9,728 research outputs found
Constructed Languages and Their Role in Drama
This paper covers the history and use of constructed language and dialect on stage and screen as well as the issues that arise concerning social awareness and intellectual property
Fiducial Stellar Population Sequences for the VJKs Photometric System
We have obtained broad-band near-infrared photometry for seven Galactic star
clusters (M92, M15, M13, M5, NGC1851, M71 and NGC6791) using the WIRCam
wide-field imager on the Canada-France-Hawaii Telescope, supplemented by images
of NGC1851 taken with HAWK-I on the VLT. In addition, 2MASS observations of the
[Fe/H] ~ 0.0 open cluster M67 were added to the cluster database. From the
resultant (V-J)-V and (V-Ks)-V colour-magnitude diagrams (CMDs), fiducial
sequences spanning the range in metallicity, -2.4 < [Fe/H] < +0.3, have been
defined which extend (for most clusters) from the tip of the red-giant branch
(RGB) to ~ 2.5 magnitudes below the main-sequence turnoff. These fiducials
provide a valuable set of empirical isochrones for the interpretation of
stellar population data in the 2MASS system. We also compare our newly derived
CMDs to Victoria isochrones that have been transformed to the observed plane
using recent empirical and theoretical colour-Teff relations. The models are
able to reproduce the entire CMDs of clusters more metal rich than [Fe/H] ~
-1.4 quite well, on the assumption of the same reddenings and distance moduli
that yield good fits of the same isochrones to Johnson-Cousins BV(RI)C
photometry. However, the predicted giant branches become systematically redder
than the observed RGBs as the cluster metallicity decreases. Possible
explanations for these discrepancies are discussed.Comment: 18 pages, 20 figures, Accepted for publication in A
Variable Side-Look Angle Concept For Radar Mapping
Radar mapping of planets can be accomplished at lower cost and with reduced emphasis on propulsion system capability from spacecraft operating in elliptical orbit than from circular orbit
Vapor crystal growth studies of single crystals of mercuric iodide (3-IML-1)
A single crystal of mercuric iodide (HgI2) will be grown during the International Microgravity Lab. (IML-1) mission. The crystal growth process takes place by sublimation of HgI2 from an aggregate of purified material, transport of the molecules in the vapor from the source to the crystal, and condensation on the crystal surface. The objectives of the experiment are as follow: to grow a high quality crystal of HgI2 of sufficient size so that its properties can be extensively analyzed; and to study the vapor transport process, specifically the rate of diffusion transport at greatly reduced gravity where convection is minimized
A Molecular Probe Finds Evidence of NIX Pathogen in Pacific Razor Clams (\u3cem\u3eSiliqua patula\u3c/em\u3e) in Oregon
The Pacific razor clam, Siliqua patula, is an important recreational fishery species that lives in the intertidal zone of sandy beaches from Alaska to central California. Populations have had periodic, but significant, declines over the past 30-40 years. These declines have correlated with an increase in the presences of an unidentified, intranuclear bacterial parasite known as Nuclear Inclusion X (NIX). NIX, which was first identified in 1986, has generally been screened using a histological approach. We developed a PCR-based screen to reduce both the time and cost of identifying infected clams. Use of this screen resulted in amplified sequences with a 97% match to the previously published 16S rDNA sequence for NIX. The sequence data supports placement of NIX into the gamma-proteobacteria, and suggests that it is related to isolates from diseased corals. Clams collected from the northern coast of Oregon showed ~50% infection rate using the PCR screen. This is the first report of NIX present in clams from Oregon, as all previous work had been in the state of Washington. Future work will identify the incidence rate and geographical spread of the NIX parasite throughout Oregon and Washington
An Examination of Recent Transformations to the BV(RI)_C Photometric System from the Perspective of Stellar Models for Old Stars
Isochrones for ages > 4 Gyr and metallicities in the range -2.5 < [Fe/H] <
+0.3 that take the diffusion of helium and recent advances in stellar physics
into account are compared with observations in the Johnson-Cousins BV(RI)_C
photometric system for several open and globular star clusters. The adopted
color-Teff relations include those which we have derived from the latest MARCS
model atmospheres and empirical transformations for dwarf and subgiant stars
given by Casagrande et al (2010, A&A, 512, 54; CRMBA). Those reported by
VandenBerg & Clem (2003, AJ, 126, 778) have also been considered, mainly to
