1,119 research outputs found
Monte-Carlo radiative transfer simulation of the circumstellar disk of the Herbig Ae star HD 144432
Studies of pre-transitional disks, with a gap region between the inner
infrared-emitting region and the outer disk, are important to improving our
understanding of disk evolution and planet formation. Previous infrared
interferometric observations have shown hints of a gap region in the
protoplanetary disk around the Herbig Ae star HD~144432. We study the dust
distribution around this star with two-dimensional radiative transfer modeling.
We compare the model predictions obtained via the Monte-Carlo radiative
transfer code RADMC-3D with infrared interferometric observations and the
{\SED} of HD~144432. The best-fit model that we found consists of an inner
optically thin component at 0.21\enDash0.32~\AU and an optically thick outer
disk at 1.4\enDash10~\AU. We also found an alternative model in which the
inner sub-AU region consists of an optically thin and an optically thick
component. Our modeling suggests an optically thin component exists in the
inner sub-AU region, although an optically thick component may coexist in the
same region. Our modeling also suggests a gap-like discontinuity in the disk of
HD~144432.Comment: 18 pages, 12 figure
Near-infrared interferometric observation of the Herbig Ae star HD144432 with VLTI/AMBER
We study the sub-AU-scale circumstellar environment of the Herbig Ae star
HD144432 with near-infrared (NIR) VLTI/AMBER observations to investigate the
structure of its inner dust disk. The interferometric observations were carried
out with the AMBER instrument in the H and K band. We interpret the measured H-
and K-band visibilities, the near- and mid-infrared visibilities from the
literature, and the SED of HD144432 by using geometric ring models and
ring-shaped temperature-gradient disk models with power-law temperature
distributions. We derived a K-band ring-fit radius of 0.17 \pm 0.01 AU and an
H-band radius of 0.18 \pm 0.01 AU (for a distance of 145 pc). This measured
K-band radius of \sim0.17 AU lies in the range between the dust sublimation
radius of \sim0.13 AU (predicted for a dust sublimation temperature of 1500 K
and gray dust) and the prediction of models including backwarming (\sim0.27
AU). We found that an additional extended halo component is required in both
the geometric and temperature-gradient modeling. In the best temperature-
gradient model, the disk consists of two components. The inner part of the disk
is a thin ring with an inner radius of \sim0.21 AU, a temperature of \sim1600
K, and a ring thickness \sim0.02 AU. The outer part extends from \sim1 AU to
\sim10 AU with an inner temperature of \sim400 K. We find that the disk is
nearly face-on with an inclination angle of < 28 degree. Our
temperature-gradient modeling suggests that the NIR excess is dominated by
emission from a narrow, bright rim located at the dust sublimation radius,
while an extended halo component contributes \sim6% to the total flux at 2
{\mu}m. The MIR model emission has a two-component structure with \sim20% flux
from the inner ring and the rest from the outer part. This two-component
structure suggests a disk gap, which is possibly caused by the shadow of a
puffed-up inner rim.Comment: 7 pages, 5 figures, accepted by A&
Revealing the inclined circumstellar disk in the UX Orionis system KK Ophiuchi
This is the final version of the article. Available from EDP Sciences via the DOI in this record.Aims. We study the inner sub-AU region of the circumstellar environment of the UX Ori-type star KK Oph with near-infrared VLTI/AMBER interferometry. We are particularly interested in the inclination of the star-disk system, and we use this information to test the current standard picture for UX Ori stars.
Methods. We recorded spectrally dispersed (R ~ 35) interferograms in the near-infrared H and K bands with the VLTI/AMBER instrument. The derived visibilities, closure phases, and the spectral energy distribution of KK Oph were compared with two-dimensional geometric and radiative transfer models (RADMC).
Results. We obtained visibilities at four different position angles. Using two-dimensional geometric models, we derive an axis ratio ~3.0 corresponding to an inclination of ~70°. A fitted inclined ring model leads to a ring radius of 2.8 ± 0.2 mas, corresponding to 0.44 ± 0.03 AU at a distance of 160 pc, which is larger than the dust sublimation radius of ~0.1 AU predicted for a dust sublimation temperature of 1500 K. Our derived two-dimensional RADMC model consists of a circumstellar disk with an inclination angle of ~70° and an additional dust envelope.
