FERMI LARGE AREA TELESCOPE DETECTION OF GRAVITATIONAL LENS DELAYED γ-RAY FLARES FROM BLAZAR B0218+357

Author/Creator ORCID

Date

2014-01-30

Department

Program

Citation of Original Publication

C. C. Cheung, S. Larsson, J. D. Scargle, M. A. Amin, R. D. Blandford, D. Bulmash, J. Chiang, S. Ciprini,R. H. D. Corbet, E. E. Falco, P. J. Marshall, D. L. Wood, M. Ajello, D. Bastieri, A. Chekhtman, F. D'Ammando, M. Giroletti, J. E. Grove, B. Lott, R. Ojha, M. Orienti, J. S. Perkins, M. Razzano, A. W. Smith, D. J. Thompson, K. S. Wood, FERMI LARGE AREA TELESCOPE DETECTION OF GRAVITATIONAL LENS DELAYED γ-RAY FLARES FROM BLAZAR B0218+357, The Astrophysical Journal, 2014, Volume 782, https://iopscience.iop.org/article/10.1088/2041-8205/782/2/L14

Rights

This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
Public Domain Mark 1.0
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law

Subjects

Abstract

Using data from the Fermi Large Area Telescope (LAT), we report the first clear γ-ray measurement of a delay between flares from the gravitationally lensed images of a blazar. The delay was detected in B0218+357, a known double-image lensed system, during a period of enhanced γ-ray activity with peak fluxes consistently observed to reach >20-50 × its previous average flux. An auto-correlation function analysis identified a delay in the γ-ray data of 11.46 ± 0.16 days (1σ) that is ~1 day greater than previous radio measurements. Considering that it is beyond the capabilities of the LAT to spatially resolve the two images, we nevertheless decomposed individual sequences of superposing γ-ray flares/delayed emissions. In three such ~8-10 day-long sequences within a ~4 month span, considering confusion due to overlapping flaring emission and flux measurement uncertainties, we found flux ratios consistent with ~1, thus systematically smaller than those from radio observations. During the first, best-defined flare, the delayed emission was detailed with a Fermi pointing, and we observed flux doubling timescales of ~3-6 hr implying as well extremely compact γ-ray emitting regions.