2,400 research outputs found
Building an Optimal Census of the Solar Neighborhood with Pan-STARRS Data
We estimate the fidelity of solar neighborhood (D < 100 pc) catalogs soon to
be derived from Pan-STARRS astrometric data. We explore two quantities used to
measure catalog quality: completeness, the fraction of desired sources included
in a catalog; and reliability, the fraction of entries corresponding to desired
sources. We show that the main challenge in identifying nearby objects with
Pan-STARRS will be reliably distinguishing these objects from distant stars,
which are vastly more numerous. We explore how joint cuts on proper motion and
parallax will impact catalog reliability and completeness. Using synthesized
astrometry catalogs, we derive optimum parallax and proper motion cuts to build
a census of the solar neighborhood with the Pan-STARRS 3 Pi Survey. Depending
on the Galactic latitude, a parallax cut pi / sigma pi > 5 combined with a
proper motion cut ranging from mu / sigma mu > 1-8 achieves 99% reliability and
60% completeness.Comment: 7 Pages, 4 Figures, 3 Tables. PASP in pres
A Search for High Proper Motion T Dwarfs with Pan-STARRS1 + 2MASS + WISE
We have searched ~8200 sq. degs for high proper motion (~0.5-2.7"/year) T
dwarfs by combining first-epoch data from the Pan-STARRS1 (PS1) 3-Pi Survey,
the 2MASS All-Sky Point Source Catalog, and the WISE Preliminary Data Release.
We identified two high proper motion objects with the very red (W1-W2) colors
characteristic of T dwarfs, one being the known T7.5 dwarf GJ 570D. Near-IR
spectroscopy of the other object (PSO J043.5+02 = WISEP J0254+0223) reveals a
spectral type of T8, leading to a photometric distance of 7.2+/-0.7 pc. The
2.56"/yr proper motion of PSO J043.5+02 is the second highest among field T
dwarfs, corresponding to an tangential velocity of 87+/-8 km/s. According to
the Besancon galaxy model, this velocity indicates its galactic membership is
probably in the thin disk, with the thick disk an unlikely possibility. Such
membership is in accord with the near-IR spectrum, which points to a surface
gravity (age) and metallicity typical of the field population. We combine
2MASS, SDSS, WISE, and PS1 astrometry to derive a preliminary parallax of
171+/-45 mas (5.8{+2.0}{-1.2} pc), the first such measurement using PS1 data.
The proximity and brightness of PSO J043+02 will facilitate future
characterization of its atmosphere, variability, multiplicity, distance, and
kinematics. The modest number of candidates from our search suggests that the
immediate (~10 pc) solar neighborhood does not contain a large reservoir of
undiscovered T dwarfs earlier than about T8.Comment: ApJL, in press. v3 is the same as v2, except that the arXiv.org
metadata has been updated to match the final order of the author lis
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. V. Variables in the Field M31F
We undertook a long term project, DIRECT, to obtain the direct distances to
two important galaxies in the cosmological distance ladder -- M31 and M33 --
using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult
to detect, DEBs provide us with the potential to determine these distances with
an accuracy better than 5%. The extensive photometry obtained in order to
detect DEBs provides us with good light curves for the Cepheid variables. These
are essential to the parallel project to derive direct Baade-Wesselink
distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries,
the distance estimates will be free of any intermediate steps.
As a first step in the DIRECT project, between September 1996 and October
1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m
telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to
search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper,
fifth in the series, we present the catalog of variable stars found in the
field M31F [(\alpha,\delta)= (10.\arcdeg10, 40.\arcdeg72), J2000.0]. We have
found 64 variable stars: 4 eclipsing binaries, 52 Cepheids and 8 other
periodic, possible long period or non-periodic variables. The catalog of
variables, as well as their photometry and finding charts, is available via
anonymous ftp and the World Wide Web. The complete set of the CCD frames is
available upon request.Comment: submitted to the Astronomical Journal, 31 pages, 18 figures; paper
and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/ and
through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT
Supersoft X-Ray Sources in M31
The nearby Andromeda galaxy (M31) has been observed with the ROSAT PSPC in a
mosaic of 6 pointings with 25 ksec each. In the paper describing the results on
the total sample of detected sources, Supper et al. (1996) also report the
positions for 15 supersoft X-ray sources and the blackbody fit results for the
brightest of these sources. We report here in more detail on the X-ray spectral
characteristics of all these 15 supersoft X-ray sources. Optical multi-colour
photometric data obtained in 1990 at the Michigan- Dartmouth-MIT Observatory at
Kitt Peak were used originally in the selection process of the supersoft
sources, and are the basis for the finding charts given here for most selected
X-ray sources.Comment: 8 pages postscript incl. figures, Proc. of Workshop on Supersoft
X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996
GMO Testing Strategies and Implications for Trade: A Game Theoretic Approach
