2,210 research outputs found
Legal Aspects of Natural Resources Legislation Enacted by the 1989 Georgia General Assembly
Proceedings of the 1989 Georgia Water Resources Conference, May 16-17, 1989, Athens, Georgia.Sponsored by U.S. Geological Survey, Georgia Department of Natural Resources, the University of Georgia, Georgia State University, and Georgia Institute of Technology.This book was published by the Institute of Natural Resources, The University of Georgia, Athens, Georgia 30602 with partial funding provided by the U.S. Department of the Interior, Geological Survey, through the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1984 (P.L. 98242).
The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia or the U.S. Geological Survey or the conference sponsors
Chandra and Suzaku observations of the Be/X-ray star HD110432
We present an analysis of a pointed 141 ks Chandra high resolution
transmission gratings observation of the Be X-ray emitting star HD110432, a
prominent member of the gamma Cas analogs. The Chandra lightcurve shows a high
variability but its analysis fails to detect any coherent periodicity up to a
frequency of 0.05 Hz. The analysis of the Chandra HETG spectrum shows that, to
correctly describe the spectrum, three model components are needed. Two of
those components are optically thin thermal plasmas of different temperatures
(kT~8-9 and 0.2-0.3 keV respectively). Two different models seem to describe
well the third component. One possibility is a third hot optically thin thermal
plasma at kT=16-21 keV with an Fe abundance Z~0.3Zo, definitely smaller than
for the other two thermal components. Alternatively, the third component can be
described by a powerlaw with a photon index Gamma=1.56. In either case, the
Chandra HETG spectrum establishes that each one of these components must be
modified by distinct absorption columns. The analysis of a non contemporaneous
25 ks Suzaku observation shows the presence of a hard tail extending up to at
least 33 keV. The Suzaku spectrum is described with the sum of two components:
an optically thin thermal plasma at kT ~ 9 keV and a very hot second plasma
with kT ~33 keV or, alternatively, a powerlaw with photon index Gamma=1.58. The
analysis of the Si XIII and S XV He like triplets present in the Chandra
spectrum point to a very dense (n_e ~ 10^13 cm^-3) plasma located either close
to the stellar surface (r<3R_*) of the Be star or, alternatively, very close (r
~1.5R_WD) to the surface of a (hypothetical) WD companion. We argue, however,
that the available data supports the first scenario.Comment: 13 pages, 21 Figures. Accepted for publication in Ap
Exclusive W^+ + photon production in proton-antiproton collisions II: results
We present results for total cross sections, single and double differential
distributions and correlations between pairs of outgoing particles in the
reactions p + antip --> W^+ + photon and p + antip --> W^+ + photon + jet at
sqrt(S)=1.8 TeV. Order alpha-strong QCD corrections and leading logarithm
photon bremsstrahlung contributions are included in the MS-bar mass
factorization scheme for three experimental scenarios: 1) 2-body inclusive
production of W^+ and photon, 2) exclusive production of W^+, photon and 1 jet
and 3) exclusive production of W^+ and photon with 0 jet.
The latest CTEQ parton distribution functions, which fit the newly released
HERA data, are used in our analysis. The dependence of our results on the mass
factorization scale is used to place error bars on our predictions for the
single differential distributions and correlations.Comment: 15 pages (LateX). 50 pages of postscript figures available via ftp
anonymous from max.physics.sunysb.edu in the directory
preprints/mendoza/EXCLUSIVE_W_GAMMA_II.dir (files named fig_*.ps)
ITP-SB-93-80. ([email protected])([email protected]
Testing of Noodle Creek Site 41JS102 Jones County, Texas
Staff Archeologists from the Environmental Affairs Division of Texas Department of Transportation discovered buried cultural resources that constitute archeological site 41JS102, in June and July 2001 at the proposed location of a bridge replacement over Noodle Creek in Jones County, Texas. Shovel testing and backhoe trenching revealed cultural material at 65 cm below the surface. Following this discovery the Texas Department of Transportation made recommendations to the Texas Historical Commission to assess site 41JS 102 and they concurred. In September 2001 archeologists from the Texas Department of Transportation initiated the site assessment phase. Landowner complications halted that work before completion. Subsequently, TRC Environmental was provided a Work Authorization under an existing general services contract to complete the assessment of 41JS102 in December 2001. The fieldwork consisted of the hand excavation and documentation of eight 1 by 1 m test units and the digging and documenting of six backhoe trenches. Limited and scattered historic artifacts were recovered from the upper parts of the two alluvial terraces (T0 and T1). A prehistoric component with quantities of lithic debitage and sparse burned rocks, limited stone tools and mussel shells, and one possible cultural feature were encountered in a sloping, but well defined 10 to 15 cm thick zone in the T1 deposits. The Principal Investigator recommended prehistoric site 4 1JS102 was eligible for inclusion in the National Register of Historic Places and as a State Archeological Landmark. However, the staff at Texas Department of Transportation disagreed with that recommendation and presented an opposing case to the Texas Historical Commission who concurred with the Texas Department of Transportation\u27s recommendations. Consequently, no further archeological investigations will occur prior to the proposed development
Exclusive W + photon production in proton-antiproton collisions I: general formalism
We present a detailed computation of the fully exclusive cross section of p +
antip --> W + photon + X with X = 0 and 1 jet in the framework of the
factorization theorem and dimensional regularization. Order alpha-strong and
photon bremsstrahlung contributions are discussed in the MS-bar mass
factorization scheme. The resulting expressions are ready to be implemented
numerically using Monte Carlo techniques to compute single and double
differential cross sections and correlations between outgoing pairs of
particles.Comment: ITP-SB-93-72, 40 pages, LateX. 3*4 figures in separate file.
