Radio-wavelength observations of magnetic fields on active dwarf-M, RS CVN and magnetic stars

Technical Report · Wed Jan 01 04:00:00 EST 1986

OSTI ID:7106438

Lang, K R

The dwarf M stars YZ Canis Minoris and AD Leonis exhibit narrow band, slowly varying (hours) microwave emission that cannot be explained by conventional thermal radiation mechanisms. The dwarf M stars AD Leonis and Wolf 424 emit rapid spikes whose high brightness temperatures similarly require a nonthermal radiation process which could result from coherent mechanisms such as an electron-cyclotron maser or coherent-plasma radiation. If the electron-cyclotron maser emits at the second or third harmonic of the gyrofrequency, the coronal magnetic field strength H = 250 or 167 G and constraints on the plasma frequency imply an electron density of 6 x 10/sup 9//cm/sup 3/. Coherent-plasma radiation requires similar values of electron density but much weaker magnetic fields. Radio spikes from AD Leonis and Wolf 424 have rise times tau/sub R/ < 5 ms, indicating a linear size of L < 1.5 x 10/sup 8/ cm, or less than 0.005 of the stellar radius. Although Ap magnetic stars have strong dipole magnetic fields, they exhibit no detectable gyroresonant radiation, suggesting that these stars do not have hot, dense coronae. The binary RS CVn star UX Arietis exhibits variable emission at 6 cm wavelength on time scales ranging from 30 s to more than one hour. The shortest variation implies a linear size much less than that of the halo observed by VLBI techniques, and most probably sizes smaller than those of the component stars. The observed variations might be due to absorption by a thermal plasma located between the stars.

• Research Organization: Tufts Univ., Medford, MA (USA). Dept. of Physics and Astronomy
• OSTI ID: 7106438
• Report Number(s): AD-A-171985/5/XAB
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics &amp; Cosmology-- Stars &amp; Quasi-Stellar
Radio &amp; X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMPLIFIERS
BINARY STARS
CYCLOTRON RESONANCE
DWARF STARS
ELECTRON DENSITY
ELECTRONIC EQUIPMENT
EMISSION SPECTRA
EQUIPMENT
MAGNETIC FIELDS
MAGNETIC STARS
MASERS
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
MICROWAVE SPECTRA
RESONANCE
SOLAR ACTIVITY
SOLAR FLARES
SPECTRA
STARS