30 research outputs found
The Northern Cross Fast Radio Burst project -- III. The FRB-magnetar connection in a sample of nearby galaxies
Fast radio bursts (FRBs) are millisecond radio transients observed at
cosmological distances. The nature of their progenitors is still a matter of
debate, although magnetars are invoked by most models. The proposed
FRB-magnetar connection was strengthened by the discovery of an FRB-like event
from the Galactic magnetar SGR J1935+2154. In this work, we aim to investigate
how prevalent magnetars such as SGR J1935+2154 are within FRB progenitors. We
carried out an FRB search in a sample of seven nearby (< 12 Mpc) galaxies with
the Northern Cross radio telescope for a total of 692 h. We detected one 1.8 ms
burst in the direction of M101 with a fluence of Jy ms. Its
dispersion measure of 303 pc cm places it most-likely beyond M101.
Considering that no significant detection comes indisputably from the selected
galaxies, we place a 38 yr upper limit on the total burst rate (i.e.
including the whole sample) at the 95\% confidence level. This upper limit
constrains the event rate per magnetar
magnetar yr or, if combined with literature observations of a
similar sample of nearby galaxies, it yields a joint constraint of
magnetar yr. We also provide the first
constraints on the expected rate of FRBs hypothetically originating from
ultraluminous X-ray (ULX) sources, since some of the galaxies observed during
our observational campaign host confirmed ULXs. We obtain yr per
ULX for the total sample of galaxies observed. Our results indicate that bursts
with energies erg from magnetars like SGR J1935+2154 appear more
rarely compared to previous observations and further disfavour them as unique
progenitors for the cosmological FRB population, leaving more space open to the
contribution from a population of more exotic magnetars, not born via
core-collapsed supernovae.Comment: 9 pages, 4 figures, published in A&
Procedura di montaggio del sistema di movimentazione e controllo del ramo N/S per il sistema BIRALES
Lo scopo di questo documento è quello di descrivere la procedura dell’installazione del nuovo sistema di movimentazione delle antenne cilindrico paraboliche del ramo Nord/Sud del radiotelescopio “Croce del Nord”, studiato per venire incontro alle esigenze del programma “Space Surveillance and Tracking”, oltre a programmi scientifici quale la ricerca degli FRB. Oltre alla procedura di installazione, è indicata la lista del materiale necessario alla replicazione e i disegni costruttivi, e viene inoltre descritta la procedura di manutenzione
Performance assessment of the multibeam radar sensor birales for space surveillance and tracking
Near-Earth space has become progressively more
crowded in active satellites, inactive spacecraft and
debris. Consequently, an international effort is currently
being devoted to improving the performance of the
network of optical and radar sensors for space objects
monitoring. Within this framework, the use of the novel
bistatic radar sensor BIRALES is investigated in this
work, which makes use of a multibeam receiver. The
tailored orbit determination algorithm is described,
which receives as input the data processed by the
acquisition system, that digitally assembles measured
radar echoes. The performances of the orbit
determination process are assessed on a set of numerical
simulations carried out on the NORAD catalogue, using
a dedicated simulator of the sensor.peer-reviewe
Towards coordinated site monitoring and common strategies for mitigation of Radio Frequency Interference at the Italian radio telescopes
We present a project to implement a national common strategy for the
mitigation of the steadily deteriorating Radio Frequency Interference (RFI)
situation at the Italian radio telescopes. The project involves the Medicina,
Noto, and Sardinia dish antennas and comprised the definition of a coordinated
plan for site monitoring as well as the implementation of state-of-the-art
hardware and software tools for RFI mitigation. Coordinated monitoring of
frequency bands up to 40 GHz has been performed by means of continuous
observations and dedicated measurement campaigns with fixed stations and mobile
laboratories. Measurements were executed on the frequency bands allocated to
the radio astronomy and space research service for shared or exclusive use and
on the wider ones employed by the current and under-development receivers at
the telescopes. Results of the monitoring campaigns provide a reference
scenario useful to evaluate the evolution of the interference situation at the
telescopes sites and a case series to test and improve the hardware and
