1,711 research outputs found
The ALMA Early Science View of FUor/EXor objects. III. The Slow and Wide Outflow of V883 Ori
We present Atacama Large Millimeter/ sub-millimeter Array (ALMA) observations
of V883 Ori, an FU Ori object. We describe the molecular outflow and envelope
of the system based on the CO and CO emissions, which together
trace a bipolar molecular outflow. The CO emission traces the rotational
motion of the circumstellar disk. From the CO blue-shifted emission, we
estimate a wide opening angle of 150 for the outflow
cavities. Also, we find that the outflow is very slow (characteristic velocity
of only 0.65 km~s), which is unique for an FU Ori object. We calculate
the kinematic properties of the outflow in the standard manner using the
CO and CO emissions. In addition, we present a P Cygni profile
observed in the high-resolution optical spectrum, evidence of a wind driven by
the accretion and being the cause for the particular morphology of the
outflows. We discuss the implications of our findings and the rise of these
slow outflows during and/or after the formation of a rotationally supported
disk.Comment: 12 pages, 7 figures, 2 tables. Accepte
Sensing Sound And Space:Auditory And Visual Spatial ImpressionIn Three Auditoria
In some contexts, the experience of sound and space are often considered as two unrelated experiences. In an auditorium, the senses of hearing and seeing are not necessary unrelated. This thesis proposes that there is a sensorial relationship between sound and space in the context of symphonic concert halls. Through a study of three auditoria, this thesis explores the relationship, and the degree of correspondence and interaction between auditory and visual spatial impression. It begins by exploring the concepts of auditory and visual spatial impression in relation with auditorium acoustics and architectural design. In auditorium acoustics, a number of terms are used to describe auditory spatial impression, such as 'spaciousness,' 'envelopment,' and 'intimacy.' These terms have connotations beyond the auditory. The thesis suggests that they may also be used to describe visual spatial impression in auditoria. Through textual analyses, the thesis finds that the auditory and visual terms do not always relate to the same physical characteristics of auditoria and can conflict with one another. Hence, it is apparent that further subjective analyses of auditory and spatial impression are needed. Three chapters in this thesis are devoted to auditory and visual subjective experiments. Their purpose is to explore the degree of correspondence or contrast, and interaction between auditory and visual spatial impression. The degree of correspondence and contrast between auditory and visual spatial impression appear to vary between auditoria and within auditoria. The relationship between auditory and visual spatial impression appear to be both necessary and arbitrary, and the degree of interaction between them appear to be strong in some cases and weak in other. From the findings, this thesis suggests that the degree of correspondence or contrast, and interaction between auditory and visual spatial impression could be used to create an audiovisual experience that suit specific musical events. Concert auditoria are culturally and artistically unique spaces. Hence, consideration must be taken to understand the relationships between, and intentions of the acoustical and architectural designs, music and architecture, for a successful and creative collaboration between designers - since the ultimate goal is to create an extraordinary audiovisual experience in a concert hall
Movements of North Carolina Striped Bass, Morone saxatilis, Inferred through Otolith Microchemistry
Striped Bass, Morone saxatilis, is an anadromous, recreationally and commercially important fish species found throughout the U.S. Atlantic east coast, whose migrations have been intensely studied. A review of the relevant literature on Striped Bass migrations revealed that the paradigm of Striped Bass migration along the U.S. Atlantic coast should be updated, as new information has shown that in addition to the Chesapeake Bay and Hudson River, the Roanoke River, NC, Delaware River, and possibly the Shubenacadie River, Nova Scotia, Canada, may also contribute fish to the mixed Atlantic Migratory Stock. The needs for an updated delineation of stocks that contribute to the Atlantic Migratory Stock and determination of inshore migrations and habitat use were identified as additional avenues for further research. In effort to answer the latter question, the inshore movements and potential mixing of North Carolina stocks of adult Striped Bass from separate management areas (Albemarle Sound Management Area, ASMA, and Central Southern Management Area, CSMA) were determined using otolith microchemistry. Trace element ratios (strontium:calcium, Sr:Ca; barium:calcium, Ba:Ca; magnesium:calcium, Mg:Ca; and manganese:calcium, Mg:Ca) measured through inductively coupled plasma optical emission spectrometry (ICP-OES) from ASMA and CSMA water samples were used to determine that each management area had different water chemistries through linear discriminant function analysis (LDFA), allowing for discrimination of otolith chemistries of fish from different management areas. Adult otolith elemental concentrations of Sr, Ba, Mg, and