title: Real-time detection of an extreme scattering event: Constraints on Galactic plasma lenses.
abstract: 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 ~10(3) 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.
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation Astronomy and Space Science, PO Box 76, Epping, New South Wales 1710, Australia. keith.bannister@csiro.au.
authors.forename: Keith W
authors.initials: KW
authors.lastname: Bannister
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation Astronomy and Space Science, PO Box 76, Epping, New South Wales 1710, Australia.
authors.forename: Jamie
authors.initials: J
authors.lastname: Stevens
authors.affiliation: Manly Astrophysics, 3/22 Cliff Street, Manly, New South Wales 2095, Australia.
authors.forename: Artem V
authors.initials: AV
authors.lastname: Tuntsov
authors.affiliation: Manly Astrophysics, 3/22 Cliff Street, Manly, New South Wales 2095, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Walker
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation Astronomy and Space Science, PO Box 76, Epping, New South Wales 1710, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Johnston
authors.affiliation: International Centre for Radio Astronomy Research-Curtin University, Perth, Western Australia 6102, Australia.
authors.forename: Cormac
authors.initials: C
authors.lastname: Reynolds
authors.affiliation: International Centre for Radio Astronomy Research-Curtin University, Perth, Western Australia 6102, Australia.
authors.forename: Hayley
authors.initials: H
authors.lastname: Bignall