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V405 Aurigae: A High Magnetic Field Intermediate Polar

Authors :
T. Vornanen
Vilppu Piirola
G. V. Coyne
Andrei Berdyugin
Source :
The Astrophysical Journal. 684:558-568
Publication Year :
2008
Publisher :
American Astronomical Society, 2008.

Abstract

Our simultaneous multicolor (UBVRI) circular polarimetry has revealed nearly sinusoidal variation over the WD spin cycle, and almost symmetric positive and negative polarization excursions. Maximum amplitudes are observed in the B and V bands (+-3 %). This is the first time that polarization peaking in the blue has been discovered in an IP, and suggests that V405 Aur is the highest magnetic field IP found so far. The polarized flux spectrum is similar to those found in polars with magnetic fields in the range B ~ 25-50 MG. Our low resolution circular spectropolarimetry has given evidence of transient features which can be fitted by cyclotron harmonics n = 6, 7, and 8, at a field of B = 31.5 +- 0.8 MG, consistent with the broad-band polarized flux spectrum. Timings of the circular polarization zero crossovers put strict upper limits on WD spin period changes and indicate that the WD in V405 Aur is currently accreting closely at the spin equilibrium rate, with very long synchronization timescales, T_s > 10^9 yr. For the observed spin to orbital period ratio, P_{spin}/P_{orb} = 0.0365, and P_{orb} ~ 4.15 hr, existing numerical accretion models predict spin equilibrium condition with B ~ 30 MG if the mass ratio of the binary components is q_1 ~ 0.4. The high magnetic field makes V405 Aur a likely candidate as a progenitor of a polar.<br />To appear in The Astrophysical Journal, September 1 Issue (2008), 9 pages, 10 figures

Details

ISSN :
15384357 and 0004637X
Volume :
684
Database :
OpenAIRE
Journal :
The Astrophysical Journal
Accession number :
edsair.doi.dedup.....e53e7b5420b2fd0d56276bef1308e32b
Full Text :
https://doi.org/10.1086/590144