Mn, measured using laser ablation inductively couple plasma mass spectroscopy, of fish from separate management areas were compared using linear discriminant function analysis, which determined that little mixing of adult fish occurred between the two management areas, except in years of high abundance of ASMA fish, in which those fish would migrate to the CSMA. The same methods were used on CSMA fish determined to be of hatchery or wild origin by Dobbs (2013) to determine that CSMA hatchery and wild fish use different habitat during their sub-adult and early adult lives, but similar habitat as they aged. Finally, otolith microchemistry was used in an attempt to determine if the Roanoke River, NC (ASMA) contributed fish to the Atlantic Migratory Stock, as North Carolina Division of Marine Fisheries (NCDMF) tag returns indicated the Roanoke River was contributing significant numbers of fish. Otolith Sr:Ca ratios were used to determine anadromous migrations, as otolith Sr:Ca is directly correlated to ambient salinity. Results did not agree well with NCDMF tagging, as many larger fish exhibited resident Sr:Ca profiles, whereas NCDMF tag returns indicated that most, larger (>800 mm total length, total length) fish were anadromous and undertook long distance migrations. It is possible that the Roanoke River harbors discrete resident and anadromous contingents of large, adult Striped Bass.M.S
The ALMA Early Science View of FUor/EXor objects. IV. Misaligned Outflows in the Complex Star-forming Environment of V1647 Ori and McNeil's Nebula
We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations
of the star-forming environment surrounding V1647 Ori, an outbursting FUor/EXor
pre-MS star. Dust continuum and the (J = 2 - 1) CO, CO, CO
molecular emission lines were observed to characterize the V1647 Ori
circumstellar disc and any large scale molecular features present. We detect
continuum emission from the circumstellar disc and determine a radius r = 40
au, inclination i = 17 and total disc mass of
M of ~0.1 M. We do not identify any disc structures
associated with nearby companions, massive planets or fragmentation. The
molecular cloud environment surrounding V1647 Ori is both structured and
complex. We confirm the presence of an excavated cavity north of V1647 Ori and
have identified dense material at the base of the optical reflection nebula
(McNeil's Nebula) that is actively shaping its surrounding environment. Two
distinct outflows have been detected with dynamical ages of ~11,700 and 17,200
years. These outflows are misaligned suggesting disc precession over ~5500
years as a result of anisotropic accretion events is responsible. The
collimated outflows exhibit velocities of ~2 km s, similar in velocity
to that of other FUor objects presented in this series but significantly slower
than previous observations and model predictions. The V1647 Ori system is
seemingly connected by an "arm" of material to a large unresolved structure
located ~20 to the west. The complex environment surrounding V1647 Ori
suggests it is in the early stages of star formation which may relate to its
classification as both an FUor and EXor type object.Comment: 18 pages, 14 figures, 4 tables; accepted for publication in MNRA
The ALMA Early Science View of FUor/EXor Objects - V. Continuum Disc Masses and Sizes
Low-mass stars build a significant fraction of their total mass during short outbursts of enhanced accretion known as FUor and EXor outbursts. FUor objects are characterized by a sudden brightening of ∼5 mag at visible wavelengths within 1 yr and remain bright for decades. EXor objects have lower amplitude outbursts on shorter time-scales. Here we discuss a 1.3 mm Atacama Large Millimeter/submillimeter Array (ALMA) mini-survey of eight outbursting sources (three FUors, four EXors, and the borderline object V1647 Ori) in the Orion Molecular Cloud. While previous papers in this series discuss the remarkable molecular outflows observed in the three FUor objects and V1647 Ori, here we focus on the continuum data and the differences and similarities between the FUor and EXor populations. We find that FUor discs are significantly more massive (∼80–600 MJup) than the EXor objects (∼0.5–40 MJup). We also report that the EXor sources lack the prominent outflows seen in the FUor population. Even though our sample is small, the large differences in disc masses and outflow activity suggest that the two types of objects represent different evolutionary stages. The FUor sources seem to be rather compact (Rc \u3c 20–40 au) and to have a smaller characteristic radius for a given disc mass when compared to T Tauri stars. V1118 Ori, the only known close binary system in our sample, is shown to host a disc around each one of the stellar components. The disc around HBC 494 is asymmetric, hinting at a structure in the outer disc or the presence of a second disc
The gravitational mass of Proxima Centauri measured with SPHERE from a microlensing event
Proxima Centauri, our closest stellar neighbour, is a low-mass M5 dwarf
orbiting in a triple system. An Earth-mass planet with an 11 day period has
been discovered around this star. The star's mass has been estimated only
indirectly using a mass-luminosity relation, meaning that large uncertainties
affect our knowledge of its properties. To refine the mass estimate, an
independent method has been proposed: gravitational microlensing. By taking
