9,070 research outputs found
Discovery of 11 New T Dwarfs in the Two Micron All-Sky Survey, Including a Possible L/T Transition Binary
We present the discovery of 11 new T dwarfs, found during the course of a
photometric survey for mid-to-late T dwarfs in the 2MASS Point Source Catalog
and from a proper motion selected sample of ultracool dwarfs in the 2MASS
Working Database. Using the NASA Infrared Telescope Facility SpeX spectrograph,
we obtained low-resolution (R~150) spectroscopy, allowing us to derive
near-infrared spectral types of T2-T8. One of these new T dwarfs, 2MASS
J13243559+6358284, was also discovered independently by Metchev et al., in
prep. This object is spectroscopically peculiar and possibly a binary and/or
very young (<300 Myr). We specifically attempted to model the spectrum of this
source as a composite binary to reproduce its peculiar spectral
characteristics. The latest-type object in our sample is a T8 dwarf, 2MASS
J07290002-3954043, now one of the four latest-type T dwarfs known. All 11 T
dwarfs are nearby given their spectrophotometric distance estimates, with 1 T
dwarf within 10 pc and 8 additional T dwarfs within 25 pc, if single. These new
additions increase the 25 pc census of T dwarfs by ~14%. Their proximity offers
an excellent opportunity to probe for companions at closer separations than are
possible for more distant T dwarfs.Comment: 45 pages, 9 figures, 9 tables. Published in AJ. Replacement: Fixed
typos in 3 tables (some reported photometry was from the 2MASS Working
Database instead of the 2MASS All Sky Catalog) and updated Fig.
Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Luminous Infrared Galaxy Candidates
We present Spitzer 3.6 and 4.5 m photometry and positions for a sample
of 1510 brown dwarf candidates identified by the WISE all-sky survey. Of these,
166 have been spectroscopically classified as objects with spectral types M(1),
L(7), T(146), and Y(12); Sixteen other objects are non-(sub)stellar in nature.
The remainder are most likely distant L and T dwarfs lacking spectroscopic
verification, other Y dwarf candidates still awaiting follow-up, and assorted
other objects whose Spitzer photometry reveals them to be background sources.
We present a catalog of Spitzer photometry for all astrophysical sources
identified in these fields and use this catalog to identify 7 fainter (4.5
m 17.0 mag) brown dwarf candidates, which are possibly wide-field
companions to the original WISE sources. To test this hypothesis, we use a
sample of 919 Spitzer observations around WISE-selected high-redshift
hyper-luminous infrared galaxy (HyLIRG) candidates. For this control sample we
find another 6 brown dwarf candidates, suggesting that the 7 companion
candidates are not physically associated. In fact, only one of these 7 Spitzer
brown dwarf candidates has a photometric distance estimate consistent with
being a companion to the WISE brown dwarf candidate. Other than this there is
no evidence for any widely separated ( 20 AU) ultra-cool binaries. As an
adjunct to this paper, we make available a source catalog of 7.33
objects detected in all of these Spitzer follow-up fields for use
by the astronomical community. The complete catalog includes the Spitzer 3.6
and 4.5 m photometry, along with positionally matched and
photometry from USNO-B; , , and photometry from 2MASS; and ,
, , and photometry from the WISE all-sky catalog
Expert evaluation of the usability of HeloVis: a 3D Immersive Helical Visualization for SIGINT Analysis
International audienceThis paper presents an evaluation of HeloVis: a 3D interactive visualization that relies on immersive properties to improve user performance during SIGnal INTelligence (SIGINT) analysis. HeloVis draws on perceptive biases, highlighted by Gestalt laws, and on depth perception to enhance the recurrence properties contained in the data. In this paper, we briefly recall what is SIGINT, the challenges that it brings to visual analytics, and the limitations of state of the art SIGINT tools. Then, we present HeloVis, and we evaluate its efficiency through the results of an evaluation that we have made with civil and military operators who are the expert end-users of SIGINT analysis
Bulletin of the Center for Children's Books 14 (01) 1960
published or submitted for publicatio
The Development of a New Methodology for Automated Sounding Selection on Nautical Charts
Conducting a manual sounding selection for display on official nautical charts is time-consuming and is becoming more challenging because of the high-quality hydrographic data. Boosted by the development of surveying technology, research of automated sounding selection capabilities is a logical step in improving production of nautical charts. In this work a new methodology for automated sounding selection based on areas of sudden change in the sea floor relief is defined. Quantitative parameters of the seafloor obtained from the survey, slope and aspect are used to segregate and classify seafloor features significant for navigation. By detecting their boundaries, principles of sounding selection for each class are applied in order to represent all the relevant information regarding a specific feature. Spatial accuracy analysis is conducted on two large multibeam hydrographic surveys by comparing the obtained results with the automated sounding selection feature within dKart Editor and the manually selected soundings on official nautical charts. The RMSE (Root Mean Square Error) of vertical deviations and its relation to terrain characteristics within the initial quality assessment is encouraging and suggests that the proposed automated methodology represents an improvement compared to dKart and could be applied with the same effectiveness as a manual method
SciTech News Volume 71, No. 1 (2017)
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MolSieve: A Progressive Visual Analytics System for Molecular Dynamics Simulations
Molecular Dynamics (MD) simulations are ubiquitous in cutting-edge
physio-chemical research. They provide critical insights into how a physical
system evolves over time given a model of interatomic interactions.
Understanding a system's evolution is key to selecting the best candidates for
new drugs, materials for manufacturing, and countless other practical
applications. With today's technology, these simulations can encompass millions
of unit transitions between discrete molecular structures, spanning up to
several milliseconds of real time. Attempting to perform a brute-force analysis
with data-sets of this size is not only computationally impractical, but would
not shed light on the physically-relevant features of the data. Moreover, there
is a need to analyze simulation ensembles in order to compare similar processes
in differing environments. These problems call for an approach that is
analytically transparent, computationally efficient, and flexible enough to
handle the variety found in materials based research. In order to address these
problems, we introduce MolSieve, a progressive visual analytics system that
enables the comparison of multiple long-duration simulations. Using MolSieve,
analysts are able to quickly identify and compare regions of interest within
immense simulations through its combination of control charts, data-reduction
techniques, and highly informative visual components. A simple programming
interface is provided which allows experts to fit MolSieve to their needs. To
demonstrate the efficacy of our approach, we present two case studies of
MolSieve and report on findings from domain collaborators.Comment: Updated references to GPCC
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