The observational data on ultrahigh energy cosmic rays (UHECR), in particular their mass composition, show strong indications for extremely hard spectra of individual mass groups of CR nuclei at Earth. In this work, we show that such hard spectra can be the result of the finite life-time of UHECR sources, if a few individual sources dominate the UHECR flux at the highest energies. In this case, time delays induced by deflections in the turbulent extragalactic magnetic field as well as from the diffusive or advective escape from the source environment can suppress low-energy CRs, leading to a steepening of the observed spectrum. Considering radio galaxies as the main source of UHECRs, we discuss the necessary conditions that few individual sources dominate over the total contribution from the bulk of sources that have been active in the past. We provide two proof-of-principle scenarios showing that for a turbulent extragalactic magnetic field with a strength $B$ and a coherence length $l_{\rm coh}$, the life-time of a source at a distance $d_{\rm src}$ should satisfy ${t_{\rm act} \sim \left( B/1\,\text{nG} \right)^2\,\left( d_{\rm src}/10\,\text{Mpc} \right)^2\,\left( l_{\rm coh}/1\,\text{Mpc} \right)\,\text{Myr}}$ to obtain the necessary hardening of the CR spectrum at Earth.

We propose a backscattering dominated prompt emission model for gamma-ray bursts (GRB) prompt phase in which the photons generated through pair annihilation at the centre of the burst are backscattered through Compton scattering by an outflowing stellar cork. We show that the obtained spectra are capable of explaining the low and high energy slopes as well as the distribution of spectral peak energies in their observed prompt spectra.

We present new results of the backscattering-dominated prompt emission model in which the photons generated through pair annihilation at the center of a gamma-ray burst (GRB) are backscattered through Compton scattering by an outflowing stellar cork. Using a Comptonized pair annihilation spectrum accompanied by bremsstrahlung radiation for seed photons, we show that the obtained spectra produce a low-energy photon index in the range α ∼ −1.95 to −1.1, steeper high-energy slopes β ∼ −3.5 to −2.4, and spectral peak energies approximately a few KeV to a few tens of MeV. These findings are consistent with the values covered in GRB prompt phase observations.

As a gamma-ray burst (GRB) jet drills its way through the collapsing star, it traps a baryonic "cork" ahead of it. Here we explore a prompt emission model for GRBs in which the jet does not cross the cork, but rather photons that are emitted deep in the flow largely by pair annihilation are scattered inside the expanding cork and escape largely from the back end of it as they push it from behind. Due to the relativistic motion of the cork, these photons are easily seen by an observer close to the jet axis peaking at epsilon(peak) similar to few x100 keV. We show that this model naturally explains several key observational features: (1) a high-energy power-law index beta(1) 2 to 5 with an intermediate thermal spectral region; (2) decay of the prompt emission light curve as similar to t(-2); (3) delay of soft photons; (4) a peak energy-isotropic energy (the so-called "Amati") correlation, epsilon(peak) similar to e(iso)(m), with m similar to 0.45, resulting from different viewing angles (at low luminosities, our model predicts an observable turnoff in the Amati relation); (4) an anticorrelation between the spectral FWHM and time as t(-1); (6) temporal evolution epsilon(peak) similar to t(-1), accompanied by an increase of the high-energy spectral slope with time; and (7) distribution of peak energies epeak in the observed GRB population. The model is applicable for single-pulse GRB light curves and their respective spectra. We discuss the consequences of our model in view of current and future prompt emission observations.

U-turns and left turns are sometimes forbidden even though it increases travel distances. The greater travel distances are sometimes outweighed by the improved movement through intersections due to there being fewer conflicting lanes of traffic. One can, further, forbid straight-throughs. Restricting a sufficient number of turns can make intersections free from crossing lanes of traffic (``zero traffic conflict,'' ``ZTC"), though there may still be merging lanes of traffic. It's possible to make \begin{it}all\end{it} intersections in a road \begin{it}network\end{it} ZTC. However, keeping all destinations accessible and travel distances moderate requires careful selection of allowed driving directions and turning directions. We demonstrate through numerical microscopic and macroscopic simulations that there are road networks and ranges of traffic loads for which, in comparison with conventional schemes, ZTC road network can carry approximately $50$\% more vehicular traffic without incurring gridlock.

