Year: 2026
Type: article
Abstract: Short-period binaries containing white dwarfs or hot subdwarfs are among the strongest Galactic sources for millihertz gravitational-wave (GW) observatories, but the confirmed sample remains small. Combining Gaia DR3 astrometry and photometry with ZTF DR23 light curves—through a Gaia selection calibrated against known systems, ZTF period searches, and machine learning morphology ranking—we assemble a catalog of 147 short-period (10.34–106.46 minutes) blue compact-binary candidates, 111 of them without a previous compact-binary classification. DESI DR1, GALEX, and AllWISE data reveal an intrinsically heterogeneous sample: on the Gaia color–magnitude diagram it comprises 52 white-dwarf-locus, 69 hot-subdwarf-region, and 26 intermediate sources, and among the 26 members with DESI spectra only about one-third lie on the white-dwarf cooling sequence, the rest being more luminous blue stars whose low-resolution spectra resemble white dwarfs. We identify a prioritized set of new short-period white-dwarf-locus candidates for time-resolved follow-up, including 10 with periods below 40 minutes and none with an existing radial-velocity series. Under fiducial binary assumptions, 17 newly identified white-dwarf-locus candidates would exceed the adopted LISA threshold, led by a 37 pc white dwarf; no candidate has a measured chirp mass, and with the signal-to-noise ratio scaling as M c 5 / 3 the count is 9 for M c = 0.15 M ⊙ , 17 for the adopted 0.3 M ⊙ , and 21 for 0.6 M ⊙ , in each case assuming the modulation is orbital. We show, however, that for the compact majority of the white-dwarf-locus sample the observed modulation amplitudes exceed any possible ellipsoidal signal by 3 to 5 orders of magnitude, so a rotating magnetic or chemically inhomogeneous single white dwarf is a competing interpretation that ZTF photometry alone cannot exclude; the catalog contains at least one confirmed case. We release the full 147-source catalog with periods, Gaia and spectroscopic classifications, harmonic and ellipsoidal diagnostics, and supplementary tables of fiducial GW estimates and ultraviolet–infrared photometry.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, U.S. Department of Energy, Gordon and Betty Moore Foundation, California Institute of Technology, Northwestern University, Drexel University, University of Warwick, National Natural Science Foundation of China, Ministerio de Ciencia e Innovación, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Stockholms Universitet, Office of Science, Science and Technology Facilities Council, National Key Research and Development Program of China, Division of Astronomical Sciences, Lawrence Berkeley National Laboratory
Awards: G1044631029, G1079818582, G1143651532, G1286236842, G1443815167, G1813527838, G1863003419, Exploring & Exploiting the Dynamic Optical Sky, G2994122026, G3083819904, G3114243037, ZWICKY TRANSIENT FACILITY, G386731499, G3880645893, G419881185, G42916606, G4501827968, G4911480515, G498139845, G6652958823, G6876926712, G704498496, Management and Operations of the National Optical Astronomy Observatory, G7350863329, G7354628648, G7376190050, G7392070127, G969889393
OpenAlex ID: W7203929877