ORCID Profile
0000-0002-5980-4287
Current Organisation
Università Vita Salute San Raffaele Biblioteca San Raffaele
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Publisher: Oxford University Press (OUP)
Date: 26-08-2020
Abstract: How does the cavity size in circumbinary discs depend on disc and binary properties? We investigate by simulating disc cavities carved by binary companions using smoothed particle hydrodynamics. We find that a cavity is quickly opened on the dynamical time, while the cavity size is set on the viscous time. In agreement with previous findings, we find long-term cavity sizes of 2–5 times the binary semimajor axis, increasing with eccentricity and decreasing with disc aspect ratio. When considering binaries inclined with respect to the disc, we find three regimes: (i) discs that evolve towards a coplanar orbit have a large cavity, slightly smaller than that of an initially coplanar disc (ii) discs that evolve towards a polar orbit by breaking have a small cavity, equal in size to that of an initially polar disc and (iii) discs that evolve towards a polar orbit via warping have an intermediate-sized cavity. We find typical gas depletions inside the cavity of ≳2 orders of magnitude in surface density.
Publisher: EDP Sciences
Date: 22-11-2019
DOI: 10.1051/0004-6361/201936707
Abstract: Context. We present a detailed analysis of the extended structure detected around the young and close-by Herbig Ae/Be star R CrA. This is a young triple system with an intermediate mass central binary whose separation is of the order of a few tens of the radii of the in idual components, and an M-star companion at about 30 au. Aims. Our aim is to understand the nature of the extended structure by means of combining integral-field and high-resolution spectroscopy. Methods. We conducted the analysis based on FEROS archival optical spectroscopy data and adaptive optics images and integral-field spectra obtained with SINFONI and SPHERE at the VLT. Results. The observations reveal a complex extended structure that is composed of at least two components: a non-uniform wide cavity whose walls are detected in continuum emission up to 400 au, and a collimated wiggling-jet detected in the emission lines of helium and hydrogen. Moreover, the presence of [Fe II ] emission projected close to the cavity walls suggests the presence of a slower moving wind, most likely a disk wind. The multiple components of the optical forbidden lines also indicate the presence of a high-velocity jet co-existing with a slow wind. We constructed a geometrical model of the collimated jet flowing within the cavity using intensity and velocity maps, finding that its wiggling is consistent with the orbital period of the central binary. The cavity and the jet do not share the same position angle, suggesting that the jet is itself experiencing a precession motion possibly due to the wide M-dwarf companion. Conclusions. We propose a scenario that closely agrees with the general expectation of a magneto-centrifugal-launched jet. These results build upon the extensive studies already conducted on R CrA.
Publisher: Elsevier BV
Date: 04-2023
Publisher: Oxford University Press (OUP)
Date: 22-02-2021
Abstract: Understanding how giant planets form requires observational input from directly imaged protoplanets. We used VLT/NACO and VLT/SPHERE to search for companions in the transition disc of 2MASS J19005804-3645048 (hereafter CrA-9), an accreting M0.75 dwarf with an estimated age of 1–2 Myr. We found a faint point source at ∼0.7-arcsec separation from CrA-9 (∼108 au projected separation). Our 3-epoch astrometry rejects a fixed background star with a 5σ significance. The near-IR absolute magnitudes of the object point towards a planetary-mass companion. However, our analysis of the 1.0–3.8$\\,\\mu$m spectrum extracted for the companion suggests it is a young M5.5 dwarf, based on both the 1.13-μm Na index and comparison with templates of the Montreal Spectral Library. The observed spectrum is best reproduced with high effective temperature ($3057^{+119}_{-36}$K) BT-DUSTY and BT-SETTL models, but the corresponding photometric radius required to match the measured flux is only $0.60^{+0.01}_{-0.04}$ Jovian radius. We discuss possible explanations to reconcile our measurements, including an M-dwarf companion obscured by an edge-on circum-secondary disc or the shock-heated part of the photosphere of an accreting protoplanet. Follow-up observations covering a larger wavelength range and/or at finer spectral resolution are required to discriminate these two scenarios.
Publisher: American Astronomical Society
Date: 10-02-2020
Location: Italy
No related grants have been discovered for Maria Giulia Ubeira-Gabellini.