Locating the γ-ray emitting region in the quasar 4C +01.28
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A4 Artikkeli konferenssijulkaisussa
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Date
2021
Department
Metsähovi Radio Observatory
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en
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Proceedings of Science, Volume 399
Abstract
Determining the location of γ-ray emission in blazar jets is a challenging task. Pinpointing the exact location of γ-ray production within a relativistic jet can place strong constraints on our understanding of high-energy astrophysics and astroparticle physics. We present a study of the radio- and γ-bright flat-spectrum radio quasar (FSRQ) 4C +01.28 (PKS B1055+018) in which we try to pinpoint the emission site of several prominent GeV flares. This source shows prominent high-amplitude broadband variability on time scales ranging from days to years. We combine high-resolution VLBI observations provided by the Boston University (BU) Blazar Monitoring Program and multi-band radio light curves over a period of around nine years. We can associate two bright and compact newly ejected jet components with bright flares observed by the Fermi/LAT γ-ray telescope and at various radio frequencies. A cross-correlation analysis reveals the radio light curves systematically lag behind the γ-rays. In combination with the jet kinematics as measured by the VLBA, we use these cross-correlations to constrain a model in which the flares become observable at a given frequency when a plasma component passes through the region at which the bulk energy dissipation takes place at that frequency. We derive a lower limit of the distance of the γ-ray emitting region in 4C +01.28 of several parsecs from the jet base, well beyond the expected extent of the broad-line region. This observational limit challenges blazar-emission models that rely on the broad-line region as a source of seed photons for inverse-Compton scattering.Description
Funding Information: F.R. and M.K. acknowledge support from Deutsche Forschungsgemeinschaft grant DFG KA3252/4-1. This study makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00001.CAL. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This study makes use of VLBA data from the VLBA-BU Blazar Monitoring Program (BEAM-ME and VLBA-BU-BLAZAR; http://www.bu.edu/blazars/BEAM-ME.html), funded by NASA through the Fermi Guest Investigator Program. The VLBA is an instrument of the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated by Associated Universities, Inc. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is fundedby the Smithsonian Institution and the Academia Sinica. Funding Information: F.R. and M.K. acknowledge support from Deutsche Forschungsgemeinschaft grant DFG KA3252/4-1. This study makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00001.CAL. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This study makes use of VLBA data from the VLBA-BU Blazar Monitoring Program (BEAM-ME and VLBA-BU-BLAZAR; http://www.bu.edu/blazars/BEAM-ME.html), funded by NASA through the Fermi Guest Investigator Program. The VLBA is an instrument of Funding Information: the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated by Associated Universities, Inc. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Publisher Copyright: © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).
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Citation
Rösch, F, Kadler, M, Ros, E, Gurwell, M, Hovatta, T, Kreter, M, MacDonald, N R & Readhead, A C S 2021, ' Locating the γ-ray emitting region in the quasar 4C +01.28 ', Proceedings of Science, vol. 399, 001 . https://doi.org/10.22323/1.399.0001
