Browsing by Department "University of Arizona"
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- Multiwavelength observations of the blazar BL Lacertae: a new fast TeV gamma-ray flare
A4 Artikkeli konferenssijulkaisussa(2017) Feng, Q.; Jorstad, S. G.; Marscher, A. P.; Lister, M. L.; Kovalev, Y. Y.; Pushkarev, A. B.; Savolainen, T.; Agudo, I.; Molina, S. N.; Gomez, J. L.; Larionov, V. M.; Borman, G. A.; Mokrushina, A. A.; Smith, P. S.Observations of fast TeV $\gamma$-ray flares from blazars reveal the extreme compactness of emitting regions in blazar jets. Combined with very-long-baseline radio interferometry measurements, they probe the structure and emission mechanism of the jet. We report on a fast TeV $\gamma$-ray flare from BL Lacertae observed by VERITAS, with a rise time of about 2.3 hours and a decay time of about 36 minutes. The peak flux at $>$200 GeV measured with the 4-minute binned light curve is $(4.2 \pm 0.6) \times 10^{-6} \;\text{photons} \;\text{m}^{-2}\, \text{s}^{-1}$, or $\sim$180% the Crab Nebula flux. Variability in GeV $\gamma$-ray, X-ray, and optical flux, as well as in optical and radio polarization was observed around the time of the TeV $\gamma$-ray flare. A possible superluminal knot was identified in the VLBA observations at 43 GHz. The flare constrains the size of the emitting region, and is consistent with several theoretical models with stationary shocks. - Optical characterization of directly deposited graphene on a dielectric substrate
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-02-08) Kaplas, Tommi; Karvonen, Lasse; Ahmadi, Sepehr; Amirsolaimani, Babak; Mehravar, Soroush; Peyghambarian, Nasser; Kieu, Khanh; Honkanen, Seppo; Lipsanen, Harri; Svirko, YuriBy using scanning multiphoton microscopy we compare the nonlinear optical properties of the directly deposited and transferred to the dielectric substrate graphene. The direct deposition of graphene on oxidized silicon wafer was done by utilizing sacrificial copper catalyst film. We demonstrate that the directly deposited graphene and bi-layered transferred graphene produce comparable third harmonic signals and have almost the same damage thresholds. Therefore, we believe directly deposited graphene is suitable for the use of e.g. nanofabricated optical setups. (C) 2016 Optical Society of America