Issue |
A&A
Volume 699, July 2025
|
|
---|---|---|
Article Number | A341 | |
Number of page(s) | 14 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/202555131 | |
Published online | 17 July 2025 |
Strongly polarised radio pulses from a new white-dwarf-hosting long-period transient
1
ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, Dwingeloo 7991 PD, The Netherlands
2
Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands
3
Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
4
The University of Texas at Austin, Department of Astronomy, 2515 Speedway, C1400, Austin, TX 78712, USA
5
Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
6
Leiden Observatory, Leiden University, PO Box 9513, Leiden 2300 RA, The Netherlands
7
Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
⋆ Corresponding author: bloot@astron.nl
Received:
11
April
2025
Accepted:
29
May
2025
Long-period transients (LPTs) are a new and enigmatic class of objects that produce bright pulsations in the radio, with periods far exceeding those seen in rotationally powered pulsars. The proposed progenitors for LPTs are contested, with white dwarfs or magnetars being likely candidates. Here, we present the discovery of ILT J163430+445010, a new LPT detected in a blind search for Stokes V transients in the LOFAR Two-Metre Sky Survey. Unusual for LPTs, J1634+44 shows pulses that are 100% circularly polarised, as well as pulses that are 100% linearly polarised, with the polarisation state changing from pulse to pulse. We detect 19 pulses in total, each with a total polarisation fraction of ∼100% and a pulse duration of at most 10 s. The pulses show a periodicity at 841.24808±0.00015 s, implying a low duty cycle of 0.012. J1634+44 has a marginally detected counterpart in the ultraviolet GALEX MIS survey and the ultraviolet/optical UNIONS survey, suggesting that it contains a white dwarf with an effective temperature between 15 000 K and 33 000 K. We do not detect J1634+44 with a deep J-band exposure with UKIRT at a 3σ AB magnitude limit of 24.7, ruling out a main-sequence star or ultracool dwarf with a spectral type earlier than M7. The pulses from J1634+44 follow a particular pattern, with two pulses being produced every five periods after a waiting time of two or three periods. This pattern could be a result of spin-orbit coupling in a binary system with a 5:2 or 5:3 resonance, where a companion induces beamed radio emission on the white dwarf. The companion is most likely an ultracool dwarf or another white dwarf, making J1634+44 unique among the currently known sample of LPTs.
Key words: white dwarfs / radio continuum: general
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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