TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Benbow, Wystan
A1  - Bird, Ralph
A1  - Brantseg, T.
A1  - Brose, Robert
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Connolly, M. P.
A1  - Cui, Wei
A1  - Daniel, M. K.
A1  - Falcone, A.
A1  - Feng, Qi
A1  - Finley, John P.
A1  - Fortson, L.
A1  - Furniss, Amy
A1  - Gillanders, Gerard H.
A1  - Gunawardhana, Isuru
A1  - Huetten, M.
A1  - Hanna, David
A1  - Hervet, O.
A1  - Holder, J.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Johnson, Caitlin A.
A1  - Kaaret, Philip
A1  - Kar, P.
A1  - Kertzman, M.
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - McArthur, S.
A1  - Moriarty, P.
A1  - Mukherjee, Reshmi
A1  - Ong, R. A.
A1  - Otte, Adam Nepomuk
A1  - Park, N.
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, Gregory T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Sadeh, I.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, Karlen
A1  - Wakely, S. P.
A1  - Weinstein, A.
A1  - Wells, R. M.
A1  - Wilcox, P.
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Jorstad, Svetlana G.
A1  - Marscher, Alan P.
A1  - Lister, Matthew L.
A1  - Kovalev, Yuri Y.
A1  - Pushkarev, A. B.
A1  - Savolainen, Tuomas
A1  - Agudo, I.
A1  - Molina, S. N.
A1  - Gomez, J. L.
A1  - Larionov, Valeri M.
A1  - Borman, G. A.
A1  - Mokrushina, A. A.
A1  - Tornikoski, Merja
A1  - Lahteenmaki, A.
A1  - Chamani, W.
A1  - Enestam, S.
A1  - Kiehlmann, S.
A1  - Hovatta, Talvikki
A1  - Smith, P. S.
A1  - Pontrelli, P.
T1  - Multiwavelength Observations of the Blazar BL Lacertae
BT  - a new Fast TeV Gamma-Ray Flare
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL. Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL. Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of similar to 2.3 hr and a decay time of similar to 36 min. The peak flux above 200 GeV is (4.2 +/- 0.6) x 10(-6) photon m(-2) s(-1) measured with a 4-minute-binned light curve, corresponding to similar to 180% of the flux that is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio polarization. Additionally, a possible moving emission feature with superluminal apparent velocity was identified in Very Long Baseline Array observations at 43 GHz, potentially passing the radio core of the jet around the time of the gamma-ray flare. We discuss the constraints on the size, Lorentz factor, and location of the emitting region of the flare, and the interpretations with several theoretical models that invoke relativistic plasma passing stationary shocks.
KW  - BL Lacertae objects: individual (BL Lacertae = VER J2202+422)
KW  - galaxies: active
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aab35c
SN  - 0004-637X
SN  - 1538-4357
VL  - 856
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archer, A.
A1  - Benbow, Wystan
A1  - Bird, Ralph
A1  - Brose, Robert
A1  - Buchovecky, M.
A1  - Bugaev, V.
A1  - Connolly, M. P.
A1  - Cui, Wei
A1  - Errando, Manel
A1  - Falcone, A.
A1  - Feng, Qi
A1  - Finley, John P.
A1  - Flinders, A.
A1  - Fortson, L.
A1  - Furniss, Amy
A1  - Gillanders, Gerard H.
A1  - Huetten, M.
A1  - Hanna, David
A1  - Hervet, O.
A1  - Holder, J.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Johnson, Caitlin A.
A1  - Kaaret, Philip
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, David
A1  - Krause, Maria
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - Maier, Gernot
A1  - McArthur, S.
A1  - Moriarty, P.
A1  - Mukherjee, Reshmi
A1  - Ong, R. A.
A1  - Park, N.
A1  - Perkins, Jeremy S.
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Popkow, Alexis
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, Gregory T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Sadeh, I.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, Karlen
A1  - Tyler, J.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wells, R. M.
A1  - Wilcox, P.
A1  - Wilhelm, Alina
A1  - Williams, David A.
A1  - Zitzer, B.
