article published yes Tim Cunningham author Ilaria Caiazzo author 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d0000-0002-4770-5388 Gracjan Sienkiewicz author Peter J. Wheatley author Boris T. Gänsicke author Kareem El-Badry author Riccardo Arcodia author David Charbonneau author Liam Connor author Kishalay De author Pasi Hakala author Scott J. Kenyon author Sumit Kumar Maheshwari author Antonio C. Rodriguez author Jan Van Roestel author Pier Emmanuel Tremblay author IlCa department We report the discovery of two new magnetic cataclysmic variables with brown dwarf companions and long orbital periods (P_{\rm orb}=95\pm1 and 104\pm2 min). This discovery increases the sample of candidate magnetic period bouncers with confirmed sub-stellar donors from four to six. We also find their X-ray luminosity from archival XMM–Newton observations to be in the range L_{\rm X}\approx10^{28}-10^{29} \mathrm{erg\,s^{-1}} in the 0.25–10 keV band. This low luminosity is comparable with the other candidates, and at least an order of magnitude lower than the X-ray luminosities typically measured in cataclysmic variables. The X-ray fluxes imply mass transfer rates that are much lower than predicted by evolutionary models, even if some of the discrepancy is due to the accretion energy being emitted in other bands, such as via cyclotron emission at infrared wavelengths. Although it is possible that some or all of these systems formed directly as binaries containing a brown dwarf, it is likely that the donor used to be a low-mass star and that the systems followed the evolutionary track for cataclysmic variables, evolving past the period bounce. The donor in long period systems is expected to be a low-mass, cold brown dwarf. This hypothesis is supported by near-infrared photometric observations that constrain the donors in the two systems to be brown dwarfs cooler than 1100 K (spectral types T5 or later), most likely losing mass via Roche Lobe overflow or winds. The serendipitous discovery of two magnetic period bouncers in the small footprint of the XMM–Newton catalogue implies a large space density of these type of systems, possibly compatible with the prediction of 40–70 per cent of magnetic cataclysmic variables to be period bouncers. https://research-explorer.ista.ac.at/download/19840/19864/2025_MonthlyNoticesRAS_Cunningham.pdf application/pdfno Oxford University Press2025 eng 0035-8711 1365-2966 2503.12675 00149314370000110.1093/mnras/staf561 5401633-649 T. Cunningham <i>et al.</i>, “Discovery of two new polars evolved past the period bounce,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 540, no. 1. Oxford University Press, pp. 633–649, 2025. T. Cunningham, I. Caiazzo, G. Sienkiewicz, P.J. Wheatley, B.T. Gänsicke, K. El-Badry, R. Arcodia, D. Charbonneau, L. Connor, K. De, P. Hakala, S.J. Kenyon, S.K. Maheshwari, A.C. Rodriguez, J. Van Roestel, P.E. Tremblay, Monthly Notices of the Royal Astronomical Society 540 (2025) 633–649. Cunningham, T., Caiazzo, I., Sienkiewicz, G., Wheatley, P. J., Gänsicke, B. T., El-Badry, K., … Tremblay, P. E. (2025). Discovery of two new polars evolved past the period bounce. <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press. <a href="https://doi.org/10.1093/mnras/staf561">https://doi.org/10.1093/mnras/staf561</a> Cunningham, Tim, et al. “Discovery of Two New Polars Evolved Past the Period Bounce.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 540, no. 1, Oxford University Press, 2025, pp. 633–49, doi:<a href="https://doi.org/10.1093/mnras/staf561">10.1093/mnras/staf561</a>. Cunningham T, Caiazzo I, Sienkiewicz G, et al. Discovery of two new polars evolved past the period bounce. <i>Monthly Notices of the Royal Astronomical Society</i>. 2025;540(1):633-649. doi:<a href="https://doi.org/10.1093/mnras/staf561">10.1093/mnras/staf561</a> Cunningham, Tim, Ilaria Caiazzo, Gracjan Sienkiewicz, Peter J. Wheatley, Boris T. Gänsicke, Kareem El-Badry, Riccardo Arcodia, et al. “Discovery of Two New Polars Evolved Past the Period Bounce.” <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press, 2025. <a href="https://doi.org/10.1093/mnras/staf561">https://doi.org/10.1093/mnras/staf561</a>. Cunningham T, Caiazzo I, Sienkiewicz G, Wheatley PJ, Gänsicke BT, El-Badry K, Arcodia R, Charbonneau D, Connor L, De K, Hakala P, Kenyon SJ, Maheshwari SK, Rodriguez AC, Van Roestel J, Tremblay PE. 2025. Discovery of two new polars evolved past the period bounce. Monthly Notices of the Royal Astronomical Society. 540(1), 633–649. 198402025-06-15T22:01:29Z2025-09-30T12:50:33Z