Context. Since July 2014, the Gaia mission of the European Space Agency has been surveying the entire sky down to magnitude 20.7 in the visible. In addition to the millions of daily observations of stars, thousands of Solar System objects (SSOs) are observed. By comparing their positions, as measured by Gaia, to those of known objects, a daily processing pipeline filters known objects from potential discoveries. However, owing to Gaia's specific observing mode, which follows a predetermined scanning law designed for stars as "fixed" objects on the celestial sphere, potential newly discovered moving objects are characterized by very few observations, which are acquired over a limited time. Furthermore, these objects cannot be specifically targeted by Gaia itself after their first detection. This aspect was recognized early on in the design of the Gaia data processing.
Aims: A daily processing pipeline dedicated to these candidate discoveries was set up to release calls for observations to a network of ground-based telescopes. Their aim is to acquire follow-up astrometry and to characterize these objects.
Methods: From the astrometry measured by Gaia, preliminary orbital solutions are determined, allowing us to predict the position of these potentially newly discovered objects in the sky while accounting for the large parallax between Gaia and the Earth (separated by 0.01 au). A specific task within the Gaia Data Processing and Analysis Consortium has been responsible for the distribution of requests for follow-up observations of potential Gaia SSO discoveries. Since late 2016, these calls for observations (nicknamed "alerts") have been published via a Web interface with a quasi-daily frequency, together with observing guides, which is freely available to anyone worldwide.
Results: Between November 2016 and the end of the first year of the extended mission (July 2020), over 1700 alerts were published, leading to the successful recovery of more than 200 objects. Among them, six have a provisional designation assigned with the Gaia observations; the others were previously known objects with poorly characterized orbits, precluding identification at the time of Gaia observations. There is a clear trend for objects with a high inclination to be unidentified, revealing a clear bias in the current census of SSOs against high-inclination populations.

This paper reports on a new analysis of archival ALMA 870 μm dust continuum observations. Along with the previously observed bright inner ring (r ~ 20-40 au), two addition substructures are evident in the new continuum image: a wide dust gap, r ~ 40-150 au, and a faint outer ring ranging from r ~ 150 au to r ~ 250 au and whose presence was formerly postulated in low-angular-resolution ALMA cycle 0 observations but never before observed. Notably, the dust emission of the outer ring is not homogeneous, and it shows two prominent azimuthal asymmetries that resemble an eccentric ring with eccentricity e = 0.07. The characteristic double-ring dust structure of HD 100546 is likely produced by the interaction of the disk with multiple giant protoplanets. This paper includes new smoothed-particle-hydrodynamic simulations with two giant protoplanets, one inside of the inner dust cavity and one in the dust gap. The simulations qualitatively reproduce the observations, and the final masses and orbital distances of the two planets in the simulations are 3.1 M_J at 15 au and 8.5 M_J at 110 au, respectively. The massive outer protoplanet substantially perturbs the disk surface density distribution and gas dynamics, producing multiple spiral arms both inward and outward of its orbit. This can explain the observed perturbed gas dynamics inward of 100 au as revealed by ALMA observations of CO. Finally, the reduced dust surface density in the ~40-150 au dust gap can nicely clarify the origin of the previously detected H₂O gas and ice emission

Context. T Tauri stars are surrounded by dust and gas disks. As material reservoirs from which matter is accreted onto the central star and planets are built, these protoplanetary disks play a central role in star and planet formation.
Aims: We aim at spatially resolving at sub-astronomical unit (sub-au) scales the innermost regions of the protoplanetary disks around a sample of T Tauri stars to better understand their morphology and composition.
Methods: Thanks to the sensitivity and the better spatial frequency coverage of the GRAVITY instrument of the Very Large Telescope Interferometer, we extended our homogeneous data set of 27 Herbig stars and collected near-infrared K-band interferometric observations of 17 T Tauri stars, spanning effective temperatures and luminosities in the ranges of ~4000-6000 K and ~0.4-10 L_⊙, respectively. We focus on the continuum emission and develop semi-physical geometrical models to fit the interferometric data and search for trends between the properties of the disk and the central star.
Results: As for those of their more massive counterparts, the Herbig Ae/Be stars, the best-fit models of the inner rim of the T Tauri disks correspond to wide rings. The GRAVITY measurements extend the radius-luminosity relation toward the smallest luminosities (0.4-10 L_⊙). As observed previously, in this range of luminosities, the R ∝ L^1∕2 trend line is no longer valid, and the K-band sizes measured with GRAVITY appear to be larger than the predicted sizes derived from sublimation radius computation. We do not see a clear correlation between the K-band half-flux radius and the mass accretion rate onto the central star. Besides, having magnetic truncation radii in agreement with the K-band GRAVITY sizes would require magnetic fields as strong as a few kG, which should have been detected, suggesting that accretion is not the main process governing the location of the half-flux radius of the inner dusty disk. The GRAVITY measurements agree with models that take into account the scattered light, which could be as important as thermal emission in the K band for these cool stars. The N-to-K band size ratio may be a proxy for disentangling disks with silicate features in emission from disks with weak and/or in absorption silicate features (i.e., disks with depleted inner regions and/or with large gaps). The GRAVITY data also provide inclinations and position angles of the inner disks. When compared to those of the outer disks derived from ALMA images of nine objects of our sample, we detect clear misalignments between both disks for four objects.
Conclusions: The combination of improved data quality with a significant and homogeneous sample of young stellar objects allows us to revisit the pioneering works done on the protoplanetary disks by K-band interferometry and to test inner disk physics such as the inner rim morphology and location.

