A new parameterization of an empirical model for wind/ocean scatterometry

The power law form of the SEASAT A Scatterometer System (SASS) empirical backscatter-to-wind model function does not uniformly meet the instrument performance over the range 4 to 24 /ms. Analysis indicates that the horizontal polarization (H-Pol) and vertical polarization (V-Pol) components of the benchmark SASS1 model function yield self-consistent results only for a small mid-range of speeds at larger incidence angles, and for a somewhat larger range of speeds at smaller incidence angles. Comparison of SASS1 to in situ data over the Gulf of Alaska region further underscores the shortcomings of the power law form. Finally, a physically based empirical SASS model is proposed which corrects some of the deficiencies of power law models like SASS1. The new model allows the mutual determination of sea surface wind stress and wind speed in a consistent manner from SASS backscatter measurements

Correspondence to General William Robertson Boggs, 1860s: October 28, 1867 - February 18, 1869

Box 1, Folder 1: W.R. Boggs Family Papers Correspondence to General William Robertson Boggs, 1860s: October 28, 1867 - February 18, 1869https://digitalcommons.wofford.edu/littlejohnboggs/1000/thumbnail.jp

Charge injection instability in perfect insulators

We show that in a macroscopic perfect insulator, charge injection at a field-enhancing defect is associated with an instability of the insulating state or with bistability of the insulating and the charged state. The effect of a nonlinear carrier mobility is emphasized. The formation of the charged state is governed by two different processes with clearly separated time scales. First, due to a fast growth of a charge-injection mode, a localized charge cloud forms near the injecting defect (or contact). Charge injection stops when the field enhancement is screened below criticality. Secondly, the charge slowly redistributes in the bulk. The linear instability mechanism and the final charged steady state are discussed for a simple model and for cylindrical and spherical geometries. The theory explains an experimentally observed increase of the critical electric field with decreasing size of the injecting contact. Numerical results are presented for dc and ac biased insulators.Comment: Revtex, 7pages, 4 ps figure

The Compton hump and variable blue wing in the extreme low-flux NuSTAR observations of 1H0707-495

The Narrow-line Seyfert I galaxy, 1H0707-495, has been well observed in the 0.3-10 keV band, revealing a dramatic drop in flux in the iron K alpha band, a strong soft excess, and short timescale reverberation lags associated with these spectral features. In this paper, we present the first results of a deep 250 ks NuSTAR observation of 1H0707-495, which includes the first sensitive observations above 10 keV. Even though the NuSTAR observations caught the source in an extreme low-flux state, the Compton hump is still significantly detected. NuSTAR, with its high effective area above 7 keV, clearly detects the drop in flux in the iron K alpha band, and by comparing these observations with archival XMM-Newton observations, we find that the energy of this drop increases with increasing flux. We discuss possible explanations for this, the most likely of which is that the drop in flux is the blue wing of the relativistically broadened iron K alpha emission line. When the flux is low, the coronal source height is low, thus enhancing the most gravitationally redshifted emission.Comment: Submitted to MNRAS, comments are welcome. 9 pages, 5 figure

Computational Controversy

Climate change, vaccination, abortion, Trump: Many topics are surrounded by fierce controversies. The nature of such heated debates and their elements have been studied extensively in the social science literature. More recently, various computational approaches to controversy analysis have appeared, using new data sources such as Wikipedia, which help us now better understand these phenomena. However, compared to what social sciences have discovered about such debates, the existing computational approaches mostly focus on just a few of the many important aspects around the concept of controversies. In order to link the two strands, we provide and evaluate here a controversy model that is both, rooted in the findings of the social science literature and at the same time strongly linked to computational methods. We show how this model can lead to computational controversy analytics that have full coverage over all the crucial aspects that make up a controversy.Comment: In Proceedings of the 9th International Conference on Social Informatics (SocInfo) 201

