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Sökning: WFRF:(Navarrini A.)

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1.
  • Navarrini, A., et al. (författare)
  • Design of PHAROS2 Phased Array Feed
  • 2018
  • Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018.
  • Konferensbidrag (refereegranskat)abstract
    • We describe the design and architecture of PHAROS2, a cryogenically cooled 4-8 GHz Phased Array Feed (PAF) demonstrator with digital beamformer for radio astronomy application. The instrument will be capable of synthesizing four independent single-polarization beams by combining 24 active elements of an array of Vivaldi antennas. PHAROS2, the upgrade of PHAROS (PHased Arrays for Reflector Observing Systems), features: a) commercial cryogenic LNAs with state-of-the-art performance, b) a 'Warm Section' for signal filtering, conditioning and single downconversion to select a≈275 MHz: Intermediate Frequency (IF) bandwidth within the 4-8 GHz Radio Frequency (RF) band, c) an IF signal transportation by analog WDM (Wavelength Division Mutiplexing) fiber-optic link, and d) a FPGA-based Italian Tile Processing Module (iTPM) digital backend. PHAROS2 will be mounted at the primary focus of the 76-m diameter Lovell radio telescope (Jodrell Bank Observatory, UK) for technical and scientific validation.
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2.
  • Egron, E., et al. (författare)
  • Single-dish and VLBI observations of Cygnus X-3 during the 2016 giant flare episode
  • 2017
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 471:3, s. 2703-2714
  • Tidskriftsartikel (refereegranskat)abstract
    • In 2016 September, the microquasar Cygnus X-3 underwent a giant radio flare, which was monitored for 6 d with the Medicina Radio Astronomical Station and the Sardinia Radio Telescope. Long observations were performed in order to follow the evolution of the flare on an hourly scale, covering six frequency ranges from 1.5 to 25.6 GHz. The radio emission reached a maximum of 13.2 +/- 0.7 Jy at 7.2 GHz and 10 +/- 1 Jy at 18.6 GHz. Rapid flux variations were observed at high radio frequencies at the peak of the flare, together with rapid evolution of the spectral index: a steepened from 0.3 to 0.6 (with S-nu alpha nu(-alpha)) within 5 h. This is the first time that such fast variations are observed, giving support to the evolution from optically thick to optically thin plasmons in expansion moving outward from the core. Based on the Italian network (Noto, Medicina and SRT) and extended to the European antennas (Torun, Yebes, Onsala), very long baseline interferometry (VLBI) observations were triggered at 22 GHz on five different occasions, four times prior to the giant flare, and once during its decay phase. Flux variations of 2 h duration were recorded during the first session. They correspond to a mini-flare that occurred close to the core 10 d before the onset of the giant flare. From the latest VLBI observation we infer that 4 d after the flare peak the jet emission was extended over 30 mas.
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