A Caltech Library Service

The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies

Abeysekara, A. U. and Readhead, A. C. S. (2020) The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies. Astrophysical Journal, 890 (2). Art. No. 97. ISSN 1538-4357.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ~27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsähovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ~25–55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ≳ 33) and the size of the emission region (δ⁻¹R_B ≲ 3.8×10¹³cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux–flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Readhead, A. C. S.0000-0001-9152-961X
Additional Information:© 2020 The American Astronomical Society. Received 2018 December 18; revised 2019 December 21; accepted 2019 December 23; published 2020 February 17. This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Smithsonian Institution, and NSERC in Canada. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy's Office of Science, and the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under contract No. DE-AC02-05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and the collaborating institutions in the construction and operation of the instrument. 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, FPA201790566REDC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, and the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia "Severo Ochoa" SEV-2016-0588 and SEV-2015-0548 and Unidad de Excelencia "María de Maeztu" MDM-2014-0369, the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782, the University of Rijeka Project, the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382, and the Brazilian MCTIC, CNPq, and FAPERJ. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University, Finland, and the OVRO 40 m monitoring program, which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911. The UMRAO data were obtained through NSF grant AST 0607523 and NASA Fermi GI award NNX09AU16G. The St. Petersburg University team acknowledges support from Russian RFBR foundation, grant 12-02-00452. The Abastumani Observatory team acknowledges financial support by the Shota Rustaveli National Science Foundation through project FR/577/6-320/13. The Steward Observatory data were obtained under Fermi Guest Investigator Program grant NNX09AU10G. The research at Boston University is supported by NASA grant 80NSSC17K0649 and NSF grant AST-1615796. Software. VEGAS (Cogan 2008), Event Display (Daniel 2008), MARS (Moralejo et al. 2009), Fermi Science Tools81, HEASoft (FTOOLS+XANADU; HEASARC 2014), REX,85 Xspec (Arnaud 1996), emcee (Foreman-Mackey et al. 2013).
Group:Astronomy Department
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-05CH11231
Smithsonian InstitutionUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Bundesministerium für Bildung und Forschung (BMBF)UNSPECIFIED
Max Planck GesellschaftUNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Swiss National Fund (SNF)UNSPECIFIED
European Regional Development Funds (ERDF)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
Ministerio de Economía, Industria y Competitividad (MINECO)FPA201790566REDC
Department of Atomic Energy (India)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Ministry of Education and Science (Bulgaria)DO1-153/28.08.2018
Centro de Excelencia Severo OchoaSEV-2016-0588
Centro de Excelencia Severo OchoaSEV-2015-0548
Ministerio de Economía, Industria y Competitividad (MINECO)MDM-2014-0369
Croatian Science FoundationIP-2016-06-9782
University of Rijeka13.
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
NSFAST 0607523
Russian Foundation for Basic Research12-02-00452
Shota Rustaveli National Science FoundationFR/577/6-320/13
Subject Keywords:BL Lacertae objects; Blazars; High energy astrophysics; Relativistic jets; Markarian galaxies; Gamma-ray astronomy; Time domain astronomy
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: BL Lacertae objects (158); Blazars (164); High energy astrophysics (739); Relativistic jets (1390); Markarian galaxies (1006); Gamma-ray astronomy (628); Time domain astronomy (2109)
Record Number:CaltechAUTHORS:20200218-103513658
Persistent URL:
Official Citation:A. U. Abeysekara et al 2020 ApJ 890 97
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101319
Deposited By: Tony Diaz
Deposited On:18 Feb 2020 20:09
Last Modified:18 Feb 2020 20:09

Repository Staff Only: item control page