Wave-driven Mass Loss of Stripped Envelope Massive Stars: Progenitor-dependence, Mass Ejection, and Supernovae

The discovery of rapidly rising and fading supernovae powered by circumstellar interaction has suggested the pre-supernova mass eruption phase as a critical phenomenon in massive star evolution. It is important to understand the mass and radial extent of the circumstellar medium (CSM) from theoretically predicted mass ejection mechanisms. In this work, we study the wave heating process in massive hydrogen-poor stars, running a suite of stellar models in order to predict the wave energy and pre-explosion timescale of surface energy deposition. We survey stellar models with main-sequence progenitor masses from 20–70 M ⊙ and metallicity from 0.002–0.02. Most of these models predict that less than ∼1047 erg is deposited in the envelope, with the majority of the energy deposited in the last week of stellar evolution. This translates to CSM masses less than ∼10−2 M ⊙ that extend to less than ∼1014 cm, too small to greatly impact the light curves or spectra of the subsequent supernovae, except perhaps during the shock breakout phase. However, a few models predict somewhat higher wave energy fluxes, for which we perform hydrodynamical simulations of the mass ejection process. Radiative transfer simulations of the subsequent supernovae predict a bright but brief shock-cooling phase that could be detected in some Type Ib/c supernovae if they are discovered within a couple days of explosion.

Trevor Evans. 26 April 1927 — 10 October 2010

Trevor Evans was responsible for revealing the main physical processes which take place in natural diamond both in the upper mantle of the earth, where it is stabilized by high pressure and temperature, and as it is ejected by volcanic action to the surface. By measuring the activation energies required for graphitization, he clarified the reason for its very long life as a metastable crystal, valuable both as a gemstone and as an industrial abrasive. He learned how to make diamond specimens for examination in the transmission electron microscope, which enabled his discovery of dislocation loops and platelet precipitates in nitrogen-containing (type 1) stones. In a series of exacting laboratory experiments under geologically relevant conditions he pioneered the study of the emergence of nitrogen from solution to precipitation during the ejection process. In synthetic diamonds, using high-energy electron irradiation, he was able to reproduce the sequence of all the various types of nitrogen aggregation found in natural diamond. His work played a major role underpinning the characterization of gemstones, explaining many features of their colour. For many years he led diamond research in the UK, supported by De Beers. His work stimulated and has been confirmed by research in many other laboratories around the world.

Influence of External Factors on Airborne Missile’s Horizontal Backward Launching

This paper studies the influence of different external disturbance factors on the horizontal backward separation of airborne missiles on large transport aircraft. The method of comparison with experiment was adopted to verify the accuracy of the finite element model during the ejection process. By comparing the finite element model, it was confirmed that the all rigid body model and partly rigid body model are inaccurate in calculating the pitch angle and pitch velocity of the missile separation. Finally, the influences of ejection force, random vibration, and missile loading position on the ejection process are analyzed. The analysis found that the ejection force and the sliding distance will increase the vibration of the launching platform, therefore increase the separation pitch angle and the pitch velocity of the missile, but the influence of random vibration on platform is much greater than the other two factors, and it will also introduce randomness into the movement of the missile.

The first microseconds of a hypervelocity impact

ABSTRACT The earliest ejection process of impact cratering involves very high pressures and temperatures and causes near-surface material to be ejected faster than the initial impact velocity. On Earth, such material may be found hundreds to even thousands of kilometers away from the source crater as tektites. The mechanism yielding such great distances is not yet fully understood. Hypervelocity impact experiments give insights into this process, particularly as the technology necessary to record such rapid events in high temporal and spatial resolution has recently become available. To analyze the earliest stage of this hypervelocity process, two series of experiments were conducted with a two-stage light-gas gun, one using aluminum and the other using quartzite as target material. The vertical impacts of this study were recorded with a high-speed video camera at a temporal resolution of tens of nanoseconds for the first three microseconds after the projectile’s contact with the target. The images show a self-luminous, ellipsoidal vapor cloud expanding uprange. In order to obtain angle-resolved velocities of the expanding cloud, its entire front and the structure of the cloud were systematically investigated. The ejected material showed higher velocities at high angles to the target surface than at small angles, providing a possible explanation for the immense extent of the strewn fields.

