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Title: Fermi Large Area Telescope detection of gravitational lens delayed γ-ray flares from Blazar B0218+357

We report the first clear γ-ray measurement of a delay between flares from the gravitationally lensed images of a blazar, using data from the Fermi Large Area Telescope (LAT). We detected a delay 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.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [5] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ;  [12] ;  [13] ;  [14] ;  [15] ;  [15] ;  [1] ;  [16] ;  [17] more »;  [15] ;  [17] ;  [18] ;  [19] ;  [17] ;  [1] « less
  1. Naval Research Lab. (NRL), Washington, DC (United States). Space Science Division
  2. Stockholm Univ. (Sweden). Dept. of Physics and Dept. of Astronomy; Oskar Klein Centre for Cosmoparticle Physics, Stockholm (Sweden)
  3. NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States). Space Sciences Division
  4. Univ. of Cambridge (United Kingdom). Kavli Inst. for Cosmology and Inst. for Astronomy
  5. Stanford Univ. and SLAC National Accelerator Lab., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology
  6. Stanford Univ., CA (United States). Dept. of Physics
  7. Agenzia Spaziale Italiana (ASI) Science Data Center, Rome (Italy); National Inst. of Astrophysics- Astronomical Observatory of Rome (Italy)
  8. Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, MD (United States); Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States)
  9. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  10. Stanford Univ. and SLAC National Accelerator Lab., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology; Oxford Univ. (United Kingdom). Dept. of Physics
  11. Praxis Inc., Alexandria, VA (United States)
  12. Univ. of California, Berkeley, CA (United States). Space Sciences Lab.
  13. National Inst. of Nuclear Physics, Padova (Italy); Univ. of Padova (Italy). Dept. of Physics and Astronomy
  14. George Mason Univ., Fairfax, VA (United States). Center for Earth Observing and Space Research
  15. National Inst. for Astrophysics (INAF), Bologna (Italy). Inst. for Radio Astronomy
  16. Univ. of Bordeaux (France). Gradignan Bordeaux Center for Nuclear Research
  17. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  18. National Inst. of Nuclear Physics, Pisa (Italy)
  19. Univ. of Utah, Salt Lake City, UT (United States). Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 782; Journal Issue: 2; Journal ID: ISSN 2041-8205
Publisher:
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: active; gamma rays: galaxies; gravitational lensing: strong; quasars: individual (B0218+357)
OSTI Identifier:
1356535

Cheung, C. C., Larsson, S., Scargle, J. D., Amin, M. A., Blandford, R. D., Bulmash, D., Chiang, J., Ciprini, S., Corbet, R. H. D., Falco, E. E., Marshall, P. J., Wood, D. L., Ajello, M., Bastieri, D., Chekhtman, A., D'Ammando, F., Giroletti, M., Grove, J. E., Lott, B., Ojha, R., Orienti, M., Perkins, J. S., Razzano, M., Smith, A. W., Thompson, D. J., and Wood, K. S.. Fermi Large Area Telescope detection of gravitational lens delayed γ-ray flares from Blazar B0218+357. United States: N. p., Web. doi:10.1088/2041-8205/782/2/L14.
Cheung, C. C., Larsson, S., Scargle, J. D., Amin, M. A., Blandford, R. D., Bulmash, D., Chiang, J., Ciprini, S., Corbet, R. H. D., Falco, E. E., Marshall, P. J., Wood, D. L., Ajello, M., Bastieri, D., Chekhtman, A., D'Ammando, F., Giroletti, M., Grove, J. E., Lott, B., Ojha, R., Orienti, M., Perkins, J. S., Razzano, M., Smith, A. W., Thompson, D. J., & Wood, K. S.. Fermi Large Area Telescope detection of gravitational lens delayed γ-ray flares from Blazar B0218+357. United States. doi:10.1088/2041-8205/782/2/L14.
Cheung, C. C., Larsson, S., Scargle, J. D., Amin, M. A., Blandford, R. D., Bulmash, D., Chiang, J., Ciprini, S., Corbet, R. H. D., Falco, E. E., Marshall, P. J., Wood, D. L., Ajello, M., Bastieri, D., Chekhtman, A., D'Ammando, F., Giroletti, M., Grove, J. E., Lott, B., Ojha, R., Orienti, M., Perkins, J. S., Razzano, M., Smith, A. W., Thompson, D. J., and Wood, K. S.. 2014. "Fermi Large Area Telescope detection of gravitational lens delayed γ-ray flares from Blazar B0218+357". United States. doi:10.1088/2041-8205/782/2/L14. https://www.osti.gov/servlets/purl/1356535.
@article{osti_1356535,
title = {Fermi Large Area Telescope detection of gravitational lens delayed γ-ray flares from Blazar B0218+357},
author = {Cheung, C. C. and Larsson, S. and Scargle, J. D. and Amin, M. A. and Blandford, R. D. and Bulmash, D. and Chiang, J. and Ciprini, S. and Corbet, R. H. D. and Falco, E. E. and Marshall, P. J. and Wood, D. L. and Ajello, M. and Bastieri, D. and Chekhtman, A. and D'Ammando, F. and Giroletti, M. and Grove, J. E. and Lott, B. and Ojha, R. and Orienti, M. and Perkins, J. S. and Razzano, M. and Smith, A. W. and Thompson, D. J. and Wood, K. S.},
abstractNote = {We report the first clear γ-ray measurement of a delay between flares from the gravitationally lensed images of a blazar, using data from the Fermi Large Area Telescope (LAT). We detected a delay 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.},
doi = {10.1088/2041-8205/782/2/L14},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 782,
place = {United States},
year = {2014},
month = {1}
}