Suchergebnisse

FU Orionis objects are low-mass pre-main sequence stars characterized by dramatic outbursts several magnitudes in brightness. These outbursts are linked to episodic accretion events in which stars gain a significant portion of their mass. The physical processes behind these accretion events are not yet well understood. The archetypal FU Ori system, FU Orionis, is composed of two young stars with detected gas and dust emission. The continuum emitting regions have not been resolved until now. Here, we present 1.3 mm observations of the FU Ori binary system using the Atacama Large Millimeter/submillimeter Array. The disks are resolved at 40 mas resolution. Radiative transfer modeling shows that the emission from FU Ori north (primary) is consistent with a dust disk with a characteristic radius of similar to 11 au. The ratio between the major and minor axes shows that the inclination of the disk is similar to 37 degrees. FU Ori south is consistent with a dust disk of similar inclination and size. Assuming the binary orbit shares the same inclination angle as the disks, the deprojected distance between the north and south components is 06, i.e., similar to 250 au. Maps of (CO)-C-12 emission show a complex kinematic environment with signature disk rotation at the location of the northern component, and also (to a lesser extent) for FU Ori south. The revised disk geometry allows us to update FU Ori accretion models, yielding a stellar mass and mass accretion rate of FU Ori north of 0.6 M and 3.8 x 10(-5) M yr(-1), respectively. ; CONICYT-Gemini grant 32130007 CONICYT-Fondecyt Regular grant 1191934 Joint Committee of ESO Government of Chile Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1171246 1171624 Ministry of Science and Technology, Taiwan 108-2112-M-001-002-MY3 108-2923-M-001-006-MY3 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3170680 Millennium Science Initiative (Chile) RC130007 Fondequip project EQM140101

We present a multi-wavelength observational study of a low-mass star-forming region, L1251-C, with observational results at wavelengths from the near-infrared to the millimeter. Spitzer Space Telescope observations confirmed that IRAS 22343+7501 is a small group of protostellar objects. The extended emission in the east-west direction with its intensity peak at the center of L1251A has been detected at 350 and 850 mu m with the Caltech Submillimeter Observatory and James Clerk Maxwell telescopes, tracing dense envelope material around L1251A. The single-dish data from the Korean VLBI Network and TRAO telescopes show inconsistencies between the intensity peaks of several molecular emission lines and that of the continuum emission, suggesting complex distributions of molecular abundances around L1251A. The Submillimeter Array interferometer data, however, show intensity peaks of CO 2-1 and (CO)-C-13 2-1 located at the position of IRS 1, which is both the brightest source in the Infrared Array Camera image and the weakest source in the 1.3 mm dust-continuum map. IRS 1 is the strongest candidate for the driving source of the newly detected compact CO 2-1 outflow. Over the entire region (14' x 14') of L125l-C, 3 Class I and 16 Class II sources have been detected, including three young stellar objects (YSOs) in L1251A. A comparison between the average projected distance among the 19 YSOs in L1251-C and that among the 3 YSOs in L1251A suggests that L1251-C is an example of low-mass cluster Formation where protostellar objects form in a small group. ; Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Education of the Korean government NRF-2012R1A1A2044689 ; BK21 plus program through the National Research Foundation (NRF) - Ministry of Education of Korea ; Korea Astronomy and Space Science Institute (KASI) grant - Korea government (MEST) ; National Science Foundation 0708158 ; NASA NNX13AE54G, 1224608, 1230782, 1407 ; Astronomy