Conclusions. The finding of an ~70° inclined disk around KK Oph is consistent with the prediction that UX Ori objects are seen under large inclination angles, and orbiting clouds in the line of sight cause the observed variability. Furthermore, our results suggest that the orbit of the companion KK Oph B and the disk plane are coplanar.A. Kreplin was supported for this research through a stipend from the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne. V.G. and L.T. were supported in part by the grant of the Presidium of RAS P 21 and grant NSh. – 1625.2012.2. They also thank the Max-Planck-Society for the support during their stay in Bonn. This research has made use of NASA’s Astrophysics Data System Bibliographic Services
Extreme Ultra-Violet Spectroscopy of the Lower Solar Atmosphere During Solar Flares
The extreme ultraviolet portion of the solar spectrum contains a wealth of
diagnostic tools for probing the lower solar atmosphere in response to an
injection of energy, particularly during the impulsive phase of solar flares.
These include temperature and density sensitive line ratios, Doppler shifted
emission lines and nonthermal broadening, abundance measurements, differential
emission measure profiles, and continuum temperatures and energetics, among
others. In this paper I shall review some of the advances made in recent years
using these techniques, focusing primarily on studies that have utilized data
from Hinode/EIS and SDO/EVE, while also providing some historical background
and a summary of future spectroscopic instrumentation.Comment: 34 pages, 8 figures. Submitted to Solar Physics as part of the
Topical Issue on Solar and Stellar Flare
Measurement of the lifetime
Using a data set corresponding to an integrated luminosity of ,
collected by the LHCb experiment in collisions at centre-of-mass energies
of 7 and 8 TeV, the effective lifetime in the
decay mode, , is measured to be ps. Assuming
conservation, corresponds to the lifetime of the light
mass eigenstate. This is the first measurement of the effective
lifetime in this decay mode.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-017.htm
Measurement of the mass and lifetime of the baryon
A proton-proton collision data sample, corresponding to an integrated
luminosity of 3 fb collected by LHCb at and 8 TeV, is used
to reconstruct , decays. Using the , decay mode for calibration, the lifetime ratio and absolute
lifetime of the baryon are measured to be \begin{align*}
\frac{\tau_{\Omega_b^-}}{\tau_{\Xi_b^-}} &= 1.11\pm0.16\pm0.03, \\
\tau_{\Omega_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the
uncertainties are statistical, systematic and from the calibration mode (for
only). A measurement is also made of the mass difference,
, and the corresponding mass, which
yields \begin{align*} m_{\Omega_b^-}-m_{\Xi_b^-} &= 247.4\pm3.2\pm0.5~{\rm
MeV}/c^2, \\ m_{\Omega_b^-} &= 6045.1\pm3.2\pm 0.5\pm0.6~{\rm MeV}/c^2.
\end{align*} These results are consistent with previous measurements.Comment: 11 pages, 5 figures, All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-008.htm
Study of J /ψ production in Jets
The production of J/ψ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/ψ meson, z(J/ψ)≡pT(J/ψ)/pT(jet), is measured using jets with pT(jet)>20 GeV in the pseudorapidity range 2.5<η(jet)<4.0. The observed z(J/ψ)distribution for J/ψ mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/ψ production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the pT fraction carried by prompt J/ψ mesons in jets at any experiment
Constraints on the unitarity triangle angle from Dalitz plot analysis of decays
The first study is presented of CP violation with an amplitude analysis of
the Dalitz plot of decays, with , and . The analysis is based on a data sample corresponding to
of collisions collected with the LHCb detector. No
significant CP violation effect is seen, and constraints are placed on the
angle of the unitarity triangle formed from elements of the
Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated
with the decay are determined for the first time. These
measurements can be used to improve the sensitivity to of existing and
future studies of the decay.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-059.html;
updated to correct figure 9 (numerical results unchanged
Observation of the decay
The decay is observed in collision
data corresponding to an integrated luminosity of 3 fb recorded by the
LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first
observation of this decay channel, with a statistical significance of 15
standard deviations. The mass of the meson is measured to be
MeV/c. The branching fraction ratio
is measured to be 0.0115\,\pm\, 0.0012\, ^{+0.0005}_{-0.0009}.
In both cases, the first uncertainty is statistical and the second is
systematic. No evidence for non-resonant or decays is found.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-033.htm
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