Supernova start

[Tom Mazanec]

What is the light curve like in the first few minutes of a supernova? I imagine Ia curves rise faster than II curves, but that is just my guess. How long does it take for the supernova types to rise one magnitude (151%)?

[antoniseb]

I think you'll have to be a little more specific:
- Do you mean brightness in optical wavelengths?
- What do you take to be the starting point for each type?

[korjik]

Has one actually been caught on film that early? From what I understood, most are found when near their brightness peak and that the early evolution was still not well seen.

[ngc3314]

A few have been caught very early - SN 1987A, for example, had photographic records right across the explosion time, IIRC, and there was that distant one with the X-ray flash caught by Swift.

For core-collapse SN, unless they have relativistic jets, the shock wave will usually take hours to reach the photosphere after core collape (which can be timed from the neutrino flash when close enough, as in 1987A), so we see nothing from the star until that happens. So a white-dwarf SN will show a much more prompt response to onset of the explosion - at whatever depth detonation begins, the wave has less far to go and is traveling through a denser medium. A couple of quick checks show that models suggest scales of a few seconds for fusion to propagate through a white dwarf. The light curve is smeared out after the explosion by the fact that we only see the outer parts of the expanding ejecta until it becomes nearly transparent, so instead of seeing a cooling surface, for a while we're seeing deeper (and hotter) into the debris - which is why the brightness grows for so long after the detonation.

[chornedsnorkack]

A few have been caught very early - SN 1987A, for example, had photographic records right across the explosion time, IIRC, and there was that distant one with the X-ray flash caught by Swift.

What was the magnitude of the presupernova before X-ray flash?

For core-collapse SN, unless they have relativistic jets, the shock wave will usually take hours to reach the photosphere after core collape (which can be timed from the neutrino flash when close enough, as in 1987A), so we see nothing from the star until that happens.

And when that does happen, there is considerable light speed delay before the supernova edges become visible.

Did we also see the propagating shock wave of SN1987A shining through translucent, as yet undisturbed upper photosphere?

[antoniseb]

... Did we also see the propagating shock wave of SN1987A shining through translucent, as yet undisturbed upper photosphere?

It's not like the telescopes were taking pictures every few milliseconds. The "translucent" upper photosphere is not very deep in this sense.

[PetTastic]

How much does gravitational time dilation effect our view of these events?
How slow could time get for the core of a star during a core collapse?