Todays’ print edition of the New York Times reported on a paper from the journal Science authored by Las Cumbres Observatory scientists Benjamin Dilday and Andy Howell, among others. The paper, widely reported in astronomy and physics media, was picked up by the Times because it demonstrates for the first time alternate means by which a supernova can form. Dilday and Howell were the lead scientists on the paper.
The study characterized supernova PTF 11kx which was discovered 16 January 2011 (UT) by the Palomar Transient Factory (PTF). The supernova was identified as a Type Ia, a supernova that results from the violent explosion of a white dwarf star.
Early spectra showed strong calcium features which are unusual for Type Ia supernovae. Additional spectra taken with the Lick low-resolution spectrograph and the Keck I High Resolution Echelle Spectrometer (HIRES) instrument continued to reveal surprises including two velocities of the circumstellar matter. Light curves captured using the Las Cumbres Observatory Faulkes Telescope North were also surprising, staying brighter for a longer period than expected.
Multiple theories were proposed and discarded in the face of each new finding. Lars Bildsten, director of UCSB's Kavli Institute for Theoretical Physics, finally hypothesized that the team was observing material shot out from a previous nova eruption, which had been slowed as it collided with the wind from the red giant star. Thus they were observing a supernova overtaking a prior nova event.
Previous observational studies suggested that many or most Type Ia supernovae originated from the merger of two white dwarf stars. But in this case, a white dwarf exploded because the white dwarf increased its mass by stealing matter from a red giant star in orbit around it. As the white dwarf grew in mass it experienced a series of smaller explosions (novae) that left the white dwarf intact. This was the first observational evidence that in fact a recurrent nova, could lead to the ultimate destruction of the star as a supernova.
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