5 Written Questions

1. system consisting of a white dwarf receiving mass via an accretion disk from a
   companion, frequently a small mass main sequence star.
2. must generate explosion in old (1 to 10 billion years) stellar system. Most plausible mechanism mass
   transfer onto white dwarf.
3. difficult. Nova explosions will reduce the mass of
   the white dwarf, not grow it. There may be too few white dwarf pairs, too few recurrent novae.
4. one possibility is that a massive white dwarf may reach mass limit of 1.4 M and explode.
5. Mass transfer begins when the originally more massive star becomes a red giant with
   a tiny core. Transfer stops only when whole envelope has been stripped from the core and passed to the
   companion or lost from the system

5 Matching Questions

1. U Sco
2. Massive star binaries
3. What must happen for a star to burn a thermonuclear fuel?
4. Forming a neutron star by core collapse produces what?
5. Jet-induced explosions

1. a An example of a recurrent nova in the constellation of Scorpius. The white dwarf has been measured to
   have a mass greater than 1.3 M and is thought to be headed to a thermonuclear supernova explosion.
2. b Supercomputer computations show that sufficiently powerful jets can blow up a star.
   The jets plow up and down along one axis creating a "breadstick" shape and driving bow shocks. The bow
   shocks propagate away from the jets toward the equator where they collide. The result of this collision is to blow
   much of the star out along the equator in a torus or "bagel" shape. The final configuration is far from spherical,
   but has jets in one direction and a torus expanding at right angles to the jet.
3. c about 100 times more energy than needed to create an
   explosion, but most of that energy is carried off by neutrinos.
4. d Explosions of massive stars in close binary systems are expected to occur in a bare thermal
   pressure-supported core from which the outer layers of hydrogen have been transferred to the companion
   star. The core, supported by the thermal pressure, will continue to evolve to iron, even in the absence of
   the hydrogen envelope. This is probably the origin of Types Ib and Ic.
5. e the star must get hotter to overcome the charge repulsion. This happens automatically in massive stars supported by the thermal pressure that regulates their burning. These stars
   produce shells of ever-heavier elements and finally a core of iron.

5 Multiple Choice Questions

1. Delayed mechanism: Neutrinos stirred out by the boiling neutron star deposit heat behind the standing
   shock and reinvigorate it. Not clear this is sufficient
   1. 3rd way a core collapse of the outer layers of a star may occur
   2. 1st way a core collapse of the outer layers of a star may occur
   3. 2nd way a core collapse of the outer layers of a star may occur
   4. What halts the collapse and allows the neutron star to form?
2. a strong pressure wave that forms due to neutron-star bounce, but which stalls a certain
   distance from the neutron star as outer material rains down on it.
   1. Standing Shock
   2. Neutron Star
   3. Accretion disk
   4. U Sco
3. intermediate elements (O, Mg, Si, S, Ca) on outside and iron-like material on inside.
   Consistent with models of Chandrasekhar mass carbon-oxygen white dwarfs that begin with a subsonic
   deflagration and then ignite a supersonic detonation
   1. Neutron Star
   2. Light curves of Type Ib and Ic
   3. Type Ib Supernovae
   4. Spectra of Type Ia reveal?
4. in addition to producing the jet/torus shape, the jet model predicts that iron is blown along the jet and other elements in the outer layers, He, is ejected in the equatorial torus. This may provide an observational test of the model
   1. Jet-induced explosions
   2. Jet-induced asymmetry
   3. Jet mechanism
   4. Neutron Star
5. matter streaming through inner Lagrangian point does not directly strike the tiny, orbiting,
   white dwarf, but circles around and forms a flat spiraling disk. The disk has its own life in the system.
   1. Neutron Star
   2. Friction
   3. Roche Lobes
   4. Accretion disk

5 True/False Questions

1. 1st way a core collapse of the outer layers of a star may occur → Prompt mechanism: The neutron star rebounds, driving a shock wave into the outer parts of the star.
   The bounce shock occurs, but is insufficient to cause an explosion

   True        False

2. All core-collapse supernovae measured to date, Type Ib, Ic, and II are not what? → spherical. They may be "breadstick"
   shaped or "bagel" shaped or some combination of elongation and flattening.

   True        False

3. Type Ib Supernovae → no hydrogen, but observe helium early on, O, Mg, Ca later. Occur in spiral arms, never in
   elliptical galaxies. Massive star core collapse.

   True        False

4. 3rd way a core collapse of the outer layers of a star may occur → Jet mechanism: the collapsing rotating neutron star squeezes the magnetic field and sends a jet up the
   rotation axis. Naturally makes asymmetric explosion, but not yet clear sufficiently strong jets are
   produced

   True        False

5. Disk radiation → the outer parts of disks typically have temperatures comparable to the Sun and shine with
   optical light. Middle parts are hotter and glow in ultraviolet light. This is appropriate for white dwarfs. The
   innermost parts can be hot enough to emit X-rays. This is appropriate to neutron stars and black holes.

   True        False