AAS 201st Meeting, January, 2003
Session 49. Eta Carinae, LBVs, and Circumstellar Disks
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[49.06] Quadrupolar Outflow: A Single-Wind Model for the \eta Carinae Nebula

S. Matt (Physics & Astronomy Dept.; McMaster University), B. Balick (Astronomy Dept.; University of Washington)

During an outburst beginning in 1837, the luminous blue variable \eta Carinae ejected at least one solar mass of material. That ejected material has been well studied and is highly structured, consisting of an outflowing equatorial ``skirt'' and bipolar lobes (the hourglass-shaped ``homunculus''). Recent proper motion measurements of Morse et al.\ (2001, ApJ, 548, 207L) suggest that at least some of the material in the skirt has the same dynamical age as the lobes, contrary to the assumptions of interacting winds models for the \eta Car nebula.

In the context of the \eta Car eruption, and relying on time-dependent, numerical, magnetohydrodynamic simulations, we present a simple stellar wind model that produces an outflowing disk and bipolar lobes in a single wind. The shape of the wind bears a remarkable resemblance to the overall shape of the \eta Car nebulae. The basic model consists of a pressure-driven wind from a rotating star with an axis-aligned dipole magnetic field. In the wind, the azimuthal component of the magnetic field (generated by the rotation of the dipolar field) compresses the wind toward the equator and also toward the rotation axis, simultaneously producing an outflowing disk and jet. In order to produce wide angle lobes similar to the homunculus (which have roughly a 30\circ opening angle), a high-speed polar wind from the star is required. We will present both steady-state and time-dependent wind models.

This research was supported by NASA grant GO 9050 awarded from STScI, by NSF grant AST-9729096, and by NSERC, McMaster University, and CITA through a CITA National Fellowship.

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