Date: Mon, 26 Aug 2002 20:08:55 -0700 (PDT) From: martin cohen 423 Please review the following abstract. Thanks Martin --------------- Predicting the photospheric radiation for target stars of the "Formation and Evolution of Planetary Systems" SIRTF Legacy program PI: M. Cohen CoIs: John Stauffer, Dana Backman, Mike Meyer, Eric Mamajek, Steve Strom, Lynne Hillenbrand, John Carpenter To recognize the existence of potentially small excesses of radiation in the F, G, K dwarf target stars of the FEPS Legacy program depends critically on accurate prediction of their expected photospheric radiation. It is also essential that these predictions are carried out in a calibration scheme identical with that underpinning the SIRTF instruments, notably IRAC and IRS. In readiness for the launch of SIRTF, the FEPS team has undertaken an extensive search of the literature to determine published estimates of fundamental stellar parameters, or at of least spectral types, and to identify and archive reliable well-characterized photometry. The methods by which these absolute photospheric spectra were generated are described, emphasizing their similarity to the way in which routine IRAC and SIRTF instrument cross-calibrators are being generated. Because the output products are complete calibrated spectra from the optical to the mid-infrared, these same photospheres support both the prediction of IRAC and MIPS magnitudes and of entire spectra for IRS. The association of meaningful quantitative uncertainties with these magnitudes and spectra is a particular focus of the approach adopted. The primary goal of these predictions in FEPS is to be able to recognize the existence of excess emission above the photospheres, and to characterize the wavelength- dependent uncertainties that can be assigned to such excesses. However, any star for which observed IRAC and MIPS magnitudes, and IRS spectra, are in agreement with predictions may serve as valuable, additional calibrators for community use. The fact that we have observed such star, as distinct from merely predicting what it would produce if it radiated purely as a photosphere, elevates its status from a FEPS target to a star whose energy distribution is predictable; i.e. to calibrator status. This paper should arise naturally from the need to document the production of our photospheric predictions. To that extent it should be quite a straightforward process, although there are details that need careful description. This paper could well be an expanded version of whatever we will need to write, pre-launch, to motivate an understanding of our techniques. I envisage the paper arising once we have studied all our observations and have settled on those stars with, and without, evidence of additional sources of radiation beyond photospheres. This makes it essentially a long duration exercise. However, shortened versions of the methodology may well appear in the "short" term, hopefully accompanying the demonstration of the existence of disk emission in some smaller sample of FEPS targets. For the PI this paper, viewed as essential SIRTF documentation, would be a high-priority commitment. Briefer descriptions will surely appear if we are successful with our observations and choice of early targets, and I would be content to contribute abbreviated sections to those science publications in the short, medium, or long duration categories. ========================================================================= Martin Cohen Office phone: 510-642-2833 Radio Astronomy Laboratory Office FAX: 510-642-3411 601 Campbell Hall University of California e-mail: mcohen@astro.berkeley.edu Berkeley, CA 94720 U.S.A.