New Findings Show Some Type Ia Supernovae Linked to Novae

In the August 24 issue of the journal Science, astronomers for the first time show at least some that thermonuclear (Type Ia) supernovae eats from a regular nova. The results of the study, led by Ben Dilday, a postdoctoral researcher in physics at UC Santa Barbara and at Las Cumbres Observatory Global Telescope Network (LCOGT), are surprising because earlier indirect - but strong - evidence had pointed to the merger of two white dwarf stars as the Originators of Type Ia supernovae other.

The authors Conclude that There are multiple ways to make a Type Ia supernova - a finding That Could have Implications for Understanding the Differences seen in these "standard candles," That Were used to reveal the Presence of dark energy.

Supernova PTF 11kx was discovered by the Palomar Transient Factory (PTF) in a galaxy 600 million light years away - in astronomical terms Relatively nearby, but like all Type Ia supernovae, much too far away to make out the details of the stars Before They exploded. However, the astronomers That Could discern the supernova was surrounded by shells of gas, some of it likely containing hydrogen that had been cast off in previous nova eruptions, Decades before the supernova occurred. These are much more frequent explosions weak that do not destroy the star. While like shells of material had been seen before in a handful of Type Ia supernovae, Their origin was debated, and They had never before been linked to Firmly novae. Some doubted that the item was even near to the supernova at all.

11kx PTF was different. The surrounding gas was moving too slowly to be from the supernova, but too fast to be a typical stellar wind. Lars Bildsten, director of UCSB's Kavli Institute for Theoretical Physics That it was hypothesized materials shot out from a previous nova eruption, which had been slowed as it collided with the wind from the red giant star. Calculations from UCSB graduate student Kevin Moore Showed this hypothesis to be plausible, and would lead to gas moving at speeds seen in the observations. Adding credence to the theory was the fact that the materials moved at two different speeds - faster-moving inner material to slower-moving material - exactly as expected. The farthest-out materials had been slowing for decades, while the interior material had less time to slow.

But if I this was the case, the very fast-moving supernova eject collided Eventually Should Have With The nova material. About two months after the explosion, this is exactly what happened. New observations Showed that the supernova ejects was smashing into the inner shell of material. It was impossible to doubt that this was near the supernova gas.

"This was the MOST exciting I've ever Studied supernova," said Dilday. "For several months, almost every new observation showed something we'd never seen before."

The team was Further Convinced of the nova hypothesis based on its similarity to RS Ophiuchi, a recurrent nova in our own galaxy. Unlike distant supernovae, RS Oph That is close enough its properties are known: It is a compact white dwarf star (similar to what the core of the sun Will Become in 5 billion years) in orbit with a red giant star. That material is being blown off the red giant in a stellar wind is landing on the white dwarf, and, as the materials builds up, it explodes as a nova periodically eruption. RS Oph has these explosions every 20 years or so, with the last occurring in 2006. But theoretical studies Indicated That White dwarfs lose more mass in a nova eruption than they gain from the red giant. Since Type Ia supernova is a thought to Occur When the white dwarf grows in mass cannot grow Until it any further, many astronomers novae Concluded That Could not produce Type Ia supernovae. The new study is the first observational evidence That They Can.

Novae could explain all supernovae? The PTF team Showed That SN 2011fe Previously, the closest Type Ia supernova in 25 years, could not be a nova of the type 11kx Suspected in TFP. And any red giant in the binary system is expected to survive the explosion of the white dwarf. A recent study found no such survivor in a nearby supernova remnant and Concluded That It Must Have Been Caused by the merger of two white dwarf stars. Finally, other studies Showed that some supernovae are so bright they almost certainly that result from the merger of two white dwarf stars.

Predicting the exact number of supernovae may arise from novae that Is Difficult, since the authors think they got lucky and saw the nova at just the right angle so that they could infer its presence. But look very different from novae different directions, so if they had seen the blast from a different perspective, They Might has missed it. Still, they give rise novae that estimate to more than one-tenth of a percent of all Type Ia supernovae, but less than 20 percent.

Andy Howell, second author on the study, said: "It is a complete surprise to Find that thermonuclear supernovae, which all seem so similar, eat from different kinds of stars. It is like discovering that some humans evolved from ape-like ancestors, and others came from giraffes. How could they look like so if They Had Such different origins? “Howell is the leader of the group at LCOGT supernova, and is an adjunct faculty member in physics at UCSB.

Recently, some studies have found Type Ia supernovae That are not perfect standard candles - their brightness depends on the type of galaxy in Which They Were discovered. The reason is a mystery, but the finding Type Ia supernovae That some eats from different progenitors That would seem to suggest the supernova's brightness may be ultimate Affected by whether or not it comes from a nova or a white dwarf merger.

"We do not think this calls the Presence of dark energy into question," said Dilday. "But it does show that if we want to make progress Understanding it, we need to understand supernovae better."

Is a privately funded LCOGT observatory building a global network of more than 30 2-meter, 1-meter, 0.4-meter telescopes and.

The Palomar Transient Factory is an international collaboration of scientists and engineers from the California Institute of Technology, DOE's National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory, NASA's Infrared Processing and Analysis Center, the University of California, Berkeley, Las Cumbres Observatory Global Telescope Network, the University of Oxford, Columbia University, the Weizmann Institute of Science in Israel, and Pennsylvania State University. The Principal Investigator of the PTF is Shri R. Kulkarni, a professor at Caltech.