article published yes Antonio C. Rodriguez author Kareem El-Badry author Valery Suleimanov author Anna F. Pala author Shrinivas R. Kulkarni author Boris Gaensicke author Kaya Mori author R. Michael Rich author Arnab Sarkar author Tong Bao author Raimundo Lopes De Oliveira author Gavin Ramsay author Paula Szkody author Matthew Graham author Thomas A. Prince author Ilaria Caiazzo author 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d0000-0002-4770-5388 Zachary P. Vanderbosch author Jan Van Roestel author Kaustav K. Das author Yu Jing Qin author Mansi M. Kasliwal author Avery Wold author Steven L. Groom author Daniel Reiley author Reed Riddle author IlCa department We present volume-limited samples of cataclysmic variables (CVs) and AM CVn binaries jointly selected from SRG/eROSITA eRASS1 and Gaia DR3 using an X-ray + optical color–color diagram (the "X-ray Main Sequence"). This tool identifies all CV subtypes, including magnetic and low-accretion rate systems, in contrast to most previous surveys. We find 23 CVs, 3 of which are AM CVns, out to 150 pc in the Western Galactic Hemisphere. Our 150 pc sample is spectroscopically verified and complete down to LX = 1.3 × 1029 erg s−1 in the 0.2–2.3 keV band, and we also present CV candidates out to 300 pc and 1000 pc. We discovered two previously unknown systems in our 150 pc sample: the third nearest AM CVn and a magnetic period bouncer. We find the mean LX of CVs to be 〈LX〉 ≈ 4.6 × 1030 erg s−1, in contrast to previous surveys which yielded 〈LX〉 ∼ 1031−1032 erg s−1. We construct X-ray luminosity functions that, for the first time, flatten out at LX ∼ 1030 erg s−1. We infer average number, mass, and luminosity densities of ρN,CV = (3.7 ± 0.7) × 10−6pc−3, (math formular), and (math formular), respectively, in the solar neighborhood. Our uniform selection method also allows us to place meaningful estimates on the space density of AM CVns, ρN,AM CVn = (5.5 ± 3.7) × 10−7 pc−3. Magnetic CVs and period bouncers make up 35% and 25% of our sample, respectively. This work, through a novel discovery technique, shows that the observed number densities of CVs and AM CVns, as well as the fraction of period bouncers, are still in tension with population synthesis estimates. https://research-explorer.ista.ac.at/download/18851/18860/2025_PASP_Rodriguez.pdf application/pdfno https://creativecommons.org/licenses/by/3.0/ IOP Publishing2025 eng 0004-6280 2408.16053 00139320470000110.1088/1538-3873/ada185 1371 A. C. Rodriguez <i>et al.</i>, “Cataclysmic variables and AM CVn binaries in SRG/eROSITA + Gaia: Volume limited samples, X-ray luminosity functions, and space densities,” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 1. IOP Publishing, 2025. Rodriguez AC, El-Badry K, Suleimanov V, et al. Cataclysmic variables and AM CVn binaries in SRG/eROSITA + Gaia: Volume limited samples, X-ray luminosity functions, and space densities. <i>Publications of the Astronomical Society of the Pacific</i>. 2025;137(1). doi:<a href="https://doi.org/10.1088/1538-3873/ada185">10.1088/1538-3873/ada185</a> Rodriguez, Antonio C., Kareem El-Badry, Valery Suleimanov, Anna F. Pala, Shrinivas R. Kulkarni, Boris Gaensicke, Kaya Mori, et al. “Cataclysmic Variables and AM CVn Binaries in SRG/EROSITA + Gaia: Volume Limited Samples, X-Ray Luminosity Functions, and Space Densities.” <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing, 2025. <a href="https://doi.org/10.1088/1538-3873/ada185">https://doi.org/10.1088/1538-3873/ada185</a>. A.C. Rodriguez, K. El-Badry, V. Suleimanov, A.F. Pala, S.R. Kulkarni, B. Gaensicke, K. Mori, R.M. Rich, A. Sarkar, T. Bao, R.L. De Oliveira, G. Ramsay, P. Szkody, M. Graham, T.A. Prince, I. Caiazzo, Z.P. Vanderbosch, J.V. Roestel, K.K. Das, Y.J. Qin, M.M. Kasliwal, A. Wold, S.L. Groom, D. Reiley, R. Riddle, Publications of the Astronomical Society of the Pacific 137 (2025). Rodriguez, A. C., El-Badry, K., Suleimanov, V., Pala, A. F., Kulkarni, S. R., Gaensicke, B., … Riddle, R. (2025). Cataclysmic variables and AM CVn binaries in SRG/eROSITA + Gaia: Volume limited samples, X-ray luminosity functions, and space densities. <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing. <a href="https://doi.org/10.1088/1538-3873/ada185">https://doi.org/10.1088/1538-3873/ada185</a> Rodriguez AC, El-Badry K, Suleimanov V, Pala AF, Kulkarni SR, Gaensicke B, Mori K, Rich RM, Sarkar A, Bao T, De Oliveira RL, Ramsay G, Szkody P, Graham M, Prince TA, Caiazzo I, Vanderbosch ZP, Roestel JV, Das KK, Qin YJ, Kasliwal MM, Wold A, Groom SL, Reiley D, Riddle R. 2025. Cataclysmic variables and AM CVn binaries in SRG/eROSITA + Gaia: Volume limited samples, X-ray luminosity functions, and space densities. Publications of the Astronomical Society of the Pacific. 137(1), 014201. Rodriguez, Antonio C., et al. “Cataclysmic Variables and AM CVn Binaries in SRG/EROSITA + Gaia: Volume Limited Samples, X-Ray Luminosity Functions, and Space Densities.” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 1, 014201, IOP Publishing, 2025, doi:<a href="https://doi.org/10.1088/1538-3873/ada185">10.1088/1538-3873/ada185</a>. 188512025-01-19T23:01:51Z2025-02-27T12:46:32Z