A1  - Vurm, Indrek
A1  - Beloborodov, Andrei
T1  - A Strong Limit on the Very-high-energy Emission from GRB 150323A
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - On 2015 March 23, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) responded to a Swift-Burst Alert Telescope (BAT) detection of a gamma-ray burst, with observations beginning 270 s after the onset of BAT emission, and only 135 s after the main BAT emission peak. No statistically significant signal is detected above 140 GeV. The VERITAS upper limit on the fluence in a 40-minute integration corresponds to about 1% of the prompt fluence. Our limit is particularly significant because the very-high-energy (VHE) observation started only similar to 2 minutes after the prompt emission peaked, and Fermi-Large Area Telescope observations of numerous other bursts have revealed that the high-energy emission is typically delayed relative to the prompt radiation and lasts significantly longer. Also, the proximity of GRB 150323A (z = 0.593) limits the attenuation by the extragalactic background light to similar to 50% at 100-200 GeV. We conclude that GRB 150323A had an intrinsically very weak high-energy afterglow, or that the GeV spectrum had a turnover below similar to 100 GeV. If the GRB exploded into the stellar wind of a massive progenitor, the VHE non-detection constrains the wind density parameter to be A greater than or similar to 3 x 10(11) g . cm(-1), consistent with a standard Wolf-Rayet progenitor. Alternatively, the VHE emission from the blast wave would be weak in a very tenuous medium such as the interstellar medium, which therefore cannot be ruled out as the environment of GRB 150323A.
KW  - gamma rays: general
KW  - gamma-ray burst: general
KW  - gamma-ray burst: individual (GRB 150323A)
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aab371
SN  - 0004-637X
SN  - 1538-4357
VL  - 857
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Byrum, K.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Christiansen, J. L.
A1  - Ciupik, L.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Eisch, J. D.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Fegan, D. J.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Huetten, M.
A1  - Hakansson, Nils
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Perkins, J. S.
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Ratliff, G.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Williams, D. A.
A1  - Zitzer, B.
T1  - A SEARCH FOR BRIEF OPTICAL FLASHES ASSOCIATED WITH THE SETI TARGET KIC 8462852
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - The F-type star KIC. 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC. 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon m(-2), is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.
KW  - astrobiology
KW  - extraterrestrial intelligence
KW  - methods: observational
KW  - stars: individual ( KIC 8462852)
KW  - techniques: photometric
Y1  - 2016
U6  - https://doi.org/10.3847/2041-8205/818/2/L33
SN  - 2041-8205
SN  - 2041-8213
VL  - 818
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Jiang, Wei
A1  - Tao, Chen
A1  - Stolterfoht, Martin
A1  - Jin, Hui
A1  - Stephen, Meera
A1  - Lin, Qianqian
A1  - Nagiri, Ravi C. R.
A1  - Burn, Paul L.
A1  - Gentle, Ian R.
T1  - Hole-transporting materials for low donor content organic solar cells
BT  - charge transport and device performance
JF  - Organic electronics : physics, materials and applications
N2  - Low donor content solar cells are an intriguing class of photovoltaic device about which there is still considerable discussion with respect to their mode of operation. We have synthesized a series of triphenylamine-based materials for use in low donor content devices with the electron accepting [6,6]-phenyl-C71-butyric acid methyl ester (PC(7)0BM). The triphenylamine-based materials absorb light in the near UV enabling the PC(7)0BM to be be the main light absorbing organic semiconducting material in the solar cell. It was found that the devices did not operate as classical Schottky junctions but rather photocurrent was generated by hole transfer from the photo-excited PC(7)0BM to the triphenylamine-based donors. We found that replacing the methoxy surface groups with methyl groups on the donor material led to a decrease in hole mobility for the neat films, which was due to the methyl substituted materials having the propensity to aggregate. The thermodynamic drive to aggregate was advantageous for the performance of the low donor content (6 wt%) films. It was found that the 6 wt% donor devices generally gave higher performance than devices containing 50 wt% of the donor.
KW  - photoexcited hole transfer
KW  - photocurrent generation
KW  - synthesis
KW  - hole
KW  - mobility
KW  - low donor content
KW  - Schottky junction
Y1  - 2020
U6  - https://doi.org/10.1016/j.orgel.2019.105480
SN  - 1566-1199
SN  - 1878-5530
VL  - 76
PB  - Elsevier
CY  - Amsterdam
ER  -