A five-wave HLL Riemann solver for relativistic MHD

We present a five-wave Riemann solver for the equations of ideal relativistic magnetohydrodynamics. Our solver can be regarded as a relativistic extension of the five-wave HLLD Riemann solver initially developed by Miyoshi and Kusano for the equations of ideal MHD. The solution to the Riemann problem is approximated by a five wave pattern, comprised of two outermost fast shocks, two rotational discontinuities and a contact surface in the middle. The proposed scheme is considerably more elaborate than in the classical case since the normal velocity is no longer constant across the rotational modes. Still, proper closure to the Rankine-Hugoniot jump conditions can be attained by solving a nonlinear scalar equation in the total pressure variable which, for the chosen configuration, has to be constant over the whole Riemann fan. The accuracy of the new Riemann solver is validated against one dimensional tests and multidimensional applications. It is shown that our new solver considerably improves over the popular HLL solver or the recently proposed HLLC schemes.Comment: 15 pages, 19 figures. Accepted for Publication in MNRA

A two-parameter criterion for classifying the explodability of massive stars by the neutrino-driven mechanism

Thus far, judging the fate of a massive star (either a neutron star (NS) or a black hole) solely by its structure prior to core collapse has been ambiguous. Our work and previous attempts find a non-monotonic variation of successful and failed supernovae with zero-age main-sequence mass, for which no single structural parameter can serve as a good predictive measure. However, we identify two parameters computed from the pre-collapse structure of the progenitor, which in combination allow for a clear separation of exploding and non-exploding cases with only few exceptions (~1-2.5%) in our set of 621 investigated stellar models. One parameter is M4, defining the normalized enclosed mass for a dimensionless entropy per nucleon of s=4, and the other is mu4 = d(m/M_sun)/d(r/1000 km) at s=4, being the normalized mass-derivative at this location. The two parameters mu4 and M4*mu4 can be directly linked to the mass-infall rate, Mdot, of the collapsing star and the electron-type neutrino luminosity of the accreting proto-NS, L_nue ~ M_ns*Mdot, which play a crucial role in the "critical luminosity" concept for the theoretical description of neutrino-driven explosions as runaway phenomenon of the stalled accretion shock. All models were evolved employing the approach of Ugliano et al. for simulating neutrino-driven explosions in spherical symmetry. The neutrino emission of the accretion layer is approximated by a gray transport solver, while the uncertain neutrino emission of the 1.1 M_sun proto-NS core is parametrized by an analytic model. The free parameters connected to the core-boundary prescription are calibrated to reproduce the observables of Supernova 1987A for five different progenitor models.Comment: 23 pages, 12 figures; accepted by ApJ; revised version considerably enlarged (Fig. 7 and Sect.3.6 added

Automatically Detecting Changes and Anomalies in Unmanned Aerial Vehicle Images

The use of unmanned aerial vehicles (UAVs) in civil aviation is growing up quickly, enabling new scenarios, especially in environmental monitoring and public surveillance services. So far, Earth observation has been carried out only through satellite images, which are limited in resolution and suffer from important barriers such as cloud occlusion. Microdrone solutions, providing video streaming capabilities, are already available on the marketplace, but they are limited to altitudes of a few hundred feet. In contrast, UAVs equipped with high quality cameras can fly at altitudes of a few thousand feet and can fill the gap between satellite observations and ground sensors. Therefore, new needs for data processing arise, spanning from computer vision algorithms to sensor and mission management. This paper presents a solution for automatically detecting changes in images acquired at different times by patrolling UAVs flying over the same targets (but not necessarily along the same path or at the same altitude). Change detection in multi-temporal images is a prerequisite for land cover inspection, which, in turn, sets up the basis for detecting potentially dangerous or threatening situations

