Idling magnetic white dwarf in the synchronizing polar BY Cam. The Noah-2 project

Андронов, И. Л.; Antoniuk, K.; Breus, V. V.; Chinarova, L. L.; Han, Wonyong; Jeon, Y. B.; Kim, Yonggi; Колесников, С. В.; Oh, Joon Young; Павленко, Е. П.; Shakhovskoy, N. M.

doi:10.2478/s11534-008-0076-3

Cited by 5 publications

(6 citation statements)

References 41 publications

(103 reference statements)

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“…The brightness minimum at beat phase 0.6 corresponds to orbital phase 0.1, while this minimum occurs at orbital phase 0.4 when the beat phase is 0.9. Similar phase shifting occurs in the observed light curves of BY Cam [6,7,15,16].…”

Section: Synthetic Light Curvessupporting

confidence: 59%

“…During these beat phases, the western hemisphere of the accretor points toward the secondary; the hot spots formed at the foot-points of the accretion stream in the western hemisphere cause an increase in the system's brightness at these beat phases. The observed light curves of BY Cam [6,7,15,16] display very similar behaviour, and also vary by about a factor of two as a function of the spin-orbit beat phase.…”

Section: Synthetic Light Curvesmentioning

confidence: 50%

“…The asynchronous rotation of the white dwarf in BY Cam and the complex structure of its magnetic field result in light curves that evolve as a function of the spin-orbit beat phase [6,7,[14][15][16]. These studies generally support the complex field model of Mason et al [5].…”

Section: Introductionmentioning

confidence: 87%

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Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

2012

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We have performed three-dimensional magnetohydrodynamical calculations of stream accretion in cataclysmic variable stars for which the white dwarf primary possesses a strong, complex magnetic field. These calculations were motivated by observations of polars: cataclysmic variables containing white dwarfs with magnetic fields sufficiently strong to prevent the formation of an accretion disk. In this case, an accretion stream flows from the L 1 point and impacts directly onto one or more spots on the surface of the white dwarf. Observations indicate that the white dwarfs in some binaries possess complex (non-dipolar) magnetic fields. We performed simulations of ten polars, with the only variable being the azimuthal angle of the secondary with respect to the white dwarf. These calculations are also applicable to asynchronous polars, where the spin period of the white dwarf differs by a few percent from the orbital period. Our results are equivalent to calculating the structure of one asynchronous polar at ten different spin-orbit beat phases. Our models have an aligned dipolar plus quadrupolar magnetic field centered on the whitedwarf primary. We find that, with a sufficiently strong quadrupolar component, an accretion spot arises near the magnetic equator for slightly less than half our simulations, while a polar accretion zone is active for most of the remaining simulations. For two configurations, accretion at a dominant polar region and in an equatorial zone occurs simultaneously. Most polar studies assume that the magnetic field is dipolar, especially for single-pole accretors. We demonstrate that, with the orbital parameters and magnetic-field strengths typical of polars, the accretion flow patterns can vary widely in the case of a complex magnetic field. This may make it difficult for many polars to determine observationally whether the field is pure dipolar or is more complex, but there shoulid be indications for some systems. In particular, a complex magnetic field should be suspected if there is an accretion zone near the white dwarf's equator (assumed to be in the orbital plane) or if there are two or more accretion regions that cannot be fitted by dipolar magnetic field. Magnetic-field constraints are expected to be substantially stronger for asynchronous polars, with clearer signs of complex field geometry due to changes in the accretion flow structure as a function of azimuthal angle. These indications become clearer in asynchronous polars because each azimuthal angle corresponds to a different spin-orbit beat phase.

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Section: Synthetic Light Curvessupporting

confidence: 59%

Section: Synthetic Light Curvesmentioning

confidence: 50%

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Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

2012

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“…The idling of the magnetic white dwarf in the asynchronous polar BY Cam was studied during the international observational campaign "Noah-2" 71 .…”

Section: Magnetic Cataclysmic Variablesmentioning

confidence: 99%

Mathematical Modelling of Astrophysical Objects and Processes

Андронов

Breus

Kudashkina

2020

Development of Scientific Schools of Odessa National Maritime University

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“…Extensive spectroscopy was used to derive a precise orbital period (Schwarz et al 2005), yielding P orb = 201.244 min. Even more comprehensive photometric campaigns were able to establish the time evolution of both the dominant photometric signal (Andronov et al 2008;Pavlenko et al 2013;Babina et al 2019) and the proposed spin period of the WD.…”

Section: Introductionmentioning

confidence: 99%

A Magnetic Valve at L1 Revealed in TESS Photometry of the Asynchronous Polar BY Cam

Mason

Monroy²,

Morales

et al. 2022

ApJ

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We present TESS photometry of the asynchronous polar BY Cam, which undergoes a beat cycle between the 199.384 min white dwarf (WD) spin period and the 201.244 min orbital period. This results in changes in the flow of matter onto the WD. The TESS light curve covers 92% of the beat cycle once and 71% of the beat cycle twice. The strongest photometric signal, at 197.560 min, is ascribed to a side-band period. During times of light-curve stability, the photometry modulates at the spin frequency, supporting our WD spin-period identification. Both one-pole and two-pole accretion configurations repeat from one beat cycle to the next with clear and repeatable beat-phase-dependent intensity variations. To explain these, we propose the operation of a magnetic valve at L1. The magnetic valve modulates the mass-transfer rate, as evidenced by a factor of 5 variation in orbital-averaged intensity, over the course of the beat cycle in a repeatable manner. The accretion stream threading distance from the WD is also modulated at the beat period, because of the variation of the WD magnetic field with respect to the stream and because of changes in the mass transfer rate due to the operation of the magnetic valve. Changes in the threading distance result in significant shifts in the position of accreting spots around the beat cycle. As a consequence, only the faintest photometric minima allow for an accurate ephemeris determination. Three regions on the WD appear to receive most of the accretion flow, suggestive of a complex WD magnetic field.

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Idling magnetic white dwarf in the synchronizing polar BY Cam. The Noah-2 project

Cited by 5 publications

References 41 publications

Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

Mathematical Modelling of Astrophysical Objects and Processes

A Magnetic Valve at L1 Revealed in TESS Photometry of the Asynchronous Polar BY Cam

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