Observations of the Prompt Gamma-Ray Emission of GRB 070125

The long, bright gamma-ray burst GRB 070125 was localized by the Interplanetary Network. We present light curves of the prompt gamma-ray emission as observed by Konus-WIND, RHESSI, Suzaku-WAM, and \textit{Swift}-BAT. We detail the results of joint spectral fits with Konus and RHESSI data. The burst shows moderate hard-to-soft evolution in its multi-peaked emission over a period of about one minute. The total burst fluence as observed by Konus is $1.79 \times 10^{-4}$ erg/cm$^2$ (20 keV--10 MeV). Using the spectroscopic redshift $z=1.548$, we find that the burst is consistent with the ``Amati'' $E_{peak,i}-E_{iso}$ correlation. Assuming a jet opening angle derived from broadband modeling of the burst afterglow, GRB 070125 is a significant outlier to the ``Ghirlanda'' $E_{peak,i}-E_\gamma$ correlation. Its collimation-corrected energy release $E_\gamma = 2.5 \times 10^{52}$ ergs is the largest yet observed.Comment: 25 pages, 6 figures; accepted for publication in ApJ. Improved spectral fits and energetics estimate

Is copyright blind to the visual?

This article argues that, with respect to the copyright protection of works of visual art, the general uneasiness that has always pervaded the relationship between copyright law and concepts of creativity produces three anomalous results. One of these is that copyright lacks much in the way of a central concept of 'visual art' and, to the extent that it embraces any concept of the 'visual', it is rooted in the rhetorical discourse of the Renaissance. This means that copyright is poorly equipped to deal with modern developments in the visual arts. Secondly, the pervasive effect of rhetorical discourse appears to have made it particularly difficult for copyright law to strike a meaningful balance between protecting creativity and permitting its use in further creative works. Thirdly, just when rhetorical discourse might have been useful in identifying the significance and materiality of the unique one-off work of visual art, copyright law chooses to ignore its implications

The distances of short-hard GRBs and the SGR connection

We present a search for nearby (D<100 Mpc) galaxies in the error boxes of six well-localized short-hard gamma-ray bursts (GRBs). None of the six error boxes reveals the presence of a plausible nearby host galaxy. This allows us to set lower limits on the distances and, hence, the isotropic-equivalent energy of these GRBs. Our lower limits are around $1 \times 10^{49}$ erg (at $2\sigma$ confidence level); as a consequence, some of the short-hard GRBs we examine would have been detected by BATSE out to distances greater than 1 Gpc and therefore constitute a bona fide cosmological population. Our search is partially motivated by the December 27, 2004 hypergiant flare from SGR 1806-20, and the intriguing possibility that short-hard GRBs are extragalactic events of a similar nature. Such events would be detectable with BATSE to a distance of \~50 Mpc, and their detection rate should be comparable to the actual BATSE detection rate of short-hard GRBs. The failure of our search, by contrast, suggests that such flares constitute less than 15% of the short-hard GRBs (<40% at 95% confidence). We discuss possible resolutions of this discrepancy.Comment: Enlarged sample of bursts; ApJ in pres

A southern hemisphere survey of the 5780 and 6284 {\AA} diffuse interstellar bands: correlation with the extinction

We present a new database of 5780.5 and 6283.8 {\AA} DIB measurements and also study their correlation with the reddening. The database is based on high-resolution, high-quality spectra of early-type nearby stars located in the southern hemisphere at an average distance of 300 pc. Equivalent widths of the two DIBs were determined by means of a realistic continuum fitting and synthetic atmospheric transmissions. For all stars that possess a precise measurement of their color excess, we compare the DIBs and the extinction. We find average linear relationships of the DIBS and the color excess that agree well with those of a previous survey of northern hemisphere stars closer than 550 pc. This similarity shows that there is no significant spatial dependence of the average relationship in the solar neighborhood within $\simeq$ 600 pc. A noticeably different result is our higher degree of correlation of the two DIBs with the extinction. We demonstrate that it is simply due to the lower temperature and intrinsic luminosity of our targets. Using cooler target stars reduces the number of outliers, especially for nearby stars, confirming that the radiation field of UV bright stars has a significant influence on the DIB strength. We have used the cleanest data to compute updated DIB shapes.Comment: Astronomy & Astrophysics (in press