Postglacial Isostatic Movement in Northeastern Devon Island, Canadian Arctic Archipelago

The limit of marine submergence of the last glaciation in the Cape Sparbo region varied in elevation from 65 m at Base Camp lowland, 73 m in Sparbo-Hardy lowland, to 82 m in the Skogn area; these variations are in part due to differences in time of deglaciation. Radiocarbon dates of marine shells indicate that the region was clear of ice by 15,500 yr BP; that the most rapid isostatic uplift occurred 9000-8000 yr BP and that the total rebound was about 110 m. The oldest dates, 15,000 and 13,000 BP, if correct, indicate the slow onset of isostatic uplift.Isostasie postglaciaire dans le nord-est de l'île Devon, Archipel Arctique canadien. Les auteurs ont étudié la morphologie isostatique des basses terres au voisinage du cap Sparbo. Les datations par le carbone-14 de coquillages marins indiquent que la région était libre de glace des 15,500 av. p. et que le relèment le plus rapide (approx. 6.5 m. par siècle) s'est produit entre le neuvième et le huitième millénaire av. p. Le rebondissement isostatique total a été d'environ 110 m. Les deux datations les plus anciennes (15,000 et 13,000 av. p.), si elles sont justes, sont une rare preuve de la lenteur du relèvement à son début

Preliminary Skylab MSS channel evaluation

The author has identified the following significant results. A set of 18 channels which were considered of usable quality were identified. These were channels 1-14, 17, 19-21. Channels 15, 16, 18, and 22 were dropped out because they were of poor quality; channels 7 and 11 were dropped to limit the total channel number to 16. From these 16 channels, a total of 22 signatures were obtained. Eight were developed from uniform blocks of the UMAP, and 14 from use of the DCLUS program. These signatures fell into six basic categories and classified more than 90% of the five scenes mapped: agriculture land (6 signatures); forest aland (4); water (2); open nonagriculture land (2); urban (6); and disturbed land (2)

Enhancement of W+/- H-/+ Production at Hadron Colliders in the Two Higgs Doublet Model

We discuss the associated W+/- H-/+ production at the CERN Large Hadron Collider. The dependence of the hadronic cross section on the Higgs sector parameters is investigated in detail in the framework of the general Two Higgs Doublet Model (THDM). We study the possible enhancement of the THDM prediction for the cross section compared to the prediction of the Minimal Supersymmetric Standard Model (MSSM). We find regions in the THDM parameter space where the THDM prediction can exceed the one of the MSSM by two orders of magnitude. These regions of large cross section are in agreement with theoretical bounds on the model, derived from the requirement of vacuum stability and perturbative unitarity, and are not excluded by experimental constraints.Comment: 19 pages, 5 figure

Are the distributions of Fast Radio Burst properties consistent with a cosmological population?

High time resolution radio surveys over the last few years have discovered a population of millisecond-duration transient bursts called Fast Radio Bursts (FRBs), which remain of unknown origin. FRBs exhibit dispersion consistent with propagation through a cold plasma and dispersion measures indicative of an origin at cosmological distances. In this paper we perform Monte Carlo simulations of a cosmological population of FRBs, based on assumptions consistent with observations of their energy distribution, their spatial density as a function of redshift and the properties of the interstellar and intergalactic media. We examine whether the dispersion measures, fluences, inferred redshifts, signal-to-noises and effective widths of known FRBs are consistent with a cosmological population. Statistical analyses indicate that at least 50 events at Parkes are required to distinguish between a constant co-moving FRB density, and a FRB density that evolves with redshift like the cosmological star formation rate density.Comment: 11 pages, 7 figures, 3 table

The broad-line region and dust torus size of the Seyfert 1 galaxy PGC50427

We present the results of a three years monitoring campaigns of the $z = 0.024$ type-1 active galactic nucleus (AGN) PGC50427. Through the use of Photometric Reverberation Mapping with broad and narrow band filters, we determine the size of the broad-line emitting region by measuring the time delay between the variability of the continuum and the H$\alpha$ emission line. The H$\alpha$ emission line responds to blue continuum variations with an average rest frame lag of $19.0 \pm 1.23$ days. Using single epoch spectroscopy we determined a broad-line H$\alpha$ velocity width of 1020 km s$^{-1}$ and in combination with the rest frame lag and adoption a geometric scaling factor $f = 5.5$, we calculate a black hole mass of $M_{BH} \sim 17 \times 10^{6} M_{\odot}$. Using the flux variation gradient method, we separate the host galaxy contribution from that of the AGN to calculate the rest frame 5100\AA~ luminosity at the time of our monitoring campaign. The rest frame lag and the host-subtracted luminosity permit us to derive the position of PGC50427 in the BLR size -- AGN luminosity diagram, which is remarkably close to the theoretically expected relation of $R \propto L^{0.5}$. The simultaneous optical and NIR ($J$ and $K_{s}$) observations allow us to determine the size of the dust torus through the use of dust reverberation mapping method. We find that the hot dust emission ($\sim 1800K$) lags the optical variations with an average rest frame lag of $46.2 \pm 2.60$ days. The dust reverberation radius and the nuclear NIR luminosity permit us to derive the position of PGC50427 on the known $\tau - M{V}$ diagram. The simultaneus observations for the broad-line region and dust thermal emission demonstrate that the innermost dust torus is located outside the BLR in PGC50427, supporting the unified scheme for AGNs. (Abstract shortened, see the manuscript.)Comment: 11 pages, 23 figures, accepted for publication in Astronomy and Astrophysic