resolve some outstanding questions concerning them. Remarkably, when the
subdwarfs in the CRMBA data set that have sigma_pi/pi < 0.15 are superimposed
on a set of 12 Gyr isochrones spanning a wide range in [Fe/H], the inferred
metallicities and effective temperatures agree, in the mean, with those given
by CRMBA to within +/- 0.05 dex and +/- 10 K, respectively. Thus the hot Teff
scale derived by CRMBA is nearly identical with that predicted by stellar
models and consequently, there is excellent consistency between theory and
observations on the H-R diagram and the different color-magnitude diagrams
considered in this investigation. To obtain similar consistency, the colors
obtained from the MARCS and VandenBerg & Clem B-V vs. Teff relations for
metal-poor dwarf stars should be adjusted to the red by 0.02-0.03 mag. In
general, isochrones that employ the CRMBA transformations provide reasonably
good fits to our BV(RI)_C photometry for main-sequence stars in the globular
clusters 47 Tuc, M3, M5, M92 and NGC 1851 - but not the cluster giants (when
adopting the synthetic MARCS colors). We speculate that differences between the
actual heavy-element mixtures and those assumed in the theoretical models may
be the primary cause of this difficulty.Comment: To appear in 2010, AJ, 140, 102
On the use of Gaia magnitudes and new tables of bolometric corrections
The availability of reliable bolometric corrections and reddening estimates,
rather than the quality of parallaxes will be one of the main limiting factors
in determining the luminosities of a large fraction of Gaia stars. With this
goal in mind, we provide Gaia G, BP and RP synthetic photometry for the entire
MARCS grid, and test the performance of our synthetic colours and bolometric
corrections against space-borne absolute spectrophotometry. We find indication
of a magnitude-dependent offset in Gaia DR2 G magnitudes, which must be taken
into account in high accuracy investigations. Our interpolation routines are
easily used to derive bolometric corrections at desired stellar parameters, and
to explore the dependence of Gaia photometry on Teff, log(g), [Fe/H],
alpha-enhancement and E(B-V). Gaia colours for the Sun and Vega, and
Teff-dependent extinction coefficients, are also provided.Comment: MNRAS Letter. Solar colours: BP-G = 0.33, G-RP = 0.49, BP-RP = 0.82.
Mean extinction coefficients at turn-off: R_G = 2.740 , R_BP = 3.374, R_RP =
2.035. Interpolation routines available at
https://github.com/casaluca/bolometric-correction
Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
After a pedagogical introduction to the main concepts of synthetic
photometry, colours and bolometric corrections in the Johnson-Cousins, 2MASS,
and HST-ACS/WFC3 photometric systems are generated from MARCS synthetic fluxes
for various [Fe/H] and [alpha/Fe] combinations, and virtually any value of
reddening E(B-V) < 0.7. The successes and failures of model fluxes in
reproducing the observed magnitudes are highlighted. Overall, extant synthetic
fluxes predict quite realistic broad-band colours and bolometric corrections,
especially at optical and longer wavelengths: further improvements of the
predictions for the blue and ultraviolet spectral regions await the use of
hydrodynamic models where the microturbulent velocity is not treated as a free
parameter. We show how the morphology of the colour-magnitude diagram (CMD)
changes for different values of [Fe/H] and [alpha/Fe]; in particular, how
suitable colour combinations can easily discriminate between red giant branch
and lower main sequence populations with different [alpha/Fe], due to the
concomitant loops and swings in the CMD. We also provide computer programs to
produce tables of synthetic bolometric corrections as well as routines to
interpolate in them. These colour-Teff-metallicity relations may be used to
convert isochrones for different chemical compositions to various bandpasses
assuming observed reddening values, thus bypassing the standard assumption of a
constant colour excess for stars of different spectral type. We also show how
such an assumption can lead to significant systematic errors. The MARCS
transformations presented in this study promise to provide important
constraints on our understanding of the multiple stellar populations found in
globular clusters (e.g., the colours of lower main sequence stars are predicted
to depend strongly on [alpha/Fe]) and of those located towards/in the Galactic
bulge.Comment: MNRAS, accepted. Tables and programs to generate synthetic colours
and bolometric corrections in various photometric systems and for different
combination of E(B-V), [Fe/H], [alpha/Fe], Teff and logg available via CDS at
http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/MNRAS/444/39
- …