Casey J. Law, Geoffrey C. Bower
We demonstrate a new technique for detecting radio transients based on
interferometric closure quantities. The technique is based on the bispectrum,
the product of visibilities around a closed-loop of baselines of an
interferometer. The bispectrum is calibration independent, resistant to
interference, and computationally efficient, so it can be built into
correlators for real-time transient detection. Such a system could find
celestial transients anywhere in the field of view and localize them to
arcsecond precision. At the Expanded Very Large Array (EVLA), such a system
would have a high survey speed and a 5-sigma sensitivity of 35 mJy on 10 ms
timescales with 1 GHz of bandwidth. The ability to localize dispersed
millisecond pulses to arcsecond precision in large volumes of interferometer
data has several unique science applications. Localizing individual pulses from
Galactic pulsars will help find X-ray counterparts that define their physical
properties, while finding host galaxies of extragalactic transients will
measure the electron density of the intergalactic medium with a single
dispersed pulse. Exoplanets and active stars have distinct millisecond
variability that can be used to identify them and probe their magnetospheres.
We use millisecond time scale visibilities from the Allen Telescope Array (ATA)
and EVLA to show that the bispectrum can detect dispersed pulses and reject
local interference. The computational and data efficiency of the bispectrum
will help find transients on a range of time scales with next-generation radio
interferometers.
View original:
http://arxiv.org/abs/1112.0308
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