THE FIRST FERMI MULTIFREQUENCY CAMPAIGN ON BL LACERTAE: CHARACTERIZING THE LOW-ACTIVITY STATE OF THE EPONYMOUS BLAZAR

Abdo AA, Ackermann M, Ajello M, Antolini E, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Cannon A, Caraveo PA, Carrigan S, Casandjian JM, Cecchi C, Celik O, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Costamante L, Cutini S, Dermer CD, De Palma F, Donato D, Do Couto E Silva E, Drell PS, Dubois R, Escande L, Favuzzi C, Fegan SJ, Finke J, Focke WB, Fortin P, Frailis M, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Guiriec S, Hadasch D, Hayashida M, Hays E, Hughes RE, Itoh R, Johannesson G, Johnson AS, Johnson WN, Kamae T, Katagiri H, Kataoka J, Knoedlseder J, Kuss MW, Lande J, Larsson S, Latronico L, Lee SH, Garde ML, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Makeev A, Mazziotta MN, Mcenery JE, Mehault J, Michelson PF, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Naumann-Godo M, Nishino S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Raino S, Rando R, Razzano M, Reimer A, Reimer O, Ritz S, Roth M, Sadrozinski HFW, Sanchez D, Sander A, Schinzel FK, Sgro C, Siskind EJ, Smith PD, Sokolovsky KV, Spandre G, Spinelli P, Strickman MS, Suson DJ, Takahashi HH, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Uehara T, Usher TL, Vandenbroucke J, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wallace E, Wang P, Winer BL, Wood KS, Yang Z, Ylinen T, Ziegler M, Berdyugin A, Boettcher M, Carraminana A, Carrasco L, De La Fuente E, Diltz C, Hovatta T, Kadenius V, Kovalev YY, Lahteenmaki A, Lindfors E, Marscher AP, Nilsson K, Pereira D, Reinthal R, Roustazadeh P, Savolainen T, Sillanpaa A, Takalo LO, Tornikoski M (2011)

Publication Type: Journal article

Publication year: 2011

Journal

Book Volume: 730

Journal Issue: 2

DOI: 10.1088/0004-637X/730/2/101

Abstract

We report on observations of BL Lacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BL Lac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Metsahovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BL Lac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.

Authors with CRIS profile

Involved external institutions

U.S. Naval Research Laboratory United States (USA) (US) Stanford University United States (USA) (US) Università degli Studi di Perugia Italy (IT) National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) Italy (IT) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot France (FR) Politecnico di Bari Italy (IT) École Polytechnique - Université Paris-Saclay France (FR) Institut d'Estudis Espacials de Catalunya (IEEC) Spain (ES) National Aeronautics and Space Administration (NASA) United States (USA) (US) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) Italy (IT) University of Padua / Universita degli Studi di Padova Italy (IT) University of Montpellier / Université Montpellier France (FR) Stockholm University / Stockholms universitet Sweden (SE) Université Bordeaux 1, Sciences et Technologies France (FR) Italian Space Agency / Agenzia Spaziale Italiana (ASI) Italy (IT) University of Udine / Università degli Studi di Udine Italy (IT) Université Toulouse III - Paul Sabatier France (FR) Hiroshima University / 広島大学 Japan (JP) Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) University of Washington United States (USA) (US) Ohio State University United States (USA) (US) Ohio University United States (USA) (US) Universidad de Guadalajara (UDEG) Mexico (MX) University of Alabama in Huntsville (UAH) United States (USA) (US) University of Iceland (UI) / Háskóli Íslands Iceland (IS) Waseda University / 早稲田大学 Japan (JP) University of Denver United States (USA) (US) Japan Aerospace eXploration Agency (JAXA) Japan (JP) Max-Planck-Institut für extraterrestrische Physik (MPE) / Max Planck Institute for Extraterrestrial Physics Germany (DE) University of California Santa Cruz United States (USA) (US) NYCB Real-Time Computing, Inc. United States (USA) (US) Purdue University Northwest / Purdue University Calumet United States (USA) (US) AlbaNova University Centre / Kungliga Tekniska Högskolan AlbaNova Universitetscentrum Sweden (SE) University of Turku / Turun yliopisto Finland (FI) Aalto University Espoo Finland (FI) Boston University United States (USA) (US)

How to cite

APA:

Abdo, A.A., Ackermann, M., Ajello, M., Antolini, E., Baldini, L., Ballet, J.,... Tornikoski, M. (2011). THE FIRST FERMI MULTIFREQUENCY CAMPAIGN ON BL LACERTAE: CHARACTERIZING THE LOW-ACTIVITY STATE OF THE EPONYMOUS BLAZAR. Astrophysical Journal, 730(2). https://doi.org/10.1088/0004-637X/730/2/101

MLA:

Abdo, A. A., et al. "THE FIRST FERMI MULTIFREQUENCY CAMPAIGN ON BL LACERTAE: CHARACTERIZING THE LOW-ACTIVITY STATE OF THE EPONYMOUS BLAZAR." Astrophysical Journal 730.2 (2011).

BibTeX: Download