Measuring an Off-center Detonation through Infrared Line Profiles: The Peculiar Type Ia Supernova SN 2020qxp/ASASSN-20jq

We present and analyze a near-infrared (NIR) spectrum of the underluminous Type Ia supernova SN 2020qxp/ASASSN-20jq obtained with NIRES at the Keck Observatory, 191 days after B-band maximum. The spectrum is dominated by a number of broad emission features, including the [Fe ii] at 1.644 μm, which is highly asymmetric with a tilted top and a peak redshifted by ≈2000 km s−1. In comparison with 2D non-LTE synthetic spectra computed from 3D simulations of off-center delayed-detonation Chandrasekhar-mass (M ch) white dwarf (WD) models, we find good agreement between the observed lines and the synthetic profiles, and are able to unravel the structure of the progenitor’s envelope. We find that the size and tilt of the [Fe ii] 1.644 μm profile (in velocity space) is an effective way to determine the location of an off-center delayed-detonation transition (DDT) and the viewing angle, and it requires a WD with a high central density of ∼4 × 109 g cm−3. We also tentatively identify a stable Ni feature around 1.9 μm characterized by a “pot-belly” profile that is slightly offset with respect to the kinematic center. In the case of SN 2020qxp/ASASSN-20jq, we estimate that the location of the DDT is ∼0.3M WD off center, which gives rise to an asymmetric distribution of the underlying ejecta. We also demonstrate that low-luminosity and high-density WD SN Ia progenitors exhibit a very strong overlap of Ca and 56Ni in physical space. This results in the formation of a prevalent [Ca ii] 0.73 μm emission feature that is sensitive to asymmetry effects. Our findings are discussed within the context of alternative scenarios, including off-center C/O detonations in He-triggered sub-M Ch WDs and the direct collision of two WDs. Snapshot programs with Gemini/Keck/Very Large Telescope (VLT)/ELT-class instruments and our spectropolarimetry program are complementary to mid-IR spectra by the James Webb Space Telescope (JWST).

Type Ia supernovae from wide white dwarfs triples

ABSTRACT For ultra-wide systems (with outer orbit >103 au) the galactic field is collisional. Hence, ultra-wide triple white dwarfs (TWDs) can be perturbed, by flyby stars, to sufficiently high outer eccentricity such that the triple becomes dynamically unstable. An unstable triple undergoes multiple binary–single resonant encounters between all three WDs. These encounters might result in a direct collision between any random two WDs and lead to a Type Ia supernova (SN Ia) event. In case where the multiple resonant encounters did not produce a collision a compact binary is formed (while the third WD is ejected), this binary either collides or merges via gravitational wave emission, similar to the classic double-degenerate (DD) channel. In this research study we estimate the galactic rates of SN Ia from the direct collision channel is to be $0.11\!-\!3.76{{\ \rm per\ cent}}$ and primarily $1\!-\!36{{\ \rm per\ cent}}$ from the DD scenario. The spread in the range is due to uncertainty in the underlying population and two types of galaxies, where elliptical galaxies host higher fraction. and primarily $2\!-\!36{{\ \rm per\ cent}}$ from the DD scenario.

The wide-binary origin of the Pluto–Charon system

ABSTRACT The Pluto–Charon binary system is the best studied representative of the binary Kuiper-belt population. Its origins are vital to understanding the formation of other Kuiper-belt objects (KBO) and binaries and the evolution of the outer Solar system. The Pluto–Charon system is believed to form following a giant impact between two massive KBOs at relatively low velocities. However, the likelihood of a random direct collision between two of the most massive KBOs is low and is further constrained by the requirement of a low-velocity collision, making this a potentially fine-tuned scenario. Here, we expand our previous studies and suggest that the proto-Pluto–Charon system was formed as a highly inclined wide-binary, which was then driven through secular/quasi-secular evolution into a direct impact. Since wide-binaries are ubiquitous in the Kuiper belt with many expected to be highly inclined, our scenario is expected to be robust. We use analytic tools and few-body simulations of the triple Sun–(proto-)Pluto–Charon system to show that a large parameter space of initial conditions leads to such collisions. The velocity of such an impact is the escape velocity of a bound system, which naturally explains the low-velocity impact. The dynamical evolution and the origins of the Pluto–Charon system could therefore be traced to similar secular origins as those of other binaries and contact-binaries (e.g. Arrokoth) and suggest that they play a key role in the evolution of KBOs.

