.; Ong, R. A.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Sadeh, I.; Sadun, A. C.; Saha, L.; Santander, M.; Sembroski, G. H.; Shang, R.; Splettstoesser, M.; Talluri, A. K.; Tucci, J. V.; Vassiliev, V. V.; Williams, D. A.; Wong, S. L.; (The VERITAS Collaboration); Hovatta, Talvikki; Jorstad, Svetlana G.; Kiehlmann, Sebastian; Lähteenmäki, Anne; Liodakis, Ioannis; Marscher, Alan P.; Max-Moerbeck, Walter; Readhead, Anthony C. S.; Reeves, Rodrigo; Smith, Paul S.; Tornikoski, Merja; Physics, School of Science
    We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13σ detection with a differential photon spectral index, Γ = 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of τobs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.