Since their commercial introduction in 1996, genetically modified (GM) crops have been quickly adopted world wide, but some GM crops/varieties have not received regulatory approval for use in some importing countries, leading to asynchronicity in regulatory approvals. In this context, the international agricultural trade relied on analytical GMO testing which is a statistical process, along with identity preserved systems to segregate GM and non-GM crops. This led to a situation where measurement uncertainty became an important issue as it can lead to potential holdups at the point of import. In this background, this paper examines the implications of measurement uncertainty associated with GMO testing on the behavior of importers and exporters in a game theoretic framework. The results indicate that relative size of identity preservation costs, testing and rejection costs, the premiums offered in the non- GM markets and measurement uncertainty all have direct impacts on the behavior of importers and exporters.GMO testing, measurement uncertainty, identity preservation systems, agricultural trade, International Relations/Trade,
Pedro de Valencia: Humanista cristiano, exĂ©geta bĂblico y crĂtico social. Defensor de mĂ©todos suaves con los moriscos
Pedro de Valencia, Christian humanist and biblical scholar; the Inquisition used his expertise for the revision of the Index of 1607 (Rome). His biblical commentary on the Acts of the Apostles and the Epistle to the Galatians examined the conflict between Paul, Peter and James concerning the new Gentile converts. Should they be circumcised and follow the Law, rites and practices of Judaism? The Council of Jerusalem absolved the new converts from these heavy burdens. However, this new era was to be introduced gradually. Valencia seems to be identifying the Moriscos with the early Christian Gentile converts as they were marginalised by the Purity of Blood Statutes; instead they, like the Gentile converts, should be treated with patience, toleration and love.Pedro de Valencia, humanista cristiano y exĂ©geta bĂblico, la InquisiciĂłn se sirviĂł de Ă©l como calificador cuando el Ăndice de 1607 (Roma) se revisaba. Su comentario sobre los Actos de los ApĂłstoles y la EpĂstola a los GĂĄlatas examina el conflicto entre Pablo, Pedro y Santiago sobre los nuevos convertidos de la gentilidad. ÂżDeberĂan circuncidarse y seguir las leyes y los ritos judaicos? El Concilio de JerusalĂ©n quitĂł estos pesos de la cerviz de los nuevos convertidos. Sin embargo, esta nueva Ă©poca habĂa de introducirse paulatinamente. Valencia parece identificar a los Moriscos con los cristianos primitivos convertidos de la gentilidad. Esos se encontraban marginalizados por los estatutos de limpieza de sangre; en cambio, como con los convertidos de la gentilidad, habĂa que tratarlos con paciencia, tolerancia y amor
The Stellar Population of the M31 Spiral Arm Around OB Association A24
A study of the stellar population of the M31 spiral arm around OB association
A24 was carried out based on the photometric data obtained from deep V and JHK
imaging. The luminosity function was obtained for -7 <~ Mbol <~ -3.5 by
applying the extinction correction corresponding to Av=1 and the bolometric
correction BC(K) as an empirical function of (J-K)o. In comparing the observed
color-luminosity diagrams with semitheoretical isochrones modified for the
dust-shell effects, we found the young population of t <~ 30 Myr with
supergiants of Mbol <~ -5, the bulk of the intermediate-age population of t ~
0.2 - 2.5 Gyr with bright asymptotic giant branch (AGB) stars of -5 <~ Mbol <~
-4, and old populations of t ~> 3 Gyr with AGB and red giant branch (RGB) stars
of Mbol ~> -4. The average star formation rate was estimated to be ~1.8x10^4
M_o/Myr and ~0.7x10^4 M_o/Myr per deprojected disk area of 1 kpc^2 from the
number density of B0 V stars around Mv=-4.0 (age ~10 Myr) and the number
density of bright AGB stars around Mbol = -4.3 (age ~1 Gyr), respectively. A
study of the local variation in the V and the J and H luminosity functions
revealed a kind of anticorrelation between the population of the young
component and that of the intermediate-age component when subdomains of ~100 pc
scales were concerned. This finding suggests that the disk domain around the
A24 area experienced a series of star formation episodes alternatively among
different subdomains with a timescale of a few spiral passage periods. Brief
discussions are given about the interstellar extinction and about the lifetimes
of bright AGB stars and the highly red objects (HROs) in the same area.Comment: 27 pages, 11 figures, accepted: ApJ, July 1, 199
Product Life Cycles and Innovation in the US Seed Corn Industry
The purpose of this study is to evaluate potential changes in the length of product life cycles in the US seed corn industry. We use the observed survival time on the market for hybrids sold during 1997-2009 to conduct a survival analysis. Our empirical results show that the average lifetimes of conventional and biotech corn hybrids have decreased over the last twelve years at similar rates and that the rate of decline in the life cycle length increased since 2004. We also find that the shorter product life cycles are closely linked to the accelerated levels of biotech product innovation in the US seed corn industry observed over the period of the analysis.Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,
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