Radio burst statistics for M dwarf flare stars

Abstract

Abstract. We present a critical analysis on the number of bursts near 21 cm from nine dMe flare stars of the solar neighborhood as reported in the literature. We compare our findings with the number of bursts detected with the Arecibo radiotelescope between 1989 and 1993, using a very reliable method to discriminate between stellar and artificial emissions. We compare the rates of radio bursts per hour inferred from both this Arecibo campaign and the literature to rates of optical flares found in the literature. We also compare the nine stars to each other, and the Arecibo results to radio surveys of two open clusters.

AE Aquarii represents a new subclass of Cataclysmic Variables

“…In contrast to other Cataclysmic Variables AE Aqr is a powerful source of non-thermal flaring radio-emission resembling some features of radio-emission from Cygnus X-3 [28]. The observed spectrum in a wide spectral range (from decimeter-wavelength radio to infrared, [29]) exhibits a power-low (ν 0.3−0.4 ) and can be described in terms of synchrotron mechanism. An absence of significant circular polarization implies that the observed radiation is generated by electrons with Lorenz factor γ ∼ 0.3 − 30 moving in the magnetic field with the strength ranging from 100 to 1000 G. Flaring character of radiation is interpreted in the frame of van der Laan model [30] describing synchrotron radiation of electrons trapped in expanding plasmons [28].…”

“…An absence of significant circular polarization implies that the observed radiation is generated by electrons with Lorenz factor γ ∼ 0.3 − 30 moving in the magnetic field with the strength ranging from 100 to 1000 G. Flaring character of radiation is interpreted in the frame of van der Laan model [30] describing synchrotron radiation of electrons trapped in expanding plasmons [28]. There are some indications that the relativistic gas is ejected from the system at velocities close to 30% of the speed of light [22,29]. The luminosity of the system in the radio band constitutes a small fraction of the spin-down power of the white dwarf: L r /L sd ∼ 10 −5 , that points out a significant contribution of the non-thermal processes to the total energy release in the system.…”

Asgard: A Large Survey for Slow Galactic Radio Transients. I. Overview and First Results

“…The rate might be increased by similar flares from substellar dwarfs (Berger 2002). Because coherent flares evolve quickly (τ ∼ 60 s) and can be fairly narrowband (∆f /f ∼ 0.1), the detectability of these events in practice will depend strongly on specific survey characteristics (Abada-Simon & Aubier 1997). A survey conducted in the same manner as AS-GARD would have extremely poor sensitivity to these events, even if it appeared to reach the necessary density limit on Figure 12, because of the very different event timescales and steep, narrow flare spectra.…”

Can late-type active stars be explained by a dipole magnetic trap?

“…KS85: Kundu & Shevgaonkar (1985). KS88: Kundu & Shevgaonkar (1988)†(taken from Abada‐Simon & Aubier 1997.) LW86: Lang & Willson (1986).…”