Texas Tech physicist’s spectroscopic camera captures day-old supernova

Lubbock, TX--With the help of a spectroscopic camera developed by a Texas Tech University physicist, researchers at the California Institute of Technology (Caltech; Pasadena, CA) and Las Cumbres Observatory Global Telescope Network (Goleta, CA) captured rare images of a star 73 million light-years away in another galaxy (NGC 6805) going supernova within a day of the star’s explosion. This is the first time scientists have pinpointed a star that eventually exploded as a stripped-envelope supernova, called a type Ib, says David Sand, an assistant professor in the Department of Physics who developed the camera.

The Intermediate Palomar Transient Factory project, which is a scientific collaboration with Caltech, Los Alamos National Laboratory (Los Alamos, NM), University of Wisconsin (Madison, WI), and several others, is an automated survey of night sky dedicated to finding transient supernova events. The survey finds hundreds of new supernovae annually, and scientists here try to understand what types of stars become which types of supernova.

320 to 1000 nm coverage
Sand led the development and operations of the camera, the "Folded Low Order whYte-pupil Double-dispersed Spectrograph" (FLOYDS), which was used to help identify the specific kind of supernova. THe FLOYDS is a low-resolution robotic spectrograph that automatically acquires scientific targets and monitors them. Its single-shot wavelength coverage spans 540 to 1000 nm for the first order and 320 to 570 nm for the second order. The FLOYDS spectrographs, of which there are only two in the world, are attached to two-meter telescopes located in Hawaii and Australia.

In the last six months, Sand and others have confirmed 25 different supernovae with the new camera. This particular supernova is one of the first published results.

“This is where FLOYDS comes in, and its robotic nature, which lets us study supernovae young,” Sand says. “That’s the first story. The second story is this lucky Hubble imaging from 2005. Someone took an image with Hubble of the galaxy where this supernova happened. Just sheer luck -- nothing to do with the supernova or seeing into the future or anything. Zoom to 2013, and we discover the supernova within a day of its explosion. We look in the Hubble data archive and notice the image from eight years prior, and we just match it up with our most recent data to see if there is a star in the old image at the exact same position as the supernova today.”

The global team of astrophysicists, led by Yi Cao of Caltech, found the supernova on June 16; the research was published online in the Astrophysical Journal Letters.

“It is very rare to catch a supernova within a day or two of explosion,” Sand said. “Up until now, it has happened at most about a dozen times. It is equally rare that we actually have Hubble Space Telescope imaging of the location of the supernova before it happened, and we were able to see the star that eventually exploded.”