Collisional Dynamics Simulations Revealing Fragmentation Properties of Zn(II)-Bound Poly-Peptide

<div> <div> <div> <p>Chemical dynamics simulations are performed to study the collision induced gas phase unimolecular fragmentation of a model peptide with the sequence acetyl-His1-Cys2-Gly3-Pro4-Tyr5-His6-Cys7 (analogue methanobactin peptide-5, amb5) and in particular to explore the role of zinc binding on reactivity. Fragmentation pathways, their mechanisms, and collision energy transfer are discussed. The probability distributions of the pathways are compared with the results of the experimental IM-MS, MS/MS spectrum and previous thermal simulations. Collisional activation gives both statistical and non-statistical fragmentation pathways with non-statistical shattering mechanisms accounting for a relevant percentage of reactive trajectories, becoming dominant at higher energies. The tetra-coordination of zinc changes qualitative and quantitative fragmentation, in particular the shattering. The collision energy threshold for the shattering mechanism was found to be 118.9 kcal/mol which is substantially higher than the statistical Arrhenius activation barrier of 35.8 kcal/mol identified previously during thermal simulations. This difference can be attributed to the tetra-coordinated zinc complex that hinders the availability of the sidechains to undergo direct collision with the Ar projectile. </p> </div> </div> </div>

Collisional Dynamics Simulations Revealing Fragmentation Properties of Zn(II)-Bound Poly-Peptide

<div> <div> <div> <p>Chemical dynamics simulations are performed to study the collision induced gas phase unimolecular fragmentation of a model peptide with the sequence acetyl-His1-Cys2-Gly3-Pro4-Tyr5-His6-Cys7 (analogue methanobactin peptide-5, amb5) and in particular to explore the role of zinc binding on reactivity. Fragmentation pathways, their mechanisms, and collision energy transfer are discussed. The probability distributions of the pathways are compared with the results of the experimental IM-MS, MS/MS spectrum and previous thermal simulations. Collisional activation gives both statistical and non-statistical fragmentation pathways with non-statistical shattering mechanisms accounting for a relevant percentage of reactive trajectories, becoming dominant at higher energies. The tetra-coordination of zinc changes qualitative and quantitative fragmentation, in particular the shattering. The collision energy threshold for the shattering mechanism was found to be 118.9 kcal/mol which is substantially higher than the statistical Arrhenius activation barrier of 35.8 kcal/mol identified previously during thermal simulations. This difference can be attributed to the tetra-coordinated zinc complex that hinders the availability of the sidechains to undergo direct collision with the Ar projectile. </p> </div> </div> </div>

Influence of floe-floe interactions on wave damping in marginal ice zones

&lt;p&gt;Numerous observations show that in spite of relative motions of floes caused by wave propagation in marginal ice zone (MIZ) direct contacts between them don&amp;#8217;t occur. Nevertheless, relative motions of floes may influence formation of oscillating water currents between them which take and dissipate the energy of incoming waves. Full-scale and laboratory experiments were performed to investigate characteristics of water currents between interacting floes. The experiments included the investigation of vertical and horizontal oscillating motions of floes in ice environment. During the experiments we recorded floe accelerations, water pressure and water velocity. Main goal of the experiments was to estimate effective viscosity of water in gapes between interacting floes, describe floe-floe forces caused by the floe accelerations, and estimate the influence of slush formation on the effective viscosity of water. The floe motion was initiated by mechanical pooling, towing with a rope and by original pendulum rig. The experiments were performed in the Van-Mijen Fjord of Spitsbergen in winter seasons of 2018 and 2019, and in the wave flume at UNIS. A lubrication theory was used to describe the dependence of water pressure between interacting floes from their relative speed and the distance between approaching surfaces. Comparison of numerical simulations with experimental records showed that the action of water pressure and the formation of flow jets can prevent direct collision of approaching floes. Obtained analytical formulas are used for the formulation of rheological equations describing the behavior of broken ice in MIZ.&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; &amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;

Splash bridge models of inclined, gas-rich, direct galaxy collisions

ABSTRACT Splash bridges are formed from the direct inelastic collision of gas-rich galaxies. Recent multiwavelength observations of the Taffy galaxies, UGC 12914/15, have revealed complicated gas structures in the bridge. We have upgraded the sticky particle simulation code of Yeager & Struck by adding: the ability to adjust the relative inclination of the gas discs, the ability to track cloud–cloud collisions over time, and additional cooling processes. Inclination effects lead to various morphological features, including filamentary streams of gas stripped from the smaller galactic disc. The offset of disc centres at impact determines whether or not these streams flow in a single direction or multiple directions, even transverse to the motion of the two galaxies. We also find that, across many types of direct collision, independent of the inclination or offset, the distributions of weighted Mach numbers and shock velocities in colliding clouds relax to a very similar form. There is good evidence of prolonged turbulence in the gas of each splash bridge for all inclinations and offsets tested, as a result of continuing cloud collisions, which in turn are the result of shearing and differentially accelerated trajectories. The number distribution of high velocity shocks in cloud collisions, produced in our low inclination models, are in agreement with those observed by Appleton et al. in the Taffy Galaxies with ALMA.

TECHNOLOGICAL ALIENATION OF A PERSON AND MORAL DILEMMAS AS ITS CONSEQUENCES

This article aims to identify new moral dilemmas generated by technological progress and its consequence - the phenomenon of technological alienation in modern society. It examines the relationship between the phenomenon of alienation, technological progress and moral dilemmas they cause in modern society. In addition to the emergence of new moral and existential issues that arises as the consequence of the direct “collision” of a person and technologies as a result of their widespread introduction into our lives, we consider moral dilemmas arising from technological progress in such areas of life as politics, economics and education. Each of them poses a deeper problem for the person - an alienation from other people, from the species essence and from oneself, which allows us to designate this question not only as social problem, but also affecting existential questions.