In the realm of energy and astrophysics, a team of researchers from the University of Stockholm, the University of Manchester, and the University of Valencia has been delving into the low-frequency radio emissions of supernovae using the LOw Frequency ARray (LOFAR). Their work, published in the journal Astronomy & Astrophysics, offers new insights into the long-term evolution of these powerful stellar explosions.
The team, led by Peter Lundqvist from the University of Stockholm, has been studying three specific supernovae: SN 1979C, SN 1986J, and SN 2006X. Using data from the LOFAR Two-metre Sky Survey (LoTSS) and the International LOFAR Telescope (ILT), they have been able to observe these supernovae at frequencies around 0.146 GHz, providing a unique perspective on their radio emissions.
For SN 2006X, a Type Ia supernova, the researchers were unable to detect any significant radio emission, setting an upper limit of 0.7 mJy at 0.146 GHz. By comparing this limit with radio emission models based on the CS15DD2 explosion model, they were able to constrain the circumstellar density to less than 10 particles per cubic centimeter, assuming certain microphysical parameters.
SN 1979C, a Type II supernova, was clearly detected in the LoTSS image, with a flux density of 4.6 ± 0.36 mJy nearly 40 years post-explosion. By modeling its radio evolution, the researchers found that the flux density of SN 1979C has been decaying steeply, following a power law with an exponent of -2.1 between 22 and 42 years post-explosion. They also detected a break in the spectrum near 1.5 GHz, which they attribute to synchrotron cooling. Based on their models, they estimate that the progenitor star had a mass of around 13 times that of the Sun, and that the density slope of the supernova ejecta steepens with velocity.
The researchers also presented the first ILT image of SN 1986J, another Type II supernova, showing a flux density of 6.77 ± 0.2 mJy at 0.146 GHz. They found that the spectral index of the shell emission is 0.66 ± 0.03, consistent with previous estimates, although they note that variations at low frequencies warrant further investigation.
In terms of practical applications for the energy sector, this research highlights the power of low-frequency radio observations for studying the long-term evolution of supernovae. By understanding the radio emissions from these events, we can gain insights into the physics of these explosions, which in turn can help us better understand the origin and evolution of the elements that make up our universe. Furthermore, studying the circumstellar environments of supernovae can provide valuable information for understanding the life cycles of stars and the interstellar medium, which are crucial for understanding the dynamics of galaxies and the large-scale structure of the universe.
The research was published in the journal Astronomy & Astrophysics.
This article is based on research available at arXiv.