1,801 research outputs found
Depth Estimation Through a Generative Model of Light Field Synthesis
Light field photography captures rich structural information that may
facilitate a number of traditional image processing and computer vision tasks.
A crucial ingredient in such endeavors is accurate depth recovery. We present a
novel framework that allows the recovery of a high quality continuous depth map
from light field data. To this end we propose a generative model of a light
field that is fully parametrized by its corresponding depth map. The model
allows for the integration of powerful regularization techniques such as a
non-local means prior, facilitating accurate depth map estimation.Comment: German Conference on Pattern Recognition (GCPR) 201
Soils of the High Terrace Remnants in the Upper Ohio Valley
Author Institution: Soil Conservation Service, U. S. Department of Agriculture, Box 248, Lisbon, Ohi
Soil and Paleosol of the Warnock Terrace
Author Institution: U. S. Department of Agriculture, Lisbon, Ohi
NLTE spectroscopic analysis of the He anomaly in subluminous B-type stars
Several B-type main-sequence stars show chemical peculiarities. A
particularly striking class are the He stars, which exhibit a remarkable
enrichment of He with respect to He. This isotopic anomaly has also
been found in blue horizontal branch (BHB) and subdwarf B (sdB) stars, which
are helium-core burning stars of the extreme horizontal branch. Using a hybrid
local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars,
we analyzed high-quality spectra of two known He BHBs and nine known He
sdBs to determine their isotopic helium abundances and He/He abundance
ratios. We redetermined their atmospheric parameters and analyzed selected
neutral helium lines, including 4922 and 6678
, which are very sensitive to He/He. Most of the He
sdBs cluster in a narrow temperature strip between 26000 K and 30000 K and are
helium deficient in accordance with previous LTE analyses. BD+48 2721
is reclassified as a BHB star because of its low temperature
( 20700 K). Whereas He is almost absent
(He/He 0.25) in most of the known He stars, other sample stars
show abundance ratios up to He/He2.51. A search for He stars in
the ESO SPY survey led to the discovery of two new He sdB stars (HE
0929-0424 and HE 1047-0436). The observed helium line profiles of all BHBs and
of three sdBs are not matched by chemically homogeneous atmospheres, but hint
at vertical helium stratification. This phenomenon has been seen in other
peculiar B-type stars, but is found for the first time for sdBs. We estimate
helium to increase from the outer to the inner atmosphere by factors ranging
from 1.4 (SB 290) up to 8.0 (BD+48 2721).Comment: 19 pages, 79 figures submitted to Astronomy&Astrophysic
Subdwarf B Stars from the ESO Supernova Ia Progenitor Survey -- Observation versus Theory
Original paper can be found at: http://www.astrosociety.org/pubs/cs/328.html--Copyright Astronomical Society of the PacificWe present the analysis of a high-quality sample of optical spectra for 76 sdB stars from the ESO Supernova Ia Progenitor Survey. Effective temperature, surface gravity, and photospheric helium abundance were derived from line profile fits. We demonstrate that our subsample of 52 single-lined sdB stars is a useful tool to compare observation and theory. The predictions of population synthesis models for close binary evolution are compared to our data. We show that the simulations cover the observed parameter range of sdBs, but fail to reproduce the observed distribution in detail
High resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia Progenitor Survey III. DA white dwarfs
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO) DOI: 10.1051/0004-6361/200912531Context. The ESO Supernova Ia Progenitor Survey (SPY) took high-resolution spectra of more than 1000 white dwarfs and pre-white dwarfs. About two thirds of the stars observed are hydrogen-dominated DA white dwarfs. Here we present a catalog and detailed spectroscopic analysis of the DA stars in the SPY. Aims. Atmospheric parameters effective temperature and surface gravity are determined for normal DAs. Double-degenerate binaries, DAs with magnetic fields or dM companions, are classified and discussed. Methods. The spectra are compared with theoretical model atmospheres using a fitting technique. Results. Our final sample contains 615 DAs, which show only hydrogen features in their spectra, although some are double-degenerate binaries. 187 are new detections or classifications. We also find 10 magnetic DAs (4 new) and 46 DA+dM pairs (10 new).Peer reviewe
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