We conduct numerical simulations of axisymmetrical jets expanding into a spherical asymptotic giant branch (AGB) slow wind. The three-dimensional flo

We calculate the X-ray luminosity and light curve for the stellar binary system Eta Carinae for the entire orbital period of 5.54 years. By using a new approach we find, as suggested before, that the collision of the winds blown by the two stars can explain the X-ray emission and temporal behavior. Most X-ray emission in the $2-10 kev$ band results from the shocked secondary stellar wind. The observed rise in X-ray luminosity just before minimum is due to increase in density and subsequent decrease in radiative cooling time of the shocked fast secondary wind. Absorption, particularly of the soft X-rays from the primary wind, increases as the system approaches periastron and the shocks are produced deep inside the primary wind. However, absorption can not account for the drastic X-ray minimum. The 70 day minimum is assumed to result from the collapse of the collision region of the two winds onto the secondary star. This process is assumed to shut down the secondary wind, hence the main X-ray source. We show that this assumption provides a phenomenological description of the X-ray behavior around the minimum.Comment: The Astrophysical Journal, in pres

We conduct 3D hydrodynamical simulations of two opposite jets that interact with a spherical slow wind that includes a denser shell embedded within it, and obtain a bipolar nebula where each of the two lobes is composed of two connected bubbles and Rayleigh–Taylor instability tongues that protrude from the outer bubble and form the ‘columns crown’. The jets are launched for a short time of 17 yr and inflate a bipolar nebula inside a slow wind. When the bipolar structure encounters the dense shell, the interaction causes each of the two lobes to split to two connected bubbles. The interaction is prone to Rayleigh–Taylor instabilities that form tongues that protrude as columns from the outer bubble. The bases of the columns form a ring on the surface of the outer bubble, and the structure resemble a crown that we term the columns crown. This structure resembles, but is not identical to, the many filaments that protrude from the lobes of the bipolar planetary nebula Menzel 3. We discuss our results in comparison to the structure of Menzel 3 and the ways by which the discrepancies can be reconciled, and possibly turn our failure to reproduce the exact structure of Menzel 3 to a success with jets–shell interaction simulations that include more ingredients.

We simulate the formation of bipolar planetary nebulae (PNe) through very short impulsive mass ejection events from binary systems, where the asymptotic giant branch star ejects a mass shell that is accelerated by jets launched from a compact companion. The acceleration process takes place at very short distances from the binary system, such that the photon-diffusion time is long enough to prevent rapid cooling of the shocked jets’ material. When the shocked jets’ gas density is lower than the shell density, the flow becomes Rayleigh–Taylor unstable and dense clumps are formed in the flow. At later times, a PN with clumpy lobes that have a linear distance–velocity relation will be observed. This process might account for the formation of bipolar PNe with clumpy lobes, such as NGC 6302. The energy radiated during the months-to-years duration of such an event will appear as an intermediate-luminosity optical transient.