482 research outputs found
Interpreting high spatial resolution line observations of planet-forming disks with gaps and rings : the case of HD 163296
Funding: C. R., G. M.-A., and C. G. acknowledge funding from the Netherlands Organisation for Scientific Research (NWO) TOP-1 grant as part of the research programme “Herbig Ae/Be stars, Rosetta stones for understanding the formation of planetary systems”, project number 614.001.552.Context. Spatially resolved continuum observations of planet-forming disks show prominent ring and gap structures in their dust distribution. However, the picture from gas observations is much less clear and constraints on the radial gas density structure (i.e. gas gaps) remain rare and uncertain. Aims. We want to investigate the importance of thermo-chemical processes for the interpretation of high-spatial-resolution gas observations of planet-forming disks and their impact on the derived gas properties. Methods. We applied the radiation thermo-chemical disk code PRODIMO (PROtoplanetary DIsk MOdel) to model the dust and gas disk of HD 163296 self-consistently, using the DSHARP (Disk Substructure at High Angular Resolution) gas and dust observations. With this model we investigated the impact of dust gaps and gas gaps on the observables and the derived gas properties, considering chemistry, and heating and cooling processes. Results. We find distinct peaks in the radial line intensity profiles of the CO line data of HD 163296 at the location of the dust gaps. Our model indicates that those peaks are not only a consequence of a gas temperature increase within the gaps but are mainly caused by the absorption of line emission from the back side of the disk by the dust rings. For two of the three prominent dust gaps in HD 163296, we find that thermo-chemical effects are negligible for deriving density gradients via measurements of the rotation velocity. However, for the gap with the highest dust depletion, the temperature gradient can be dominant and needs to be considered to derive accurate gas density profiles. Conclusions. Self-consistent gas and dust thermo-chemical modelling in combination with high-quality observations of multiple molecules are necessary to accurately derive gas gap depths and shapes. This is crucial to determine the origin of gaps and rings in planet-forming disks and to improve the mass estimates of forming planets if they are the cause of the gap.PostprintPeer reviewe
Gas phase mean opacities for varying [M/H], N/O, and C/O
We present a set of gas-phase Planck mean and Rosseland mean opacity tables
applicable for simulations of star and planet formation, stellar evolution,
disk modelling at various metallicities in hydrogen-rich environments. The
tables are calculated for gas temperatures between 1000K and 10000K and total
hydrogen number densities between 10^2 cm^-3 and 10^17 cm^-3. The
carbon-to-oxygen ratio is varied from 0.43 to well above 2.0, the
nitrogen-to-oxygen ration between 0.14 and 100.0. The tables are calculated for
a range of metallicities down to [M/H]'= log N_M/N_H=-7.0. We demonstrate how
the mean opacities and the abundances of the opacity species vary with C/O,
N/O, and [M/H]'. We use the element abundances from Grevesse, Asplund & Sauval
(2007), and we provide additional tables for the oxygen-abundance value from
Caffau et al.(2008). All tables will be available online under
http://star-www.st-and.ac.uk/ch80/datasources.htmlComment: 10 pages, accepted for publication in MNRA
Probing the Early Evolution of Young High-Mass Stars
Near-infrared imaging surveys of high-mass star-forming regions reveal an
amazingly complex interplay between star formation and the environment
(Churchwell et al. 2006; Alvarez et al. 2004). By means of near-IR spectroscopy
the embedded massive young stars can be characterized and placed in the context
of their birth site. However, so far spectroscopic surveys have been hopelessly
incomplete, hampering any systematic study of these very young massive stars.
New integral field instrumentation available at ESO has opened the possibility
to take a huge step forward by obtaining a full spectral inventory of the
youngest massive stellar populations in star-forming regions currently
accessible. Simultaneously, the analysis of the extended emission allows the
characterization of the environmental conditions. The Formation and Early
Evolution of Massive Stars (FEMS) collaboration aims at setting up a large
observing campaign to obtain a full census of the stellar content, ionized
material, outflows and PDR's over a sample of regions that covers a large
parameter space. Complementary radio, mm and infrared observations will be used
for the characterization of the deeply embedded population. For the first eight
regions we have obtained 40 hours of SINFONI observations. In this
contribution, we present the first results on three regions that illustrate the
potential of this strategy.Comment: To appear in ASP Conf. Proceedings of "Massive Star Formation:
Observations confront Theory", H. Beuther et al. (eds.), held in Heidelberg,
September 200
OGLE-2005-BLG-018: Characterization of Full Physical and Orbital Parameters of a Gravitational Binary Lens
We present the analysis result of a gravitational binary-lensing event
OGLE-2005-BLG-018. The light curve of the event is characterized by 2 adjacent
strong features and a single weak feature separated from the strong features.
The light curve exhibits noticeable deviations from the best-fit model based on
standard binary parameters. To explain the deviation, we test models including
various higher-order effects of the motions of the observer, source, and lens.
From this, we find that it is necessary to account for the orbital motion of
the lens in describing the light curve. From modeling of the light curve
considering the parallax effect and Keplerian orbital motion, we are able to
measure not only the physical parameters but also a complete orbital solution
of the lens system. It is found that the event was produced by a binary lens
located in the Galactic bulge with a distance kpc from the Earth.
