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A. Buffington, A.C. Smith, B.V. Jackson, P.P. Hick ()
The Solar Mass Ejection Imager (SMEI) was designed to record a photometric white-light response of the interplanetary medium from Earth over most of the sky in near real time, using Thomson scattered sunlight. In its first two years the instrument has observed several hundred Coronal Mass Ejections. Quantitative interpretations of these data requires that the Analog Data Units (ADUs) of the instrument's CCD responses be converted to an effective stellar brightness. The present work provides a preliminary report on establishing this relationship.
An appropriate unit here is an "S10", the equivalent brightness of a 10th magnitude star spread over one square degree. The relationship between ADUs and S10s is established by using the SMEI response to bright stars having known visual magnitude and spectral type. These latter are converted to a "SMEI magnitude" by integrating the various star's spectra over the nominal SMEI bandpass, which extends between 0.4 and 1.1 microns and peaks at 0.7 microns, to obtain a spectral scaling factor which is set to unity for G-type stars and relates visual magnitudes to SMEI magnitudes. The final overall conversion factor is then determined from the ADU measurements of the individual stars.
This work was supported in part by NSF contract ATM0331513 and NASA grant NAG 5-134543.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.