One-year modulation in the flux density time series of low frequency variables

Details One-year modulation in the flux density time series of low frequency variables One-year modulation in the flux density time series of low frequency variables

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...287..390b&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 287, no. 2, p. 390-402

Astronomy and Astrophysics

Astrophysics

22

Extragalactic Radio Sources, Flux Density, Modulation, Scintillation, Time Series Analysis, Variability, Astronomical Models, Earth Motion, Monte Carlo Method, Simulation, Solar Orbits, Statistical Analysis

Scientific paper

Low frequency variability (LFV) of extragalactic radio sources is commonly interpreted in terms of refractive interstellar scintillation. In order to study the effect of the Earth orbital motion through the scintillation pattern we have analyzed 408 MHz variability data on 43 sources in a search for statistically significant one year periodicity which could be attributed to such a motion. This analysis has been carried out by calculating an average flux density structure for all sources, as well as for subgroups based on galactic latitude, galactic longitude, ecliptic latitude. In all cases we find a clear characteristic time scale of about 0.5 years corresponding to a one year modulation in the time series. The statistical significance of this result is confirmed by Monte Carlo simulations of variable sources and calibrators. This result is also consistent with numerical simulations of both thin and thick screen scattering models based on the refractive interstellar scintillation theory. A significant constraint on the propagation velocity of the turbulent irregularities has been obtained (Virr less than 10 km/s), suggesting that the motion between the Earth and the scattering pattern is, on average, mainly determined by the motion of the Earth-Sun system with respect to the Local Standard of Rest and the Earth orbital motion around the Sun.

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