Groenewegen, m.a.t.

Poster presented at EWASS, Lyon (FR) on 2019-06-24

Abstract: Groenewegen (2018) presented an analysis of a sample of about 450 classical Cepheids (CCs) with metallicies available from high-resolution spectroscopy. All except three had a parallax available from Gaia DR2 (not necessarily of high quality) and many had a parallax available from Hipparcos and/or several Hubble space telescope programs. Based on nine CCs with a goodness-of-fit (GOF) statistic smaller than 8 and with an accurate non-Gaia parallax, a parallax zero-point offset of -0.049 $\pm$ 0.018 mas was derived. Imposing some selection criteria and limiting myself to fundamental mode CCs period-luminosity relations in the $V$, $K$ and Wesenheit $VK$ bands were presented that strongly depended on the parallax zero-point offset, for a sample of 200 CCs. One possible issue that arose from the study is the classification as CCs that was taken from the literature. To study the sample of 450 CCs in an entirely different way the spectral energy distributions from the UV to the far infrared have been compiled from the literature and fitted with the 1D dust radiative transfer code "More of DUSTY". For the overall majority of stars no dust is present and the analysis gives the (mean) effective temperature and (mean) luminosity (for an assumed distance). This allows to construct the Hertzsprung-Russell diagram and construct a PL-relation using the bolometric luminosity. Both may help is identifying possible stars misclassified as CCs. Some CCs are known to show some infrared excess and these stars are studied in more detail.