Astronomers used a new astronomical software system called the intermediate Palomar Transient Factory to discover a new Type Ib supernova and link it to the star from which it exploded.
This image shows the galaxy NGC5806 and the location of the Type Ib supernova iPTF13bvn. Image credit: Yi Cao et al.
Type Ib supernovae are rare explosions where the progenitor star lacks an outer layer of hydrogen. It has proven difficult to pin down which kinds of stars give rise to these supernovae. One of the most promising ideas is that they originate from Wolf-Rayet stars.
These stars are about ten times more massive and thousands of times brighter than the Sun and have lost their hydrogen envelope by means of very strong stellar winds. Until recently, no strong evidence existed to support this theory.
Using the intermediate Palomar Transient Factory (iPTF), Dr Yi Cao from California Institute of Technology with colleagues spotted a new supernova in the galaxy NGC 5806 on 16 June 2013 – less than a day after the onset of its explosion. Baby pictures of this one-day-old supernova, labeled iPTF13bvn, were promptly taken by telescopes in the radio, X-ray, ultra-violet and infrared wavelengths, providing vital clues about its origins.
Detailed analysis of iPTF13bvn observations confirmed that it was, indeed, a Type Ib, and that it reached full luminosity 2 weeks from its initial explosion.
The team also detected a progenitor candidate for the explosion in Hubble imaging, linking the supernova to its predecessor star.
“Observations are consistent with the progenitor having been a Wolf Rayet star. If so this would be a breakthrough discovery,” said the astronomers, who described the discovery of iPTF13bvn in the paper appearing in the Astrophysical Journal Letters (arXiv.org).
This image shows the Type Ib supernova iPTF13bvn and its progenitor star. Image credit: Yi Cao et al.
The team also used the iPTF system to pinpoint a gamma ray burst afterglow called iPTF13bxl.
Gamma ray bursts are high-energy explosions that form some of the brightest celestial events. They can signify energy released during a supernova. Each burst is followed by an afterglow, which emits lower wavelength radiation than the original explosion.
Soon after the detection of iPTF13bxl by the Fermi satellite, the team started hunting for the afterglow over a huge field more than 360-times the size of the full Moon.
The astronomers then had to narrow a list of more than 27,000 gamma-ray burst candidates down to a single afterglow. Follow-up research confirmed the relationship between the iPTF13bxl afterglow and a particular gamma-ray burst called GRB 130702A.
They then used the Magellan telescope to find the afterglow’s so-called redshift value. It reveals the afterglow’s distance and tells scientists where to look for an object, such as a supernova, which might emerge in the wake of the explosion.
“The sophisticated intermediate Palomar Transient Factory software we used to identify iPTF13bxl now prepares us to locate about 10 gamma-ray bursts every year going forward. And future endeavors could help us identify other, fainter signatures, such as those accompanying the merger of binary neutron stars,” said Dr John Mulchaey from Observatories of the Carnegie Institution for Science, a co-author of a paper on the iPTF13bxl afterglow also published in the Astrophysical Journal Letters (arXiv.org).
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Bibliographic information: Yi Cao et al. 2013. Discovery, Progenitor and Early Evolution of a Stripped Envelope Supernova iPTF13bvn. ApJ 775, L7; doi: 10.1088/2041-8205/775/1/L7
Leo P. Singer et al. 2013. Discovery and Redshift of an Optical Afterglow in 71 deg2: iPTF13bxl and GRB 130702A. ApJ 776, L34; doi: 10.1088/2041-8205/776/2/L34
