📄 Detection of Millimeter-wavelength Flares from Two Accreting White Dw…
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Wan, Y. et al. (2026) · The Astrophysical Journal
Reads: 281 · Citations: 0
DOI: 10.3847/1538-4357/ae2de8
🔗 https://ui.adsabs.harvard.edu/abs/2026ApJ...997..133W/abstract
#Astronomy #Astrophysics #MillimeterAstronomy #Surveys #GalacticCenter
Blind discoveries of millimeter-wave transient events in nontargeted 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, millimeter-wave survey of the Galactic Plane, conducted with the South Pole Telescope (SPT) using the SPT-3G camera. The survey field covers approximately 100 deg<SUP>2</SUP> near the Galactic center. In 2023 and 2024, this survey consisted of roughly 1500 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 5σ threshold in both the 95 and 150 GHz bands in the first 2 yr of SPT-3G Galactic Plane Survey data. Both events are unpolarized and exhibit durations of approximately 1 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<SUP>31</SUP> erg s<SUP>−1</SUP>. 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.
Dr. Dana Alina from Nazarbayev University has lead a team that has revealed the magnetic field structure of the ring-like molecular cloud G111 (near NGC7538, an active star forming region).
The ring shape could have several origins: it could be a remnant of a past massive supernova explosion, or very strong stellar winds; or the result of two colliding clouds of molecular gas. Each option has different magnetic signatures.
Thanks to the IRAM 30-meter telescope, the team obtained high-sensitivity observations of carbon monoxide (CO). Using the Velocity Gradients Technique, they derived a detailed magnetic blueprint of the cloud. Then, they combined these observations with data from telescopes such as the Kanata telescope (Japan) and the Planck satellite.
Their study revealed an ordered magnetic structure that follows the ring’s curvature, the same structure traced by the cold dust.
This suggests that magnetic forces were strong enough to remain organized throughout the cloud’s evolution, possibly guiding the gas motion during either an expansion or a large-scale interaction. This supports the hypotheses of G111 being a past supernova explosion remnant, or a stellar wind-blown structure.
This is not related to ALMA, but enabled by the IRAM-30m, the second largest millimeter-length radio telescope in operation. It is very dear to me because I did my first observations with it… on my namesake's day, March 8 (St. Juan de Dios). And is based in Granada, where I was born!
https://iram-institute.org/newsroom/general/unraveling-the-magnetic-blueprint-of-g111/
#StarFormation #MolecularClouds #IRAM #InstitutoRadioAstronomíaMilimétrica #InstituteRadioAstronomieMillimetrique #IRAM30m #MMAstronomy #MillimeterAstronomy #MagneticFields #CosmicMagnetism
German Virtual Observatory
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Dr. Juande Santander-Vela