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Last night I received six or seven text messages from the eSTAR network telling me that it was responding to GRBs and checking if they could be observed on UKIRT. This all probably sounds like gobbledygook, so let me explain.

Gamma-ray bursts are massively bright flashes of gamma rays coming from outer space. They were originally discovered by American nuclear test detection satellites, but instead of finding nuclear tests, they serendipitously discovered bright flashes of gamma rays coming from random directions in deep space. These days, a network of spacecraft in orbit around the Earth watches for GRBs.

So what is a GRB anyhow? They’re bright and short flashes of gamma-rays, which are high-energy photons. These things are so bright — hundreds of times brighter than a typical supernova — that astronomers had a hard time figuring out what they could be caused by. Their duration is also amazingly short — anywhere from a few milliseconds to a few minutes — that getting any good data on them is difficult. It’s now understood that there are two types of GRBs: “short” and “long”. Short GRBs last less than two seconds, and long ones last longer than that.

Short GRBs are thought to be caused by an extreme event: the collision of two neutron stars, or a neutron star with a black hole. Because GRBs are so bright, and short ones spew out massive amounts of energy in typically a fraction of a second, extreme theories are needed to explain them. Imagine it: two stars weighing more than the Sun but only 15 kilometers across orbiting each other. As they do so, they give off gravitational radiation and slowly spiral closer and closer. Eventually they collide, and the extreme physics almost demands an extreme response: an explosion lasting a fraction of a second but outshining galaxies.

Long GRBs are a little more sedate. They’re probably caused by a hypernova, which is like a supernova but even more violent. Hypernovas are caused by the core collapse of extremely massive stars, stars with more mass than 100 Suns. What happens is when they run out of fuel to burn, their interior collapses in on itself, because there isn’t enough pressure from nuclear fusion to counteract gravity. When the core collapses it forms a black hole, and spews out massive amounts of plasma through two jets at nearly the speed of light. These jets emit gamma rays, and if the jets are pointing at us, we see a GRB.

Now, here’s the problem: these things don’t last very long. Short GRBs last at most a couple of seconds, and long ones last maybe a few minutes. However, this duration only applies to the actual burst of gamma radiation — long GRBs show an “afterglow” in longer wavelengths (and thus lower energy photons). If you can respond to a long GRB quick enough, you can look at it in different wavelengths and get more data on it. You can even get its spectrum, and by looking at various components of that, you can figure out how far away these things are.

That’s what the eSTAR Network is for. Here’s what happens:

1. various satellites in orbit around the Earth detect a GRB
2. the position is triangulated and sent out over the Gamma ray bursts Coordinates Network
3. eSTAR software receives a position and tries to figure out if this alert is “interesting”
4. if the burst is “interesting”, eSTAR sends out requests to various ground-based telescopes (including UKIRT) to find out if the telescope can observe the sky at the GRB position (at this point I get a text message)
5. the telescope says “yes” or “no”
6. if the telescope says “yes”, then eSTAR software asks the telescope to actually observe the position (I get another text message here)
7. the position is observed, and Science Happens

This happened last night! At 12:25:56 UT, Swift detected a burst. At 12:28:29 UT, the eSTAR software submitted an observation to UKIRT, and at 12:28:36 UT the observer at the telescope was alerted. Less than three minutes after a burst went off, UKIRT could have observed it!

I say “could have” because it didn’t: the weather was crap last night. That’s the way it goes sometimes.

But just think about how cool this is: satellites see something go “KA-BLAMMO”, they send out a message, software finds it and decides whether or not to deal with it, that software then asks telescopes around the world to observe it, and they do!