Irritation: opaque press releases

By sb admin on May 8, 2007.

I'd love to write something about the biggest-ass supernova ever observed, confirmed to be "something new" based on Chandra observations. There is a press release about it here.

Alas, my web-fu has not been good enough yet to turn up an actual preprint or scientific article. The press release says that the paper will appear in the Astrophysical Journal (ApJ, pronounced "ap jay", to those of us in the biz). That generally means the paper is accepted. Alas, I could not find the preprint on the arxiv.org preprint server. I hope that it's just a timing issue, and that the preprint will show up in a day or two. Or, if anybody knows where I can get my hands on a preprint, please point me (and the world) to it.

The press release sounds pretty cool, but one of my pet peeves is when there are press releases (which, I know from personal experience, get filtered through PR people and as such are at least as much marketing as they are the presentation of scientific results) without the corresponding meaty journal article.

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I was trying to look up the pair-instability

The basic idea is pretty simple: Suppose the photons are just below the pair production threshold (511 keV). These are really bloody hot, and produce a lot of pressure. Now, suppose they hit 511 keV and pair produce. Instead of these really hot photons, you have just a cold electron and positron (all the photon energy goes into rest mass). The cold matter supplies almost no restoring force. Once you're at the point that photons can pair produce, the equation of state can become very very soft. The star thus tends to become unstable and blow apart pretty quickly at this point.

A fantastic review of stellar collapse is by Heger et al,

http://www.arxiv.org/abs/astro-ph/0212469

There's some discussion of the pair production instability in there, along with references. In searching for this paper, I found a couple of other papers by Woosley and collaborators that also might be edifying --- definitely recommend looking through his stuff.

I was trying to look up the pair-instability, but couldn't find anything available to non-members. I know it has to do with electron-positron pairs created from gamma-ray photons, but beyond that I could find nothing. I can think of two possible mechanisms:
pair production and consumption leaks energy from the star via neutrinos, are any created?
I would expect the electrons/positrons to reach equilibrium with the gas, so all we really have is a change in the heat capacity of a radiation pressure gas, as temperatures become high enough to allow a significant concentration of the electrons/positrons.
I bet you know -or can quickly find out -hopefully explaining how that can destabilize the star.

Mike -- that's on the same SN, but is the optical discovery (not the Chandra data that goes along with the press release).

And, yeah, I should probably write about that, since it's pretty cool already :)

-Rob

Funny, I was just having this very conversation with a colleague. I remember 2006gy as being something of an issue last year, but this PR caught me off guard. I'm getting email, but without a journal paper to read, what can I say? I dislike doing science by press release!

Here you go: http://arxiv.org/abs/astro-ph/0612617

I only happened to have it because I'm in the UT Astronomy Dept and we're currently bragging on Robert for the initial discovery. :) I had a group of school kids in today and they were all curious about it, even though they were only 3rd graders!

I should have added that it looks like the paper that I linked to is an updated version of the original paper and now includes the Chandra observations.

This was the comment with the abstract:
Comments: 13 pages, 5 color figs. submitted to ApJ. greatly expanded from previous version, but with original conclusions unchanged

Lara -- ah, thanks! I didn't realize that the paper was updated.

One of these years, PR flaks are going to figure out that including an astro-ph number with press releases is good PR for us nerd bloggers who might spread the word....

Lara -- are you a prof at UT? Grad student? Something else?

-Rob

I'm a 'something else'. :)

I got my Bachelor's in Astronomy at UT in 94 and I was accepted to a grad school who only had money for one new student but accepted 8 or so of us and basically told us we could come but we'd have to cover all our own costs. I had a chance to continue to work here at UT, so I just stayed. I mainly do outreach and instructional technology stuff now, but I get to keep up with things and I get to play with a 16-inch telescope and a heliostat!

Did you notice how many news sources reused the "Artist's Impression" without labeling it as such?

The mainstream press did a poor job with this story because they could not locate any dazed victims into whose faces could be shoved a microphone and the question: "how do you FEEL about the total destruction of your solar system?"