Sky surveys have been helping astronomers learn more about the universe since the start of the 20th century. In February, the intermediate Palomar Transient Factor began scanning the skies for particular kinds of stars and related phenomena. iPTF has been very successful in the early finding and follow-up examinations of transients — astronomical objects whose brightness alters over timescales ranging from hours to days. Two recent papers utilized information from the iPTF to detail two new spectacular cosmic explosions: the progenitor of a rare kind of supernova in a nearby galaxy and the afterglow of a gamma-ray burst in July.

According to a news release from the California Institute of Technology, the Caltech-led Palomar Transient Factory (PTF) was created in 2008 to systematically map the transient sky by utilizing a robotic observing system placed on the 48-inch Samuel Oschin Telescope on Palomar Mountain. Since PTF began charting the transient sky four years ago, it has detected more than 2,000 spectroscopically classified supernovae. The iPTF has new technology that conducts a fully automated, quick response and follow-up within hours of finding a new supernova.

The first paper details the discovery of a so-called Type Ib supernova, known as iPTF13bvn. The supernova was detected on June 16, less than a day after the beginning of its explosion. Using the 10-meter Keck telescopes in Hawaii, the astronomers obtained a high-resolution image of this supernova to calculate its exact position. Then they compared the Keck photograph to a number of pictures of the same galaxy snapped by the Hubble Space Telescope, and discovered one star-like source spatially coincident to the supernova.

“All evidence is consistent with the theoretical expectation that the progenitor of this Type Ib supernova is a Wolf-Rayet star,” says graduate student and lead author Yi Cao. “Our next step is to check for the disappearance of this progenitor star after the supernova fades away. We expect that it will have been destroyed in the supernova explosion.”

The new research represents the first time astronomers have been able to make a connection between theory and observation, reports study co-author and Caltech alumna Mansi Kasliwal.

The second paper details the detection and characterization of the afterglow of a long gamma-ray burst in July. Long GRBs are linked with the deaths of quickly spinning, massive stars. GRB 130702A was first detected by NASA’s Fermi Gamma-ray Space Telescope. However, iPTF was able to narrow down the GRB’s location by looking at an area of the sky more than 360 times larger than the face of the moon and combing through hundreds of images utilizing advanced machine-learning software. iPTF also detected the visible-light counterpart of the burst, known as iPTF13bxl.

“First, by measuring its redshift, we learned that it was pretty nearby as far as GRBs go,” says lead author Leo Singer, a Caltech grad student. “It was pretty wimpy compared to most GRBs, liberating only about a thousandth as much energy as the most energetic ones. But we did see it eventually turn into a supernova. Typically we only detect supernovae in connection with nearby, subluminous GRBs, so we can’t be certain that cosmologically distant GRBs are caused by the same kinds of explosions.”

Caltech astronomers expect that the iPTF will lead to the finding of “many more supernovae in their infancy and many more afterglows from the Fermi satellite.”

The first study’s findings are detailed in Astrophysical Journal Letters.

The second study’s findings are also detailed in Astrophysical Journal Letters.