Journal Article

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

Stephen B. Potter, Encarni Romero-Colmenero, Marissa Kotze, Ewald Zietsman, O. W. Butters, Nikki Pekeur and David A. H. Buckley

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 3, pages 2596-2602
Published in print March 2012 | ISSN: 0035-8711
Published online February 2012 | e-ISSN: 1365-2966 | DOI:
On the spin modulated circular polarization from the intermediate polars NY Lup and IGR J15094–6649

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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.

Keywords: accretion, accretion discs; methods: analytical; techniques: polarimetric; binaries: close; novae, cataclysmic variables; X-rays: stars

Journal Article.  4535 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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