([email protected]) ([email protected]
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How is open solar magnetic flux lost over the solar cycle?
The Sun's open magnetic field, magnetic flux dragged out into the heliosphere by the solar wind, varies by approximately a factor of 2 over the solar cycle. We consider the evolution of open solar flux in terms of a source and loss term. Open solar flux creation is likely to proceed at a rate dependent on the rate of photospheric flux emergence, which can be roughly parameterized by sunspot number or coronal mass ejection rate, when available. The open solar flux loss term is more difficult to relate to an observable parameter. The supersonic nature of the solar wind means open solar flux can only be removed by near-Sun magnetic reconnection between open solar magnetic field lines, be they open or closed heliospheric field lines. In this study we reconstruct open solar flux over the last three solar cycles and demonstrate that the loss term may be related to the degree to which the heliospheric current sheet (HCS) is warped, i.e., locally tilted from the solar rotation direction. This can account for both the large dip in open solar flux at the time of sunspot maximum as well as the asymmetry in open solar flux during the rising and declining phases of the solar cycle. The observed cycle-to-cycle variability is also well matched. Following Sheeley et al. (2001), we attribute modulation of open solar flux by the degree of warp of the HCS to the rate at which opposite polarity open solar flux is brought together by differential rotation
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Intermittent release of transients in the slow solar wind: 2. In situ evidence
In paper 1, we showed that the Heliospheric Imager (HI) instruments on the pair of NASA STEREO spacecraft can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates near helmet streamers. The observation of intense intermittent transient outflow by HI implies that the corresponding in situ observations of the slow solar wind and corotating interaction regions (CIRs) should contain many signatures of transients. In the present paper, we compare the HI observations with in situ measurements from the STEREO and ACE spacecraft. Analysis of the solar wind ion, magnetic field, and suprathermal electron flux measurements from
the STEREO spacecraft reveals the presence of both closed and partially disconnected interplanetary magnetic field lines permeating the slow solar wind. We predict that one of the transients embedded within the second CIR (CIR‐D in paper 1) should impact the near‐Earth ACE spacecraft. ACE measurements confirm the presence of a transient at the time of CIR passage; the transient signature includes helical magnetic fields and bidirectional suprathermal electrons. On the same day, a strahl electron dropout is observed at STEREO‐B, correlated with the passage of a high plasma beta structure. Unlike ACE, STEREO‐B observes the transient a few hours ahead of the CIR. STEREO‐A, STEREO‐B, and ACE spacecraft observe very different slow solar wind properties ahead of and during the CIR analyzed in this paper, which we associate with the intermittent release of transients
The Remarkable Be Star HD110432
HD110432 has gained considerable attention because it is a hard, variable
X-ray source similar to gamma Cas. From time-serial echelle data obtained over
two weeks during 2005 January and February, we find several remarkable
characteristics in the star's optical spectrum. The line profiles show rapid
variations on some nights which can be most likely be attributed to irregularly
occurring and short-lived migrating subfeatures. Such features have only been
observed to date in gamma Cas and AB Dor, two stars for which it is believed
magnetic fields force circumstellar clouds to corotate over the stellar
surface. The star's optical spectrum also exhibits a number of mainly FeII and
HeI emission features with profiles typical of an optically thin disk viewed
edge-on. Using spectral synthesis techniques, we find that its temperature is
9800K +/-300K, that its projected area is a remarkably large 100 stellar areas,
and its emitting volume resides at a distance of 1 AU from the star. We also
find that the star's absorption profiles extend to +/-1000 km/s, a fact which
we cannot explain. Otherwise, HD110432 and gamma Cas share similarly peculiar
X-ray and optical characteristics such as high X-ray temperature, erratic X-ray
variability on timescales of a few hours, optical emission lines, and
submigrating features in optical line profiles. Because of these similarities,
we suggest that this star is a new member of a select class of "gamma Cas
analogs."Comment: 31 pages, 9 figures, accepted by ApJ (3/20/06
Gamma-Ray Burst 980329 and its X-Ray Afterglow
GRB 980329 is the brightest gamma-ray burst detected so far with the Wide
Field Cameras aboard BeppoSAX, both in gamma-rays and X-rays. With respect to
its fluence (2.6 X 10**-5 erg/s/cm**2 in 50 to 300 keV) it would be in the top
4% of gamma-ray bursts in the 4B catalog (Meegan et al. 1998). The
time-averaged burst spectrum from 2 to 20 and 70 to 650 keV can be well
described by the empirical model of Band et al. (1993). The resulting photon
index above the break energy is exceptionally hard at -1.32 +/- 0.03. An X-ray
afterglow was detected with the narrow-field instruments aboard BeppoSAX 7 h
after the event within the error box as determined with the Wide Field Cameras.
Its peak flux is (1.4 +/- 0.2) X 10**-12 erg/s/cm**2 (2 to 10 keV). The
afterglow decayed according to a power law function with an index of -1.35 +/-
0.03. GRB 980329 is characterized by being bright and hard, and lacking strong
spectral evolution.Comment: 13 pages with 3 figures. Accepted for publication in ApJ Let
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