Astronomer Alicia Soderberg, a postdoctoral fellow at Princeton University and the first author of the report, was using the Burst Alert Telescope, an instrument on NASA's orbiting Swift observatory, on January 9 to study a supernova in NGC 2770 that was then two weeks in progress (but still 88 million years old, given the transit time of light). In a stroke of luck, the same galaxy suddenly flared with x-rays. "The probability of that happening is about one in 10,000," she says. "It was really exciting. We caught the whole thing on tape, basically."
They really had the luck of the Devil in catching a serendipitous supernova explosion as it happened... and in X-ray emission too. Hubble can't do that! ;) . Scientific American and Nature (*) have more information.
The image is a 3-color composite image of NGC 2770 [NASA Extragalactic Database] using 2MASS data. If you like google sky then NGC 2770 is here.
Why two supernovae so close together in time in the same galaxy? Most probably its just a statistical fluke. Prominent star-forming spiral arms are evident in the image of the galaxy, but the IRAS 60 and 100 micron flux ratio of this galaxy (~0.3) are firmly in the range of a "normal" spiral galaxy, so its not a starburst.
(*) Reading the on-line comments to the Nature article makes it clear that some people think that the World Wide Telescope (which I commented on here) is actually hooked-up, live, to real telescopes. Sadly not, but it highlights that World Wide Telescope was not a very well chosen name, perhaps even downright misleading.