Cosmic rays (CRs) in the Galaxy are an important dynamical component of the interstellar medium (ISM) that interact with the other major components (interstellar gas and magnetic and radiation ...fields) to produce broadband interstellar emissions that span the electromagnetic spectrum. The standard modeling of CR propagation and production of the associated emissions is based on a steady-state assumption, where the CR source spatial density is described using a smoothly varying function of position that does not evolve with time. While this is a convenient approximation, reality is otherwise, where primary CRs are produced in and about highly localized regions, e.g., supernova remnants, which have finite lifetimes. In this paper, we use the latest version of the GALPROP CR propagation code to model time-dependent CR injection and propagation through the ISM from a realistic 3D discretized CR source density distribution, together with full 3D models for the other major ISM components, and make predictions of the associated broadband nonthermal emissions. We compare the predictions for the discretized and equivalent steady-state model, finding that the former predicts novel features in the broadband nonthermal emissions that are absent for the steady-state case. Some of the features predicted by the discretized model may be observable in all-sky observations made by WMAP and Planck, the recently launched eROSITA, the Fermi-LAT, and ground-based observations by HESS, HAWC, and the forthcoming CTA. The nonthermal emissions predicted by the discretized model may also provide explanations of puzzling anomalies in high-energy γ-ray data, such as the Fermi-LAT north/south asymmetry and residuals like the so-called "Fermi bubbles."
ABSTRACT
Cosmic rays (CRs) interact with the diffuse gas, radiation, and magnetic fields in the interstellar medium (ISM) to produce electromagnetic emissions that are a significant component of the ...all-sky flux across a broad wavelength range. The Fermi–Large Area Telescope (LAT) has measured these emissions at GeV γ-ray energies with high statistics. Meanwhile, the high-energy stereoscopic system (H.E.S.S.) telescope array has observed large-scale Galactic diffuse emission in the TeV γ-ray energy range. The emissions observed at GeV and TeV energies are connected by the common origin of the CR particles injected by the sources, but the energy dependence of the mixture from the general ISM (true ‘diffuse’), those emanating from the relatively nearby interstellar space about the sources, and the sources themselves, is not well understood. In this paper, we investigate predictions of the broad-band emissions using the galprop code over a grid of steady-state 3D models that include variations over CR sources, and other ISM target distributions. We compare, in particular, the model predictions in the very-high energy ( VHE; ≳100 GeV) γ-ray range with the H.E.S.S. Galactic plane survey (HGPS) after carefully subtracting emission from catalogued γ-ray sources. Accounting for the unresolved source contribution, and the systematic uncertainty of the HGPS, we find that the galprop model predictions agree with lower estimates for the HGPS source-subtracted diffuse flux. We discuss the implications of the modelling results for interpretation of data from the next generation Cherenkov Telescope Array (CTA).
Purpose
To investigate the effect of aging on ocular parameters, including intraocular pressure (IOP), measured with different tonometry methods in healthy young (HY) and healthy elderly (HE) ...subjects and to study the effect of corneal parameters on tonometry methods.
Methods
In this prospective, cross-sectional study, fifty eyes of 50 HY subjects (28 females, 22–31 years of age) and 43 eyes of 43 HE subjects (22 females, 64–79) were included. IOP was measured with four tonometry methods in a standardized order: ocular response analyser (ORA), dynamic contour tonometry (DCT), applanation resonance tonometry (ART) and Goldmann applanation tonometry (GAT). Other measurements included axial length (AL), central corneal thickness (CCT), corneal curvature (CC), anterior chamber volume (ACV), corneal hysteresis (CH) and corneal resistance factor (CRF).
Results
The mean IOP (HY/HE; mmHg ± standard deviation (SD)) was 12.2 ± 2.2/14.1 ± 3.5 with GAT. IOP was significantly higher (difference ± standard error) in HE compared to HY measured with an ORA (+3.1 mmHg ± 0.6), GAT (+1.9 ± 0.6) and DCT (+1.6 ± 0.6). No significant difference was found in IOP measured with ART. CH and ACV were significantly lower in HE compared to HY. There was no difference between the groups in CCT, CC, AL or CRF. No tonometry method was dependant on CCT or CC.
Conclusions
IOP measured with an ORA and via DCT and GAT was higher in HE compared to HY Swedish subjects, while IOP measured with ART did not differ between the groups. In these homogeneous groups, tonometry methods were independent of CCT and CC.
GALPROP is a numerical code for calculating the galactic propagation of relativistic charged particles and the diffuse emissions produced during their propagation. The code incorporates as much ...realistic astrophysical input as possible together with latest theoretical developments and has become a
de facto standard in astrophysics of cosmic rays. We present GALPROP WebRun, a service to the scientific community enabling easy use of the freely available GALPROP code via web browsers. In addition, we introduce the latest GALPROP version 54, available through this service.
