---
OA_place: publisher
OA_type: gold
_id: '19840'
abstract:
- lang: eng
  text: "We report the discovery of two new magnetic cataclysmic variables with brown
    dwarf companions and long orbital periods (P_{\\rm orb}=95\\pm1 and 104\\pm2 min).
    This discovery increases the sample of candidate magnetic period bouncers with
    confirmed sub-stellar donors from four to six. We also find their X-ray luminosity
    from archival XMM–Newton observations to be in the range L_{\\rm X}\\approx10^{28}-10^{29}
    \\mathrm{erg\\,s^{-1}} in the 0.25–10 keV band. This low luminosity is comparable
    with the other candidates, and at least an order of magnitude lower than the X-ray
    luminosities typically measured in cataclysmic variables. The X-ray fluxes imply
    mass transfer rates that are much lower than predicted by evolutionary models,
    even if some of the discrepancy is due to the accretion energy being emitted in
    other bands, such as via cyclotron emission at infrared wavelengths. Although
    it is possible that some or all of these systems formed directly as binaries containing
    a brown dwarf, it is likely that the donor used to be a low-mass star and that
    the systems followed the evolutionary track for cataclysmic variables, evolving
    past the period bounce. The donor in long period systems is expected to be a low-mass,
    cold brown dwarf. This hypothesis is supported by near-infrared photometric observations
    that constrain the donors in the two systems to be brown dwarfs cooler than \r\n1100 K
    (spectral types T5 or later), most likely losing mass via Roche Lobe overflow
    or winds. The serendipitous discovery of two magnetic period bouncers in the small
    footprint of the XMM–Newton catalogue implies a large space density of these type
    of systems, possibly compatible with the prediction of 40–70 per cent of magnetic
    cataclysmic variables to be period bouncers."
acknowledgement: "We thank Matthias Schreiber for his insightful comments. Support
  for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51527.001-A
  awarded by the Space Telescope Science Institute, which is operated by the Association
  of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.
  Support for this work was provided by NASA through Chandra Award Number GO4-25014X
  issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical
  Observatory for and on behalf of NASA under contract NAS8-03060. IC was also supported
  by NASA through grants from the Space Telescope Science Institute, under NASA contracts
  NASA.22K1813, NAS5-26555, and NAS5-03127. This project has received funding from
  the European Research Council (ERC) under the European Union’s Horizon 2020 research
  and innovation programme (grant agreement no. 101020057). This research was supported
  in part by grant NSF PHY-1748958 to the Kavli Institute for Theoretical Physics
  (KITP). PJW acknowledges support from the UK Science and Technology Facilities Council
  (STFC) through consolidated grants ST/T000406/1 and ST/X001121/1. RA was supported
  by NASA through the NASA Hubble Fellowship grant #HST-HF2-51499.001-A awarded by
  the Space Telescope Science Institute, which is operated by the Association of Universities
  for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.\r\n\r\nThis
  research has made use of data obtained from the 4XMM XMM–Newton Serendipitous Source
  Catalogue compiled by the 10 institutes of the XMM–Newton Survey Science Centre
  selected by ESA. 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. The Pan-STARRS1 Surveys
  (PS1) and the PS1 public science archive have been made possible through contributions
  by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project
  Office, the Max-Planck Society and its participating institutes, the Max Planck
  Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial
  Physics, Garching, The Johns Hopkins University, Durham University, the University
  of Edinburgh, the Queen’s University Belfast, the Harvard–Smithsonian Center for
  Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated,
  the National Central University of Taiwan, the Space Telescope Science Institute,
  the National Aeronautics and Space Administration under grant no. NNX08AR22G issued
  through the Planetary Science Division of the NASA Science Mission Directorate,
  the National Science Foundation grant no. AST–1238877, the University of Maryland,
  Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon
  and Betty Moore Foundation. This work is based in part on data obtained as part
  of the UKIDSS. This research made use of hips2fits,4 a service provided by CDS,
  and of astropy (Astropy Collaboration 2013)."
