Detection of millimeter-wavelength flares from two accreting white dwarf systems in the SPT-3G Galactic Plane Survey

Wan, Y., Vieira, J. D., Chichura, P. M., Maccarone, T. J., Anderson, A. J., Ansarinejad, B., Anumarlapudi, A., Archipley, M., Balkenhol, L., Barry, P. S., Benabed, K., Bender, A. N., Benson, B. A., Bianchini, F., Bleem, L. E., Bouchet, F. R., Bryant, L., Camphuis, E., Campitiello, M. G., Carlstrom, J. E., Chang, C. L., Chaubal, P., Chokshi, A., Chou, T.-L., Coerver, A., Crawford, T. M., Daley, C., de Haan, T., Dibert, K. R., Dobbs, M. A., Doohan, M., Doussot, A., Dutcher, D., Everett, W., Feng, C., Ferguson, K. R., Fichman, K., Foster, A., Galli, S., Gambrel, A. E., Gardner, R. W., Ge, F., Goeckner-Wald, N., Gualtieri, R., Guidi, F., Guns, S., Halverson, N. W., Hivon, E., Holder, G. P., Holzapfel, W. L., Hood, J. C., Hryciuk, A., Huang, N., Kaplan, D. L., Kéruzoré, F., Khalife, A. R., Knox, L., Korman, M., Kornoelje, K., Kuo, C.-L., Levy, K., Lowitz, A. E., Lu, C., Lynch, G. P., Maniyar, A., Martsen, E. S., Menanteau, F., Millea, M., Montgomery, J., Nakato, Y., Natoli, T., Noble, G. I., Omori, Y., Ouellette, A., Pan, Z., Paschos, P., Phadke, K. A., Pollak, A. W., Prabhu, K., Quan, W., Rahimi, M., Rahlin, A., Reichardt, C. L., Rouble, M., Ruhl, J. E., Schiappucci, E., Simpson, A., Sobrin, J. A., Stark, A. A., Stephen, J., Tandoi, C., Thorne, B., Trendafilova, C., Umilta, C., Vitrier, A., Whitehorn, N., Wu, W. L. K., Young, M. R. and Zebrowski, J. A. 2026. Detection of millimeter-wavelength flares from two accreting white dwarf systems in the SPT-3G Galactic Plane Survey. The Astrophysical Journal 997 (2) , 133. 10.3847/1538-4357/ae2de8

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Abstract

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 deg2 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 1031 erg s−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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Type: cc-by
Publisher:	American Astronomical Society
ISSN:	0004-637X
Date of Acceptance:	4 December 2025
Last Modified:	27 Jan 2026 11:52
URI:	https://orca.cardiff.ac.uk/id/eprint/184226

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