ABSTRACT
The Swift era has posed a challenge to the standard blast‐wave model of gamma‐ray burst (GRB) afterglows. The key observational features expected within the model are rarely observed, such ...as the achromatic steepening (‘jet break’) of light curves. The observed afterglow light curves showcase additional complex features requiring modifications within the standard model. Here we present optical/near‐infrared observations, millimetre upper limits and comprehensive broad‐band modelling of the afterglow of the bright GRB 0505025A, detected by Swift. This afterglow cannot be explained by the simplistic form of the standard blast‐wave model. We attempt modelling multiwavelength light curves using (i) a forward–reverse shock model, (ii) a two‐component outflow model and (iii) a blast‐wave model with a wind termination shock. The forward–reverse shock model cannot explain the evolution of the afterglow. The two‐component model is able to explain the average behaviour of the afterglow very well but cannot reproduce the fluctuations in the early X‐ray light curve. The wind termination shock model reproduces the early light curves well but deviates from the global behaviour of the late‐time afterglow.
We present the results of a comprehensive study of the gamma-ray burst 080928 and of its afterglow. GRB 080928 was a long burst detected by Swift/BAT and Fermi/GBM. It is one of the exceptional cases ...where optical emission had already been detected when the GRB itself was still radiating in the gamma-ray band. For nearly 100 s simultaneous optical, X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. In particular, we show that the SED during the main prompt emission phase agrees with synchrotron radiation. We constructed the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT, ROTSE-IIIa (Australia), and GROND (La Silla) data and compared it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy-injections into the forward shock. Furthermore, weinvestigate whether the temporal and spectral evolution of the tail emission of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission (LAE). We find that a nonstandard LAE model is required to explain the observations. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.
Recent accurate measurements of cosmic-ray (CR) protons and nuclei by ATIC-2, CREAM, and PAMELA reveal (1) unexpected spectral hardening in the spectra of CR species above a few hundred GeV per ...nucleon, (2) a harder spectrum of He compared to protons, and (3) softening of the CR spectra just below the break energy. These newly discovered features may offer a clue to the origin of the observed high-energy Galactic CRs. We discuss possible interpretations of these spectral features and make predictions for the secondary CR fluxes and secondary-to-primary ratios, anisotropy of CRs, and diffuse Galactic gamma -ray emission in different phenomenological scenarios. Our predictions can be tested by currently running or near-future high-energy astrophysics experiments.
Presentation skills for oral presentations Johannesson, G
Acta ophthalmologica (Oxford, England),
October 2016, 2016-10-00, 20161001, Letnik:
94, Številka:
S256
Journal Article
Recenzirano
Odprti dostop
Summary
An important part of being a scientist is communicating findings and results to fellow colleagues and the public. This is often achieved through oral presentation in front of a group of ...people. How well the message is conveyed to the crowd depends largely on the presentation skills of the oral presenter. Yet many scientists do not get adequate education or training in presentation skills and techniques. Consequently many presenters are forced to learning by doing. This short talk will highlight a selection of tips and tricks to improve the presentation skills for oral presentations.
We develop a global‐scale P wave velocity model (LLNL‐G3Dv3) designed to accurately predict seismic travel times at regional and teleseismic distances simultaneously. The model provides a new image ...of Earth's interior, but the underlying practical purpose of the model is to provide enhanced seismic event location capabilities. The LLNL‐G3Dv3 model is based on ∼2.8 millionP and Pnarrivals that are re‐processed using our global multiple‐event locator called Bayesloc. We construct LLNL‐G3Dv3 within a spherical tessellation based framework, allowing for explicit representation of undulating and discontinuous layers including the crust and transition zone layers. Using a multiscale inversion technique, regional trends as well as fine details are captured where the data allow. LLNL‐G3Dv3 exhibits large‐scale structures including cratons and superplumes as well numerous complex details in the upper mantle including within the transition zone. Particularly, the model reveals new details of a vast network of subducted slabs trapped within the transition beneath much of Eurasia, including beneath the Tibetan Plateau. We demonstrate the impact of Bayesloc multiple‐event location on the resulting tomographic images through comparison with images produced without the benefit of multiple‐event constraints (single‐event locations). We find that the multiple‐event locations allow for better reconciliation of the large set of direct P phases recorded at 0–97° distance and yield a smoother and more continuous image relative to the single‐event locations. Travel times predicted from a 3‐D model are also found to be strongly influenced by the initial locations of the input data, even when an iterative inversion/relocation technique is employed.
Key Points
A global P‐wave model (LLNL‐G3Dv3) is produced
The LLNL‐G3Dv3 model is designed to enhance seismic event monitoring
Accurate seismic location prior to tomographic inversion is essential
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