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

被引：54

作者：

Abdo, A. A. ^{[2
,3
]}

Ackermann, M. ^{[4
,5
]}

Ajello, M. ^{[4
,5
]}

Antolini, E. ^{[1
,6
]}

Baldini, L. ^{[7
]}

Ballet, J. ^{[8
]}

Barbiellini, G. ^{[9
,10
]}

Bastieri, D. ^{[11
,12
]}

Bechtol, K. ^{[4
,5
]}

Bellazzini, R. ^{[7
]}

Berenji, B. ^{[4
,5
]}

Blandford, R. D. ^{[4
,5
]}

Bonamente, E. ^{[1
,6
]}

Borgland, A. W. ^{[4
,5
]}

Bregeon, J. ^{[7
]}

Brez, A. ^{[7
]}

Brigida, M. ^{[13
,14
]}

Bruel, P. ^{[15
]}

Buehler, R. ^{[4
,5
]}

Buson, S. ^{[11
,12
]}

Caliandro, G. A. ^{[16
]}

Cameron, R. A. ^{[4
,5
]}

Cannon, A. ^{[17
,18
]}

Caraveo, P. A. ^{[19
]}

Carrigan, S. ^{[12
]}

Casandjian, J. M. ^{[8
]}

Cecchi, C. ^{[1
,6
]}

Celik, Oe ^{[17
,20
,21
,22
,23
]}

Charles, E. ^{[4
,5
]}

Chekhtman, A. ^{[2
,24
]}

Cheung, C. C. ^{[2
,3
]}

Chiang, J. ^{[4
,5
]}

Ciprini, S. ^{[1
]}

Claus, R. ^{[4
,5
]}

Cohen-Tanugi, J. ^{[25
]}

Conrad, J. ^{[26
,27
]}

Costamante, L. ^{[4
,5
]}

Cutini, S. ^{[28
]}

Dermer, C. D. ^{[2
,43
]}

de Palma, F. ^{[13
,14
]}

Donato, D. ^{[20
,21
,29
,30
]}

do Couto e Silva, E. ^{[4
,5
]}

Drell, P. S. ^{[4
,5
]}

Dubois, R. ^{[4
,5
]}

Escande, L. ^{[31
]}

Favuzzi, C. ^{[13
,14
]}

Fegan, S. J. ^{[15
]}

Finke, J. ^{[2
,3
]}

Focke, W. B. ^{[4
,5
]}

Fortin, P. ^{[15
]}

机构：

[1] Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy

[2] USN, Div Space Sci, Res Lab, Washington, DC 20375 USA

[3] Natl Acad Sci, Natl Res Council Res Associate, Washington, DC 20001 USA

[4] Stanford Univ, Dept Phys, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA

[5] Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA

[6] Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy

[7] Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy

[8] Univ Paris Diderot, CEA Saclay, Serv Astrophys, Lab AIM,CEA IRFU,CNRS, F-91191 Gif Sur Yvette, France

[9] Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy

[10] Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy

[11] Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy

[12] Univ Padua, Dipartimento Fis G Galilei, I-35131 Padua, Italy

[13] Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy

[14] Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy

[15] Ecole Polytech, CNRS, IN2P3, Lab Leprince Ringuet, F-91128 Palaiseau, France

[16] Inst Ciencies Espai IEEC CSIC, Barcelona 08193, Spain

[17] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA

[18] Univ Coll Dublin, Dublin 4, Ireland

[19] INAF Ist Astrofis Spaziale & Fis Cosm, I-20133 Milan, Italy

[20] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA

[21] CRESST, Greenbelt, MD 20771 USA

[22] Univ Maryland Baltimore Cty, Dept Phys, Baltimore, MD 21250 USA

[23] Univ Maryland Baltimore Cty, Ctr Space Sci & Technol, Baltimore, MD 21250 USA

[24] George Mason Univ, Fairfax, VA 22030 USA

[25] Univ Montpellier 2, Lab Phys Theor & Astroparticules, CNRS, IN2P3, Montpellier, France

[26] Stockholm Univ, Dept Phys, SE-10691 Stockholm, Sweden

[27] Oskar Klein Ctr Cosmoparticle Phys, SE-10691 Stockholm, Sweden

[28] Agenzia Spaziale Italiana ASI Sci Data Ctr, I-00044 Rome, Italy

[29] Univ Maryland, Dept Phys, College Pk, MD 20742 USA

[30] Univ Maryland, Dept Astron, College Pk, MD 20742 USA

[31] Univ Bordeaux 1, CNRS, IN2P3, Ctr Etud Nucl Bordeaux Gradignan, F-33175 Gradignan, France

[32] Univ Udine, Dipartimento Fis, I-33100 Udine, Italy

[33] Ist Nazl Fis Nucl, Sez Trieste, Grp Collegato Udine, I-33100 Udine, Italy

[34] Ist Nazl Astrofis, Osservatorio Astron Trieste, I-34143 Trieste, Italy

[35] Hiroshima Univ, Dept Phys Sci, Hiroshima 7398526, Japan

[36] INAF Ist Radioastron, I-40129 Bologna, Italy

[37] Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA

[38] Ohio State Univ, Dept Phys, Ctr Cosmol & Astro Particle Phys, Columbus, OH 43210 USA

[39] Univ Iceland, Inst Sci, IS-107 Reykjavik, Iceland

[40] Waseda Univ, Res Inst Sci & Engn, Shinjuku Ku, Tokyo 1698555, Japan

[41] CNRS UPS, Ctr Etud Spatiale Rayonnements, F-30128 Toulouse 4, France

[42] Stockholm Univ, Dept Astron, SE-10691 Stockholm, Sweden

[43] Ist Nazl Fis Nucl, Sez Roma Tor Vergata, I-00133 Rome, Italy

[44] Univ Denver, Dept Phys & Astron, Denver, CO 80208 USA

[45] Hiroshima Univ, Hiroshima Astrophys Sci Ctr, Hiroshima 7398526, Japan

[46] JAXA, Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan

[47] Max Planck Inst Extraterr Phys, D-85748 Garching, Germany

[48] Leopold Franzens Univ Innsbruck, Inst Astro & Teilchenphys, A-6020 Innsbruck, Austria

[49] Leopold Franzens Univ Innsbruck, Inst Theoret Phys, A-6020 Innsbruck, Austria

[50] Univ Calif Santa Cruz, Dept Phys, Santa Cruz Inst Particle Phys, Santa Cruz, CA 95064 USA

来源：

ASTROPHYSICAL JOURNAL | 2011年 / 730卷 / 02期

基金：

美国国家科学基金会; 芬兰科学院;

关键词：

BL Lacertae objects: general; BL Lacertae objects: individual (BL Lacertae); galaxies: jets; gamma rays: galaxies; radiation mechanisms: non-thermal; X-rays: galaxies; LARGE-AREA TELESCOPE; SPECTRAL ENERGY-DISTRIBUTIONS; RAY LIGHT CURVES; GAMMA-RAY; MULTIWAVELENGTH OBSERVATIONS; WEBT CAMPAIGNS; VARIABILITY; QUASARS; FLARE; LAC;

D O I：

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

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

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.

引用

页数：14

共 70 条

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