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) × 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) × 10–7 photons m–2 s–1 above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 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 τ = 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.

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

BALDINI, LUCA;RAZZANO, MASSIMILIANO;TINIVELLA, MARCO;
2014

Abstract

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) × 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) × 10–7 photons m–2 s–1 above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 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 τ = 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.
S., Archambault; T., Aune; B., Behera; M., Beilicke; W., Benbow; K., Berger; R., Bird; J., Biteau; V., Bugaev; K., Byrum; J. V., Cardenzana; M., Cerruti; X., Chen; L., Ciupik; M. P., Connolly; W., Cui; J., Dumm; M., Errando; A., Falcone; S., Federici; Q., Feng; J. P., Finley; H., Fleischhack; L., Fortson; A., Furniss; N., Galante; G. H., Gillanders; S., Griffin; S. T., Griffiths; J., Grube; G., Gyuk; D., Hanna; J., Holder; G., Hughes; T. B., Humensky; C. A., Johnson; P., Kaaret; M., Kertzman; Y., Khassen; D., Kieda; H., Krawczynski; F., Krennrich; S., Kumar; M. J., Lang; A. S., Madhavan; G., Maier; A., Mccann; K., Meagher; P., Moriarty; R., Mukherjee; D., Nieto; A., O'Faol?in de Bhr?ithe; R. A., Ong; A. N., Otte; N., Park; M., Pohl; A., Popkow; H., Prokoph; J., Quinn; K., Ragan; J., Rajotte; L. C., Reyes; P. T., Reynolds; G. T., Richards; E., Roache; G. H., Sembroski; K., Shahinyan; D., Staszak; I., Telezhinsky; J. V., Tucci; J., Tyler; A., Varlotta; V. V., Vassiliev; S., Vincent; S. P., Wakely; A., Weinstein; R., Welsing; A., Wilhelm; D. A., Williams; M., Ackermann; M., Ajello; A., Albert; Baldini, Luca; D., Bastieri; R., Bellazzini; E., Bissaldi; J., Bregeon; R., Buehler; S., Buson; G. A., Caliandro; R. A., Cameron; P. A., Caraveo; E., Cavazzuti; E., Charles; J., Chiang; S., Ciprini; R., Claus; S., Cutini; F., D'Ammando; A., de Angelis; F., de Palma; C. D., Dermer; S. W., Digel; L., Di Venere; P. S., Drell; C., Favuzzi; A., Franckowiak; P., Fusco; F., Gargano; D., Gasparrini; N., Giglietto; F., Giordano; M., Giroletti; I. A., Grenier; S., Guiriec; T., Jogler; M., Kuss; S., Larsson; L., Latronico; F., Longo; F., Loparco; P., Lubrano; G. M., Madejski; M., Mayer; M. N., Mazziotta; P. F., Michelson; T., Mizuno; M. E., Monzani; A., Morselli; S., Murgia; E., Nuss; T., Ohsugi; J. F., Ormes; D., Paneque; J. S., Perkins; F., Piron; G., Pivato; S., Rain?; Razzano, Massimiliano; A., Reimer; O., Reimer; S., Ritz; M., Schaal; C., Sgr?; E. J., Siskind; P., Spinelli; H., Takahashi; L., Tibaldo; Tinivella, Marco; E., Troja; G., Vianello; M., Werner; M., Wood
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/504468
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