Different forms of long gamma-ray bursts (GRBs) Luminosity Functions are considered on the basis of an explicit physical model. The inferred flux distributions are compared with the observed ones from two samples of GRBs, Swift and Fermi GBM. The best fit parameters of the Luminosity functions are found and the physical interpretations are discussed. The results are consistent with the observation of a comparable number of flat phase afterglows and monotonic decreasing ones.

Some subtle distinctions between optically thin emission and optically thick emission (with a dynamically passive source of opacity) from an emitting surface are drawn. It is noted that photons may escape a region of high optical depth by dragging the opaque material with them, and that optically thick emission can have a shorter scale of variation than optically thin emission and less light echoing.

We demonstrate that young star clusters have a $\gamma$-ray surface brightness comparable to that of the diffuse Galactic emission (DGE), and estimate that their sky coverage in the direction of the inner Galaxy exceeds unity. We therefore suggest that they comprise a significant fraction of the DGE.

ABSTRACT Cosmic ray (CR) sources leave signatures in the isotopic abundances of CRs. Current models of Galactic CRs that consider supernovae (SNe) shocks as the main sites of particle acceleration cannot satisfactorily explain the higher 22Ne/20Ne ratio in CRs compared to the interstellar medium. Although stellar winds from massive stars have been invoked, their contribution relative to SNe ejecta has been taken as a free parameter. Here, we present a theoretical calculation of the relative contributions of wind termination shocks (WTSs) and SNe shocks in superbubbles, based on the hydrodynamics of winds in clusters, the standard stellar mass function, and stellar evolution theory. We find that the contribution of WTSs towards the total CR production is at least $25{{\ \rm per\ cent}}$, which rises to $\gtrsim 50{{\ \rm per\ cent}}$ for young (≲10 Myr) clusters, and explains the observed 22Ne/20Ne ratio. We argue that since the progenitors of apparently isolated supernovae remnants (SNRs) are born in massive star clusters, both WTS and SNe shocks can be integrated into a combined scenario of CRs being accelerated in massive clusters. This scenario is consistent with the observed ratio of SNRs to γ-ray bright (Lγ ≳ 1035 erg s−1) star clusters, as predicted by star cluster mass function. Moreover, WTSs can accelerate CRs to PeV energies, and solve other long-standing problems of the standard SN paradigm of CR acceleration.

With upcoming (continuum) surveys of high-resolution radio telescopes, detection rates of fast radio bursts (FRBs) might approach 105 per sky per day by future extremely large observatories, such as the possible extension of the Square Kilometer Array (SKA) to a phase-2 array. Depending on the redshift distribution of FRBs and using the repeating FRB121102 as a model, we calculate a detection rate of multiply imaged FRBs with their multiply imaged hosts caused by the distribution of galaxy-cluster-scale gravitational lenses of the order of 10−4 per square degree per year for a minimum total flux of the host of 10 μJy at 1.4 GHz for SKA phase 2. Our comparison of estimated detection rates for quasars (QSOs), supernovae (SNe), gamma ray bursts (GRBs), and FRBs shows that multiple images of FRBs could be more numerous than those of GRBs and SNe and as numerous as multiple images of QSOs. Time delays between the multiple images of an FRB break degeneracies in model-based and model-independent lens reconstructions as other time-varying sources do, yet without a microlensing bias, as FRBs are more point-like and have shorter duration times. We estimate the relative imprecision of FRB time-delay measurements to be 10−10 for time delays on the order of 100 days for galaxy-cluster-scale lenses, yielding more precise (local) lens properties than time delays from the other time-varying sources. Using the lens modelling software Grale, we show the increase in accuracy and precision of the reconstructed scaled surface mass density map of a simulated cluster-scale lens when adding time delays for one set of multiple images to the set of observational constraints.

