Kavli Affiliate: Chao-Lin Kuo
| First 5 Authors: Y. Wan, Y. Wan, , ,
| Summary:
Blind discoveries of millimeter-wave (mm-wave) transient events in
non-targeted surveys, as opposed to follow-up or pointed observations, have
only become possible in the past decade using cosmic microwave background
surveys. Here we present the first results from the SPT-3G Galactic Plane
Survey — the first dedicated high-sensitivity, wide-field, time-domain,
mm-wave survey of the Galactic Plane, conducted with the South Pole Telescope
(SPT) using the SPT-3G camera. The survey field covers approximately 100
$textdeg^2$ near the Galactic center. In 2023 and 2024, this survey consists
of roughly 1,500 individual 20-minute observations in three bands centered at
95, 150, and 220 GHz, with plans for more observations in the coming years. We
report the detection of two transient events exceeding a 5$sigma$ threshold in
both the 95 and 150 GHz bands in the first two years of SPT-3G Galactic Plane
Survey data. Both events are unpolarized and exhibit durations of approximately
one day, with peak flux densities at 150 GHz of at least 50 mJy. The peak
isotropic luminosities at 150 GHz are on the order of
$10^31~texterg~texts^-1$. Both events are associated with previously
identified accreting white dwarfs. Magnetic reconnection in the accretion disk
is a likely explanation for the observed millimeter flares. In the future, we
plan to expand the transient search in the Galactic Plane by lowering the
detection threshold, enabling single-band detections, analyzing lightcurves on
a range of timescales, and including additional data from future observations.
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