24,291 research outputs found
The Eurovision St Andrews collection of photographs
This report describes the Eurovision image collection compiled for the ImageCLEF (Cross Language Evaluation Forum) evaluation exercise. The image collection consists of around 30,000 photographs from the collection provided by the University of St Andrews Library. The construction and composition of this unique image collection are described, together with the necessary information to obtain and use the image collection
Brown dwarfs in the Hyades and beyond?
We have used both the Low-Resolution Imaging Spectrograph and the HIRES
echelle spectrograph on the Keck telescopes to obtain spectra of twelve
candidate members of the Hyades cluster identified by Leggett and Hawkins
(1988, 1989). All of the objects are chromospherically-active, late-type
M-dwarfs, with H equivalent widths varying from 1 to 30\AA. Based on
our measured radial velocities, the level of stellar activity and other
spectroscopic features, only one of the twelve stars has properties consistent
with cluster membership. We consider how this result affects estimates of the
luminosity and mass function of the Hyades cluster. Five of the eleven field
stars have weak K I 7665/7699\AA and CaH absorption as compared with M-dwarf
standards of the same spectral type, suggesting a lower surface gravity. Two of
these sources, LH0416+14 and LH0419+15, exhibit significant lithium 6708 \AA
absorption. Based partly on parallax measurements by the US Naval Observatory
(Harris et al, 1998), we identify all five as likely to be young, pre-main
sequence objects in or near the Taurus-Auriga association at distances of
between 150 and 250 parsecs. A comparison with theoretical models of pre-main
sequence stars indicates masses of less than 0.05 M.Comment: to appear in AJ, January 1999; 34 pages, (Latex format), including 10
embedded postscript figures and two table
General Relativistic Description of the Observed Galaxy Power Spectrum: Do We Understand What We Measure?
We extend the general relativistic description of galaxy clustering developed
in Yoo, Fitzpatrick, and Zaldarriaga (2009). For the first time we provide a
fully general relativistic description of the observed matter power spectrum
and the observed galaxy power spectrum with the linear bias ansatz. It is
significantly different from the standard Newtonian description on large scales
and especially its measurements on large scales can be misinterpreted as the
detection of the primordial non-Gaussianity even in the absence thereof. The
key difference in the observed galaxy power spectrum arises from the real-space
matter fluctuation defined as the matter fluctuation at the hypersurface of the
observed redshift. As opposed to the standard description, the shape of the
observed galaxy power spectrum evolves in redshift, providing additional
cosmological information. While the systematic errors in the standard Newtonian
description are negligible in the current galaxy surveys at low redshift,
correct general relativistic description is essential for understanding the
galaxy power spectrum measurements on large scales in future surveys with
redshift depth z>3. We discuss ways to improve the detection significance in
the current galaxy surveys and comment on applications of our general
relativistic formalism in future surveys.Comment: accepted for publication in Physical Review
Haptic feedback in the training of veterinary students
This paper reports on an initial study into the use of haptic (or touch) technology in the training of veterinary students. One major problem faced in veterinary education is that animals can be harmed by inexperienced students who are trying to learn the skills they need. The aim of the work described here is to provide haptic models to simulate internal examinations of horses so that students can learn the basic skills required on computer and then transfer to real animals with much less risk of doing them injury
The \chi Factor: Determining the Strength of Activity in Low Mass Dwarfs
We describe a new, distance-independent method for calculating the magnetic
activity strength in low mass dwarfs, L_{H\alpha}/L_{bol}. Using a
well-observed sample of nearby stars and cool standards spanning spectral type
M0.5 to L0, we compute ``\chi'', the ratio between the continuum flux near
H-alpha and the bolometric flux, f_{\lambda6560}/f_{bol}. This ratio may be
multiplied by the measured equivalent width of the H-alpha emission line to
yield L_{H\alpha}/L_{bol}. We provide \chi values for all objects in our
sample, as well as fits to \chi as a function of color and average values by
spectral type. This method was used by West et al.(2004) to examine trends in
magnetic activity strength in low mass stars.Comment: 11 pages, 5 figures. Accepted for publication in PAS
Accurate measurement of telemetry performance
Performance of high rate telemetry stations used in the Deep Space Network is verified. Measurement techniques are discussed
Search for nearby stars among proper motion stars selected by optical-to-infrared photometry. II. Two late M dwarfs within 10 pc
We have identified two late M dwarfs within 10 parsecs of the Sun, by
cross-correlating the Luyten NLTT catalogue of stars with proper motions larger
than 0.18 arcsec/yr, with objects lacking optical identification in the 2MASS
data base. The 2MASS photometry was then combined with improved optical
photometry obtained from the SuperCOSMOS Sky Surveys. The two objects (LP775-31
and LP655-48) have extremely red optical-to-infrared colours ((R-K)~7) and very
bright infrared magnitudes (K_s<10): follow-up optical spectroscopy with the
ESO 3.6-m telescope gave spectral types of M8.0 and M7.5 dwarfs, respectively.
Comparison of their near-infrared magnitudes with the absolute magnitudes of
known M8 and M7.5 dwarfs with measured trigonometric parallaxes yields
spectroscopic distance estimates of 6.4+/-1.4 parsecs and 8.0+/-1.6 parsecs for
LP775-31 and LP655-48, respectively. In contrast, Cruz & Reid (2002) recently
determined spectral types of M6 for both objects, and commensurately larger
distances of 11.3+/-1.3 parsecs and 15.3+/-2.6 parsecs. LP655-48 is also a
bright X-ray source (1RXS J044022.8-053020). With only a few late M dwarfs
previously known within 10 parsecs, these two objects represent an important
addition to the census of the Solar neighbourhood.Comment: Astronomy & Astrophysics (Letters), in press; 5 pages, 1 figure, uses
aa.cls version 5.
Jointly Evaluating the Federal Reserve’s Forecasts of GDP Growth and Inflation
In this paper we jointly evaluate the Federal Reserve staff forecasts of U.S. real output growth and the inflation rate assuming the forecasts are to be used as inputs for the Taylor rule. Our simple methodology generates “policy forecast errors” which have a direct interpretation for the impact of forecast errors on the target interest rate given by the Taylor rule. Without interest rate smoothing, we find that, on average, the Taylor rule target interest rate would have been approximately a full percentage point away from the intended target because of errors in forecasting output growth and inflation. Our results are robust to changes in the forecast horizon and to changes in the weights on the variables in the policy rule.Evaluating Forecasts, Macroeconomic Forecasts, Loss Function,Inflation Forecasting, GDP Growth Forecasting, Monetary Policy
Future air traffic - A study of the terminal area
Systems analysis approach to airport planning and predicting terminal facility and aircraft demands in year 2000 for air traffic control system
The distance to a star forming region in the Outer arm of the Galaxy
We performed astrometric observations with the VLBA of WB89-437, an H2O maser
source in the Outer spiral arm of the Galaxy. We measure an annual parallax of
0.167 +/- 0.006 mas, corresponding to a heliocentric distance of 6.0 +/- 0.2
kpc or a Galactocentric distance of 13.4 +/- 0.2 kpc. This value for the
heliocentric distance is considerably smaller than the kinematic distance of
8.6 kpc. This confirms the presence of a faint Outer arm toward l = 135
degrees. We also measured the full space motion of the object and find a large
peculiar motion of ~20 km/s toward the Galactic center. This peculiar motion
explains the large error in the kinematic distance estimate. We also find that
WB89-437 has the same rotation speed as the LSR, providing more evidence for a
flat rotation curve and thus the presence of dark matter in the outer Galaxy.Comment: The Astrophysical Journal, accepted, 16 pages, 4 Figure
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