Time-resolved spectroscopy of the polar EU cancri in the open cluster messier 67

Kurtis A. Williams, Steve B. Howell, James Liebert, Paul S. Smith, Andrea Bellini, Kate H.R. Rubin, Michael Bolte

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We present time-resolved spectroscopic and polarimetric observations of the AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster Messier 67; new proper motion measurements indicate that EU Cnc is indeed a member of the star cluster, and this system therefore is useful to constrain the formation and evolution of magnetic cataclysmic variables. The spectra exhibit two-component emission features with independent radial velocity variations as well as time-variable cyclotron emission indicating a magnetic field strength of 41 MG. The period of the radial velocity and cyclotron hump variations are consistent with the previously known photometric period, and the spectroscopic flux variations are consistent in amplitude with previous photometric amplitude measurements. The secondary star is also detected in the spectrum. We also present polarimetric imaging measurements of EU Cnc that show a clear detection of polarization, and the degree of polarization drops below our detection threshold at phases when the cyclotron emission features are fading or not evident. The combined data are all consistent with the interpretation that EU Cnc is a low-state polar in the cluster Messier 67. The mass function of the system gives an estimate of the accretor mass of M WD ≥ 0.68 M· with M WD ≈ 0.83 M· for an average inclination. We are thus able to place a lower limit on the progenitor mass of the accreting white dwarf of ≥1.43 M·.

Original languageEnglish (US)
Article number129
JournalAstronomical Journal
Issue number5
StatePublished - May 2013


  • accretion, accretion disks
  • novae, cataclysmic variables
  • open clusters and associations: individual (Messier 67)
  • stars: individual (EU Cnc)
  • white dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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