The individual lens components with masses and are separated with a semi-major axis of AU and
orbiting each other with a period yr. The event demonstrates
that it is possible to extract detailed information about binary lens systems
from well-resolved lensing light curves.Comment: 19 pages, 6 figure
Searching for ß-delayed protons from 11 Be
ISOLDE Workshop and Usersmeeting. Wednesday 05 December - Friday 07 December 2018 .CERN ( ISOLDE User Support. PH Departmen - CERN/CH-1211 Geneve 23). --.https://indico.cern.ch/event/736872/contributions
OGLE-2009-BLG-092/MOA-2009-BLG-137: A Dramatic Repeating Event With the Second Perturbation Predicted by Real-Time Analysis
We report the result of the analysis of a dramatic repeating gravitational
microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light
curve is characterized by two distinct peaks with perturbations near both
peaks. We find that the event is produced by the passage of the source
trajectory over the central perturbation regions associated with the individual
components of a wide-separation binary. The event is special in the sense that
the second perturbation, occurring days after the first, was
predicted by the real-time analysis conducted after the first peak,
demonstrating that real-time modeling can be routinely done for binary and
planetary events. With the data obtained from follow-up observations covering
the second peak, we are able to uniquely determine the physical parameters of
the lens system. We find that the event occurred on a bulge clump giant and it
was produced by a binary lens composed of a K and M-type main-sequence stars.
The estimated masses of the binary components are
and , respectively, and they are separated in
projection by . The measured distance to the
lens is . We also detect the orbital motion
of the lens system.Comment: 18 pages, 5 figures, 1 tabl
Correlation between the Josephson coupling energy and the condensation energy in bilayer cuprate superconductors
We review some previous studies concerning the intra-bilayer Josephson
plasmons and present new ellipsometric data of the c-axis infrared response of
almost optimally doped Bi_{2}Sr_{2}CaCu_{2}O_{8}. The c-axis conductivity of
this compound exhibits the same kind of anomalies as that of underdoped
YBa_{2}Cu_{3}O_{7-delta}. We analyze these anomalies in detail and show that
they can be explained within a model involving the intra-bilayer Josephson
effect and variations of the electric field inside the unit cell. The Josephson
coupling energies of different bilayer compounds obtained from the optical data
are compared with the condensation energies and it is shown that there is a
reasonable agreement between the values of the two quantities. We argue that
the Josephson coupling energy, as determined by the frequency of the
intra-bilayer Josephson plasmon, represents a reasonable estimate of the change
of the effective c-axis kinetic energy upon entering the superconducting state.
It is further explained that this is not the case for the estimate based on the
use of the simplest ``tight-binding'' sum rule. We discuss possible
interpretations of the remarkable agreement between the Josephson coupling
energies and the condensation energies. The most plausible interpretation is
that the interlayer tunneling of the Cooper pairs provides the dominant
contribution to the condensation energy of the bilayer compounds; in other
words that the condensation energy of these compounds can be accounted for by
the interlayer tunneling theory. We suggest an extension of this theory, which
may also explain the high values of T_{c} in the single layer compounds
Tl_{2}Ba_{2}CuO_{6} and HgBa_{2}CuO_{4}, and we make several experimentally
verifiable predictions.Comment: 16 pages (including Tables) and 7 figures; accepted for publication
in Physical Review
Observing the gas component of circumplanetary disks around wide-orbit planet-mass companions in the (sub)mm regime
C.R., G.M.-A., and C.G. acknowledge funding from the Netherlands Organisation for Scientific Research (NWO) TOP-1 grant as part of the research programme “Herbig Ae/Be stars, Rosetta stones for understanding the formation of planetary systems”, project number 614.001.552.Context. Several detections of wide-orbit planet-mass/sub-stellar companions around young solar-like stars were reported in the last decade. The origin of those possible planets is still unclear but accretion tracers and VLT/SPHERE observations indicate that they are surrounded by circumplanetary material or even a circumplanetary disk. Aims. We want to investigate if the gas component of disks around wide-orbit companions is detectable with current (ALMA) and future (ngVLA) (sub)mm telescopes and what constraints such gas observations can provide on the nature of the circumplanetary material and on the mass of the companion. Methods. We applied the radiation thermo-chemical disk code PRODIMOto model the dust and gas component of passive circum-planetary disks and produced realistic synthetic observables. We considered different companion properties (mass, luminosity), disk parameters (mass, size, dust properties) and radiative environments (background fields) and compared the resulting synthetic observables to telescope sensitivities and to existing dust observations. Results. The main criterion for a successful detection is the size of the circumplanetary disk. At a distance of about 150 pc, acircumplanetary disk with an outer radius of about 10 au is detectable with ALMA in about 6 hours in optically thick CO lines.Other aspects such as the companion’s luminosity, disk inclination and background radiation fields are also relevant, and should be considered to optimize the observing strategy for detection experiments. Conclusions. For most of the known wide-orbit planet-mass companions, their maximum theoretical disk size of one third of the Hill radius would be sufficient to allow detection of CO lines. It is therefore feasible to detect their gas disks and constrain the mass of the companion through the kinematic signature. Even in the case of non-detections such observations will provide stringent constraints on disk size and gas mass, information crucial for formation theories.PostprintPeer reviewe
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