Caltech-led GROWTH Strikes Gold

Caltech-led GROWTH Strikes Gold

On August 17th 2017, two neutron stars smashed into each other and sent ripples of space-time detected by gravitational wave interferometers right here on Earth. For the first time in history, these gravitational waves were accompanied by electromagnetic radiation. There literally was light. This is probably the most important astrophysical transient of the century. We saw gamma rays in just two seconds, and then in a few hours we saw optical light and infrared light and ultraviolet light. We are now seeing and hearing the violent universe. We have gravitational waves providing information we’ve never known before by this kind of event. Immediately afterwards, there’s an explosion, and in that explosion most of the heavy elements of the universe are actually formed, elements like gold. What we were witnessing for the very very first time is evidence of a cosmic mine. In fact, it’s probably a little bit of each star merger in all of us. At roughly about 7:00 a.m., the cell phones rang of the GROWTH team members. GROWTH stands for the Global Relay of Observatories Watching Transients Happen. And this is a Caltech led global collaboration. This is a network not only a telescopes but of people all united in this goal of looking for electromagnetic counterparts gravitationally. They can follow the flash of light continuously as a ring of telescopes around the world can do. Within minutes of this phone call, the entire GROWTH team assembled, and each of us knew what we had to do. A postdoc Dave Cook went and took a galaxy catalog and cross-matched it with the rough location of the gravitational waves. He found only 49 galaxies. This is an amazing way to limit the amount of universe we’re trying to survey. It is a huge advantage. Immediately all of us got to work to try and point every telescope possible to this. So the first search that we began was with the x-rays with both the Swift satellite and NuSTAR satellite right at Caltech. Now the problem became the optical and the infrared searches because here we were in a little bit of a fix. The position was down in the southern hemisphere. The telescopes in the GROWTH network are up in the northern hemisphere. We couldn’t even look at this positions. So I called up my friends at Carnegie Observatories and they could have the optical part of the search covered. For the infrared, we reach out to the Gemini South Telescope, also in Chile, and within an hour of sunset the Carnegie team was the first to announce the coordinates in the third galaxy on the list, NGC 4993. They were able to find a bright optical transient. Within minutes, we were able to then confirm it in the infrared and confirm it in the ultraviolet. In the infrared we saw in the spectrum bumps and wiggles that tell us what the astrochemistry here is. These bumps and wiggles matched for theorists had predicted as evidence for heavy element signature. We had actually struck gold. So we had optical, infrared, and ultraviolet. The last wavelength that we had to cover was the radio. For radio astronomers like myself things take a bit longer. Radio comes last. We didn’t know what time the radio was going to show up. We were talking to theorists in the GROWTH network, and 16 days after the event happened , up popped this very faint radio source. The radio emission comes bearing gifts.. We learn things like: Is there a jet? How much mass there is? And the best picture that we came up with which beautifully explains all the data is what we call the cocoon model. A cocoon is a material that engulfs the jet when the jet breaks out. We show through a hydrodynamical simulation that this all does hang together. We’ve learned so much, but we don’t know how we seen some sort of weird event or is that the population. The education aspect is just as important as the research. One of our goals is to train the next generation in time-domain astronomy. There is just no better way than living a legend and seeing it unfold right in front of your eyes.

7 thoughts on “Caltech-led GROWTH Strikes Gold

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  2. "Cocoon" – I'm totally borrowing that verbiage for my Grand Fission theorem. It fits perfectly seeing as our universe is encased in various degrees of Hydrogen (crystallized, frozen, liquefied metallic, etc..) and during "fission" the rind breaks and seels within a few minutes creating the "Big Bang" effect. ;O)-

    P.s. Yes, but I thought "seel" was more fitting and ominous. We are creating new science, are we not?

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