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The Deeper, Wider, Faster (DWF) program coordinates simultaneous
observations between telescopes across the entire electromagnetic
spectrum to study astrophysical transients on timescales of
milliseconds to days. The tenth DWF observing run was carried out in
September 2021 and consisted of six consecutive days of observations
with ASKAP, the Dark Energy
Camera, the Hard X-ray Modulation Telescope and the Parkes 64m
“Murriyang” radio telescope.
Dobie et al. present the results of an
image-domain search for transient, variable and circularly polarised
sources carried out with ASKAP using data from the observing run. One
of the variable sources detected was SCR J1845–6357, a
nearby binary system. The figure above shows the intra-observation
light curve, with the data avergaed into 15-minute samples,
demonstrating that the variability stems from a series of pulses, each
lasting ∼2 h. The shaded region denotes the duration of the
simultaneous Swift observation, in which no X-ray or UV emission was
detected, suggesting that previously observed X-ray variability and
radio activity are not coupled. The radio emission is highly (∼90%)
circularly polarised during the pulses, but not in the quiescent
state. An optical period of 14.1±0.2 h was measured for SCR
J1845–6357 from NASA's Transiting Exoplanet Survey Satellite (TESS),
and the flares detected in the ASKAP data are consistent with this
periodicity. The team conclude that the observed radio variability
stems from rotational modulation, making this the slowest rotating
radio-pulsing ultra-cool dwarf discovered to-date.
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