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Extreme HBL behavior of Markarian 501 during 2012

Ahnen, M. L. and Readhead, A. C. S. (2018) Extreme HBL behavior of Markarian 501 during 2012. Astronomy and Astrophysics, 620 . Art. No. A181. ISSN 0004-6361. https://resolver.caltech.edu/CaltechAUTHORS:20190107-111729912

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Abstract

Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios. Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Results. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of ∼0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was ∼3 CU, and the peak of the high-energy spectral component was found to be at ∼2 TeV. Both the X-ray and VHE gamma-ray spectral slopes were measured to be extremely hard, with spectral indices < 2 during most of the observing campaign, regardless of the X-ray and VHE flux. This study reports the hardest Mrk 501 VHE spectra measured to date. The fractional variability was found to increase with energy, with the highest variability occurring at VHE. Using the complete data set, we found correlation between the X-ray and VHE bands; however, if the June 9 flare is excluded, the correlation disappears (significance < 3σ) despite the existence of substantial variability in the X-ray and VHE bands throughout the campaign. Conclusions. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency-peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The data set acquired shows that the broadband spectral energy distribution (SED) of Mrk 501, and its transient evolution, is very complex, requiring, within the framework of synchrotron self-Compton (SSC) models, various emission regions for a satisfactory description. Nevertheless the one-zone SSC scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behavior seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1051/0004-6361/201833704DOIArticle
https://arxiv.org/abs/1808.04300arXivDiscussion Paper
ORCID:
AuthorORCID
Readhead, A. C. S.0000-0001-9152-961X
Additional Information:© 2018 ESO. Article published by EDP Sciences. Received 23 June 2018; Accepted 3 August 2018; Published online 14 December 2018. The MAGIC collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662-C2-2-P, CSD2009-00064), and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2012-0234 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project 09/176 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ. VERITAS is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Smithsonian Institution, and by NSERC in Canada. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. This work performed in part under DOE Contract DE-AC02-76SF00515. The St.Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. The Abastumani team acknowledges financial support by the by Shota Rustaveli NSF under contract FR/577/6-320/13. This research was partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grants DN 08-1/2016 and DN 18-13/2017. The Skinakas Observatory is a collaborative project of the University of Crete, the Foundation for Research and Technology –Hellas, and the Max-Planck-Institut für Extraterrestrische Physik. We would like to thank the American Association of Variable Star Observers (AAVSO) for making some of the observations used in this study. M.I.C acknowledges financial support by PRIN-SKA-CTA-INAF 2016. This article is partly based on observations made with the IAC80 telescope operated on the island of Tenerife by the Instituto de Astrofisica de Canarias in the Spanish Observatorio del Teide. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. This work is partly based upon observations carried out at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir (OAN-SPM), Baja California, Mexico. The Steward Observatory spectropolarimetric monitoring program is supported by Fermi Guest Investigator grants NNX09AU10G and NNX12AO93G. The OVRO 40-m monitoring program is supported in part by NASA grants NNX08AW31G, NNX11A043G and NNX14AQ89G, and NSF grants AST-0808050 and AST-1109911. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University, Finland.
Group:Astronomy Department
Funders:
Funding AgencyGrant Number
Bundesministerium für Bildung und Forschung (BMBF)UNSPECIFIED
Max Planck SocietyUNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Swiss National Fund (SNF)UNSPECIFIED
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2015-69818-P
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2012-36668
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2015-68378-P
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2015-69210-C6-2-R
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2015-69210-C6-4-R
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2015-69210-C6-6-R
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2015-71042-P
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2016-76012-C3-1-P
Ministerio de Economía, Industria y Competitividad (MINECO)ESP2015-71662-C2-2-P
MultiDarkCSD2009-00064
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Centro de Excelencia Severo OchoaSEV-2012-0234
Centro de Excelencia Severo OchoaSEV-2015-0548
Ministerio de Economía, Industria y Competitividad (MINECO)MDM-2014-0369
Croatian Science Foundation (HrZZ)09/176
University of Rijeka13.12.1.3.02
Deutsche Forschungsgemeinschaft (DFG)SFB823/C4
Deutsche Forschungsgemeinschaft (DFG)SFB876/C3
National Science Centre (Poland)UMO-2016/22/M/ST9/00382
Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC)UNSPECIFIED
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNSPECIFIED
Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)UNSPECIFIED
Department of Energy (DOE)DE-AC02-76SF00515
Smithsonian InstitutionUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Russian Science Foundation17-12-01029
Shota Rustaveli National Science FoundationFR/577/6-320/13
National Science Fund (Bulgaria)UNSPECIFIED
Ministry of Education and Science (Bulgaria)DN 08-1/2016
Ministry of Education and Science (Bulgaria)DN 18-13/2017
PRIN-SKA-CTA-INAF 2016UNSPECIFIED
NASANNX09AU10G
NASANNX12AO93G
NASANNX08AW31G
NASANNX11A043G
NASANNX14AQ89G
NSFAST-0808050
NSFAST-1109911
Subject Keywords:astroparticle physics – acceleration of particles – radiation mechanisms: non-thermal – BL Lacertae objects: general – BL Lacertae objects: individual: Mrk501
Record Number:CaltechAUTHORS:20190107-111729912
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190107-111729912
Official Citation:Extreme HBL behavior of Markarian 501 during 2012. M. L. Ahnen, et. al. A&A, 620 (2018) A181. DOI: https://doi.org/10.1051/0004-6361/201833704
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92116
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:07 Jan 2019 20:57
Last Modified:03 Oct 2019 20:41

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