The impact of stellar model spectra in disc detection

We present a study of the impact of different model groups in the detection of circumstellar debris discs. Almost all previous studies in this field have used KURUCZ (ATLAS9) model spectra to predict the stellar contribution to the flux at the wavelength of observation, thus determining the existence of a disc excess. Only recently have other model groups or families like MARCS and NEXTGEN (PHOENIX) become available to the same extent as ATLAS9. This study aims to determine whether the predicted stellar flux of a disc target can change with the choice of model family - can a disc excess be present in the use of one model family whilst being absent from another. A simple comparison of KURUCZ model spectra with MARCS and NEXTGEN model spectra of identical stellar parameters was conducted and differences were present at near-infrared wavelengths. Model spectra often do not extend in wavelength to that of observation and therefore extrapolation of the spectrum is required. In extrapolation of model spectra to the Spitzer MIPS passbands, prediction of the stellar contribution differed by 5 per cent at 70 mu m for F, G and early K spectral types with differences increasing to 15 per cent for early M dwarfs. Analysis of the Spitzer MIPS 24-mu m observations of 37 F, G and K solar-like stars in the Pleiades cluster was conducted. In using KURUCZ model spectra, seven disc excesses were detected while only three and four excesses were detected in using MARCS and NEXTGEN (PHOENIX) model spectra, respectively.