3 research outputs found
Magnetic Nested-wind Scenarios for Bipolar Outflows: Pre-planetary and YSO nebular shaping
We present results of a series of magnetohydrodynamic (MHD) and hydro-
dynamic (HD) 2.5D simulations of the morphology of outflows driven by nested
wide-angle winds - i.e. winds which eminate from a central star as well as from
an orbiting accretion disk. While our results are broadly relevent to nested
wind systems we have tuned the parameters of the simulations to touch on issues
in both Young Stellar Objects and Planetary Nebula studies. In particular our
studies connect to open issues in the early evolution of Planetary Nebulae. We
find that nested MHD winds exhibit marked morphological differences from the
single MHD wind case along both dimensions of the flow. Nested HD winds on the
other hand give rise mainly to geometric distortions of an outflow that is
topologically similar to the flow arising from a single stellar HD wind. Our
MHD results are insensitive to changes in ambient temperature between ionized
and un-ionized circumstellar environments. The results are sensitive to the
relative mass-loss rates, and to the relative speeds of the stellar and disk
winds. We also present synthetic emission maps of both nested MHD and HD
simulations. We find that nested MHD winds show knots of emission appearing
on-axis that do not appear in the HD case.Comment: 28 pages, 8 figure
A search for type Ia supernova progenitors: The central stars of the planetary nebulae NGC 2392 and NGC 6026
We use photoionization modeling to assess the binary nature of the central stars of NGC 2392 and NGC 6026. If they are close binaries, they are potential Type Ia supernovae (SNe Ia) progenitors if the total mass exceeds the Chandrasekhar limit. We show that the nucleus of NGC 2392 likely has a hot, massive (≃1 M⊙) white dwarf companion, and a total mass of ~1.6 M⊙, making it an especially interesting system. The binary mass in NGC 6026 is less, ~1.1 M⊙. Even though its orbital period is short, it is not considered to be an SNe Ia progenitor. Copyright © International Astronomical Union 2013.link_to_subscribed_fulltex