Terpenoids and norisoprenoids in Italian red wines

AIM Terpene compounds are associated with fl oral notes and are characteristic of aromatic grape varieties such as Muscat (Jackson,2008). They are generally considered to potentially contribute to the aroma of white wines. However, there is a growing interesttowards the potential contribution of terpene compounds to the aroma of red wines. The aim of this work was to investigate theoccurrence of diff erent terpenes in red wines from Italian varieties. METHODS For this study wines from 11 mono-varietal Italian redwines from 12 regions were used (19 Sangiovese, 11 Nebbiolo, 10 Aglianico, 11 Primitivo, 10 Raboso del Piave, 9 Cannonau, 11 Teroldego,3 Nerello, 9 Montepulciano, 7 Corvina). All samples were from vintage 2016 and none of them had been in contact with wood. A totalof 19 terpenes and 7 norisoprenoids were analysed by mean of SPME-GC-MS analysis using a DVB-CAR-PDMS fi ber. The wines werecollected in the framework of the activities of the D-Wines (Diversity of Italian wines) project. RESULTS Signifi cant diff erences amongvarieties were observed for basically all the compounds analyzed with the exception of limonene. Overall, the concentrations of thevarious terpenes remained in the same order of magnitude. However, some diff erences are noticeable between varieties. Corvina wascharacterized by higher level of linalool, followed by Aglianico, Nebbiolo, Primitivo and Sangiovese. Cyclic terpenoids appeared asgood varietal markers, for instances Montepulciano was characterized by 1,4-cineole and 1,8-cineole, whereas Sangiovese showedhigher levels of p-cymene, \u3b1-terpinene and 1,4-cineole. Higher terpinene-1-ol content was characteristic of Montepulciano and Rabosowines. Relatively high levels of the norisoprenoid \u3b2-damascenone were found in Cannonau up to 3.68 \u3bcg/L. CONCLUSIONS This studyprovide the fi rst survey of a large number of terpenoids and norisoprenoids in diff erent mono-varietal Italian red wines. The resultsshowed that a large number of terpenoids were present in Italian red wines with specifi c profi les related to the varieties

Progenitor neutron stars of the lightest and heaviest millisecond pulsars

The recent mass measurements of two binary millisecond pulsars, PSR J1614-2230 and PSR J0751+1807 with a mass M=1.97+/-0.04 Msun and M= 1.26 +/- 0.14 Msun, respectively, indicate a wide range of masses for such objects and possibly also a broad spectrum of masses of neutron stars born in core-collapse supernovae. Starting from the zero-age main sequence binary stage, we aim at inferring the birth masses of PSR J1614-2230 and PSR J0751+1807 by taking the differences in the evolutionary stages preceding their formation into account. Using simulations for the evolution of binary stars, we reconstruct the evolutionary tracks leading to the formation of PSR J1614-2230 and PSR J0751+1807. We analyze in detail the spin evolution due to the accretion of matter from a disk in the intermediate-mass/low-mass X-ray binary. We consider two equations of state of dense matter, one for purely nucleonic matter and the other one including a high-density softening due to the appearance of hyperons. Stationary and axisymmetric stellar configurations in general relativity are used, together with a recent magnetic torque model and observationally-motivated laws for the decay of magnetic field. The estimated birth mass of the neutron stars PSR J0751+1807 and PSR J1614-2230 could be as low as 1.0 Msun and as high as 1.9 Msun, respectively. These values depend weakly on the equation of state and the assumed model for the magnetic field and its accretion-induced decay. The masses of progenitor neutron stars of recycled pulsars span a broad interval from 1.0 Msun to 1.9 Msun. Including the effect of a slow Roche-lobe detachment phase, which could be relevant for PSR J0751+1807, would make the lower mass limit even lower. A realistic theory for core-collapse supernovae should account for this wide range of mass.Comment: 13 pages, 10 figures, accepted in A&

Menus for Feeding Black Holes

Black holes are the ultimate prisons of the Universe, regions of spacetime where the enormous gravity prohibits matter or even light to escape to infinity. Yet, matter falling toward the black holes may shine spectacularly, generating the strongest source of radiation. These sources provide us with astrophysical laboratories of extreme physical conditions that cannot be realized on Earth. This chapter offers a review of the basic menus for feeding matter onto black holes and discusses their observational implications.Comment: 27 pages. Accepted for publication in Space Science Reviews. Also to appear in hard cover in the Space Sciences Series of ISSI "The Physics of Accretion onto Black Holes" (Springer Publisher