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Tim
  full_name: Cunningham, Tim
  last_name: Cunningham
- first_name: Ilaria
  full_name: Caiazzo, Ilaria
  id: 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d
  last_name: Caiazzo
  orcid: 0000-0002-4770-5388
- first_name: Gracjan
  full_name: Sienkiewicz, Gracjan
  last_name: Sienkiewicz
- first_name: Peter J.
  full_name: Wheatley, Peter J.
  last_name: Wheatley
- first_name: Boris T.
  full_name: Gänsicke, Boris T.
  last_name: Gänsicke
- first_name: Kareem
  full_name: El-Badry, Kareem
  last_name: El-Badry
- first_name: Riccardo
  full_name: Arcodia, Riccardo
  last_name: Arcodia
- first_name: David
  full_name: Charbonneau, David
  last_name: Charbonneau
- first_name: Liam
  full_name: Connor, Liam
  last_name: Connor
- first_name: Kishalay
  full_name: De, Kishalay
  last_name: De
- first_name: Pasi
  full_name: Hakala, Pasi
  last_name: Hakala
- first_name: Scott J.
  full_name: Kenyon, Scott J.
  last_name: Kenyon
- first_name: Sumit Kumar
  full_name: Maheshwari, Sumit Kumar
  last_name: Maheshwari
- first_name: Antonio C.
  full_name: Rodriguez, Antonio C.
  last_name: Rodriguez
- first_name: Jan
  full_name: Van Roestel, Jan
  last_name: Van Roestel
- first_name: Pier Emmanuel
  full_name: Tremblay, Pier Emmanuel
  last_name: Tremblay
citation:
  ama: Cunningham T, Caiazzo I, Sienkiewicz G, et al. Discovery of two new polars
    evolved past the period bounce. <i>Monthly Notices of the Royal Astronomical Society</i>.
    2025;540(1):633-649. doi:<a href="https://doi.org/10.1093/mnras/staf561">10.1093/mnras/staf561</a>
  apa: Cunningham, T., Caiazzo, I., Sienkiewicz, G., Wheatley, P. J., Gänsicke, B.
    T., El-Badry, K., … Tremblay, P. E. (2025). Discovery of two new polars evolved
    past the period bounce. <i>Monthly Notices of the Royal Astronomical Society</i>.
    Oxford University Press. <a href="https://doi.org/10.1093/mnras/staf561">https://doi.org/10.1093/mnras/staf561</a>
  chicago: Cunningham, Tim, Ilaria Caiazzo, Gracjan Sienkiewicz, Peter J. Wheatley,
    Boris T. Gänsicke, Kareem El-Badry, Riccardo Arcodia, et al. “Discovery of Two
    New Polars Evolved Past the Period Bounce.” <i>Monthly Notices of the Royal Astronomical
    Society</i>. Oxford University Press, 2025. <a href="https://doi.org/10.1093/mnras/staf561">https://doi.org/10.1093/mnras/staf561</a>.
  ieee: T. Cunningham <i>et al.</i>, “Discovery of two new polars evolved past the
    period bounce,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol.
    540, no. 1. Oxford University Press, pp. 633–649, 2025.
  ista: Cunningham T, Caiazzo I, Sienkiewicz G, Wheatley PJ, Gänsicke BT, El-Badry
    K, Arcodia R, Charbonneau D, Connor L, De K, Hakala P, Kenyon SJ, Maheshwari SK,
    Rodriguez AC, Van Roestel J, Tremblay PE. 2025. Discovery of two new polars evolved
    past the period bounce. Monthly Notices of the Royal Astronomical Society. 540(1),
    633–649.
  mla: Cunningham, Tim, et al. “Discovery of Two New Polars Evolved Past the Period
    Bounce.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 540, no.
    1, Oxford University Press, 2025, pp. 633–49, doi:<a href="https://doi.org/10.1093/mnras/staf561">10.1093/mnras/staf561</a>.
  short: T. Cunningham, I. Caiazzo, G. Sienkiewicz, P.J. Wheatley, B.T. Gänsicke,
    K. El-Badry, R. Arcodia, D. Charbonneau, L. Connor, K. De, P. Hakala, S.J. Kenyon,
    S.K. Maheshwari, A.C. Rodriguez, J. Van Roestel, P.E. Tremblay, Monthly Notices
    of the Royal Astronomical Society 540 (2025) 633–649.
date_created: 2025-06-15T22:01:29Z
date_published: 2025-06-01T00:00:00Z
date_updated: 2025-09-30T12:50:33Z
day: '01'
ddc:
- '520'
department:
- _id: IlCa
doi: 10.1093/mnras/staf561
external_id:
  arxiv:
  - '2503.12675'
  isi:
  - '001493143700001'
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fulldoi: https://doi.org/10.1093/mnras/staf561
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language:
- iso: eng
month: '06'
oa: 1
oa_version: Published Version
page: 633-649
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
  eissn:
  - 1365-2966
  issn:
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publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: Discovery of two new polars evolved past the period bounce
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  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
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type: journal_article
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