Using the Atacama Large Millimeter/submillimeter Array, we observed the young Herbig star HD 100546, host to a prominent disk with a deep, wide gap in the dust. The high-resolution 1.3 mm continuum observation reveals fine radial and azimuthal substructures in the form of a complex maze of ridges and trenches sculpting a dust ring. The (CO)-C-12(2-1) channel maps are modulated by wiggles or kinks that deviate from Keplerian kinematics particularly over the continuum ring, where deviations span 90 degrees in azimuth, covering similar to 5 km s(-1). The most pronounced wiggle resembles the imprint of an embedded massive planet of at least 5 M-Jup predicted from previous hydrodynamical simulations. Such a planet is expected to open a deep gap in both gas and dust density fields within a few orbital timescales, yet the kinematic wiggles lie near ridges in the continuum. The lesser strength of the wiggles in the (CO)-C-13 and (CO)-O-18 isotopologues show that the kinematic signature weakens at lower disk heights, and suggests qualitatively that it is due to vertical flows in the disk surface. Within the gap, the velocity field transitions from Keplerian to strongly non-Keplerian via a twist in position angle, suggesting the presence of another perturber and/or an inner warp. We also present Very Large Telescope/SPHERE sparse aperture masking data that recover scattered light emission from the gap's edges but show no evidence for signal within the gap, discarding a stellar binary origin for its opening. ; government of Chile grant Millennium Scientific Initiative RC130007 government of Chile grant CONICYT-Gemini 32130007 government of Chile grant CONICYT-FONDECYT 1171624 1171246 1191934 Government of Chile CONICYT PAI 2017 PAI77170087 European Union (EU) 748544 Joint Committee of ESO

We present adaptive optics (AO) near-infrared (NIR) observations using VLT/NACO and Keck/NIRC2 of Ophiuchus DIsc Survey Employing ALMA (ODISEA) targets. ODISEA is an ALMA survey of the entire population of circumstellar discs in the Ophiuchus molecular cloud. From the whole sample of ODISEA, we select all the discs that are not already observed in the NIR with AO and that are observable with NACO or NIRC2. The NIR-ODISEA survey consists of 147 stars observed in NIR AO imaging for the first time, as well as revisiting almost all the binary systems of Ophiuchus present in the literature (20 out of 21). In total, we detect 20 new binary systems and one triple system. For each of them, we calculate the projected separation and position angle of the companion, as well as their NIR and millimetre flux ratios. From the NIR contrast, we derived the masses of the secondaries, finding that nine of them are in the substellar regime (30-50 M-Jup). Discs in multiple systems reach a maximum total dust mass of similar to 50 M-circle plus, while discs in single stars can reach a dust mass of 200 M-circle plus. Discs with masses above 10 M-circle plus are found only around binaries with projected separations larger than similar to 110 au. The maximum disc size is also larger around single star than binaries. However, since most discs in Ophiuchus are very small and low-mass, the effect of visual binaries is relatively weak in the general disc population. ; FONDECYT Iniciacion en investigacion project 11190837 Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 1171246 1191934 ESO Government of Chile Swiss National Science Foundation (SNSF) European Commission Swiss National Science Foundation (SNSF) ESO observations 099.C-0465 0103.C-0466 089.D-0199 075.C-0042 60.A-9800 079.C-0307 Keck observations GN-2017A-Q-29 ALMA observations 2016.1.00545.S

Tidal encounters in star clusters perturb discs around young protostars. In Cuello et al., we detailed the dynamical signatures of a stellar flyby in both gas and dust. Flybys produce warped discs, spirals with evolving pitch angles, increasing accretion rates, and disc truncation. Here, we present the corresponding observational signatures of these features in optical/near-infrared scattered light and (sub) millimetre continuum and CO line emission. Using representative prograde and retrograde encounters for direct comparison, we post-process hydrodynamical simulations with radiative transfer methods to generate a catalogue of multiwavelength observations. This provides a reference to identify flybys in recent near-infrared and submillimetre observations (e.g. RW Aur, AS 205, HV Tau and DO Tau, FU Ori, V2775 Ori, and Z CMa). ; Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3170680 3170360 1171246 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) Basal AFB-170002 European Union (EU) 823823 Australian Research Council FT170100040 FT130100034 DP180104235 French National Research Agency (ANR) ANR-16-CE31-0013 European Research Council (ERC) 681601 Iniciativa Cientifica Milenio via the Nucleo Milenio de Formacion Planetaria Chinese Academy of Sciences (CAS) through a CAS-CONICYT Postdoctoral Fellowship FONDEQUIP AIC-57 QUIMAL 130008 BASAL PFB-06 CATA Anillo ACT86