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State-of-the-art surveys reveal that most massive stars in the Universe evolve in close binaries. Massive stars in such systems are expected to develop aspherical envelopes due to tidal interactions and/or rotational effects. Recently, it was shown that point explosions in oblate stars can produce relativistic equatorial ring-like outflows. Moreover, since stripped-envelope stars in binaries can expand enough to fill their Roche lobes anew, it is likely that these stars die with a greater degree of asphericity than the oblate spheroid geometry previously studied. We investigate the effects of this asymmetry by studying the gas dynamics of axisymmetric point explosions in stars in various stages of filling their Roche lobes. We find that point explosions in these pear-shaped stars produce transrelativistic ejecta that coalesce into bullets pointed both toward and away from the binary companion. We present this result and comment on key morphological differences between core-collapse explosions in spherical versus distorted stars in binary systems, effects on gravitational wave sources, and observational signatures that could be used to glean these explosion geometries from current and future surveys.

Evolutionary calculations for stars in close binary systems are in high demand to obtain better constraints on gravitational-wave source progenitors, understand transient events from stellar interactions, and more. Modern one-dimensional (1D) stellar codes make use of the Roche lobe radius R _L concept in order to treat stars in binary systems. If the stellar companion is approaching its R _L , mass transfer treatment is initiated. However, the effective acceleration also affects the evolution of a star in a close binary system. This is different from the gravity inside a single star, whether that single star is rotating or not. Here, we present numerically obtained tables of properties of stars in a binary system as a function of the effective potential: volume-equivalent radii of the equipotential surfaces, effective accelerations and the inverse effective accelerations averaged over the same equipotential surfaces, and the properties of the L _1 -plane cross sections. The tables are obtained for binaries where the ratios of the primary star mass to the companion star mass are from 10 ^−6 to 10 ^5 and include equipotential surfaces up to the star’s outer Lagrangian point. We describe the numerical methods used to obtain these quantities and report how we verified the numerical results. We also describe and verify the method to obtain the effective acceleration for nonpoint mass distributions. We supply a sample code showing how to use our tables to get the average effective accelerations in 1D stellar codes.

The concept of mutual illumination between texts, genres, arts, and disciplines has been used in scholarly work for decades (Weisstein, 1973, 1993). Nevertheless, much of this literature lacks a firm anchor with regard to a literal source of the analogy "mutual illumination." We argue that by observing natural phenomena that actually mutually illuminate, influence and otherwise affect each other, greater insight into how texts interact in similar ways can be achieved. Thus, drawing concepts from astrophysics, with specific reference to multiple star systems, a conceptual framework is derived in which analogous relations are proposed and interrogated. This framework couches the discussion in a stylistic analysis of our primary text, Jími Ṣólańkẹ́'s Ọ̀nà Là , which is analyzed both on its own and also with reference to other texts which are interconnected, interrelated, and serve to "mutually illuminate" each other. We find that when considered in light of other related texts, the analysis of Ọ̀nà Là becomes much richer and, in the process, the understanding of the other texts is also enriched. Stylistic tools used in the analysis include various types of intertextual and intratextual parallelism, repetition, and silence. [ABSTRACT FROM AUTHOR]

The concept of mutual illumination between texts, genres, arts, and disciplines has been used in scholarly work for decades (Weisstein, 1973, 1993). Nevertheless, much of this literature lacks a firm anchor with regard to a literal source of the analogy “mutual illumination.” We argue that by observing natural phenomena that actually mutually illuminate, influence and otherwise affect each other, greater insight into how texts interact in similar ways can be achieved. Thus, drawing concepts from astrophysics, with specific reference to multiple star systems, a conceptual framework is derived in which analogous relations are proposed and interrogated. This framework couches the discussion in a stylistic analysis of our primary text, Jimi Solanke’s Ona La, which is analyzed both on its own and also with reference to other texts which are interconnected, interrelated, and serve to “mutually illuminate” each other. We find that when considered in light of other related texts, the analysis of Ona Lạ̀ becomes much richer and, in the process, the understanding of the other texts is also enriched. Stylistic tools used in the analysis include various types of intertextual and intratextual parallelism, repetition, and silence.

The intense stellar SXR and EUV radiation exposure at “Hot Jupiters” causes profound responses to their upper atmosphere structures. Thermospheric temperatures can reach several thousands of Kelvins, which result in dissociation of H2 to H and ionization of H to H+. Depending on the density and orbit location of the exoplanet, as a result of these high temperatures the thermosphere expands dynamically up to the Roche lobe, so that geometric blow-off with large mass loss rates and intense interaction with the stellar wind plasma can occur. UV transit observations together with advanced numerical models can be used to gain knowledge on stellar plasma and the planet's magnetic properties, as well as the upper atmosphere. [ABSTRACT FROM PUBLISHER]

Abstract: We investigate the efficiency of the atmospheric mass loss due to hydrodynamic blow-off over the lifetime of the exoplanet HD209458b by studying numerically its hydrogen wind for host star X-ray and EUV (XUV) fluxes between 1 and 100 times that of the present Sun. We apply a time-dependent numerical algorithm which is able to solve the system of hydrodynamic equations straight through the transonic point of the flow including Roche lobe effects. The mass loss rates are calculated as functions of the absorbed energy in the thermosphere. Depending on the heating efficiency for a hydrogen-rich thermosphere the maximum temperature obtained in our study at by neglecting IR cooling is about 5000–10,000K for heating efficiencies of 10% and 60%, respectively. We find that the upper atmosphere of HD209458b experiences hydrodynamic blow-off even at such low temperatures if one does not neglect gravitational effects caused by the proximity of the planet to its Roche lobe boundary. Depending on the heating efficiency, we find from the solution of the hydrodynamic equations of mass, momentum, and energy balance that energy-limited mass loss rate estimations overestimate the realistic mass loss rate at present time for HD209458b by several times. Using the maximum heating efficiency for hydrogen–rich atmospheres of 60% we find that HD209458b may experience an atmospheric mass loss rate at present time of about . The mass loss rate evolves to higher values for higher XUV fluxes expected during the early period of the planet''s host star evolution, reaching values of several times . The integrated mass loss is found to be between 1.8% and 4.4% of the present mass of HD209458b. We found that the influence of the stellar tidal forces on atmospheric loss (the Roche lobe effect) is not significant at 0.045AU. For a similar exoplanet, but at closer orbital distances , the combined effect of the Roche lobe and the high XUV radiation result in much higher thermal loss rates of about and even more for early stages. This leads to a total loss over 4Gyr of 27.5% of the planetary mass. [Copyright &y& Elsevier]