{"year":"2025","has_accepted_license":"1","oa_version":"Published Version","publisher":"IOP Publishing","PlanS_conform":"1","external_id":{"arxiv":["2508.20170"]},"DOAJ_listed":"1","department":[{"_id":"IlCa"}],"volume":990,"date_updated":"2026-02-19T07:27:01Z","date_created":"2026-02-18T10:17:04Z","scopus_import":"1","publication_identifier":{"issn":["2041-8205"],"eissn":["2041-8213"]},"publication_status":"published","article_type":"original","author":[{"last_name":"Galiullin","first_name":"Ilkham","full_name":"Galiullin, Ilkham"},{"first_name":"Antonio C.","last_name":"Rodriguez","full_name":"Rodriguez, Antonio C."},{"last_name":"El-Badry","first_name":"Kareem","full_name":"El-Badry, Kareem"},{"full_name":"Caiazzo, Ilaria","first_name":"Ilaria","last_name":"Caiazzo","id":"8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d","orcid":"0000-0002-4770-5388"},{"first_name":"Paula","last_name":"Szkody","full_name":"Szkody, Paula"},{"first_name":"Pranav","last_name":"Nagarajan","full_name":"Nagarajan, Pranav"},{"first_name":"Samuel","last_name":"Whitebook","full_name":"Whitebook, Samuel"}],"day":"08","intvolume":"       990","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","article_processing_charge":"Yes","publication":"The Astrophysical Journal Letters","doi":"10.3847/2041-8213/adff82","type":"journal_article","month":"09","title":"Optical spectroscopy of the most compact accreting binary harboring a magnetic White Dwarf and a hydrogen-rich donor","language":[{"iso":"eng"}],"oa":1,"acknowledgement":"Based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grants No. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 nonprofit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have had the opportunity to conduct observations from this mountain. We are grateful to the staff of the Palomar and Keck Observatories for their work in helping us carry out our observations.\r\n\r\nI.G. acknowledges support from Kazan Federal University. A.C.R. acknowledges support from the National Science Foundation via an NSF Graduate Research Fellowship. We thank the anonymous referee for useful comments and suggestions, which contributed to the improvement of this manuscript.","date_published":"2025-09-08T00:00:00Z","file_date_updated":"2026-02-19T07:24:10Z","status":"public","quality_controlled":"1","abstract":[{"text":"Accreting white dwarfs (WDs) in close binary systems, commonly known as cataclysmic variables (CVs), with orbital periods below the canonical period minimum (≈80 minutes) are rare. Such short periods can only be reached if the donor star in the CV is either significantly evolved before initiating mass transfer to the WD or is metal-poor. We present optical photometry and spectroscopy of Gaia19bxc, a high-amplitude variable identified as a polar CV with an exceptionally short orbital period of 64.42 minutes—well below the canonical CV period minimum. High-speed photometry confirms persistent double-peaked variability consistent with cyclotron beaming, thus indicating the presence of a magnetic WD. Phase-resolved Keck/Low-Resolution Imaging Spectrometer (LRIS) spectroscopy reveals strong hydrogen and helium emission lines but no donor features, indicating the accretor is a magnetic WD and the donor is hydrogen-rich, but cold and faint. The absence of a detectable donor and the low inferred temperature (≲3500 K) disfavor an evolved donor scenario. Instead, the short period and the system’s halo-like kinematics suggest Gaia19bxc may be the first known metal-poor polar. Because metal-poor donors are more compact than solar-metallicity donors of the same mass, they can reach shorter minimum periods. Gaia19bxc is one of only a handful of known metal-poor CVs below the canonical period minimum and has the shortest period of any such magnetic system discovered to date.","lang":"eng"}],"OA_type":"gold","OA_place":"publisher","citation":{"mla":"Galiullin, Ilkham, et al. “Optical Spectroscopy of the Most Compact Accreting Binary Harboring a Magnetic White Dwarf and a Hydrogen-Rich Donor.” <i>The Astrophysical Journal Letters</i>, vol. 990, no. 2, L57, IOP Publishing, 2025, doi:<a href=\"https://doi.org/10.3847/2041-8213/adff82\">10.3847/2041-8213/adff82</a>.","ama":"Galiullin I, Rodriguez AC, El-Badry K, et al. Optical spectroscopy of the most compact accreting binary harboring a magnetic White Dwarf and a hydrogen-rich donor. <i>The Astrophysical Journal Letters</i>. 2025;990(2). doi:<a href=\"https://doi.org/10.3847/2041-8213/adff82\">10.3847/2041-8213/adff82</a>","short":"I. Galiullin, A.C. Rodriguez, K. El-Badry, I. Caiazzo, P. Szkody, P. Nagarajan, S. Whitebook, The Astrophysical Journal Letters 990 (2025).","chicago":"Galiullin, Ilkham, Antonio C. Rodriguez, Kareem El-Badry, Ilaria Caiazzo, Paula Szkody, Pranav Nagarajan, and Samuel Whitebook. “Optical Spectroscopy of the Most Compact Accreting Binary Harboring a Magnetic White Dwarf and a Hydrogen-Rich Donor.” <i>The Astrophysical Journal Letters</i>. IOP Publishing, 2025. <a href=\"https://doi.org/10.3847/2041-8213/adff82\">https://doi.org/10.3847/2041-8213/adff82</a>.","apa":"Galiullin, I., Rodriguez, A. C., El-Badry, K., Caiazzo, I., Szkody, P., Nagarajan, P., &#38; Whitebook, S. (2025). Optical spectroscopy of the most compact accreting binary harboring a magnetic White Dwarf and a hydrogen-rich donor. <i>The Astrophysical Journal Letters</i>. IOP Publishing. <a href=\"https://doi.org/10.3847/2041-8213/adff82\">https://doi.org/10.3847/2041-8213/adff82</a>","ista":"Galiullin I, Rodriguez AC, El-Badry K, Caiazzo I, Szkody P, Nagarajan P, Whitebook S. 2025. Optical spectroscopy of the most compact accreting binary harboring a magnetic White Dwarf and a hydrogen-rich donor. The Astrophysical Journal Letters. 990(2), L57.","ieee":"I. Galiullin <i>et al.</i>, “Optical spectroscopy of the most compact accreting binary harboring a magnetic White Dwarf and a hydrogen-rich donor,” <i>The Astrophysical Journal Letters</i>, vol. 990, no. 2. IOP Publishing, 2025."},"file":[{"content_type":"application/pdf","date_created":"2026-02-19T07:24:10Z","date_updated":"2026-02-19T07:24:10Z","file_id":"21329","file_name":"2025_AstrophysicalJournal_Galiullin.pdf","success":1,"creator":"dernst","access_level":"open_access","relation":"main_file","file_size":3772189,"checksum":"f76556d129aa0e9facc85602b0b5b54d"}],"issue":"2","article_number":"L57","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png","short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"arxiv":1,"ddc":["520"],"_id":"21317"}