OA@INAF - Istituto Nazionale di Astrofisica
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Il ricevitore 4.2-5.6 GHz per SRT
Get PDFQuesto rapporto tecnico descrive lo schema, la funzionalità e le prestazioni del ricevitore radio nella banda 4.2-5.6 GHz, appositamente costruito per essere usato al radio telescopio della Sardegna SRT
Sardinia Radio Telescope observations of the Coma cluster
Get PDFWe present deep total intensity and polarization observations of the Coma cluster at 1.4 and 6.6 GHz performed with the Sardinia Radio Telescope. By combining the single-dish 1.4 GHz data with archival Very Large Array observations, we obtain new images of the central radio halo and of the peripheral radio relic where we properly recover the brightness from the large-scale structures. At 6.6 GHz, we detect both the relic and the central part of the halo in total intensity and polarization. These are the highest frequency images available to date for these radio sources in this galaxy cluster. In the halo, we find a localized spot of polarized signal, with fractional polarization of about 45 per cent. The polarized emission possibly extends along the north-east side of the diffuse emission. The relic is highly polarized, up to 55 per cent, as usually found for these sources. We confirm the halo spectrum is curved, in agreement with previous single-dish results. The spectral index is α = 1.48 ± 0.07 at a reference frequency of 1 GHz and varies from α ≃ 1.1, at 0.1 GHz, up to α ≃ 1.8, at 10 GHz. We compare the Coma radio halo surface brightness profile at 1.4 GHz (central brightness and e-folding radius) with the same properties of the other haloes, and we find that it has one of the lowest emissivities observed so far. Reanalysing the relic's spectrum in the light of the new data, we obtain a refined radio Mach number of M = 2.9 ± 0.1
Laboratorio di coding unplugged “I pianeti in pixel art” mediante il riutilizzo di risorse open del sito play.inaf.it - progettazione e risultati della valutazione effettuata in occasione dell’evento di public engagement “Non solo stelle cadenti” edizione 2023.
Get PDFSi ringraziano i membri del comitato organizzativo dell'evento "Non Solo Stelle cadenti, edizione 2023, della Fondazione Musei Civici di Rovereto (TN), Osservatorio Astronomico di Monte Zugna.Nell’ambito delle attività di terza missione, in occasione dell’evento di public engagement Non Solo Stelle Cadenti, edizione 2023, organizzato dalla Fondazione Musei Civici di Rovereto (TN), è stata proposta e quindi progettata un’attività di educazione non formale e informale di coding unplugged, i pianeti in pixel art, basata sul riuso delle risorse digitali open disponibili sul sito play.inaf.it sviluppate dal gruppo di lavoro sul coding della struttura di Presidenza per la comunicazione Didattica e Divulgazione dell’INAF. L’attività è stata svolta in forma di laboratorio ed è stata corredata dal monitoraggio ai fini della valutazione di impatto. Il report propone la descrizione della progettazione dell'attività e fornisce i dati e risultati ottenuti dal processo di valutazione, evidenziando il gradimento di proposte di coding unplugged per un target della scuola primaria. Si evidenzia infine la possibilità di offrire tale attività come proposta all’interno di altre manifestazioni, eventi o festival locali, fornendo alcuni dati di stima sui relativi costi
Characterization of wedge windows for the absorption cells of GIANO-B
Get PDFThis document aims to explain the characterization work of two wedge windows, which currently serve as spares for the absorption cells of GIANO-B spectrograph
Probing diffuse radio emission in bridges between galaxy clusters with uGMRT
Get PDFAims. Recent X-ray and Sunyaev-Zeldovich (SZ) observations have detected thermal emission between early-stage merging galaxy clusters. The main purpose of this work is to investigate the properties of the non-thermal emission in the interacting cluster pairs Abell 0399-Abell 0401 and Abell 21-PSZ2 G114.9. Methods. These two unique cluster pairs have been found in an interacting state. In both cases, their connection along a filament is supported by an SZ effect detected by the Planck satellite and, in the special case of Abell 0399-Abell 0401, the presence of a radio bridge has been already confirmed by LOFAR observations at 140 MHz. Here, we analyse new high-sensitivity, wideband (250-500 MHz) uGMRT data of these two systems and describe an injection procedure to place limits on the spectrum of Abell 0399-Abell 0401 and on the radio emission between Abell 21-PSZ2 G114.9. Results. In both cases, the low-surface-brightness diffuse emission is not detected in Band 3 (250-500 MHz). For the A399-A401 pair, we are able to constrain the steep spectral index of the bridge emission to be α > 2:2 with a 95% confidence level between 140MHz and 400 MHz. We also detect a small patch of the bridge with a flatter spectral index, which may suggest a variable spectral index distribution across the bridge area. For the A21-PSZ2 G114.9 pair, we are able to place an upper limit on the flux density of the bridge emission with two different methods, finding at the central frequency of 383MHz a conservative value of f1u < 260 mJy at a 95% confidence level, and a lower value of f2u < 125 mJy at an 80% confidence level, based on visual inspection and a morphological criterion. Conclusions. Our work provides a constraint on the spectrum in the bridge A399-A401 that disfavours shock acceleration as the main mechanism for the radio emission. The methods that we propose for the limits on the radio emission in the A21-PSZ2 G114.9 system represent a first step towards a systematic study of these sources
