To understand the formation of planetary systems, one needs to understand the initial conditions of planet formation, i.e. the young gas-rich planet forming disks. Spatially resolved high-contrast ...observations are of particular interest, since substructures in disks, linked to planet formation, can be detected and close companions or even planets in formation embedded in the disk can be revealed. In this study we present the first result of the DESTINYS survey (Disk Evolution Study Through Imaging of Nearby Young Stars). DESTINYS is an ESO/SPHERE large program that aims at studying disk evolution in scattered light, mainly focusing on a sample of low-mass stars (<1\(M_\odot\)) in nearby (~200 pc) star-forming regions. In this particular study we present the observations of the ET Cha (RECX 15) system, a nearby 'old' classical T Tauri star (5-8 Myr, ~100 pc), which is still strongly accreting. We use SPHERE/IRDIS in H-band polarimetric imaging mode to obtain high contrast images of the ET Cha system to search for scattered light from the circumstellar disk as well as thermal emission from close companions. We additionally employ VLT/NACO total intensity archival data taken in 2003. We report here the discovery of a low-mass (sub)stellar companion with SPHERE/IRDIS to ET Cha. We are estimating the mass of this new companion based on photometry. Depending on the system age it is a 5 Myr, 50 \(M_{Jup}\) brown dwarf or an 8 Myr, 0.10 \(M_\odot\) M-type pre-main-sequence star. We explore possible orbital solutions and discuss the recent dynamic history of the system. Independent of the precise companion mass we find that the presence of the companion likely explains the small size of the disk around ET Cha. The small separation of the binary pair indicates that the disk around the primary component is likely clearing from the outside in, explaining the high accretion rate of the system.
Circumstellar disks do not evolve in isolation, as about half of solar-type stars were born in binary or multiple systems. Resolving disks in binary systems provides the opportunity to examine the ...influence of stellar companions on the outcomes of planet formation. We aim to investigate and compare disks in stellar multiple systems with near-infrared scattered-light imaging as part of the Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS) program. We used polarimetric differential imaging with SPHERE/IRDIS at the VLT to search for scattered light from the circumstellar disks in three multiple systems, CHX 22, S CrA, and HP Cha. We performed astrometric and orbit analyses for the stellar companions using archival HST, VLT/NACO, and SPHERE data. Combined with the age and orbital constraints, the observed disk structures provide insights into the evolutionary history and the impact of the stellar companions. The small grains in CHX 22 form a tail-like structure surrounding the close binary, which likely results from a close encounter and capture of a cloudlet. S CrA shows intricate structures (tentative ringed and spiral features) in the circumprimary disk as a possible consequence of perturbations by companions. The circumsecondary disk is truncated and connected to the primary disk via a streamer, suggesting tidal interactions. In HP Cha, the primary disk is less disturbed and features a tenuous streamer, through which the material flows towards the companions. The comparison of the three systems spans a wide range of binary separation (50 - 500 au) and illustrates the decreasing influence on disk structures with the distance of companions. This agrees with the statistical analysis of exoplanet population in binaries, that planet formation is likely obstructed around close binary systems, while it is not suppressed in wide binaries.
We reflect upon the meaning of freedom and autonomy in nursing behaviour, attempting to outline the contemporary situation of nursing in Italy, where the profession is achieving important results ...after a long period of submission and subordination. The way to real emancipation is not easy, but a statement of law on the one hand - abolishing constraints such as the Mansionario - and professional self-regulation on the other - the recent new Deontological Code - represent a real conquest in that direction. However, no statement of law or deontology can be sufficient without deeper reflection by the profession on itself and its tasks, potentiality, social importance and self-esteem.
