The study of the cosmos is not a journey that should be traveled alone. The Fermi symposium last week offered plenty of reminders that other telescopes are working with Fermi to study new objects of interest, in as many wavelengths as possible.
After only a few months of data collection, Fermi created a list of bright gamma ray sources it saw in the sky, some of which had not been identified by any other telescope. Other observatories immediately turned their eyes to those objects. In some cases, the objects emitted distinct signals in wavelengths other than gamma rays, such as with some radio pulsars or TeV blazars. This correlating of signals is necessary to officially identify an object, and some point-sources spotted by Fermi have not yet been correlated.
One major contributor to the Fermi/LAT multiwavelength approach is the Swift Gamma Ray Burst Mission, a NASA orbital observatory that includes instruments to collect light in the gamma-ray, X-ray, optical, and ultraviolet wavebands. Before the Fermi telescope had launched, Swift planned a campaign to do targeted monitoring of the brightest gamma ray sources that Fermi identified. Swift has already collected data on all of Fermi’s 23 brightest sources, as well as 25 additional sources.
Now, Swift has made that data available to anyone who wants it. Abe Falcone of the University of Pennsylvania, and a Swift collaboration member, announced in his talk at the meeting that all of Swift’s monitoring data on the Fermi objects are now freely available online. “It’s there for you to just grab and go have fun with,” he said. As nearly all of the top 23 brightest sources observed by Fermi are blazars, Swift is also working closely with the VERITAS collaboration (Very Energetic Radiation Imaging Telescope Array System) to also study the objects in even more energetic wavelengths than Fermi (see our previous post).
Swift’s prime advantage for astronomers is its ability to monitor point-sources of interest over longer periods of time than Fermi. Swift can also monitor those bright sources simultaneously with Fermi, which Falcone explains can be crucial to understanding rapidly changing blazars, which can change their flaring behavior over the course of just minutes.
“With a time variability that short, if you try to look at the same blazar with another telescope that is a month behind Fermi, then you might be sampling a different population of particles all together,” said Falcone, after his talk. He emphasized that by monitoring objects and gamma ray flares in different wavelengths simultaneously, scientists can hope to truly begin to describe and categorize objects like blazars. Up until now, the extreme variability of these objects, and their unpredictable flaring cycle, made it very difficult to draw conclusions about their behavior and make up. Some blazars stay quiet for decades, then suddenly burst into brilliant action for just a few days; while others may burst very frequently every year. “We don’t know why one is one way and one is another,” said Falcone. “Blazars might tell us where cosmic rays from; we could finally understand that age old problem.”
Still some astronomers want even more eyes pointed at the sky. David Paneque of the Kavli Institute for Particle Astrophysics and Cosmology at SLAC National Accelerator Laboratory and Stanford University just wrapped up two observation campaigns for which he recruited twenty different observatories. Paneque selected two blazars to observe, and coordinated the effort so that every two days the telescope observed one blazar for a few hours, and every five days observed the other. Paneque said it was crucial to have all the observatories watching the objects simultaneously, so that the same events could be seen in various wavelengths.
“For me, there is only multiwavelength observation,” said Paneque. “With multiwavelength you can do so much more, and get such a better understanding of what you are looking at.” The campaign lasted four and a half months and included observatories stretching from weak radio waves to the most powerful gamma rays in the TeV range. Paneque had to write computer algorithms to make the data from all the different observatories directly comparable. He presented his work in a poster, but has not yet prepared it for publication.
Paneque isn’t the only one who feels so strongly about multiwavelength surveys. Kent S. Wood of the Naval Research Laboratory stated in his talk that “the age of ASM [all-sky-monitoring] has arrived.” Wood strongly promoted the need not only for targeted multiwavelength astronomical studies, but to do simultaneous all-sky surveys.
Wood dedicated most of his talk to promoting such a complimentary agreement between Fermi and the optical telescope Pan STARRS, which stands for the Panoramic Survey Telescope & Rapid Response System. Located at the University of Hawaii, Pan STARRS will include four optical telescopes on two Hawaiian islands, and is set to be completed in 2012. The first of the four, a prototype telescope, has already been built and began taking images in December 2008. Pan STARRS will be able to survey about three quarters of the night sky, with the dual objective of producing new astronomical data for general study, as well as looking for objects like asteroids that might collide with Earth.
According to Wood, Fermi and Pan STARRS have already created a memorandum to work collaboratively, although he pushed to have more time dedicated to combining the two efforts and having both observatories create simultaneous all sky maps in the visual and gamma ray wavelengths. He also said that scientists at NASA Ames are working on software to bridge the data from the two observatories and make it comparable. Ideally this kind of software would enable Fermi to compare data with any other all-sky observatory.
Many telescopes, observatories, and institutions are working with the Fermi collaboration or utilizing Fermi data, and are making tremendous contributions to turning the Fermi data into knowledge and understanding. Many of those groups were represented at the meeting by talks and by attending representatives.
