Hunting For Gamma Ray Bursts

The scoop: Mike Simonsen, Development Director of the American Association of Variable Star Observers (AAVSO) and variable star blogger on Simostronomy, shares his passion of variable stars with Discovery Space.

Variable star amateur astronomers are now getting some help from space-based observatories to look out for the most energetic events in the cosmos: gamma-ray bursts. Variable stars don't get more variable than GRBs!

I am an active observer, and I like to observe things that change over time, either hour-to-hour or night-to-night.

There just isn't anything that can compare to watching the Moon slide in front of a bright star, or a feature on the surface of Mars rotate out of view, or tracking the shadow of a Jovian moon as it transits the face of Jupiter, or even a meteor shooting across the sky during one of those rare moments my eye isn't glued to the eyepiece of a telescope.

So I was naturally drawn to variable stars, and cataclysmic variables (CVs) quickly became my favorite variables to follow.

Stellar Outbursts

Their sudden and unpredictable outbursts (brightening by several magnitudes) made them fun to monitor, and there were many professional astronomers trying to figure out what was going on with this strange population of close binaries. The late nineties were heady times to be involved in CV research and monitoring.

The characteristics and behaviors of many of these stars were not well known at all, and some of them were known to be very inactive, sometimes taking decades between outbursts. Professional astronomers relied almost entirely on amateur astronomers to tell them when something interesting or rare was happening.

Typically, a report of an event would go out over the internet from one observer, another observer somewhere else on the globe would confirm it, and then professional astronomers would use discretionary time on big ground-based telescopes, or space telescopes like Hubble, and wheel around to point at whatever it was the observers had reported was going on.

Detecting a rare outburst after waiting and monitoring a star for a long time was a real feather in your cap, and there was some pretty interesting competition at times!

The Turn of the GRB

At the turn of the century, gamma-ray bursts (GRBs) had begun to take hold of the imagination of astronomers. They were an entirely new animal in the celestial zoo, and we knew next to nothing about them.

Chasing after the optical afterglow of these events became new challenge. GRBs don't last very long, and they become very faint very quickly, so it is imperative the observers know as soon as possible after an event is detected.

The American Association of Variable Star Observers (AAVSO) International High Energy Network is dedicated to the optical monitoring of high-energy astrophysical phenomena in the universe.

AAVSO International Gamma-Ray Burst Network

It is an expansion of the AAVSO International Gamma-Ray Burst Network, started in 2000, which has had great success in discovering and observing the optical afterglows of GRBs. Observers around the world are able to respond in seconds or minutes to burst alerts sent by satellite, and are able to catch these rapidly evolving phenomena as quickly as professionals, if not more so.

The AAVSO currently redistributes notices from the Swift, INTEGRAL, AGILE and Fermi Gamma-Ray Space Telescopes to over 250 observers worldwide. Many of these observers are the ones who used to report activity that re-pointed satellites before. Now, in less than ten years, we've come full circle, and the satellites are telling us where to point!

It's all still a matter of luck and persistence, but the competition to record the next optical afterglow of a GRB is just as lively and exciting as detecting CV outbursts was in the nineties.

The views expressed are the author's alone and do not represent the official position of the Discovery Channel.