Get access

On the spin modulated circular polarization from the intermediate polars NY Lup and IGR J15094–6649

Authors

  • Stephen B. Potter,

    Corresponding author
    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    Search for more papers by this author
  • Encarni Romero-Colmenero,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
    Search for more papers by this author
  • Marissa Kotze,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Astronomy Department, Astrophysics, Cosmology and Gravity Centre (ACGC), University of Cape Town, Rondebosch 7701, South Africa
    Search for more papers by this author
  • Ewald Zietsman,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Department of Mathematical Sciences, The University of South Africa, PO Box 392, UNISA 0003, South Africa
    Search for more papers by this author
  • O. W. Butters,

    1. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH
    2. Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA
    Search for more papers by this author
  • Nikki Pekeur,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Centre for Space Research, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa
    Search for more papers by this author
  • David A. H. Buckley

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
    Search for more papers by this author

E-mail: sbp@saao.ac.za

ABSTRACT

We report on high-time-resolution, high-signal-to-noise ratio (S/N), photopolarimetry of the intermediate polars NY Lup and IGR J15094–6649. Our observations confirm the detection and colour dependence of circular polarization from NY Lup and additionally show a clear white dwarf, spin modulated signal. From our new high-S/N photometry, we have unambiguously detected wavelength-dependent spin and beat periods and harmonics thereof. IGR J15094–6649 is also discovered to have a particularly strong spin modulated circularly polarized signal. It appears double peaked through the I filter and single peaked through the B filter, consistent with cyclotron emission from a white dwarf with a relatively strong magnetic field.

We discuss the implied accretion geometries in these two systems and any bearing this may have on the possible relationship with the connection between polars and soft X-ray-emitting intermediate polars. The relatively strong magnetic fields are also suggestive of them being polar progenitors.

Ancillary