Substellar companions at wide separation around stars hosting planets or brown dwarfs (BDs) yet close enough for their formation in the circumstellar disc are of special interest. In this letter we ...report the discovery of a wide (projected separation \(\sim\)16.0arcsec, or 2400 AU, and position angle 114.61\(^\circ\)) companion of the GQ Lup A-B system, most likely gravitationally bound to it. A VLT/X-Shooter spectrum shows that this star, 2MASS J15491331-3539118, is a bonafide low-mass (\(\sim\)0.15 M\(_\odot\)) young stellar object (YSO) with stellar and accretion/ejection properties typical of Lupus YSOs of similar mass, and with kinematics consistent with that of the GQ Lup A-B system. A possible scenario for the formation of the triple system is that GQ Lup A and 2MASS J15491331-3539118 formed by fragmentation of a turbulent core in the Lup I filament, while GQ Lup B, the BD companion of GQ Lup A at 0.7arcsec, formed in situ by the fragmentation of the circumprimary disc. The recent discoveries that stars form along cloud filaments would favour the scenario of turbulent fragmentation for the formation of GQ Lup A and 2MASS J15491331-3539118.
A hybrid numerical technique based on the finite-element method (FEM) is exploited to define a numerical diffraction coefficient for irregular wedge configurations as, for instance, a perfectly ...conducting wedge with an inhomogeneously filled cavity-backed aperture in one of its faces, or a wedge with a rounded edge. The hybrid technique combines the FEM with the uniform geometrical theory of diffraction (UTD), and is used to develop a numerical diffraction coefficient to account for contributions to the scattered field due to localized inhomogeneities in an otherwise canonical perfectly conducting wedge.
We reflect upon the meaning of freedom and autonomy in nursing behaviour, attempting to outline the contemporary situation of nursing in Italy, where the profession is achieving important results ...after a long period of submission and subordination. The way to real emancipation is not easy, but a statement of law on the one hand--abolishing constraints such as the Mansionario--and professional self-regulation on the other--the recent new Deontological Code--represent a real conquest in that direction. However, no statement of law or deontology can be sufficient without deeper reflection by the profession on itself and its tasks, potentiality, social importance and self-esteem.
A&A 675, A153 (2023) Observing the spatial distribution and excitation processes of atomic and
molecular gas in the inner regions (< 20 au) of young (< 10 Myr) protoplanetary
disks helps us to ...understand the conditions for the formation and evolution of
planetary systems. In the framework of the PENELLOPE and ULLYSES projects, we
aim to characterize the atomic and molecular component of protoplanetary disks
in a sample of 11 Classical T Tauri Stars (CTTs) of the Orion OB1 and
$\sigma$-Orionis associations. We analyzed the flux-calibrated
optical-forbidden lines and the fluorescent ultraviolet $\rm H_2$ progressions
using spectra acquired with ESPRESSO at VLT, UVES at VLT and HST-COS. Line
morphologies were characterized through Gaussian decomposition. We then focused
on the properties of the narrow low-velocity (FWHM < 40 $km$ $s^{-1}$ and
|$v_p$| < 30 $km$ $s^{-1}$) component (NLVC) of the OI 630 nm line, compared
with the properties of the UV-$\rm H_2$ lines. We found that the OI630 NLVC
and the UV-$\rm H_2$ lines are strongly correlated in terms of peak velocities,
full width at half maximum, and luminosity. The luminosities of the OI630
NLVC and UV-$\rm H_2$ correlate with the accretion luminosity with a similar
slope, as well as with the luminosity of the CIV 154.8, 155 nm doublet. We
discuss such correlations in the framework of the currently suggested
excitation processes for the OI630 NLVC. Our results can be interpreted in a
scenario in which the OI630 NLVC and UV-$\rm H_2$ have a common disk origin
with a partially overlapped radial extension. We also suggest that the
excitation of the OI NLVC is mainly induced by stellar FUV continuum photons
more than being of thermal origin. This study demonstrates the potential of
contemporaneous wide-band high-resolution spectroscopy in linking different
tracers of protoplanetary disks.
On the tag detection in near-field UHF RFID applications Michel, Andrea; Pino, Marcos R.; Nepa, Paolo ...
2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS),
2017-Aug.
Conference Proceeding
Odprti dostop
The UHF RFID tag detection is here investigated when the transponder and the reader antenna are placed close each other. Differently from long-range RFID applications, in near-field applications the ...field distribution generated by the reader antenna as well as the tag layout play an important role in the tag detection. In this paper, considerations on the tag readability are proposed on the basis of both simulated and measured results.
PDF
