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Context.Accreting ultracompact white dwarf binaries contain a white dwarf that is accreting from a degenerate object. They have orbital periods shorter than 65 min. Aims.We report the discovery and the orbital period of four new eclipsing accreting ultracompact white dwarf binaries found using the Zwicky Transient Facility (ZTF) and discuss their photometric properties. Methods.We searched through a list of 4171 dwarf novae compiled using the ZTF and used the box least square method to search for periodic signals in the data. Results.We found four eclipsing accreting ultracompact binaries with orbital periods between 25.9 and 56 min. One had previously been published as an AM Canum Venaticorum (AM CVn), and the other three systems are new discoveries. The two shorter-period systems are likely also AM CVn systems, while the longest-period system, with a period of 56 min, showed multiple super-outbursts over two years, which is more consistent with it being a helium CV.
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This content will become publicly available on April 24, 2027
No period change in two long-period AM CVn binaries
ABSTRACT Ultracompact binary systems, consisting of two compact objects in an orbit $$\lesssim 0.5 {\rm R}_\odot$$, should exhibit measurable rates of orbital period change ($$\dot{P} \ne 0$$) due to the emission of gravitational waves (GWs). Measurements of $$\dot{P}$$ have so far been limited to the shortest-period ultracompact binaries ($$\lesssim 20$$ min). Among the AM CVn-type subclass, several works have proposed the presence of extra angular momentum loss beyond GW emission, with magnetic braking being a widely discussed mechanism. If present, this magnetic braking would dominate the angular momentum loss of AM CVn-type binaries with orbital periods $$\gtrsim 30$$ min. In this work, we present a long-term eclipse timing study of two AM CVn-type binaries, YZ LMi and Gaia14aae, with respective orbital periods of 28.3 min and 49.7 min and continuous observations since 2006 and 2015. Both systems show $$\dot{P}$$ consistent with zero within $$2\sigma$$. Their $$3\sigma$$ upper limits are $$1.1 \times 10^{-13}\, {\rm s \, s}^{-1}$$ and $$9.7 \times 10^{-14}\, {\rm s \, s}^{-1}$$, respectively. These non-detections are most simply explained by a scenario in which secular angular momentum loss is not substantially stronger than GW emission at all orbital periods, but is combined with deviations from the secular $$\dot{P}$$ whose time-scales span decades but whose amplitude is $$\lesssim 10^{-13}\, {\rm s \, s}^{-1}$$. Our non-detections of $$\dot{P}$$ represent a limit on the strength of any enhanced angular momentum loss beyond pure GW emission.
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- Award ID(s):
- 2508429
- PAR ID:
- 10688993
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 548
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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