DEEP BROADBAND OBSERVATIONS OF THE DISTANT GAMMA-RAY BLAZAR PKS 1424+240

被引：39

作者：

Archambault, S. ^{[1
]}

Aune, T. ^{[2
]}

Behera, B. ^{[3
]}

Beilicke, M. ^{[4
]}

Benbow, W. ^{[5
]}

Berger, K. ^{[6
,7
]}

Bird, R. ^{[8
]}

Biteau, J. ^{[9
,10
]}

Bugaev, V. ^{[4
]}

Byrum, K. ^{[11
]}

Cardenzana, J. V. ^{[12
]}

Cerruti, M. ^{[5
]}

Chen, X. ^{[3
,13
]}

Ciupik, L. ^{[14
]}

Connolly, M. P. ^{[15
]}

Cui, W. ^{[16
]}

Dumm, J. ^{[17
]}

Errando, M. ^{[18
]}

Falcone, A. ^{[19
]}

Federici, S. ^{[3
,13
]}

Feng, Q. ^{[16
]}

Finley, J. P. ^{[16
]}

Fleischhack, H. ^{[3
]}

Fortson, L. ^{[17
]}

Furniss, A. ^{[31
]}

Galante, N. ^{[5
]}

Gillanders, G. H. ^{[15
]}

Griffin, S. ^{[1
]}

Griffiths, S. T. ^{[20
]}

Grube, J. ^{[14
]}

Gyuk, G. ^{[14
]}

Hanna, D. ^{[1
]}

Holder, J. ^{[6
,7
]}

Hughes, G. ^{[3
]}

Humensky, T. B. ^{[21
]}

Johnson, C. A. ^{[9
,10
]}

Kaaret, P. ^{[20
]}

Kertzman, M. ^{[22
]}

Khassen, Y. ^{[8
]}

Kieda, D. ^{[23
]}

Krawczynski, H. ^{[4
]}

Krennrich, F. ^{[12
]}

Kumar, S. ^{[6
,7
]}

Lang, M. J. ^{[15
]}

Madhavan, A. S. ^{[12
]}

Maier, G. ^{[3
]}

McCann, A. ^{[24
]}

Meagher, K. ^{[25
]}

Moriarty, P. ^{[26
,27
]}

Mukherjee, R. ^{[18
]}

机构：

[1] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada

[2] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA

[3] DESY, D-15738 Zeuthen, Germany

[4] Washington Univ, Dept Phys, St Louis, MO 63130 USA

[5] Harvard Smithsonian Ctr Astrophys, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA

[6] Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA

[7] Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA

[8] Univ Coll Dublin, Sch Phys, Dublin 4, Ireland

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

[10] Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA

[11] Argonne Natl Lab, Argonne, IL 60439 USA

[12] Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA

[13] Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany

[14] Adler Planetarium & Astron Museum, Dept Astron, Chicago, IL 60605 USA

[15] Natl Univ Ireland Galway, Sch Phys, Galway, Ireland

[16] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA

[17] Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA

[18] Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA

[19] Penn State Univ, Davey Lab 525, Dept Astron & Astrophys, University Pk, PA 16802 USA

[20] Stanford Univ, SLAC Natl Accelerator Lab, Kavli Inst Particle Astrophys & Cosmol, Stanford, CA 94305 USA

[21] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA

[22] Columbia Univ, Dept Phys, New York, NY 10027 USA

[23] Depauw Univ, Dept Phys & Astron, Greencastle, IN 46135 USA

[24] Univ Utah, Dept Phys & Astron, Salt Lake City, UT 84112 USA

[25] Univ Chicago, Kavli Inst Cosmol Phys, Chicago, IL 60637 USA

[26] Georgia Inst Technol, Sch Phys, Atlanta, GA 30332 USA

[27] Georgia Inst Technol, Ctr Relativist Astrophys, Atlanta, GA 30332 USA

[28] Galway Mayo Inst Technol, Dept Life & Phys Sci, Galway, Ireland

[29] Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA

[30] Calif Polytech State Univ San Luis Obispo, Dept Phys, San Luis Obispo, CA 94307 USA

[31] Cork Inst Technol, Dept Appl Phys & Instrumentat, Cork, Ireland

[32] DESY, D-15738 Zeuthen, Germany

[33] Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA

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

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

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

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

[38] Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy

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

[40] Univ Trieste, I-34127 Trieste, Italy

[41] Univ Montpellier 2, CNRS, IN2P3, Lab Univers & Particules Montpellier, Montpellier, France

[42] CIFS, I-10133 Turin, Italy

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

[44] Agenzia Spaziale Italiana, Sci Data Ctr, I-00133 Rome, Italy

[45] Osserv Astron Roma, Ist Nazl Astrofis, I-00040 Rome, Italy

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

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

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

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

[50] Politecn Bari, I-70126 Bari, Italy

来源：

ASTROPHYSICAL JOURNAL LETTERS | 2014年 / 785卷 / 01期

基金：

爱尔兰科学基金会; 美国国家科学基金会; 加拿大自然科学与工程研究理事会;

关键词：

BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation; gamma rays: galaxies; EXTRAGALACTIC BACKGROUND LIGHT; LARGE-AREA TELESCOPE; ENERGY COSMIC-RAY; SPECTRA; RADIATION; LIMITS;

D O I：

10.1088/2041-8205/785/1/L16

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z >= 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 +/- 0.3) x 10(-7) photons m(-2) s(-1) above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 +/- 0.08) x 10-7 photons m(-2) s(-1) above 120 GeV. The measured differential very high energy (VHE; E >= 100 GeV) spectral indices are Gamma = 3.8 +/- 0.3, 4.3 +/- 0.6 and 4.5 +/- 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than tau = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics.

引用

页数：8

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