Il feed system per il ricevitore multibeam nella banda 33-50 GHz (Q-band)
Get PDFIl presente rapporto tecnico descrive i 19 feed system utilizzati nel ricevitore multibeam operante nella banda 33-50 GHz (Q-band) per osservazioni radio astronomiche con il Sardinia Radio Telescope (SRT)
The GAPS Programme at TNG LI. Investigating the correlations between transiting system parameters and host chromospheric activity
Get PDFContext. Stellar activity is the most relevant types of astrophysical noise that affect the discovery and characterization of extrasolar planets. On the other hand, the amplitude of stellar activity could hint at an interaction between the star and a close-in giant planet. Progress has been made in recent years in understanding how to deal with stellar activity and search for observational evidence of star-planet interactions. Aims. The aim of this work is to characterize the chromospheric activity of stars hosting short-period exoplanets by studying the correlations between the chromospheric emission (CE) in the Ca II H&K and the planetary parameters. Methods. We measured CE in the Ca II H&K lines using more than 1900 high-resolution spectra of a sample composed of 76 targets, observed with the HARPS-N spectrograph between 2012 and 2020. We transformed the fluxes into bolometric- and photospheric-corrected chromospheric emission ratios, R′HK. Furthermore, we completed the sample of hosts digging for data in previous works. Stellar parameters Teff, B−V, and V were retrieved homogeneously from the Gaia DR3. Then, M*, R*, and ages were determined from isochrone fitting. We retrieved planetary data from the literature and catalogs. The search for correlations between the log(R′HK) and planetary parameters have been performed through both Spearman’s rank and its statistics as well as the more sophisticated Gaussian mixture model method. Results. We found that the distribution of log(R′HK) for the transiting planet hosts is different from the distribution of field main-sequence and sub-giant stars. The log(R′HK) of planetary hosts is correlated with planetary parameters proportional to the planetary radius to the power of n (RnP), indicating a common origin for the correlations. The statistical analysis has also highlighted four clusters of host stars with different behavior in terms of their stellar activity with respect to the planetary surface gravity. Some of the host stars have a value of log(R′HK) that is lower than the basal level of activity for main sequence stars. The planets of these systems are very close to filling their Roche lobe, suggesting that they evaporate through hydrodynamic escape under the strong irradiation of the host star, creating shrouds that absorb the core of the chromospheric resonance lines
The MUSE Ultra Deep Field (MUDF). VI. The Relationship between Galaxy Properties and Metals in the Circumgalactic Medium
Get PDFFundamental physics with ESPRESSO: a new determination of the D/H ratio towards PKS1937-101
Get PDFPrimordial abundances of light elements are sensitive to the physics of the early Universe and can directly constrain cosmological quantities, such as the baryon-to-photon ratio , the baryon density, and the number of neutrino families. Deuterium is especially suited for these studies: its primordial abundance is sensitive and monotonically dependent on , allowing an independent measurement of the cosmic baryon density that can be compared, for instance, against the Planck satellite data. The primordial deuterium abundance can be measured in high H I column density absorption systems towards distant quasars. We report here a new measurement, based on high-resolution ESPRESSO data, of the primordial D I abundance of a system at redshift , towards PKS1937-101. Using only ESPRESSO data, we find a D /H ratio of , while including the available UVES data improves the precision, leading to a ratio of . The results of this analysis agree with those of the most precise existing measurements. We find that the relatively low column density of this system () introduces modelling uncertainties, which become the main contributor to the error budget
Theoretical Modeling of the Exceptional GRB 221009A Afterglow
Get PDFThe extraordinary gamma-ray burst GRB 221009A provides a great opportunity to investigate the enigmatic origin and evolution of gamma-ray bursts (GRBs). However, the complexity of the observations associated with this GRB provides significant challenges to developing a theoretical modeling in a coherent framework. In this paper, we present a theoretical interpretation of the GRB 221009A afterglow within the relativistic fireball scenario, aiming to describe the broadband data set with a consistent model evolution. We find that the adiabatic fireball evolution in the slow-cooling regime provides a viable scenario in good agreement with observations. Crucial to our analysis is the set of simultaneous GeV and TeV gamma-ray data obtained by AGILE and LHAASO during the early afterglow phases. Having successfully modeled as inverse Compton emission the high-energy spectral and lightcurve properties of the afterglow up to 104 s, we extend our model to later times when also optical and X-ray data are available. This approach results in a coherent physical framework that successfully describes all observed properties of the afterglow up to very late times, approximately 106 s. Our model requires time-variable microphysical parameters, with a moderately increasing efficiency ɛ e of a few percent for transferring the shock energy to radiating particles and a decreasing efficiency for magnetic field generation ɛ B in the range 10‑5–10‑7. Fitting the detailed multifrequency spectral data across the afterglow provides a unique test of our model