With upcoming (continuum) surveys of high-resolution radio telescopes, detection rates of fast radio bursts (FRBs) might approach 10(5) per sky per day by future extremely large observatories, such as the possible extension of the Square Kilometer Array (SKA) to a phase-2 array. Depending on the redshift distribution of FRBs and using the repeating FRB121102 as a model, we calculate a detection rate of multiply imaged FRBs with their multiply imaged hosts caused by the distribution of galaxy-cluster-scale gravitational lenses of the order of 10(-4) per square degree per year for a minimum total flux of the host of 10 mu Jy at 1.4 GHz for SKA phase 2. Our comparison of estimated detection rates for quasars (QSOs), supernovae (SNe), gamma ray bursts (GRBs), and FRBs shows that multiple images of FRBs could be more numerous than those of GRBs and SNe and as numerous as multiple images of QSOs. Time delays between the multiple images of an FRB break degeneracies in model-based and model-independent lens reconstructions as other time-varying sources do, yet without a microlensing bias, as FRBs are more point-like and have shorter duration times. We estimate the relative imprecision of FRB time-delay measurements to be 10(-10) for time delays on the order of 100 days for galaxy-cluster-scale lenses, yielding more precise (local) lens properties than time delays from the other time-varying sources. Using the lens modelling software Grale, we show the increase in accuracy and precision of the reconstructed scaled surface mass density map of a simulated cluster-scale lens when adding time delays for one set of multiple images to the set of observational constraints.

The variation in the intensity of cosmic rays at small angular scales is attributed to the interstellar turbulence in the vicinity of the Solar system. We show that {a turbulent origin of the small-scale structures implies that} the morphology of the observed cosmic-ray intensity skymap varies with our location in the interstellar turbulence. The gyroradius of cosmic rays is shown to be the length scale associated with an observable change in the skymap over a radian angular scale. The extent to which the intensity \mpo{at a certain} angular scale varies is proportional to the change in our location with a maximum change of about the amplitude of intensity variation at that scale in the existing skymap.} We suggest that for TeV cosmic rays a measurable variation could occur over a time scale of a decade due to the Earth's motion through the interstellar medium, if interstellar turbulence persists down to the gyroradius, \mpo{about $00\ \mu\mathrm{pc}$ for TeV-ish cosmic rays}. Observational evidence of the variability, or an absence of it, could provide a useful insight into the physical origin of the small-scale anisotropy.

Neutron star mergers, referring to both binary neutron star and neutron star black hole mergers, are the canonical multimessenger events. They have been detected across the electromagnetic spectrum, have recently been detected in gravitational waves, and are likely to produce neutrinos over several decades in energy. The non-thermal prompt and afterglow emission of short gamma-ray bursts and the quasi-thermal emission from the radioactively powered kilonovae provide distinct insights into the physics of neutron star mergers. When combined with direct information on coalescence from gravitational waves and neutrinos these sources may become the best understood astrophysical transients. Multimessenger observations of these cataclysmic events will determine sources of gravitational waves and astrophysical neutrinos, enable precision cosmology, and unique tests of fundamental physics, the origin of heavy elements, the behavior of relativistic jets, and the equation of state of supranuclear matter. In this white paper we present a summary of the science discoveries possible with multimessenger observations of neutron star mergers and provide recommendations to enable them in the new era of time-domain, multimessenger astronomy.

Background: Volatile organic compounds (VOCs) in urine may provide information about biomarkers of tumors in their early stages and about tumor growth. Methods: This study demonstrates that the effect of low protein diet on the pattern of VOCs in the urine of healthy and cancer bearing mice is significant. Results: Pentanal, found in nine out of the ten breast cancer-bearing mice on a high protein (HP) diet, was not found in any of the cancer bearing mice under a low protein (LP) diet, even after tumor development. In addition, the concentration of 3-heptanone, also elevated in the HP group, was not found in the LP group. Benzoic acid, 4-ethoxy-, ethyl ester, 2-pentanone, and propane, 1-isothiocyanato-3-(methylthio), all associated with anti-cancer properties or activity, were observed in the LP group, but not in the HP group. 6-methyl-3-heptanone exhibited a marked increase in concentration as a function of tumor growth when mice were maintained on an HP diet; however, its concentration exhibited no change in mice on the LP diet. The LP group showed much better survival, and even spontaneous recovery from cancer. Conclusion: Our results give an insight into the effects of an LP diet on the management of breast cancer and melanoma. While other research groups focus on improving the relative rates of efficacy and accuracy of cancer biopsy results, this study attempted to monitor the initial appearance of cancer by VOCs excreted in urine that may be associated with metabolic and other physiological changes associated with tumor development, and with a diet that inhibits such development. Keywords: mouse urine composition, breast cancer, melanoma, cancer biomarkers, low protein diet

