article published yes Antonio C. Rodriguez author Kareem El-Badry author Pasi Hakala author Pablo Rodríguez-Gil author Tong Bao author Ilkham Galiullin author Jacob A. Kurlander author Casey J. Law author Ingrid Pelisoli author Matthias R. Schreiber author Kevin Burdge author Ilaria Caiazzo author 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d0000-0002-4770-5388 Jan Van Roestel author Paula Szkody author Andrew J. Drake author David A.H. Buckley author Stephen B. Potter author Boris Gaensicke author Kaya Mori author Eric C. Bellm author Shrinivas R. Kulkarni author Thomas A. Prince author Matthew Graham author Mansi M. Kasliwal author Sam Rose author Yashvi Sharma author Tomás Ahumada author Shreya Anand author Akke Viitanen author Avery Wold author Tracy X. Chen author Reed Riddle author Roger Smith author IlCa department White dwarfs (WDs) are the most abundant compact objects, and recent surveys have suggested that over a third of WDs in accreting binaries host a strong (B ≳ 1 MG) magnetic field. However, the origin and evolution of WD magnetism remain under debate. Two WD pulsars, AR Sco and J191213.72–441045.1 (J1912), have been found, which are non-accreting binaries hosting rapidly spinning (1.97 minutes and 5.30 minutes, respectively) magnetic WDs. The WD in AR Sco is slowing down on a (math formular) yr timescale. It is believed they will eventually become polars, accreting systems in which a magnetic WD (B ≈ 10−240 MG) accretes from a Roche lobe-filling donor spinning in sync with the orbit (≳78 minutes). Here, we present multiwavelength data and analysis of Gaia22ayj, which outbursted in 2022 March. We find that Gaia22ayj is a magnetic accreting WD that is rapidly spinning down (math formular yr) like WD pulsars, but shows clear evidence of accretion, like polars. Strong linear polarization (40%) is detected in Gaia22ayj; such high levels have only been seen in the WD pulsar AR Sco and demonstrate the WD is magnetic. High speed photometry reveals a 9.36 minutes period accompanying a high amplitude (∼2 mag) modulation. We associate this with a WD spin or spin–orbit beat period, not an orbital period as was previously suggested. Fast (60 s) optical spectroscopy reveals a broad "hump," reminiscent of cyclotron emission in polars, between 4000 and 8000 Å. We find an X-ray luminosity of (math formular) in the 0.3–8 keV energy range, while two very large array radio campaigns resulted in a non-detection with a Fr < 15.8 μJy 3σ upper limit. The shared properties of both WD pulsars and polars suggest that Gaia22ayj is a missing link between the two classes of magnetic WD binaries. https://research-explorer.ista.ac.at/download/19439/19455/2025_PubAstronomSocPacific_Rodriguez.pdf application/pdfno https://creativecommons.org/licenses/by/4.0/ IOP Publishing2025 eng 0004-6280 2501.01490 00142787770000110.1088/1538-3873/adb0f1 1372 Rodriguez AC, El-Badry K, Hakala P, Rodríguez-Gil P, Bao T, Galiullin I, Kurlander JA, Law CJ, Pelisoli I, Schreiber MR, Burdge K, Caiazzo I, Roestel JV, Szkody P, Drake AJ, Buckley DAH, Potter SB, Gaensicke B, Mori K, Bellm EC, Kulkarni SR, Prince TA, Graham M, Kasliwal MM, Rose S, Sharma Y, Ahumada T, Anand S, Viitanen A, Wold A, Chen TX, Riddle R, Smith R. 2025. A link between White Dwarf pulsars and polars: Multiwavelength observations of the 9.36-minute period variable Gaia22ayj. Publications of the Astronomical Society of the Pacific. 137(2), 024202. Rodriguez, A. C., El-Badry, K., Hakala, P., Rodríguez-Gil, P., Bao, T., Galiullin, I., … Smith, R. (2025). A link between White Dwarf pulsars and polars: Multiwavelength observations of the 9.36-minute period variable Gaia22ayj. <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing. <a href="https://doi.org/10.1088/1538-3873/adb0f1">https://doi.org/10.1088/1538-3873/adb0f1</a> A. C. Rodriguez <i>et al.</i>, “A link between White Dwarf pulsars and polars: Multiwavelength observations of the 9.36-minute period variable Gaia22ayj,” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 2. IOP Publishing, 2025. Rodriguez, Antonio C., Kareem El-Badry, Pasi Hakala, Pablo Rodríguez-Gil, Tong Bao, Ilkham Galiullin, Jacob A. Kurlander, et al. “A Link between White Dwarf Pulsars and Polars: Multiwavelength Observations of the 9.36-Minute Period Variable Gaia22ayj.” <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing, 2025. <a href="https://doi.org/10.1088/1538-3873/adb0f1">https://doi.org/10.1088/1538-3873/adb0f1</a>. Rodriguez, Antonio C., et al. “A Link between White Dwarf Pulsars and Polars: Multiwavelength Observations of the 9.36-Minute Period Variable Gaia22ayj.” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 2, 024202, IOP Publishing, 2025, doi:<a href="https://doi.org/10.1088/1538-3873/adb0f1">10.1088/1538-3873/adb0f1</a>. A.C. Rodriguez, K. El-Badry, P. Hakala, P. Rodríguez-Gil, T. Bao, I. Galiullin, J.A. Kurlander, C.J. Law, I. Pelisoli, M.R. Schreiber, K. Burdge, I. Caiazzo, J.V. Roestel, P. Szkody, A.J. Drake, D.A.H. Buckley, S.B. Potter, B. Gaensicke, K. Mori, E.C. Bellm, S.R. Kulkarni, T.A. Prince, M. Graham, M.M. Kasliwal, S. Rose, Y. Sharma, T. Ahumada, S. Anand, A. Viitanen, A. Wold, T.X. Chen, R. Riddle, R. Smith, Publications of the Astronomical Society of the Pacific 137 (2025). Rodriguez AC, El-Badry K, Hakala P, et al. A link between White Dwarf pulsars and polars: Multiwavelength observations of the 9.36-minute period variable Gaia22ayj. <i>Publications of the Astronomical Society of the Pacific</i>. 2025;137(2). doi:<a href="https://doi.org/10.1088/1538-3873/adb0f1">10.1088/1538-3873/adb0f1</a> 194392025-03-23T23:01:26Z2025-09-30T11:15:10Z