Fermion and Anti-Fermion Effective Masses in High Temperature Gauge Theories in CPCP-Asymmetric Background

We calculate the splitting between fermion and anti-fermion effective masses in high temperature gauge theories in the presence of a non-vanishing chemical potential due to the $CP$-asymmetric fermionic background. In particular we consider the case of left-handed leptons in the $SU(2)\otimes U(1)$ theory when the temperature is above $250$ GeV and the gauge symmetry is restored.Comment: 13 pages, TIPAC-93001

Performance of Multi-Beacon DGPS

Historically, maritime organizations seeking accurate shipboard positioning have relied upon some form of differential GNSS, such as DGPS, WAAS, or EGNOS, to improve the accuracy and integrity of the GPS. Groundbased augmentation systems, such as DGPS, broadcast corrections to the GPS signal from geographically distributed terrestrial stations, often called beacons. Specifically, pseudorange corrections for the GPS L1 C/A signal are computed at each reference site, then broadcast in the nearby geographic area using a medium frequency (approximately 300 kHz) communications link. The user then adds these corrections onto their measured pseudoranges before implementing a position solution algorithm. Within the United States, the U.S. Coast Guard operates 86 DGPS reference beacons. Similar DGPS systems are operated in Europe and elsewhere around the globe. While current DGPS receiver algorithms typically use one set of pseudorange corrections from one DGPS reference site (often the one with the “strongest” signal), many user locations can successfully receive two or more different DGPS broadcasts. This brings to mind obvious questions: “If available, how does one select the corrections to use from multiple sets of corrections?” and “Is it advantageous to combine corrections in some way?” We note that a number of factors might influence the effectiveness of any particular station’s corrections. Some of these refer to the effectiveness of the communications link itself, including concerns about interference from other beacons (skywave interference from far-away beacons on similar frequencies, a notable problem in Europe) and self-interference (skywave fading). Other factors refer to the accuracies of pseudorange corrections. For example, ionospheric storm-enhanced plasma density (SED) events can cause the corrections to have large spatial variation, making them poor choices even for users close to a beacon. Earlier work in the area of DGPS beacon selection has identified several options including choosing the beacon closest to the user or the beacon with the least skywave interference. There have also been suggestions on how to combine corrections when multiple beacons are available. The most common of these is a weighted sum of the corrections, where the weights are typically inversely proportional to the distance from the user to the individual beacon. This paper reexamines the concept of multi-beacon DGPS by evaluating methods of combining beacon corrections based on spatial relativity. Of relevance to this topic is our recent observation that DGPS accuracy performance is biased. The mean of the error scatter with DGPS corrections does not fall on the actual receiver position. We established this both by processing GPS L1 C/A observables from hundreds of CORS (Continuously Operating References Station) sites around the U.S.A. and via simulation using a Spirent GSS8000 GPS simulator. Specifically, we found that the position solution computed using DGPS beacon corrections is typically biased in a direction away from the beacon, and that the size of the bias depends upon the distance from the beacon. This bias grows with a slope of approximately one-third of a meter per 100 km of user-to-beacon distance. This paper compares the performance of several multibeacon algorithms assessed using GPS simulator data. These algorithms include the nearest beacon, a weighted sum based on distances, and a spatial linearly-interpolated correction using the actual locations of the transmitters (distance and angle). We note that as part of this research effort we developed a DGPS receiver using software-defined radio (USRP). A complete description of this system is included in the paper

The UTMOST pulsar timing programme I: overview and first results

We present an overview and the first results from a large-scale pulsar timing programme that is part of the UTMOST project at the refurbished Molonglo Observatory Synthesis Radio Telescope (MOST) near Canberra, Australia. We currently observe more than 400 mainly bright southern radio pulsars with up to daily cadences. For 205 (8 in binaries, 4 millisecond pulsars) we publish updated timing models, together with their flux densities, flux density variability, and pulse widths at 843 MHz, derived from observations spanning between 1.4 and 3 yr. In comparison with the ATNF pulsar catalogue, we improve the precision of the rotational and astrometric parameters for 123 pulsars, for 47 by at least an order of magnitude. The time spans between our measurements and those in the literature are up to 48 yr, which allows us to investigate their long-term spin-down history and to estimate proper motions for 60 pulsars, of which 24 are newly determined and most are major improvements. The results are consistent with interferometric measurements from the literature. A model with two Gaussian components centred at 139 and $463~\text{km} \: \text{s}^{-1}$ fits the transverse velocity distribution best. The pulse duty cycle distributions at 50 and 10 per cent maximum are best described by log-normal distributions with medians of 2.3 and 4.4 per cent, respectively. We discuss two pulsars that exhibit spin-down rate changes and drifting subpulses. Finally, we describe the autonomous observing system and the dynamic scheduler that has increased the observing efficiency by a factor of 2-3 in comparison with static scheduling.Comment: 31 pages, 14 figures, 6 tables, accepted for publication in MNRA