software tools we conceived to counteract radio frequency interference. We
developed a multi-purpose digital backend for high spectral and time resolution
observations over large bandwidths. Observational results demonstrate that the
spectrometer robustness and sensitivity enable the efficient detection and
analysis of interfering signals in radio astronomical data. A prototype
off-line software tool for interference detection and flagging has been also
implemented. This package is capable to handle the huge amount of data
delivered by the most modern instrumentation on board of the Italian radio
telecsopes, like dense focal plane arrays, and its modularity easen the
integration of new algorithms and the re-usability in different contexts or
telescopes.Comment: 39 pages, 10 Figures and 7 Tables. INAF Technical Report n. 149
(2022). http://hdl.handle.net/20.500.12386/3208
Exploration of an innovative ranging method for bi-static radar, applied in LEO Space Debris surveying and tracking
Space Situational Awareness (SSA) is referred as one of the capacitive areas of strategic interest to be developed/completed in the future in the short and medium term, for any nation with the target of the access to the space. One of the fundamental components is the Space Surveillance and Tracking (SST) program, considered as the capability to build a spatial mapping of the objects in orbit, their classification and the exact identification of their orbital characteristics. For this reason, radar measurements are relevant, in particular to observe objects in Low Earth Orbit. The Italian National Institute of Astrophysics together with Vitrociset company and Politecnico di Milano, studied and developed a new and innovative method for the range measure applied to bi-static radars to support the European Union Space Surveillance and Tracking (EUSST) program. Several tests have been carried out using the BIRALES and BIRALET sensors for survey and tracking observations respectively. Finally, the results obtained from observations have been compared with the real positions of the targets in order to validate the system. The ranging method relies on the synchronization of the transmitting and receiving antennas and on the correlation of the echo received from the scattering of the orbiting object. To do that, the transmitting antenna emits simultaneously two different signals: a Chirp signal for range measurement and a second “Continuous Wave” (CW) for Doppler shift measurement and object track reconstruction. Overall, we simultaneously obtain time profiles for range, angular position (azimuth and elevation), and Doppler during the passage of the objects inside the sensor Field of View. By virtue of the above plethora of measurements, this method guarantees also the possibility to produce an Initial Orbital Determination (IOD) for unknown objects
Exploitation of bi-static radar architectures for LEO Space Debris surveying and tracking: The BIRALES/BlRALET project
The space debris population is continuously growing and it represents a potential issue for spacecraft. New collisions could exponentially rise the amount of debris and so the level of risk represented by these objects. The monitoring of space environment is necessary to prevent new collisions. For this reason, radar measurements are relevant, in particular to observe objects in Low Earth Orbit. Regarding the Italian contribution, there are two radars based on two different radio telescopes as receivers: the BIRALES and the BIRALET systems. We propose a detailed description of these systems, focusing on hardware and software components that permit to perform range and range rate measurement of resident space objects
Surgical treatment of small bowel neoplasms.
Small intestinal neoplasms are uncommon cancers. Benign small intestinal tumors (e.g., leiomyoma, lipoma, hamartoma, or desmoid tumor) usually are asymptomatic but may present with complications. Primary malignancies of the small intestine, including adenocarcinoma, leiomyosarcoma, carcinoid, and lymphoma, are often symptomatic and may present with intestinal obstruction, jaundice, bleeding, or pain. Metastatic neoplasms may involve the small intestine via contiguous spread, peritoneal metastases or hematogenous metastases. Because the small intestine is relatively inaccessible to routine endoscopy, diagnosis of small intestinal neoplasms is often delayed for months after onset of symptoms. During last years the increase of small bowel endoscopy and other diagnostic tools allow earlier non-operative diagnosis. Even though radical resection of small bowel cancer plays an important role, the 5 yr overall survival remains low