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The SAGUARO Project and Multi-Messenger Astronomy

Since April 2019 , Michael Lundquist and David Sand of Steward Observatory along with a team of astronomers from Northwestern University have partnered with Eric Christensen (LPL) and the Catalina Sky Survey (CSS) on the Searches After Gravitational-waves using ARizona Observatories (SAGUARO) project. This project uses the Steward Observatory Mount Lemmon 60” telescope to search for optical counterparts to gravitational wave events using the CSS asteroid survey. CSS provides two years worth of historical imaging that is used with image subtraction to more easily identify new events.  Many in the Steward community are involved, with the team, in the follow-up observations of these events.

In April 2019  the Advanced LIGO and Virgo facilities turned on and began their third observing run looking for the gravitational wave signals indicative of the mergers of compact objects such as neutron stars and black holes. While no optical counterparts to the gravitational wave event were found, by anyone in the world, the SAGUARO team was able to test and improve its telescope response to the LIGO alerts. In this test, it discovered two new supernovae (unrelated to detected gravitational waves) and utilized the Large Binocular Telescope Observatory to spectroscopically classify one promising optical counterpart from another group. This object, PS19eq, was also determined to be a supernova and unfortunately not a kilonova.

To date, only one optical counterpart to a gravitational wave event, AT2017gfo, has been found. Part of the reason for this is that the gravitational wave observatories can only localize events to tens or hundreds (or even thousands) of square degrees.The image shows the gravitational wave localization of this object as well as field centers of observed images. Teams such as SAGUARO are able to image many square degrees of sky quickly, looking for things that have changed brightness, and then to use large telescopes for spectroscopic followup of the most likely transient sources.

This is a new and exciting field that will open up our understanding of heavy element production in the universe, provide independent measurements of cosmological parameters, and provide clues to the structure of neutron stars. The current LIGO and Virgo observing run continues through April 2020. SAGUARO represents the one of the most significant additions to the search for optical counterparts. The SAGUARO team is ready and able to follow up these detections searching for the elusive optical counterparts.

You can read the Saguaro paper HERE. The UA News article is HERE.

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