| 1. |
- Wagner, J., et al.
(author)
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First 230? : GHz VLBI fringes on 3C 279 using the APEX Telescope (Research Note)
- 2015
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 581
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Journal article (peer-reviewed)abstract
- Aims. We report about a 230? GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT of the Arizona Radio Observatory (ARO). Methods. We installed VLBI equipment and measured the APEX station position to 1? cm accuracy (1σ). We then observed 3C 279 on 2012 May 7 in a 5? h 230? GHz VLBI track with baseline lengths of 2800? Mλ to 7200? Mλ and a finest fringe spacing of 28.6? μas. Results. Fringes were detected on all baselines with signal-to-noise ratios of 12 to 55 in 420? s. The correlated flux density on the longest baseline was ∼0.3? Jy beam-1, out of a total flux density of 19.8? Jy. Visibility data suggest an emission region ≤ 38? μas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 1010? K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ∼ 38? μas. Conclusions. With APEX the angular resolution of 230? GHz VLBI improves to 28.6? μas. This allows one to resolve the last-photon ring around the Galactic Center black hole event horizon, expected to be 40? μas in diameter, and probe radio jet launching at unprecedented resolution, down to a few gravitational radii in galaxies like M 87. To probe the structure in the inner parsecs of 3C 279 in detail, follow-up observations with APEX and five other mm-VLBI stations have been conducted (March 2013) and are being analyzed.
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| 2. |
- Roy, Alan, et al.
(author)
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VLBI at APEX: First Fringes
- 2012
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In: Proceedings of Science. - 1824-8039. ; 2012-October
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Conference paper (peer-reviewed)
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| 3. |
- Tuccari, G., et al.
(author)
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DBBC3: VLBI at 32 Gbits per second
- 2012
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In: Proceedings of Science. - 1824-8039. ; 2012-October
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Conference paper (peer-reviewed)abstract
- The project to develop the third generation of a digital backend system (DBBC3) for VLBI and other applications is presented, including an overview of the evolution of this system. The initial development started about ten years ago and evolved in the course of time by improving all its components: hardware, firmware and software going from DBBC1 to DBBC2. The latest, now third generation will be able to fully implement digitally all the functionality required of a complete 32 Gbps VLBI backend for the EVN and VLBI2010. The architecture and adopted methods are described. The implementation of the astronomical version is financially supported by RadioNet3.
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| 4. |
- Alef, Walter, et al.
(author)
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BRAND - The next generation receiver for VLBI
- 2018
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In: Proceedings of Science. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 344
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Conference paper (peer-reviewed)abstract
- The aim of the BRAND EVN project is to build a very wide receiver prototype for primary focus with a frequency range from 1.5 GHz to 15.5 GHz In addition we will investigate solutions for secondary focus telescopes. The project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 [RadioNet]. We present the status of the project which was started on January 1st, 2017 and is progressing smoothly: Feed, LNA, filters, major digital components, and some of the firmware are available now. © Copyright owned by the author(s) under the terms of the Creative Commons.
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| 5. |
- Tuccari, G., et al.
(author)
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DBBC3 development
- 2014
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In: Proceedings of Science. - 1824-8039.
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Conference paper (peer-reviewed)abstract
- The RadioNet3 JRA project named 'DBBC3' is progressing as planned. The first units of the 4 GHz bandwidth samplers are available as well as the CORE3 processing elements. The first functional mode for both of them has been successfully tested and the construction of two further DBBC3 units is under way. The main parts of the system are shown together with their performance, and an overview of the implementation is presented for data-rates of 32 and 64 Gbps with two examples of their application: a) astronomical for the EVN and for millimetre VLBI with the EHT (Event Horizon Telescope), and b) geodetic for the VGOS broadband network.
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