M. Buttu

Diving into the Sardinia Radio Telescope minor servo system

The Sardinia Radio Telescope (SRT) is a new 64-metre, Gregorian-shaped antenna built in Sardinia (Italy). It is designed to carry out observations up to 100 GHz. The telescope is provided with six focal positions: primary, Gregorian and four beam-waveguide foci. This paper describes the project of the servo system which allows the focus and receiver selection during the instrument setup. This system also operates, at the observation stage, the compensation of some of the stucture deformations due to gravity, temperature variations and other environmental effects. We illustrate the system features following a bottom-up approach, analysing all the project layers ranging from low-level systems, as the hardware controls, to the design and implementation of high-level software, which is based on the distributed objects ACS (ALMA Common Software) framework. Particular focus will be put on the links among the hierarchical levels of the system, and on the solutions adopted in order to guarantee that the control of the servo system is abstracted from the underlying hardware.

The control software for the Sardinia Radio Telescope

The Sardinia Radio Telescope (SRT) is a new 64-meter shaped antenna designed to carry out observations up to 100 GHz. This large instrument has been built in Sardinia, 35 km north of Cagliari, and is now facing the technical commissioning phase. This paper describes the architecture, the implementation solutions and the development status of NURAGHE, the SRT control software. Aim of the project was to produce a software which is reliable, easy to keep up to date and flexible against other telescopes. The most ambitious goal will be to install NURAGHE at all the three italian radio telescopes, allowing the astronomers to access these facilities through a common interface with very limited extra effort. We give a description of all the control software subsystems (servo systems, backends, receivers, etc.) focusing on the resulting design, which is based on the ACS (Alma Common Software) patterns and comes from linux-based, LGPL, Object-Oriented development technologies. We also illustrate how NURAGHE deals with higher level requirements, coming from the telescope management or from the system users.

Single-dish and VLBI observations of Cygnus X-3 during the 2016 giant flare episode

In September 2016, the microquasar Cygnus X-3 underwent a giant radio flare, which was monitored for 6 days 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 a hourly scale, covering six frequency ranges from 1.5 GHz 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: α steepened from 0.3 to 0.6 (with S

Imaging of SNR IC443 and W44 with the Sardinia Radio Telescope at 1.5 and 7 GHz

_\nu

The Sardinia Radio Telescope (SRT): A large modern radio telescope for observations from meter to mm wavelengths

\alpha

Status report of the SRT radiotelescope control software: the DISCOS project

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Nuraghe 0.6 user manual and developer documentation

within 5 hours. 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), 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-hour duration were recorded during the first session. They correspond to a mini-flare that occurred close to the core ten days before the onset of the giant flare. From the latest VLBI observation we infer that four days after the flare peak the jet emission was extended over 30 mas.

The SRT: Astronomical Validation & Scientific Perspectives

Observations of supernova remnants (SNRs) are a powerful tool for investigating the later stages of stellar evolution, the properties of the ambient interstellar medium, and the physics of particle acceleration and shocks. For a fraction of SNRs, multi-wavelength coverage from radio to ultra high-energies has been provided, constraining their contributions to the production of Galactic cosmic rays. Although radio emission is the most common identifier of SNRs and a prime probe for refining models, high-resolution images at frequencies above 5 GHz are surprisingly lacking, even for bright and well-known SNRs such as IC443 and W44. In the frameworks of the Astronomical Validation and Early Science Program with the 64-m single-dish Sardinia Radio Telescope, we provided, for the first time, single-dish deep imaging at 7 GHz of the IC443 and W44 complexes coupled with spatially-resolved spectra in the 1.5-7 GHz frequency range. Our images were obtained through on-the-fly mapping techniques, providing antenna beam oversampling and resulting in accurate continuum flux density measurements. The integrated flux densities associated with IC443 are S_1.5GHz = 134 +/- 4 Jy and S_7GHz = 67 +/- 3 Jy. For W44, we measured total flux densities of S_1.5GHz = 214 +/- 6 Jy and S_7GHz = 94 +/- 4 Jy. Spectral index maps provide evidence of a wide physical parameter scatter among different SNR regions: a flat spectrum is observed from the brightest SNR regions at the shock, while steeper spectral indices (up to 0.7) are observed in fainter cooling regions, disentangling in this way different populations and spectra of radio/gamma-ray-emitting electrons in these SNRs.