174 research outputs found
The Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
We present the science database produced by the Formation and Evolution of
Planetary Systems (FEPS) Spitzer Legacy program. Data reduction and validation
procedures for the IRAC, MIPS, and IRS instruments are described in detail. We
also derive stellar properties for the FEPS sample from available broad-band
photometry and spectral types, and present an algorithm to normalize Kurucz
synthetic spectra to optical and near-infrared photometry. The final FEPS data
products include IRAC and MIPS photometry for each star in the FEPS sample and
calibrated IRS spectra.Comment: 64 pages, 12 figures, 5 tables; accepted for publication in ApJ
HERSCHEL OBSERVATIONS OF EXTRA-ORDINARY SOURCES: H2S AS A PROBE OF DENSE GAS AND POSSIBLY HIDDEN LUMINOSITY TOWARD THE ORION KL HOT CORE
We present Herschel/HIFI observations of the light hydride H2S obtained from the full spectral scan of the Orion Kleinmann-Low nebula (Orion KL) taken as part of the Herschel Observations of EXtra-Ordinary Sources GT (guaranteed time) key program. In total, we observe 52, 24, and 8 unblended or slightly blended features from H2 32S, H2 34S, and H2 33S, respectively. We only analyze emission from the so-called hot core, but emission from the plateau, extended ridge, and/or compact ridge are also detected. Rotation diagrams for ortho and para H2S follow straight lines given the uncertainties and yield T rot = 141 ± 12 K. This indicates H2S is in local thermodynamic equilibrium and is well characterized by a single kinetic temperature or an intense far-IR radiation field is redistributing the population to produce the observed trend. We argue the latter scenario is more probable and find that the most highly excited states (E up gsim 1000 K) are likely populated primarily by radiation pumping. We derive a column density, N tot(H2 32S) = 9.5 ± 1.9 × 1017 cm–2, gas kinetic temperature, T kin = 120 K, and constrain the H2 volume density, gsim 9 × 10 7 cm–3, for the H2S emitting gas. These results point to an H2S origin in markedly dense, heavily embedded gas, possibly in close proximity to a hidden self-luminous source (or sources), which are conceivably responsible for Orion KL's high luminosity. We also derive an H2S ortho/para ratio of 1.7 ± 0.8 and set an upper limit for HDS/H2S of <4.9 × 10 –3
MSLICE Sequencing
MSLICE Sequencing is a graphical tool for writing sequences and integrating them into RML files, as well as for producing SCMF files for uplink. When operated in a testbed environment, it also supports uplinking these SCMF files to the testbed via Chill. This software features a free-form textural sequence editor featuring syntax coloring, automatic content assistance (including command and argument completion proposals), complete with types, value ranges, unites, and descriptions from the command dictionary that appear as they are typed. The sequence editor also has a "field mode" that allows tabbing between arguments and displays type/range/units/description for each argument as it is edited. Color-coded error and warning annotations on problematic tokens are included, as well as indications of problems that are not visible in the current scroll range. "Quick Fix" suggestions are made for resolving problems, and all the features afforded by modern source editors are also included such as copy/cut/paste, undo/redo, and a sophisticated find-and-replace system optionally using regular expressions. The software offers a full XML editor for RML files, which features syntax coloring, content assistance and problem annotations as above. There is a form-based, "detail view" that allows structured editing of command arguments and sequence parameters when preferred. The "project view" shows the user s "workspace" as a tree of "resources" (projects, folders, and files) that can subsequently be opened in editors by double-clicking. Files can be added, deleted, dragged-dropped/copied-pasted between folders or projects, and these operations are undoable and redoable. A "problems view" contains a tabular list of all problems in the current workspace. Double-clicking on any row in the table opens an editor for the appropriate sequence, scrolling to the specific line with the problem, and highlighting the problematic characters. From there, one can invoke "quick fix" as described above to resolve the issue. Once resolved, saving the file causes the problem to be removed from the problem view
Clinical and Molecular Characteristics of Post-Colonoscopy Colorectal Cancer: A Population-based Study
Colonoscopy provides incomplete protection from colorectal cancer (CRC), but determinants of post-colonoscopy CRC are not well understood. We compared clinical features and molecular characteristics of CRCs diagnosed at different time intervals after a previous colonoscopy
MPS Editor
Previously, it was time-consuming to hand-edit data and then set up simulation runs to find the effect and impact of the input data on a spacecraft. MPS Editor provides the user the capability to create/edit/update models and sequences, and immediately try them out using what appears to the user as one piece of software. MPS Editor provides an integrated sequencing environment for users. It provides them with software that can be utilized during development as well as actual operations. In addition, it provides them with a single, consistent, user friendly interface. MPS Editor uses the Eclipse Rich Client Platform to provide an environment that can be tailored to specific missions. It provides the capability to create and edit, and includes an Activity Dictionary to build the simulation spacecraft models, build and edit sequences of commands, and model the effects of those commands on the spacecraft. MPS Editor is written in Java using the Eclipse Rich Client Platform. It is currently built with four perspectives: the Activity Dictionary Perspective, the Project Adaptation Perspective, the Sequence Building Perspective, and the Sequence Modeling Perspective. Each perspective performs a given task. If a mission doesn't require that task, the unneeded perspective is not added to that project's delivery. In the Activity Dictionary Perspective, the user builds the project-specific activities, observations, calibrations, etc. Typically, this is used during the development phases of the mission, although it can be used later to make changes and updates to the Project Activity Dictionary. In the Adaptation Perspective, the user creates the spacecraft models such as power, data store, etc. Again, this is typically used during development, but will be used to update or add models of the spacecraft. The Sequence Building Perspective allows the user to create a sequence of activities or commands that go to the spacecraft. It provides a simulation of the activities and commands that have been created
Precise Infrared Radial Velocities from Keck/NIRSPEC and the Search for Young Planets
We present a high-precision infrared radial velocity study of late-type stars
using spectra obtained with NIRSPEC at the W. M. Keck Observatory. Radial
velocity precisions of 50 m/s are achieved for old field mid-M dwarfs using
telluric features for precise wavelength calibration. Using this technique, 20
young stars in the {\beta} Pic (age ~12 Myr) and TW Hya (age ~8 Myr)
Associations were monitored over several years to search for low mass
companions; we also included the chromospherically active field star GJ 873 (EV
Lac) in this survey. Based on comparisons with previous optical observations of
these young active stars, radial velocity measurements at infrared wavelengths
mitigate the radial velocity noise caused by star spots by a factor of ~3.
