Showing papers by "Jean-Pierre Macquart published in 2000"
TL;DR: In this article, strong (> 1%) circular polarization in the intraday-variable radio source PKS1519-273 was found, implying that the variable component of the source is -3.8 ± 0.4% circularly polarized at 4.8 GHz.
Abstract: We find strong (> 1%) circular polarization in the intraday-variable radio source PKS1519-273. The source exhibits ~ 12 hourly variability in all four Stokes parameters at 4.8 and8.6 GHz, and longer timescale variability at 2.5 and 1.4 GHz. The characteristics and frequencydependence of the variability suggest that it is due to interstellar scintillation. VSOP limits on thedistance to the scattering screen constrain the brightness temperature to T B > 5 x 1013 K. Thefluctuations in total intensity are well-correlated with those in circular polarization, implying that thevariable component of the source is -3.8 ± 0.4% circularly polarized at 4.8 GHz. The origin of thecircular polarization is unclear.
74 citations
TL;DR: In this article, the authors present a physical interpretation for the generation of circular polarization resulting from the propagation of radiation through a magnetized plasma in terms of a rotation measure gradient, or "Faraday wedges".
Abstract: We present a physical interpretation for the generation of circular polarization resulting from the propagation of radiation through a magnetized plasma in terms of a rotation measure gradient, or "Faraday wedges." Criteria for the observability of scintillation-induced circular polarization are identified. Application of the theory to the circular polarization in pulsars and compact extragalactic sources is discussed.
55 citations
TL;DR: A theory is presented for the development of circular polarization as radio waves propagate through the turbulent, birefringent interstellar medium, and it is shown that unpolarized incident radiation develops a nonzero variance in circular polarization.
Abstract: A theory is presented for the development of circular polarization as radio waves propagate through the turbulent, birefringent interstellar medium. The fourth order moments of the wave field are calculated, and it is shown that unpolarized incident radiation develops a nonzero variance in circular polarization. A magnetized turbulent medium causes the Stokes parameters to scintillate in a nonidentical manner. A specific model for this effect is developed for the case of density fluctuations in a uniform magnetic field.
18 citations
01 Jan 2000
TL;DR: In this paper, the authors measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz and obtained a decorrelation bandwidth of v d = 244±4 Hz and diffractive decorrelation timescale of t diff = 3.3±0.3s.
Abstract: We have measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz. We obtain a decorrelation bandwidth of v d = 244±4 Hz and diffractive decorrelation timescale of t diff = 3.3±0.3s. Our measurement of the modulation indices m = 0.87±0.003±0.05 and m = 0.93±0.03±0.05 (one For each polarization stream), are at variance with the modulation index of the Vela pulsar obtained at 2.3 GHz by Gwinn et al. (F997) if the deviation from a modulation index of unity is ascribed to a source size effect.
3 citations
Posted Content•
TL;DR: In this article, the authors measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz and obtained a decorrelation bandwidth of $nu_d = 244 \pm 4$ Hz and diffractive decorrelation timescale of 3.3$ s.
Abstract: We have measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz. We obtain a decorrelation bandwidth of $
u_d = 244 \pm 4$ Hz and diffractive decorrelation timescale of $t_{\rm diff} = 3.3\pm 0.3$ s. Our measurement of the modulation indices $m=0.87\pm 0.003\pm 0.05$ and $m=0.93\pm 0.03 \pm 0.05$ (one for each polarization stream), are at variance with the modulation index of the Vela pulsar obtained at 2.3 GHz by Gwinn et al. (1997) {\it if} the deviation from a modulation index of unity is ascribed to a source size effect.
1 citations
TL;DR: In this article, the authors report strong variability in the circular and linear polarization of the intraday variable source PKS 1519-273 at frequencies between 1.4 and 8.6 GHz and argue that the variability is due to interstellar scintillation of a highly compact (15-35 \mu as) component of the source with -3.8 ± 0.4% circular polarization at 4.8 GHz.
Abstract: We report strong variability in the circular and linear polarization of the intraday variable source PKS 1519-273. The circular polarization varies on a timescale of hours to days at frequencies between 1.4 and 8.6 GHz, and is strongly correlated with variations in the total intensity at 4.8 and 8.6 GHz. We argue that the variability is due to interstellar scintillation of a highly compact (15-35 \mu as) component of the source with -3.8\pm 0.4% circular polarization at 4.8 GHz. We find that no simple model for the circular polarization can account for both the high magnitude and the frequency dependence in PKS 1519-273 at centimeter wavelengths.