A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries

Kára, Jan; Rivera Sandoval, Liliana; Mendoza, Wendy; Maccarone, Thomas; Pichardo Marcano, Manuel; Salazar Manzano, Luis E.; Oelkers, Ryan J.; van Roestel, Joannes C

A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries

Kára J, Rivera Sandoval L, Mendoza W, Maccarone T, Pichardo Marcano M, Salazar Manzano LE, Oelkers RJ, van Roestel JC. 2026. A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries. Publications of the Astronomical Society of Australia. 43, e052.

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DOI

10.1017/pasa.2026.10184

Journal Article | Published | English

Scopus indexed

Author

Kára, Jan; Rivera Sandoval, Liliana; Mendoza, Wendy; Maccarone, Thomas; Pichardo Marcano, Manuel; Salazar Manzano, Luis E.; Oelkers, Ryan J.; van Roestel, Joannes C^ISTA

Department

Caiazzo Group

Abstract

AM CVn stars are ultra-compact semi-detached binaries consisting of a white dwarf primary and a hydrogen-depleted secondary. In this paper, we present spectroscopic and photometric results of 15 transient sources pre-classified as AM CVn candidates. Our analysis confirms 9 systems of the type AM CVn, 3 hydrogen-rich cataclysmic variables (accreting white dwarfs with near-main-sequence stars for donors), and 3 systems that could be evolved cataclysmic variables. Eight of the AM CVn stars are analysed spectroscopically for the first time, which increases the number of spectroscopically confirmed AM CVns by about 10%. TESS data revealed the orbital period of the AM CVn star ASASSN-20pv to be Porb =27.282 min, which helps to constrain the possible values of its mass ratio. TESS also helped to determine the superhump periods of one AM CVn star (ASASSN-19ct, Psh =30.94 min) and two cataclysmic variables we classify as WZ Sge stars (Psh =90.77 min for ZTF18aaaasnn and Psh =91.6min for ASASSN-15na).We identified very different abundances in the spectra of theAM CVns binaries ASASSN-15kf and ASASSN-20pv (both Porb ∼27.5min), suggesting different type of donors. Six of the studied AMCVns are X-ray sources, which helped to determine their mass accretion rates. Photometry shows that the duration of all the superoutbursts detected in the AM CVns is consistent with expectations from the disc instability model. Finally, we provide refined criteria for the identification of new systems using all-sky surveys such as LSST.

Publishing Year

2026

Date Published

2026-03-27

Journal Title

Publications of the Astronomical Society of Australia

Publisher

Cambridge University Press

Acknowledgement

We are grateful to the anonymous referee for providing us with useful comments and suggestions that improved our manuscript. JK and LRS acknowledge support from NASA grants NNH22ZDA001N-6152 and 80NSSC24K0638. MPM is partially supported by the Swiss National Science Foundation IZSTZ0_216537 and by UNAM PAPIIT-IG101224. Based on observations obtained at the international Gemini Observatory, a program of NSF NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the U.S. National Science Foundation on behalf of the Gemini Observatory partnership: the U.S. National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). The Gemini data were obtained from programs GN-2023B-Q-310 and GS-2024A-Q-311 (PI: Rivera Sandoval) and processed using DRAGONS (Data Reduction for Astronomy from Gemini Observatory North and South) The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. The National Geographic Society – Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. The Oschin Schmidt Telescope is operated by the California Institute of Technology and Palomar Observatory. The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council), until 1988 June, and thereafter by the Anglo-Australian Observatory. The blue plates of the southern Sky Atlas and its Equatorial Extension (together known as the SERC-J), as well as the Equatorial Red (ER), and the Second Epoch [red] Survey (SES) were all taken with the UK Schmidt. Supplemental funding for sky-survey work at the ST ScI is provided by the European Southern Observatory. 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 Oskar Klein Center at Stockholm University, the University of Maryland, University of California, Berkeley, the University of Wisconsin at Milwaukee, University of Warwick, Ruhr University, Cornell University, Northwestern University, and Drexel University. Operations are conducted by COO, IPAC, and UW. This work has used 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. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Science Mission Directorate. Some of the data presented in this paper were obtained from the B. Mikulski Archive for Space Telescopes (MAST). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has made use of ‘Aladin sky atlas’ developed at CDS, Strasbourg Observatory, France. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France.

Volume

Article Number

e052

ISSN

1323-3580

eISSN

1448-6083

IST-REx-ID

21842

Cite this

Kára J, Rivera Sandoval L, Mendoza W, et al. A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries. Publications of the Astronomical Society of Australia. 2026;43. doi:10.1017/pasa.2026.10184

Kára, J., Rivera Sandoval, L., Mendoza, W., Maccarone, T., Pichardo Marcano, M., Salazar Manzano, L. E., … van Roestel, J. C. (2026). A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries. Publications of the Astronomical Society of Australia. Cambridge University Press. https://doi.org/10.1017/pasa.2026.10184

Kára, Jan, Liliana Rivera Sandoval, Wendy Mendoza, Thomas Maccarone, Manuel Pichardo Marcano, Luis E. Salazar Manzano, Ryan J. Oelkers, and Joannes C van Roestel. “A Study of Transients from Ground-Based Surveys Reveals New Ultra-Compact Accreting White Dwarf Binaries.” Publications of the Astronomical Society of Australia. Cambridge University Press, 2026. https://doi.org/10.1017/pasa.2026.10184.

J. Kára et al., “A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries,” Publications of the Astronomical Society of Australia, vol. 43. Cambridge University Press, 2026.

Kára, Jan, et al. “A Study of Transients from Ground-Based Surveys Reveals New Ultra-Compact Accreting White Dwarf Binaries.” Publications of the Astronomical Society of Australia, vol. 43, e052, Cambridge University Press, 2026, doi:10.1017/pasa.2026.10184.

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