• DOI:10.1126/science.aac7673
• Corpus ID: 206640348

Real-time detection of an extreme scattering event: Constraints on Galactic plasma lenses

@article{Bannister2016RealtimeDO,
  title={Real-time detection of an extreme scattering event: Constraints on Galactic plasma lenses},
  author={Keith W. Bannister and Jamie Stevens and Artem V. Tuntsov and Mark A. Walker and Simon Johnston and Cormac Reynolds and Hayley E. Bignall},
  journal={Science},
  year={2016},
  volume={351},
  pages={354 - 356}
}

• K. Bannister, J. Stevens, +4 authors H. Bignall
• Published 22 January 2016
• Physics
• Science

Identifying live radio scattering events Radio emissions from distant quasars are occasionally modified for a few weeks by foreground interstellar plasma, in an extreme scattering event (ESE). Understanding this process has been difficult, because existing techniques do not allow events to be identified fast enough for follow-up before they finish. Bannister et al. developed a radio survey technique that allows ESEs to be identified in real time. After finding their first live ESE, they followed it up with additional radio and optical telescopes. The results constrain the size and density of the plasma and rule out one popular model of ESEs. Science, this issue p. 354 Interstellar extreme scattering events are identified in real time with radio observations. Extreme scattering events (ESEs) are distinctive fluctuations in the brightness of astronomical radio sources caused by occulting plasma lenses in the interstellar medium. The inferred plasma pressures of the lenses are ~103 times the ambient pressure, challenging our understanding of gas conditions in the Milky Way. Using a new survey technique, we discovered an ESE while it was in progress. Here we report radio and optical follow-up observations. Modeling of the radio data demonstrates that the lensing structure is a density enhancement and the lens is diverging, ruling out one of two competing physical models. Our technique will uncover many more ESEs, addressing a long-standing mystery of the small-scale gas structure of our Galaxy.