A Possible Mechanism for the Radio Emission of Polars

Kurbatov, E. P.; Жилкин, А. Г.; Bisikalo, D. V.

doi:10.1134/s1063772919010050

Cited by 7 publications

(3 citation statements)

References 25 publications

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“…Numerous magnetic CVs have been detected in the radio, though a number of magnetic CVs show circular polarization indicative of electron-cyclotron maser emission (Abada-Simon et al 1993;Chanmugam 1987;Barrett et al 2017). This maser emission has been suggested to be produced near the companion star (Mason & Gray 2007), or to be produced near the WD (Kurbatov et al 2019). Radio luminosities for all CVs tend to be rather low (10s to 100s of µJy at 300 pc; e.g.…”

Section: Radio Sources In Globular Clustersmentioning

confidence: 99%

The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

Zhao

Heinke

Tudor

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Using a 16.2 hr radio observation by the Australia Telescope Compact Array (ATCA) and archival Chandra data, we found > 5σ radio counterparts to 4 known and 3 new X-ray sources within the half-light radius (r h ) of the Galactic globular cluster NGC 6397. The previously suggested millisecond pulsar (MSP) candidate, U18, is a steep-spectrum (S ν ∝ ν α ; α = −2.0 +0.4 −0.5 ) radio source with a 5.5 GHz flux density of 54.7 ± 4.3 µJy. We argue that U18 is most likely a "hidden" MSP that is continuously hidden by plasma shocked at the collision betwen the winds from the pulsar and companion star. The nondetection of radio pulsations so far is probably the result of enhanced scattering in this shocked wind. On the other hand, we observed the 5.5 GHz flux of the known MSP PSR J1740-5340 (U12) to decrease by a factor of >2.8 during epochs of 1.4 GHz eclipse, indicating that the radio flux is absorbed in its shocked wind. If U18 is indeed a pulsar whose pulsations are scattered, we note the contrast with U12's flux decrease in eclipse, which argues for two different eclipse mechanisms at the same radio frequency. In addition to U12 and U18, we also found radio associations for 5 other Chandra X-ray sources, four of which are likely background galaxies. The last, U97, which shows strong Hα variability, is mysterious; it may be either a quiescent black hole low-mass X-ray binary, or something more unusual.

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Section: Radio Sources In Globular Clustersmentioning

confidence: 99%

The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

Zhao

Heinke

Tudor

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…This model is based on the equations system of modified magnetic hydrodynamics, which describes astrophysical flows under conditions of a strong external magnetic field. We have successfully applied this approach to modeling the flow structure for both polars and intermediate polars [5,[16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Section: Numerical Modelmentioning

confidence: 99%

Hot Spots Drift in Synchronous and Asynchronous Polars: Results of Three-Dimensional Numerical Simulation

2021

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In this paper, the characteristics of hot spots on an accretor surface are investigated for two types of polars: the eclipsing synchronous polar V808 Aur and the non-eclipsing asynchronous polar CD Ind in configuration of an offset and non-offset magnetic dipole. The drift of hot spots is analyzed based on the results of numerical calculations and maps of the temperature distribution over the accretor surface. It is shown that a noticeable displacement of the spots is determined by the ratio of ballistic and magnetic parts of the jet trajectory. In the synchronous polar, the dominant influence on the drift of hot spots is exerted by variations in the mass transfer rate, which entail a change in the ballistic part of the trajectory. It was found that when the mass transfer rate changes within the range of 10−10M⊙/year to 10−7M⊙/year, the displacement of the hot spot in latitude and longitude can reach 30∘. In the asynchronous polar, a change in the position of hot spots is mainly defined by the properties of the white dwarf magnetosphere, and the displacement of hot spots in latitude and longitude can reach 20∘.

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“…They found V834 Cen to be variable on time-scales as short as one minute and reaching peak flux densities of 35 mJy. The emission from V834 Cen was attributed to an electron-cyclotron maser, although the maser emission suggestions in polars has recently been challenged by Kurbatov et al (2019). Instead they suggest the radio emission arises from Alfvenic turbulence.…”

Section: Introductionmentioning

confidence: 99%

A spectroscopic, photometric, polarimetric, and radio study of the eclipsing polar UZ Fornacis: the first simultaneous SALT and MeerKAT observations

Khangale

Potter

Woudt

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present phase-resolved spectroscopy, photometry and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at ∼4500Å, 6000 A and 7700Å, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of ∼57 MG. We also present phaseresolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source which has a peak flux density of 30.7 ± 5.4 µJy/beam at 1.28 GHz at the position of UZ For.

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A Possible Mechanism for the Radio Emission of Polars

Cited by 7 publications

References 25 publications

The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

Hot Spots Drift in Synchronous and Asynchronous Polars: Results of Three-Dimensional Numerical Simulation

A spectroscopic, photometric, polarimetric, and radio study of the eclipsing polar UZ Fornacis: the first simultaneous SALT and MeerKAT observations

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