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Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. I. The Stellar Calibrator Sample and the 24 μm Calibration
We present the stellar calibrator sample and the conversion frominstrumental to physical units for the 24 μm channel of the MultibandImaging Photometer for Spitzer (MIPS). The primary calibrators are Astars, and the calibration factor based on those stars is4.54×10-2 MJy sr-1 (DNs-1)-1, with a nominal uncertainty of 2%. Wediscuss the data reduction procedures required to attain this accuracy;without these procedures, the calibration factor obtained using theautomated pipeline at the Spitzer Science Center is 1.6%+/-0.6% lower.We extend this work to predict 24 μm flux densities for a sample of238 stars that covers a larger range of flux densities and spectraltypes. We present a total of 348 measurements of 141 stars at 24 μm.This sample covers a factor of ~460 in 24 μm flux density, from 8.6mJy up to 4.0 Jy. We show that the calibration is linear over that rangewith respect to target flux and background level. The calibration isbased on observations made using 3 s exposures; a preliminary analysisshows that the calibration factor may be 1% and 2% lower for 10 and 30 sexposures, respectively. We also demonstrate that the calibration isvery stable: over the course of the mission, repeated measurements ofour routine calibrator, HD 159330, show a rms scatter of only 0.4%.Finally, we show that the point-spread function (PSF) is well measuredand allows us to calibrate extended sources accurately; InfraredAstronomy Satellite (IRAS) and MIPS measurements of a sample of nearbygalaxies are identical within the uncertainties.
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
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