Accession Number : ADA136205

Title :   Bright, Rapid, Highly Polarized Radio Spikes from the M Dwarf and Leo.

Descriptive Note : Interim rept.,


Personal Author(s) : Lang,K R ; Bookbinder,J ; Golub,L

PDF Url : ADA136205

Report Date : May 1983

Pagination or Media Count : 15

Abstract : We have observed a radio burst from the main sequence (dM4.5e) star AD Leo at 1400 MHz from 0536 to 0556 UT on 1983 February 1 at the Arecibo Observatory. A rapid sequence of highly polarized spikes was observed during the gradual rise of a longer lasting, unpolarized event. The maximum flux density of the spikes was S(max) = 130 mJy, and they had rise times less than or approx. 200 ms. The spikes were all 100% left hand circularly polarized with an instrumental uncertainty of 5%. The rise times provide an upper limit to the linear size L less than or approx. 6 x 10 to the 9th power cm for the emitter. Provided that the source is symmetric, it has an area that is less than three hundredths of the star's surface area. In this case, the lower limit to the brightness temperature of the spikes is TB greater than or approx. 10 to the 13th power K. The high brightness temperatures and high degrees of circular polarization are explained in terms of electron-cyclotron maser emission at the second harmonic of the gyrofrequency in longitudinal magnetic fields of strength Hl approx. 250 gauss. The unpolarized gradual component did not exhibit any rapid fluctuations, and it was entirely analogous to the thermal emission of solar bursts. (Author)

Descriptors :   *Radio astronomy, *Cyclotron resonance, *Variable stars, *Harmonic generators, *Astrophysics, *Plasmas(Physics), Solar flares, Area coverage, Coherent radiation, Pulse rate, Dwarf stars, Burst transmission, Loops, Magnetic fields, Disks, Flux density, Solar radiation, Brightness, Very high frequency, Polarization, High temperature, Photosphere, Sequences, Thermal radiation, High rate, Emission, Spikes

Subject Categories : Astrophysics
      Plasma Physics and Magnetohydrodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE