The X‐ray binary system GX 301−2 consists of a neutron star in an eccentric orbit accreting from the massive early‐type star Wray 977. It has previously been shown that the X‐ray orbital light curve is consistent with the existence of a gas stream flowing out from Wray 977 in addition to its strong stellar wind. Here, X‐ray monitoring observations by the Rossi X‐ray Timing Explorer (RXTE)/All‐Sky Monitor and pointed observations by the RXTE/Proportional Counter Array over the past decade are analysed. We analyse both the flux and column density dependence on orbital phase. The wind and stream dynamics are calculated for various system inclinations, companion rotation rates and wind velocities, as well as parametrized by the stream width and density. These calculations are used as inputs to determine both the expected accretion luminosity and the column density along the line‐of‐sight to the neutron star. The model luminosity and column density are compared to observed flux and column density versus orbital phase, to constrain the properties of the stellar wind and the gas stream. We find that the change between bright and medium intensity levels is primarily due to decreased mass loss in the stellar wind, but the change between medium and dim intensity levels is primarily due to decreased stream density. The mass‐loss rate in the stream exceeds that in the stellar wind by a factor of ∼2.5. The quality of the model fits is better for lower inclinations, favouring a higher mass for Wray 977 in its allowed range of 40–60 M⊙.

Aims. We present r-Java 2.0, a nucleosynthesis code for open use that performs r-process calculations, along with a suite of other analysis tools. Methods. Equipped with a straightforward graphical user interface, r-Java 2.0 is capable of simulating nuclear statistical equilibrium (NSE), calculating r-process abundances for a wide range of input parameters and astrophysical environments, computing the mass fragmentation from neutron-induced fission and studying individual nucleosynthesis processes. Results. In this paper we discuss enhancements to this version of r-Java, especially the ability to solve the full reaction network. The sophisticated fission methodology incorporated in r-Java 2.0 that includes three fission channels (beta-delayed, neutron-induced, and spontaneous fission), along with computation of the mass fragmentation, is compared to the upper limit on mass fission approximation. The effects of including beta-delayed neutron emission on r-process yield is studied. The role of Coulomb interactions in NSE abundances is shown to be significant, supporting previous findings. A comparative analysis was undertaken during the development of r-Java 2.0 whereby we reproduced the results found in the literature from three other r-process codes. This code is capable of simulating the physical environment of the high-entropy wind around a proto-neutron star, the ejecta from a neutron star merger, or the relativistic ejecta from a quark nova. Likewise the users of r-Java 2.0 are given the freedom to define a custom environment. This software provides a platform for comparing proposed r-process sites.

The extremely luminous supernova 2006gy (SN 2006gy) is among the most energetic ever observed. The peak brightness was 100 times that of a typical supernova and it spent an unheard of 250 days at magnitude -19 or brighter. Efforts to describe SN 2006gy have pushed the boundaries of current supernova theory. In this work we aspire to simultaneously reproduce the photometric and spectroscopic observations of SN 2006gy using a quark nova model. This analysis considers the supernova explosion of a massive star followed days later by the quark nova detonation of a neutron star. We lay out a detailed model of the interaction between the supernova envelope and the quark nova ejecta paying special attention to a mixing region which forms at the inner edge of the supernova envelope. This model is then fit to photometric and spectroscopic observations of SN 2006gy. This QN model naturally describes several features of SN 2006gy including the late stage light curve plateau, the broad H{\alpha} line and the peculiar blue H{\alpha} absorption. We find that a progenitor mass between 20Msun and 40Msun provides ample energy to power SN 2006gy in the context of a QN.Comment: 15 pages, 9 figure

We present r-Java, an r-process code for open use that performs r-process nucleosynthesis calculations. Equipped with a simple graphical user interface, r-Java is capable of carrying out nuclear statistical equilibrium (NSE), as well as static and dynamic r-process calculations, for a wide range of input parameters. In this introductory paper, we present the motivation and details behind r-Java and results from our static and dynamic simulations. Static simulations are explored for a range of neutron irradiation and temperatures. Dynamic simulations are studied with a parameterized expansion formula. Our code generates the resulting abundance pattern based on a general entropy expression that can be applied to both degenerate and non-degenerate matter, allowing us to track the rapid density and temperature evolution of the ejecta during the initial stages of ejecta expansion. At present, our calculations are limited to the waiting-point approximation. We encourage the nuclear astrophysics community to provide feedback on the code and related documentation, which is available for download from the website of the Quark-Nova Project: http://quarknova.ucalgary.ca/.

The X‐ray binary system 4U 1907+09 contains an accretion‐powered X‐ray pulsar in an eccentric orbit around a massive early‐type companion star. It has been previously suggested that a trailing gas stream along with strong stellar winds could describe the orbital variations in X‐ray flux. In this work, 12 yr of X‐ray observations from the Rossi X‐ray Timing Explorer/All‐Sky Monitor are analysed. We study both the X‐ray flux and column density dependence on the orbital phase. The dynamics of the wind and stream are calculated for various companion star radii, system inclinations and eccentricities; the wind and stream model is parametrized by companion star rotation, stellar wind velocity, stream width and density. These parameters are taken as inputs to compute the expected accretion luminosity which is then compared to the observed flux versus the orbital phase. The column density along the line of sight to the neutron star is calculated using the best‐fitting results from the flux analysis and verifies the high extinction in the direction of 4U 1907+09. We find that the stream component of accretion contributes significantly to describing the orbital variations in X‐ray flux observed in 4U 1907+09. The best‐fitting free parameters of our wind and stream model such as mass‐loss rate, terminal wind velocity, companion star rotation speed and interstellar extinction are found to be consistent with literature values for 4U 1907+09. The best fit to the data was found at higher values of eccentricity (e= 0.31) and lower companion star radii (Rc= 16–21 R⊙).