Open AccessDiscovery of the high‐field polar RX J1724.0+4114
Author(s) -
Greiner Jochen,
Schwarz Robert,
Wenzel Wolfgang
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01469.x
Subject(s) - physics , balmer series , astrophysics , rosat , polar , sky , magnetic field , spectroscopy , astronomy , emission spectrum , spectral line , galaxy , quantum mechanics
We report the discovery of a new AM Herculis binary (polar) as the optical counterpart of the soft X‐ray source RX J1724.0+4114 detected during the ROSAT all‐sky survey. The magnetic nature of this V ∼ 17 mag object is confirmed by low‐resolution spectroscopy showing strong Balmer and He II emission lines superimposed on a blue continuum, which is deeply modulated by cyclotron humps. The inferred magnetic field strength is 50 ± 4 MG (or possibly even ≈ 70 MG). Photometric observations spanning ∼ 3 yr reveal a period of 119.9 min, directly below the period gap. The morphology of the optical and X‐ray light curves, which do not show eclipses by the secondary star, suggests a self‐eclipsing geometry. We derive a lower limit on the distance of d ≳ 250 pc.