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
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.
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