The transient radio sky at megahertz frequencies is a new frontier in radio science.
Because VLITE operates commensally with the VLA, it observes the sky > 6000 hours
each year. A single pointing of VLITE images 5.5 deg2, enabling tens of thousands of
square degrees to be imaged over the course of a month. Integration times for
these observations vary from tens of seconds to several hours. Further,
repeated visits to the same field give cadences of day-long to year-long
timescales. Using existing catalogs and archival data, we can increase the
cadence to decade-long timescales. Consequently, VLITE provides a unique tool
for exploration of the transient radio sky.
The above image shows the sky coverage after 30 months of VLITE observations. Some of the 30-month milestones include:
The transient search component of the VLITE project is divided into:
For transients shorter than 1 second, dedicated hardware is being developed to sample the raw voltages upstream of the correlator. This part of the project is still under development, with a goal towards realizing the capabilities to search for highly dispersed, msec timescale transients.
The VLITE slow transient mode has made several detections of known, non-radio
selected transients. An example of one such detection, the low mass X-ray
binary system V404 Cyg, is shown below.
While VLITE has not yet found any new radio-selected transients, VLITE observations do allow us to set stringent upper limits on transients at mJy levels and at low frequencies where comparatively few transient surveys have been carried out to date. VLITE is not expected to probe the known populations of slow transients such as NSM-Magnetars or dMe flare stars. However, VLITE has been designed with the intention of expanding it from 10 to all 27 VLA antennas and transitioning from narrow-band (64 MHz passband) to the full bandwidth of P-band (256 MHz). This new LOw Band Observatory (LOBO) will provide significantly increased imaging fidelity, much lower rms noise levels, and broader spectral coverage. The expansion of VLITE to LOBO will have a major impact on megahertz transient detection because it will be possible to detect known classes of megahertz transients. On 10 minute timescales, LOBO is expected to detect dMe flare stars. For longer (≥ 6 hr) timescales, LOBO will be sensitive to neutron star mergers that create magnetars as well as off-axis TDEs.
Modified on Monday, 16-Oct-2017 13:50:37 MDT