We report here on a series of medium resolution spectro-photometric observations of the enigmatic long period eclipsing binary epsilon Aurigae, during its eclipse interval of 2009-2011, using near-infrared spectra obtained with SpeX on the Infrared Telescope Facility (IRTF), mid-infrared spectra obtained with BASS on AOES and IRTF, MIRSI on IRTF, and MIRAC4 on the MMT, along with mid-infrared photometry using MIRSI on IRTF and MIRAC4 on the MMT, plus 1995-2000 timeframe published photometry and data obtained with Denver's TNTCAM2 at WIRO. The goals of these observations included: (1) comparing eclipse depths with prior eclipse data, (2) confirming the reappearance of CO absorption bands at and after mid-eclipse, associated with sublimation in the disk, (3) seeking evidence for any mid-infrared solid state spectral features from particles in the disk, and (4) providing evidence that the externally irradiated disk has azimuthal temperature differences. IR eclipse depths appear similar to those observed during the most recent (1983) eclipse, although evidence for post-mid-eclipse disk temperature increase is present, due to F star heated portions of the disk coming into view. Molecular CO absorption returned 57 days after nominal mid-eclipse, but was not detected at mid-eclipse plus 34 days, narrowing the association with differentially heated sub-regions in the disk. Transient He i 10830A absorption was detected at mid-eclipse, persisting for at least 90 days thereafter, providing a diagnostic for the hot central region. The lack of solid-state features in Spitzer Infrared Spectrograph, BASS, and MIRAC spectra to date suggests the dominance of large particles (micron-sized) in the disk. Based on these observations, mid-infrared studies out of eclipse can directly monitor and map the disk thermal changes, and better constrain disk opacity and thermal conductivity.
Experimental observations of very low frequency (VLF) triggered emissions are an important resource in investigation of nonlinear wave‐particle interactions between whistler mode waves and energetic electrons in the Earth's radiation belts. Magnetospherically generated whistler mode sidebands observed during the Siple Station wave injection experiment are analyzed using a mixed modulation model and the MINUIT minimization package. The observed sidebands are found to exhibit features of both amplitude and frequency modulation of the input carrier wave with frequency modulation becoming more prominent as the observed amplitudes of the carrier and sidebands increase. A nonlinear whistler mode wave growth formulation based on phase bunching of counterstreaming electrons within a well‐defined phase trap is shown to reproduce the salient features of the sideband observations. Whistler mode sideband amplitude is shown to be affected by the shape and uniformity of the trap.
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