2,481 research outputs found
Spectroscopy, MOST Photometry, and Interferometry of MWC 314: Is it an LBV or an interacting binary?
MWC 314 is a bright candidate luminous blue variable that resides in a fairly
close binary system, with an orbital period of 60.7530.003 d. We observed
MWC 314 with a combination of optical spectroscopy, broad-band ground- and
space-based photometry, as well as with long baseline, near-infrared
interferometry. We have revised the single-lined spectroscopic orbit and
explored the photometric variability. The orbital light curve displays two
minima each orbit that can be partially explained in terms of the tidal
distortion of the primary that occurs around the time of periastron. The
emission lines in the system are often double-peaked and stationary in their
kinematics, indicative of a circumbinary disc. We find that the stellar wind or
circumbinary disc is partially resolved in the K\prime-band with the longest
baselines of the CHARA Array. From this analysis, we provide a simple,
qualitative model in an attempt to explain the observations. From the
assumption of Roche Lobe overflow and tidal synchronisation at periastron, we
estimate the component masses to be M1 M and M2
M, which indicates a mass of the LBV that is extremely low. In addition
to the orbital modulation, we discovered two pulsational modes with the MOST
satellite. These modes are easily supported by a low-mass hydrogen-poor star,
but cannot be easily supported by a star with the parameters of an LBV. The
combination of these results provides evidence that the primary star was likely
never a normal LBV, but rather is the product of binary interactions. As such,
this system presents opportunities for studying mass-transfer and binary
evolution with many observational techniques.Comment: 26 pages, 7 figures, 5 tables, 2 appendices with 7 additional tables
and 2 additional figures. Accepted for publication in MNRA
Constraints on the origin and evolution of Iani Chaos, Mars
[1] The origin mechanisms and geologic evolution of chaotic terrain on Mars are poorly constrained. Iani Chaos, located at the head Ares Vallis, is among the most geomorphologically complex of the chaotic terrains. Its morphology is defined by (1) multiple, 1 to 2 km deep basins, (2) flat‐topped, fractured plateaus that are remnants of highland terrain, (3) knobby, fractured remnants of highland terrain, (4) plateaus with a knobby surface morphology, (5) interchaos grooved terrain, (6) interior layered deposits (ILDs), and (7) mantling material. Topography, the observed geomorphology, and measured fracture patterns suggest that the interchaos basins formed as a result of subsurface volume loss and collapse of the crust, likely owing to effusion of groundwater to the surface. Regional patterns in fracture orientation indicate that the basins developed along linear zones of preexisting weakness in the highland crust. Multiple overlapping basins and fracture systems point to multiple stages of collapse at Iani Chaos. Furthermore, the total estimated volume loss from the basins (104 km3) is insufficient to explain erosion of 104–105 km3 of material from Ares Vallis by a single flood. Comparisons with the chronology of Ares Vallis indicate multiple water effusion events from Iani Chaos that span the Hesperian, with termination of activity in the early Amazonian. Recharge of groundwater through preexisting fracture systems may explain this long‐lived, but likely episodic, fluvial activity. Late‐stage, early to middle Amazonian aqueous processes may have deposited the ILDs. However, the topography data indicate that the ILDs did not form within lacustrine environments
The ASTRO-H X-ray Observatory
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly
successful X-ray missions initiated by the Institute of Space and Astronautical
Science (ISAS). ASTRO-H will investigate the physics of the high-energy
universe via a suite of four instruments, covering a very wide energy range,
from 0.3 keV to 600 keV. These instruments include a high-resolution,
high-throughput spectrometer sensitive over 0.3-2 keV with high spectral
resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in
the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers
covering 5-80 keV, located in the focal plane of multilayer-coated, focusing
hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12
keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and
a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the
40-600 keV band. The simultaneous broad bandpass, coupled with high spectral
resolution, will enable the pursuit of a wide variety of important science
themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to
Gamma Ray
Advanced Technology Large-Aperture Space Telescope (ATLAST): A Technology Roadmap for the Next Decade
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a set of
mission concepts for the next generation of UVOIR space observatory with a
primary aperture diameter in the 8-m to 16-m range that will allow us to
perform some of the most challenging observations to answer some of our most
compelling questions, including "Is there life elsewhere in the Galaxy?" We
have identified two different telescope architectures, but with similar optical
designs, that span the range in viable technologies. The architectures are a
telescope with a monolithic primary mirror and two variations of a telescope
with a large segmented primary mirror. This approach provides us with several
pathways to realizing the mission, which will be narrowed to one as our
technology development progresses. The concepts invoke heritage from HST and
JWST design, but also take significant departures from these designs to
minimize complexity, mass, or both.
Our report provides details on the mission concepts, shows the extraordinary
scientific progress they would enable, and describes the most important
technology development items. These are the mirrors, the detectors, and the
high-contrast imaging technologies, whether internal to the observatory, or
using an external occulter. Experience with JWST has shown that determined
competitors, motivated by the development contracts and flight opportunities of
the new observatory, are capable of achieving huge advances in technical and
operational performance while keeping construction costs on the same scale as
prior great observatories.Comment: 22 pages, RFI submitted to Astro2010 Decadal Committe
Design, Performance, and Calibration of the CMS Hadron-Outer Calorimeter
The CMS hadron calorimeter is a sampling calorimeter with brass absorber and plastic scintillator tiles with wavelength shifting fibres for carrying the light to the readout device. The barrel hadron calorimeter is complemented with an outer calorimeter to ensure high energy shower containment in the calorimeter. Fabrication, testing and calibration of the outer hadron calorimeter are carried out keeping in mind its importance in the energy measurement of jets in view of linearity and resolution. It will provide a net improvement in missing \et measurements at LHC energies. The outer hadron calorimeter will also be used for the muon trigger in coincidence with other muon chambers in CMS
Erratum to: Methods for evaluating medical tests and biomarkers
[This corrects the article DOI: 10.1186/s41512-016-0001-y.]
Clinical Sequencing Exploratory Research Consortium: Accelerating Evidence-Based Practice of Genomic Medicine
Despite rapid technical progress and demonstrable effectiveness for some types of diagnosis and therapy, much remains to be learned about clinical genome and exome sequencing (CGES) and its role within the practice of medicine. The Clinical Sequencing Exploratory Research (CSER) consortium includes 18 extramural research projects, one National Human Genome Research Institute (NHGRI) intramural project, and a coordinating center funded by the NHGRI and National Cancer Institute. The consortium is exploring analytic and clinical validity and utility, as well as the ethical, legal, and social implications of sequencing via multidisciplinary approaches; it has thus far recruited 5,577 participants across a spectrum of symptomatic and healthy children and adults by utilizing both germline and cancer sequencing. The CSER consortium is analyzing data and creating publically available procedures and tools related to participant preferences and consent, variant classification, disclosure and management of primary and secondary findings, health outcomes, and integration with electronic health records. Future research directions will refine measures of clinical utility of CGES in both germline and somatic testing, evaluate the use of CGES for screening in healthy individuals, explore the penetrance of pathogenic variants through extensive phenotyping, reduce discordances in public databases of genes and variants, examine social and ethnic disparities in the provision of genomics services, explore regulatory issues, and estimate the value and downstream costs of sequencing. The CSER consortium has established a shared community of research sites by using diverse approaches to pursue the evidence-based development of best practices in genomic medicine
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