The recent radio observations of a superluminal radio afterglow following gamma-ray burst (GRB) 179817A are interpreted in terms of a jet impacting a baryonic cloak, which is presumably the material caught at the front of the jet as the latter emerges from a denser ejected material. Assuming that we, the observers, are located at a viewing angle of similar to 0.2 radians from the emitting material (perhaps slightly more from jet axis), we suggest that the Lorentz factor of the jet is less than or similar to 20 at the time of the prompt emission, and that, as suggested previously, it is accelerated to much higher values before finally decelerating during the afterglow phase. A less extreme example of a short GRB being observed off-axis may have been GRB 150101B. A feature of GRBs viewed from large offset angles is a large afterglow isotropic equivalent energy as compared to prompt emission, as predicted, and this is born out by the observations of these two GRB. It is also shown that the prompt emission of GRB 170817A, if seen way offaxis (theta >> 1/F), could not be made by internal shocks in the baryonic material that powers the afterglow.

The extraordinary giant flare (GF) of 2004 December 27 from the soft gamma repeater (SGR) 1806-20 was followed by a bright radio afterglow. We present an analysis of VLA observations of this radio afterglow from SGR1806-20, consisting of previously reported 8.5 GHz data covering days 7 to 20 after the GF, plus new observations at 8.5 and 22 GHz from day 24 to 81. We detect motion in the flux centroid of the afterglow, at an average velocity of 0.26 ± 0.03 c (assuming a distance of 15 kpc) at a position angle of −45◦. This motion, in combination with the growth and polarization measurements, suggests an asymmetric outflow, mainly from one side of the magnetar. We find a deceleration in the expansion, from ∼9 mas/day to <5 mas/day. The time of deceleration is roughly coincident with the rebrightening in the radio light curve, as expected to result when the ejecta from the GF sweeps up enough of the external medium, and transitions from a coasting phase to the Sedov-Taylor regime. The radio afterglow is elongated and maintains a 2:1 axis ratio with an average position angle of−40◦ (north through east), oriented perpendicular to the average intrinsic linear polarization angle. Kavli Institute of Particle Astrophysics and Cosmology, Menlo Park, CA 94025, USA National Radio Astronomy Observatory, Socorro, NM 87801, USA Harvard-Smithsonian Center for Astrophysics, 60 Garden Streen, Cambridge, MA 02138, USA NASA/MSFC, XD-12, NSSTC, 320 Sparkman Dr., Huntsville, AL 35805, USA School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK IAS, Einstein Drive, Princeton, NJ 08540, USA Dept. of Phys., BGU, P.O. Box 653, Beér Sheva 84105, Israel Joint Institute for VLBI in Europe, Postbus 2, 7990 AA, Dwingeloo, The Netherlands Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, The Netherlands

It is noted that the duration of a fast radio burst (FRB), about $10^{-3}$ s, is a smaller fraction of the time delay between multiple images of a source gravitationally lensed by a galaxy or galaxy cluster than the human lifetime is to the age of the universe. Thus repeating, strongly lensed FRBs may offer an unprecedented opportunity for observing cosmological evolution in "real time". The possibility is discussed of observing cosmic expansion, transverse proper motion, mass accretion and perhaps growth of density perturbations, as a function of redshift.

Using analytic methods and 1D two-fluid simulations, we study the effect of cosmic rays (CRs) on the dynamics of interstellar superbubbles (ISBs) driven by multiple supernovae (SNe)/stellar winds in OB associations. In addition to CR advection and diffusion, our models include thermal conduction and radiative cooling. We find that CR injection at the reverse shock or within a central wind-driving region can affect the thermal profiles of ISBs and hence their X-ray properties. Even if a small fraction (10-20 per cent) of the total mechanical power is injected into CRs, a significant fraction of the ram pressure at the reverse shock can be transferred to CRs. The energy transfer becomes efficient if (1) the reverse shock gas Mach number exceeds a critical value (M-th greater than or similar to 12) and (2) the CR acceleration time-scale tau(acc) similar to k(cr)/v(2) is shorter than the dynamical time, where k(cr) is a CR diffusion coefficient and v is the upstream velocity. We show that CR affected bubbles can exhibit a volume-averaged hot gas temperature 1-5 x 10(6) K, lower by a factor of 2 -10 than without CRs. Thus, CRs can potentially solve the long-standing problem of the observed low ISB temperatures.