Double trouble: Gaia reveals (proto)planetary systems that may experience more than one dense star-forming environment

ABSTRACT Planetary systems appear to form contemporaneously around young stars within young star-forming regions. Within these environments, the chances of survival, as well as the long-term evolution of these systems, are influenced by factors such as dynamical interactions with other stars and photoevaporation from massive stars. These interactions can also cause young stars to be ejected from their birth regions and become runaways. We present examples of such runaway stars in the vicinity of the Orion Nebula Cluster (ONC) found in Gaia DR2 data that have retained their discs during the ejection process. Once set on their path, these runaways usually do not encounter any other dense regions that could endanger the survival of their discs or young planetary systems. However, we show that it is possible for star–disc systems, presumably ejected from one dense star-forming region, to encounter a second dense region, in our case the ONC. While the interactions of the ejected star–disc systems in the second region are unlikely to be the same as in their birth region, a second encounter will increase the risk to the disc or planetary system from malign external effects.

Disc formation and jet inclination effects in common envelopes

ABSTRACT The evolution and physics of the common envelope (CE) phase are still not well understood. Jets launched from a compact object during this stage may define the evolutionary outcome of the binary system. We focus on the case in which jets are launched from a neutron star (NS) engulfed in the outer layers of a red giant (RG). We run a set of three-dimensional hydrodynamical simulations of jets with different luminosities and inclinations. The luminosity of the jet is self-regulated by the mass accretion rate and an efficiency η. Depending on the value of η the jet can break out of the previously formed bulge (‘successful jet’) and aligns against the incoming wind, in turn, it will realign in favour of the direction of the wind. The jet varies in size and orientation and may present quiescent and active epochs. The inclination of the jet and the Coriolis and centrifugal forces, only slightly affect the global evolution. As the accretion is hypercritical, and the specific angular momentum is above the critical value for the formation of a disc, we infer the formation of a disc and launching of jets. The discs’ mass and size would be ∼10−2 M⊙ and ≳1010 cm, and it may have rings with different rotation directions. In order to have a successful jet from a white dwarf, the ejection process needs to be very efficient (η ∼ 0.5). For main-sequence stars, there is not enough energy reservoir to launch a successful jet.

Fragmentation of steaming Surtseyan bombs

<p>A Surtseyan volcanic eruption involves a bulk interaction between water and hot magma, mediated by the return of ejected ash. Surtsey Island, off the coast of Iceland, was born during such an eruption process in the 1940s. Mount Ruapehu in New Zealand also undergoes Surtseyan eruptions, due to its crater lake. </p><p>One feature of such eruptions is ejected lava bombs, trailing steam, with evidence that watery slurry was trapped inside them during the ejection process. Simple calculations indicate that the pressures developed due to boiling inside such a bomb should shatter it. Yet intact bombs are routinely discovered in debris piles. In an attempt to crack this problem, and provide a criterion for fragmentation of Surtseyan bombs, a transient mathematical model of the flashing of water to steam inside one of these hot erupted lava balls is developed, with a particular focus on the maximum pressure attained, and how it depends on magma and fluid properties. Numerical and asymptotic solutions provide some answers for volcanologists.</p>

Merger and Mass Ejection of Neutron Star Binaries

Mergers of binary neutron stars and black hole–neutron star binaries are among the most promising sources for ground-based gravitational-wave (GW) detectors and are also high-energy astrophysical phenomena, as illustrated by the observations of GWs and electromagnetic (EM) waves in the event of GW170817. Mergers of these neutron star binaries are also the most promising sites for r-process nucleosynthesis. Numerical simulation in full general relativity (numerical relativity) is a unique approach to the theoretical prediction of the merger process, GWs emitted, mass ejection process, and resulting EM emission. We summarize the current understanding of the processes of neutron star mergers and subsequent mass ejection based on the results of the latest numerical-relativity simulations. We emphasize that the predictions of the numerical-relativity simulations agree broadly with the optical and IR observations of GW170817.