Comments on: Tycho's Supernova Went Boom After Slurping Up Some of Its Neighbor http://blogs.discovermagazine.com/80beats/2011/04/28/tychos-supernova-went-boom-after-slurping-up-some-of-its-neighbor/ Mon, 22 Apr 2013 21:34:00 +0000 hourly 1 http://wordpress.org/?v=3.4.2 By: amphiox http://blogs.discovermagazine.com/80beats/2011/04/28/tychos-supernova-went-boom-after-slurping-up-some-of-its-neighbor/#comment-26878 amphiox Fri, 29 Apr 2011 21:51:44 +0000 http://blogs.discovermagazine.com/80beats/?p=28562#comment-26878 With respect to the White Dwarf collision hypothesis, it was my understanding that Type Ia supernovae make good standard candles (ie are always the same brightness) because they are all the same "sized" explosion. All white dwarfs start out below the Chandresekar limit of 1.4 solar masses (because if they were bigger, they would have exploded as Type II supernovae instead of becoming white dwarfs in the first place). The Type Ia supernovae goes up if a white dwarf gains mass, causing it to exceeds the Chandresekar limit, or so I have always thought. In the gradual acretion from a close companion star model, the white dwarf will be gaining mass gradually, so it will always go supernova immediately upon exceeding the Chandresekar limit, and hence all of them will be explosions of 1.4 Solar Mass objects, thus all of them will have much the same luminosity. But in the white dwarf collision model, we shouldn't expect this sort of gradual mass gain, would we? So two 1.0 solar mass white dwarfs colliding should end up a Type Ia supernova of a 2.0 solar mass merged object, for example. And this should break the "standard candle" feature these supernova, which should mean that white dwarf collision Type Ia supernovae should not necessarily adhere to the same similar luminosity of companion star-acretion Type Ia supernovae (we should expect some of them to be brighter). The fact that we have not observed many (any?) anomalously bright Type Ia supernovae would suggest that the white dwarf collision scenario at best can only account for a small minority of the observed Type Ia supernovae (unless we've been erroneously assuming standard luminosity and miscalculating the distance to some of them). With respect to the White Dwarf collision hypothesis, it was my understanding that Type Ia supernovae make good standard candles (ie are always the same brightness) because they are all the same “sized” explosion. All white dwarfs start out below the Chandresekar limit of 1.4 solar masses (because if they were bigger, they would have exploded as Type II supernovae instead of becoming white dwarfs in the first place). The Type Ia supernovae goes up if a white dwarf gains mass, causing it to exceeds the Chandresekar limit, or so I have always thought.

In the gradual acretion from a close companion star model, the white dwarf will be gaining mass gradually, so it will always go supernova immediately upon exceeding the Chandresekar limit, and hence all of them will be explosions of 1.4 Solar Mass objects, thus all of them will have much the same luminosity.

But in the white dwarf collision model, we shouldn’t expect this sort of gradual mass gain, would we? So two 1.0 solar mass white dwarfs colliding should end up a Type Ia supernova of a 2.0 solar mass merged object, for example. And this should break the “standard candle” feature these supernova, which should mean that white dwarf collision Type Ia supernovae should not necessarily adhere to the same similar luminosity of companion star-acretion Type Ia supernovae (we should expect some of them to be brighter).

The fact that we have not observed many (any?) anomalously bright Type Ia supernovae would suggest that the white dwarf collision scenario at best can only account for a small minority of the observed Type Ia supernovae (unless we’ve been erroneously assuming standard luminosity and miscalculating the distance to some of them).

]]> By: Messier Tidy Upper http://blogs.discovermagazine.com/80beats/2011/04/28/tychos-supernova-went-boom-after-slurping-up-some-of-its-neighbor/#comment-26877 Messier Tidy Upper Fri, 29 Apr 2011 14:37:19 +0000 http://blogs.discovermagazine.com/80beats/?p=28562#comment-26877 Thanks for this - great science, great write-up & great illustration too. :-) Thanks for this – great science, great write-up & great illustration too. :-)

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