advantage of the close passage of Proxima Cen in front of two background stars,
it is possible to measure the astrometric shift caused by the microlensing
effect due to these close encounters and estimate the gravitational mass of the
lens (Proxima Cen). Microlensing events occurred in 2014 and 2016 with impact
parameters, the closest approach of Proxima Cen to the background star, of
1\farcs6 0\farcs1 and 0\farcs5 0\farcs1, respectively. Accurate
measurements of the positions of the background stars during the last two years
have been obtained with HST/WFC3, and with VLT/SPHERE from the ground. The
SPHERE campaign started on March 2015, and continued for more than two years,
covering 9 epochs. The parameters of Proxima Centauri's motion on the sky,
along with the pixel scale, true North, and centering of the instrument
detector were readjusted for each epoch using the background stars visible in
the IRDIS field of view. The experiment has been successful and the astrometric
shift caused by the microlensing effect has been measured for the second event
in 2016. We used this measurement to derive a mass of
0.150 (an error of 40\%) \MSun for Proxima
Centauri acting as a lens. This is the first and the only currently possible
measurement of the gravitational mass of Proxima Centauri.Comment: 10 pages, 6 figures, accepted by MNRA
Constraining the mass of the planet(s) sculpting a disk cavity. The intriguing case of 2MASS J16042165-2130284
The large cavities observed in the dust and gas distributions of transition
disks may be explained by planet-disk interactions. At ~145 pc, 2MASS
J16042165-2130284 (J1604) is a 5-12 Myr old transitional disk with different
gap sizes in the mm- and m-sized dust distributions (outer edges at ~79
and at ~63 au, respectively). Its CO emission shows a ~30 au cavity.
This radial structure suggests that giant planets are sculpting this disk. We
aim to constrain the masses and locations of plausible giant planets around
J1604. We observed J1604 with the Spectro-Polarimetric High-contrast Exoplanet
REsearch (SPHERE) at the Very Large Telescope (VLT), in IRDIFS\_EXT,
pupil-stabilized mode, obtaining YJH- band images with the integral field
spectrograph (IFS) and K1K2-band images with the Infra-Red Dual-beam Imager and
Spectrograph (IRDIS). The dataset was processed exploiting the angular
differential imaging (ADI) technique with high-contrast algorithms. Our
observations reach a contrast of ~12 mag from 0.15" to 0.80"
(~22 to 115 au), but no planet candidate is detected. The disk is directly
imaged in scattered light at all bands from Y to K, and it shows a red color.
This indicates that the dust particles in the disk surface are mainly
m-sized grains. We confirm the sharp dip/decrement in
scattered light in agreement with polarized light observations. Comparing our
images with a radiative transfer model we argue that the southern side of the
disk is most likely the nearest. This work represents the deepest search yet
for companions around J1604. We reach a mass sensitivity of from ~22 to ~115 au according to a hot start scenario. We propose
that a brown dwarf orbiting inside of ~15 au and additional Jovian planets at
larger radii could account for the observed properties of J1604 while
explaining our lack of detection.Comment: 10 pages, 7 Figures. Accepted for publication in A&A . Abridged
abstrac
Exploring dust around HD142527 down to 0.025" / 4au using SPHERE/ZIMPOL
We have observed the protoplanetary disk of the well-known young Herbig star
HD 142527 using ZIMPOL Polarimetric Differential Imaging with the VBB (Very
Broad Band, ~600-900nm) filter. We obtained two datasets in May 2015 and March
2016. Our data allow us to explore dust scattering around the star down to a
radius of ~0.025" (~4au). The well-known outer disk is clearly detected, at
higher resolution than before, and shows previously unknown sub-structures,
including spirals going inwards into the cavity. Close to the star, dust
scattering is detected at high signal-to-noise ratio, but it is unclear whether
the signal represents the inner disk, which has been linked to the two
prominent local minima in the scattering of the outer disk, interpreted as
shadows. An interpretation of an inclined inner disk combined with a dust halo
is compatible with both our and previous observations, but other arrangements
of the dust cannot be ruled out. Dust scattering is also present within the
large gap between ~30 and ~140au. The comparison of the two datasets suggests
rapid evolution of the inner regions of the disk, potentially driven by the
interaction with the close-in M-dwarf companion, around which no polarimetric
signal is detected.Comment: 11 pages, 7 figures, accepted for publication in A
Monotonicity of quantum ground state energies: Bosonic atoms and stars
The N-dependence of the non-relativistic bosonic ground state energy is
studied for quantum N-body systems with either Coulomb or Newton interactions.
The Coulomb systems are "bosonic atoms," with their nucleus fixed, and the
Newton systems are "bosonic stars". In either case there exists some third
order polynomial in N such that the ratio of the ground state energy to the
respective polynomial grows monotonically in N. Some applications of these new
monotonicity results are discussed
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