GTO programs with run IDs: 0103.C-0347, 0102.C-0408, 0101.C-0311, 0100.C-0278, and 099.C-0667.

We examine the particle acceleration mechanism in the Mpc-scale bridge between Abell 399 and Abell 401 and assess in particular if the synchrotron emission originates from first-order or second-order Fermi re-acceleration. We use deep (~40 hours) LOw-Frequency ARray (LOFAR) observations from Abell 399 and Abell 401 and apply improved direction-dependent calibration to produce deep radio images at three different resolutions at 144 MHz. With a point-to-point analysis we find in the bridge trends between the radio emission from our new maps and X-ray emission from an XMM Newton observation. By analyzing our observations and results, we argue that second-order Fermi re-acceleration is currently the most favoured process to explain the emission from the radio bridge, where past AGN activity may be responsible for the supply of fossil plasma needed for in-situ re-acceleration. The radio halos from Abell 401 and Abell 399 are also consistent with a second-order Fermi re-acceleration model.

We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We used the second data release of the 144 MHz LOFAR Two-metre Sky Survey to produce circularly polarised maps with a median noise of 140 µJy beam⁻¹ and resolution of 20″ for ≈27% of the northern sky (5634 deg²). The leakage of total intensity into circular polarisation is measured to be ≈0.06%, and our survey is complete at flux densities ≥1 mJy. A detection is considered reliable when the circularly polarised fraction exceeds 1%. We find the population of circularly polarised sources is composed of four distinct classes: stellar systems, pulsars, active galactic nuclei, and sources unidentified in the literature. The stellar systems can be further separated into chromospherically active stars, M dwarfs, and brown dwarfs. Based on the circularly polarised fraction and lack of an optical counterpart, we show it is possible to infer whether the unidentified sources are likely unknown pulsars or brown dwarfs. By the completion of this survey of the northern sky, we expect to detect 300±100 circularly polarised sources.

V-LoTSS catalogue is only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/670/A124

Dal 5 dicembre 2019 OA@INAF è aperto all'immissione dei RAPPORTI TECNICI. Prima di fare una submission o una review si prega di seguire attentamente le istruzioni riportate nel Manuale d'uso per l'inserimento dei rapporti tecnici in OA@INAF [versione aggiornata al 24.5.2021].
Dal 24 febbraio 2020 i ricercatori possono inserire i prodotti della ricerca. Prima di procedere, si raccomanda un'attenta lettura delle Istruzioni per l'inserimento dei prodotti della ricerca nel repository OA@INAF [versione aggiornata al 15.5.2020].

A causa di un bug di ADS che espone una lista di autori e una di ORCID non coerenti fra loro, il recupero delle pubblicazioni e il loro legame con gli autori non è possibile. Pertanto, fino a risoluzione del bug, il pregresso (fino al 2014) non sarà più importato come inizialmente previsto.

Le pubblicazioni indicizzate in ADS dal 2015 al 2019 verranno recuperate a blocchi di anni. I ricercatori troveranno nel workspace le submissions da completare con i metadati mancanti e il full text. Perché questo sia possibile, è necessario aver fatto il claim delle pubblicazioni in ADS con il proprio ORCID. Chi non ha fatto il claim non troverà nulla.. Per gli anni dal 2016 in poi le submissions da completare andranno a finire solo nel workspace del primo autore INAF, a cui spetterà il compito di completare l'inserimento nel repository.

Ciò che non è indicizzato in ADS o non viene recuperato a causa del bug potrà essere inserito nel modo semi-automatico, con ricerca per ID (DOI, ORCID, ADSBibCode).

Il repository inserisce automaticamente tutte le pubblicazioni presenti nel SitoDocente che ciascuno ha in LoginMIUR. Perché possano essere prese in considerazione per la VQR 2015-2019 è necessario, al momento del caricamento del full text, selezionare SI nel menu a discesa in corrispondenza dell'etichetta MIUR