32,557 research outputs found
Astrometry with the Hubble Space Telescope: Trigonometric Parallaxes of Selected Hyads
We present absolute parallaxes and proper motions for seven members of the
Hyades open cluster, pre-selected to lie in the core of the cluster. Our data
come from archival astrometric data from FGS 3, and newer data for 3 Hyads from
FGS 1R, both white-light interferometers on the Hubble Space Telescope (HST).
We obtain member parallaxes from six individual Fine Guidance Sensor (FGS)
fields and use the field containing van Altena 622 and van Altena 627 (= HIP
21138) as an example. Proper motions, spectral classifications and VJHK
photometry of the stars comprising the astrometric refer- ence frames provide
spectrophotometric estimates of reference star absolute parallaxes. Introducing
these into our model as observations with error, we determine absolute
parallaxes for each Hyad. The parallax of vA 627 is significantly improved by
including a perturbation orbit for this previously known spectroscopic binary,
now an astrometric binary. Compared to our original (1997) determina- tions, a
combination of new data, updated calibration, and improved analysis lowered the
individual parallax errors by an average factor of 4.5. Comparing parallaxes of
the four stars contained in the Hipparcos catalog, we obtain an average factor
of 11 times improvement with the HST . With these new results, we also have
better agreement with Hipparcos for the four stars in common. These new
parallaxes provide an average distance for these seven members, = 47.5
pc, for the core a \pm 1 - {\sigma} dispersion depth of 3.6 pc, and a minimum
depth from individual components of 16.0 \pm 0.9 pc. Absolute magnitudes for
each member are compared to established main sequences, with excellent
agreement. We obtain a weighted average distance modulus for the core of the
Hyades of m-M=3.376 \pm 0.01, a value close to the previous Hipparcos values,
m-M=3.33\pm 0.02.Comment: 21 pages, 7 figures, Astronomical Journal, accepted 2011-3-
Hardy-Orlicz spaces of conformal densities
We define and prove characterizations of Hardy-Orlicz spaces of conformal
densities.Comment: 12 page
On the distribution law in locally rapidly fluctuating fields which are steady when averaged over a sufficient time interval
Thomas(1) and later Fermi(2) have attempted to determine the time average electrical potential around the nucleus of a heavy atom. They treat the electrons as if they formed an ideal degenerate Fermi gas which becomes statistically distributed in the steady field due to the nucleus plus the locally rapidly fluctuating field due to the electrons themselves. This method is apparently fully justified and it is hard to see, at first, why the numerical solutions given by the above writers turn out to be so roughly approximate, especially for heavy atoms with many electrons. The following investigation purports to show that the roughness of the method is due to the unjustified, except for approximation purposes, use of the statistical distribution law of an ideal gas in a steady field in the case where the field is steady only when averaged over a sufficiently long time interval and is locally fluctuating
Whose International Law?: Sovereignty and Non-State Groups
This is the first of three keynote panels at this 88th Annual Meeting, under the overarching theme of The Transformation of Sovereignty
Computational reverse mathematics and foundational analysis
Reverse mathematics studies which subsystems of second order arithmetic are
equivalent to key theorems of ordinary, non-set-theoretic mathematics. The main
philosophical application of reverse mathematics proposed thus far is
foundational analysis, which explores the limits of different foundations for
mathematics in a formally precise manner. This paper gives a detailed account
of the motivations and methodology of foundational analysis, which have
heretofore been largely left implicit in the practice. It then shows how this
account can be fruitfully applied in the evaluation of major foundational
approaches by a careful examination of two case studies: a partial realization
of Hilbert's program due to Simpson [1988], and predicativism in the extended
form due to Feferman and Sch\"{u}tte.
Shore [2010, 2013] proposes that equivalences in reverse mathematics be
proved in the same way as inequivalences, namely by considering only
-models of the systems in question. Shore refers to this approach as
computational reverse mathematics. This paper shows that despite some
attractive features, computational reverse mathematics is inappropriate for
foundational analysis, for two major reasons. Firstly, the computable
entailment relation employed in computational reverse mathematics does not
preserve justification for the foundational programs above. Secondly,
computable entailment is a complete relation, and hence employing it
commits one to theoretical resources which outstrip those available within any
foundational approach that is proof-theoretically weaker than
.Comment: Submitted. 41 page
A Grotian Tradition of Theory and Practice: Grotius, Law, and Moral Skepticism in the Thought of Hedley Bull
This paper describes a system that incrementally constructs an increasingly accurate road map from GPS traces from a single vehicle. The resulting road map contains information about the road such as road gradient which can be used by functions in a heavy vehicle to drive more effectively. The system is supposed to run on an embedded system in a heavy vehicle and is therefore design to require as little working memory and processing time as possible.Pre- and post processing techniques that counters GPS noise, random movements and improve the quality of the road map are also described, for example tunnel estimation where GPS signals are missing. An aging method, designed for data from a single vehicle, that eventually removes closed and rarely used roads is proposed.A comparison between the constructed road map and a commercial one shows that the algorithms described creates a very accurate roadmap. The performance of the system is evaluated and it is concluded that it would be possible to run it on an embedded system in a heavyvehicle
The Mass of the Candidate Exoplanet Companion to HD136118 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities
We use Hubble Space Telescope Fine Guidance Sensor astrometry and
high-cadence radial velocities for HD136118 from the HET with archival data
from Lick to determine the complete set of orbital parameters for HD136118b. We
find an orbital inclination for the candidate exoplanet of i_{b} = 163.1 +- 3.0
deg. This establishes the actual mass of the object, M_{b} = 42^{+11}_{-18}
MJup, in contrast to the minimum mass determined from the radial velocity data
only, M_{b}sin{i} ~ 12 MJup. Therefore, the low-mass companion to HD 136118 is
now identified as a likely brown dwarf residing in the "brown dwarf desert".Comment: 35 pages, 12 figures, 10 tables. Accepted for publication in
Astrophysical Journa
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