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Studying the
Explosions of Stars

  Iair Arcavi  

What do we know?
Massive stars end their lives as core collapse supernovae. These are explosions which release a large amount of energy and are so bright they can briefly outshine an entire galaxy. They are responsible for releasing and creating most of the elements critical for life. We see many different types of core collapse explosions, which makes sense, since there are different kinds of massive stars.
What don't we know?
We still can't explain how each type of star will explode. This is because we donít quite understand the physics of what goes on when a massive star evolves and finally explodes as a supernova. In a few cases, astronomers were able to identify a star before it exploded and then see the type of explosion that came out of it. But this can only be done for the nearest supernovae, and is therefore very rare.

What am I working on?
I am collecting observations of many core collapse supernovae, mainly from the Palomar Transient Factory survey. Analyzing these observations, I am trying to understand the underlying classes of events and to relate these classes (and the enviornments in which they happen) to the properties of their progenitor systems. I am also looking at the information that can be deduced about the exploding star by catching the supernova during its first hours.

What have we found?
When looking at the hydrogen-rich ("Type II") supernovae from the Caltech Core Collapse Program, we found a subdivision into three very distinct sub-types in the R-band light curves: constant luminosity Type IIP's, slowsly declining Type IIL's and rapidly declining Type IIb's.

This suggests that these three types of explosions come from distinct progenitor systems.
More: ApJ - Arcavi et al. 2012.

With the Palomar Transient Factory, we are able to conduct statstical studies on the properties of the galaxies hosting the different types of core collapse supernovae. We find that small, faint galaxies host more of certain types of explosions compared to large bright galaxies. This is an important clue into the role played by metallicity in the evolution of massive stars.
More: ApJ - Arcavi et al. 2010, IAUS - Arcavi 2012.

In 2011 we discovered a supernova in M51 (the "Whirpool Galaxy") only hours after it exploded. Using valuble early time data, we are able to test models of different exploding stars to determine what the star that exploded looked like.

We are now finding more and more supernovae right after they go off, allowing us to test these models more robustly and to see the early explosion properties as never before.
More: ApJ - Arcavi et al. 2011, Galileo (in Hebrew).

Who am I?
My name is Iair (ya-eer) Arcavi. I'm a graduate student at the Weizmann Institute of Science, working under the supervision of Avishay Gal-Yam. iair.arcavi [at]
Dept. of Particle Physics and Astrophysics
Weizmann Instiute of Science
Rehovot, 76100