We present a systematic survey for mass-transferring and recently-detached cataclysmic variables (CVs) with evolved secondaries, which are progenitors of extremely low-mass white dwarfs (ELM WDs), AM CVn systems, and detached ultracompact binaries. We select targets below the main sequence in the Gaia color-magnitude diagram with ZTF light curves showing large-amplitude ellipsoidal variability and orbital period $P_{\rm orb} < 6$ hr. This yields 51 candidates brighter than G=18, of which we have obtained many-epoch spectra for 21. We confirm all 21 to be completely -- or nearly -- Roche lobe filling close binaries. 13 show evidence of ongoing mass transfer, which has likely just ceased in the other 8. Most of the secondaries are hotter than any previously known CV donors, with temperatures $4700<T_{\rm eff}/{\rm K}<8000$. Remarkably, all secondaries with $T_{\rm eff} \gtrsim 7000\,\rm K$ appear to be detached, while all cooler secondaries are still mass-transferring. This transition likely marks the temperature where magnetic braking becomes inefficient due to loss of the donor's convective envelope. Most of the proto-WD secondaries have masses near $0.15\,M_{\odot}$; their companions have masses near $0.8\,M_{\odot}$. We infer a space density of $\sim 60\,\rm kpc^{-3}$, roughly 80 times lower than that of normal CVs and three times lower than that of ELM WDs. The implied Galactic birth rate, $\mathcal{R}\sim 60\,\rm Myr^{-1}$, is half that of AM CVn binaries. Most systems are well-described by MESA models for CVs in which mass transfer begins only as the donor leaves the main sequence. All are predicted to reach minimum periods $5\lesssim P_{\rm orb}/{\rm min}\lesssim30$ within a Hubble time, where they will become AM CVn binaries or merge. This sample triples the known evolved CV population and offers broad opportunities for improving understanding of the compact binary population.
ZTF J191814.28+010850.2: An eclipsing cataclysmic-variable candidate in the SW Sextantis period range
Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V.（德国变星工作组）；American Association of Variable Star Observers (AAVSO)（美国变星观测者协会）；Department of Physics and Astronomy, University of Sussex（萨塞克斯大学物理与天文学系）
ZTF J021804.16+071152.93: a dead cataclysmic variable and potential solution to the missing period bouncers
University of Sheffield（谢菲尔德大学）；University of Hamburg（汉堡大学）；University of Leicester（莱斯特大学）；Institute of Science and Technology Austria（奥地利科学技术研究所）；University of Amsterdam（阿姆斯特丹大学）；Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）；Institut d’Estudis Espacials de Catalunya（加泰罗尼亚空间研究所）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心（CAB），西班牙国家航空航天技术研究所/西班牙国家科学研究委员会）；Universidad de Valparaíso（瓦尔帕莱索大学）
TESS light curves of two new magnetic cataclysmic variables: an asynchronous polar at the period minimum, and an eclipsing system with a large spin-to-orbit ratio
Bay Area Environmental Research Institute（湾区环境研究所）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；New Mexico State University（新墨西哥州立大学）；Picture Rocks Observatory（皮克洛克天文台）；Department of Physics, University of Notre Dame（圣母大学物理系）；Centre for Extragalactic Astronomy, Department of Physics, Durham University（达勒姆大学物理系河外天文中心）；INAF – Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）
Circular polarimetry of suspect wind-accreting pre-polars II
Department of Physics and Astronomy, University of Sheffield（谢菲尔德大学物理与天文学系）；Armagh Observatory and Planetarium（阿马赫天文台和行星馆）；Department of Physics, University of Warwick（华威大学物理系）；Hamburger Sternwarte, University of Hamburg（汉堡天文台，汉堡大学）
IPHAS J190812.63+045728.1: A deeply eclipsing, X-ray bright cataclysmic variable with frequent outbursts
Universidade Federal de Sergipe（塞尔希培联邦大学）；Observatório Nacional（国家天文台）；Laboratório Nacional de Astrofísica（国家天体物理实验室）；NASA/GSFC（美国宇航局戈达德太空飞行中心）；University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）；Instituto Nacional de Pesquisas Espaciais（国家空间研究所）
The evolutionary history of ultra-compact accreting binaries. I. Chemical abundances and formation channel of the eclipsing AM CVn system ZTF J225237.05-051917.4 from HST spectroscopy
Hamburg Observatory, University of Hamburg（汉堡天文台，汉堡大学）；European Southern Observatory（欧洲南方天文台）；Department of Physics and Astronomy, Texas Tech University（德克萨斯理工大学物理与天文学系）；Department of Physics, University of Warwick（华威大学物理系）；Institut für Theoretische Physik und Astrophysik, University of Kiel（基尔大学理论物理与天体物理研究所）；São Paulo State University (UNESP), School of Engineering and Sciences（圣保罗州立大学（UNESP）工程与科学学院）；The Observatories of the Carnegie Institution for Science（卡内基科学机构天文台）；Department of Physics, University of California, Santa Barbara（加州大学圣塔芭芭拉分校物理系）；Departamento de Física, Universidad Técnica Federico Santa María（费德里科·圣玛丽亚技术大学物理系）；Institute of Science and Technology Austria（奥地利科学技术研究所）；Anton Pannekoek Institute for Astronomy, University of Amsterdam（阿姆斯特丹大学安东·潘农克天文研究所）
A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries
University of Texas Rio Grande Valley（德克萨斯大学里奥格兰德河谷分校）；South Texas Space Science Institute, University of Texas Rio Grande Valley（德克萨斯大学里奥格兰德河谷分校南德克萨斯空间科学研究所）；Texas Tech University（德克萨斯理工大学）；Universidad Nacional Autónoma de México, Instituto de Astronomía（墨西哥国立自治大学天文学研究所）；University of Michigan（密歇根大学）；Institute of Science and Technology Austria（奥地利科学技术研究所）
COPAS: Compact Objects and the Physics of Accretion Survey I. Accreting Binaries with P < 83 Minutes
University of Texas Rio Grande Valley（德克萨斯大学里奥格兰德河谷分校）；South Texas Space Science Institute, University of Texas Rio Grande Valley（南德克萨斯空间科学研究所，德克萨斯大学里奥格兰德河谷分校）；Universidad de La Laguna（拉帕鲁纳大学）；Instituto de Astrofísica de Canarias (IAC)（加那利群岛天体物理研究所）；Texas Tech University（德克萨斯理工大学）；Universidad Nacional Autónoma de México, Instituto de Astronomía（墨西哥国立自治大学，天文研究所）；Durham University（杜伦大学）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所（ICE，CSIC））