Nevertheless, star spot noise is still the dominant source of measurement error
for young stars at 2.3 {\mu}m, and limits the precision to ~77 m/s for the
slowest rotating stars (v sin i < 6 km/s), increasing to ~168 m/s for rapidly
rotating stars (v sin i > 12 km/s). The observations reveal both GJ 3305 and
TWA 23 to be single-lined spectroscopic binaries; in the case of GJ 3305, the
motion is likely caused by its 0.09" companion, identified after this survey
began. The large amplitude, short-timescale variations of TWA 13A are
indicative of a hot Jupiter-like companion, but the available data are
insufficient to confirm this. We label it as a candidate radial velocity
variable. For the remainder of the sample, these observations exclude the
presence of any 'hot' (P < 3 days) companions more massive than 8 MJup, and any
'warm' (P < 30 days) companions more massive than 17 MJup, on average. Assuming
an edge-on orbit for the edge-on disk system AU Mic, these observations exclude
the presence of any hot Jupiters more massive than 1.8 MJup or warm Jupiters
more massive than 3.9 MJup.Comment: Accepted for publication in The Astrophysical Journal. 18 pages, 7
figure
Formation and Evolution of Planetary Systems: Placing Our Solar System in Context with Spitzer
We summarize the progress to date of our Legacy Science Program entitled "The
Formation and Evolution of Planetary Systems" (FEPS) based on observations
obtained with the Spitzer Space Telescope during its first year of operation.
In addition to results obtained from our ground-based preparatory program and
our early validation program, we describe new results from a survey for
near-infrared excess emission from the youngest stars in our sample as well as
a search for cold debris disks around sun-like stars. We discuss the
implications of our findings with respect to current understanding of the
formation and evolution of our own solar system.Comment: 8 postscript pages including 3 figures. To appear in "Spitzer New
Views of the Cosmos" ASP Conference Series, eds. L. Armus et al. FEPS website
at http://feps.as.arizona.ed
Dose-Additive Carcinogenicity of a Defined Mixture of “Dioxin-like Compounds”
Use of the dioxin toxic equivalency factor (TEF) approach in human risk assessments assumes that the combined effects of dioxin-like compounds in a mixture can be predicted based on a potency-adjusted dose-additive combination of constituents of the mixture. In this study, we evaluated the TEF approach in experimental 2-year rodent cancer bioassays with female Harlan Sprague-Dawley rats receiving 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3,3′,4,4′,5-pentachlorobiphenyl (PCB-126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), or a mixture of the three compounds. Statistically based dose–response modeling indicated that the shape of the dose–response curves for hepatic, lung, and oral mucosal neoplasms was the same in studies of the three individual chemicals and the mixture. In addition, the dose response for the mixture could be predicted from a combination of the potency-adjusted doses of the individual compounds. Finally, we showed that use of the current World Health Organization dioxin TEF values adequately predicted the increased incidence of liver tumors (hepatocellular adenoma and cholangiocarcinoma) induced by exposure to the mixture. These data support the use of the TEF approach for dioxin cancer risk assessments
The PTF Orion Project: a Possible Planet Transiting a T-Tauri Star
We report observations of a possible young transiting planet orbiting a
previously known weak-lined T-Tauri star in the 7-10 Myr old Orion-OB1a/25-Ori
region. The candidate was found as part of the Palomar Transient Factory (PTF)
Orion project. It has a photometric transit period of 0.448413 +- 0.000040
days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision
radial velocity (RV) observations and adaptive optics imaging suggest that the
star is not an eclipsing binary, and that it is unlikely that a background
source is blended with the target and mimicking the observed transit. RV
observations with the Hobby-Eberly and Keck telescopes yield an RV that has the
same period as the photometric event, but is offset in phase from the transit
center by approximately -0.22 periods. The amplitude (half range) of the RV
variations is 2.4 km/s and is comparable with the expected RV amplitude that
stellar spots could induce. The RV curve is likely dominated by stellar spot
modulation and provides an upper limit to the projected companion mass of M_p
sin i_orb < 4.8 +- 1.2 M_Jup; when combined with the orbital inclination, i
orb, of the candidate planet from modeling of the transit light curve, we find
an upper limit on the mass of the planetary candidate of M_p < 5.5 +- 1.4
M_Jup. This limit implies that the planet is orbiting close to, if not inside,
its Roche limiting orbital radius, so that it may be undergoing active mass
loss and evaporation.Comment: Corrected typos, minor clarifications; minor updates/corrections to
affiliations and bibliography. 35 pages, 10 figures, 3 tables. Accepted to
Ap
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