From erik Fri Dec 1 11:19:12 2000 Subject: SAG-CUO-081.txt workshop at CUO To: gaia-sag@astro.estec.esa.nl (GAIA SAG), straizys@itpa.lt (Vytas Straizys), wladas@itpa.lt (Vladas Vansevicius), Frederic.Arenou@obspm.fr (F. Arenou), Daniel.Hestroffer@bdl.fr (D. Hestroffer), Carine.Babusiaux@obspm.fr (Carine Babusiaux), catherine.turon@obspm.fr (C. Turon), brown@bufadora.astrosen.unam.mx (A. Brown), indus (Jens Knude), cf (Claus Fabricius), makarov@astro.ku.dk (V.V. Makarov), ntk (Nadia Kaltcheva), munari@astras.pd.astro.it (Ulysses Munari), BERNACCA@ASTRAS.pd.astro.it (P.L. Bernacca), cflynn@astro.utu.fi (C. Flynn), calj@mpia-hd.mpg.de (Coryn Bailer-Jones), csterken@vub.ac.be (Chris Sterken), weiss@astro.univie.ac.at (Werner W. Weiss), kerschbaum@astro.univie.ac.at (Franz Kerschbaum), michel.grenon@obs.unige.ch (M. Grenon), per.lilje@astro.uio.no (Per Lilje), kaare.aksnes@astro.uio.no (Kaare Aksnes), dominik@stsci.edu (Martin Dominik), janerik@phys.uit.no (Jan-Erik Solheim), egret@simbad.u-strasbg.fr (D. Egret) Date: Fri, 1 Dec 2000 11:19:12 +0100 (MET) X-Mailer: ELM [version 2.5 PL2] Content-Length: 9516 Status: OR GAIA photometry workshop in Copenhagen, in Nov. 2000 ==================================================== SAG-CUO-081 E. Hoeg, C. Flynn, J. Knude, V. Vansevicius 1 Dec. 2000 ABSTRACT: Overviews of GAIA mission aspects were given. A software for simulation of photometric observations based on realistic assumptions was presented. It includes, e.g., 4-dim automatic classification (Teff, log g, [Fe/H], E(B-V)), assuming R_BV to be known. Only a naive, non-astrophysical weighting of colour indices were applied so far. Results from comparison of BBP+MBP photometry with the 1F and 3G systems by means of the software were shown for O-K stars; the 3G seems to be better by 10 to 20 per cent. Significant differences depending on the width of the v and u bands in 3G, corresponding to U and X in the Vilnius system, have been found. Methods to determine interstellar absorption were discussed: use of the DIB at 862 nm only works for V<13 mag; the mapping method described in the GAIA Study Report can be much improved. The following contains: List of participants; Agenda; Some of the agreed actions; Appendix with summaries of four presentations PARTICIPANTS: Contributions were presented by Audrius Bridzius (AB), Vladas Vansevicius (VV) from Vilnius, Claus Fabricius (CFa), Erik Hoeg (EH), Jens Knude (JK) from Copenhagen, Lennart Lindegren from Lund, and Chris Flynn (CFl) from Turku. About fifteen persons attended on 29 Nov. Agenda ====== AB VV CFa EH JK and CFl met at CUO during the week 27 Nov.-1 Dec. AB+CFa visited LL in Lund during the following week. 29 Nov: 9:00 - 16:00 Optimization of CCD measurements (Erik Høg) Photometric data analysis (Claus Fabricius) The photometric systems proposed for GAIA (Erik Høg) Automatic classification based on simulated observations (Audrius Bridzius) Determination of interstellar extinction with GAIA (Vladas Vansevicius) Institute Colloqium on GAIA by Lennart Lindegren From Q indices to absolute mag and absorption (Jens Knude) Late type stars, K dwarfs, clump giants etc (Chris Flynn) Organizers: Erik Høg, Claus Fabricius, Jens Knude Some of the agreed actions ========================== 3. VV, 1 Sep.: filter transmissions in files for 1F and 3G; CCDs; always in step of 2 nm (0, 2, 4...). Expected in Jan. 2001. 4. VV+V. Deveikis, 1 Aug.: spectra of some spectral types from Kurucz models (lg Teff, log g, [M/H]) [photons/m^2] for V=15. Expected in report Jan. 2001. 6. EH+VV, 1. Aug.: instrument: entrance pupil etc. Expected in Dec. 2000; tables in ascii format. 10. VV+A.Kucinskas 1 Sep.: sigma_DIB versus V, cf CUO_73. Expected in Jan. 2001. 13. J. Sudzius, 1 Oct.: investigate bandwidth effects due to strong reddening, especially in Ug, Bg and Vg of the 3G system. Expected in Jan. 2001. 15. GAIA workshop at CUO on Wednesday 21 March 2001. Visitors from Turku and Vilnius arriving on 19 March for 1 or 2 weeks. 17. JK+EH+VS+VV ... Are observational tests of systems required ? Why and how ? Answer required in Jan. 2001 so that filters may be funded in due time. 18. VV+AB by March 2001 : Compare the BBP systems, especially at V=19.0. Does MBP improve significantly what is obtained by BBP alone at V=19.0 ? Introduce Galactic model of star distributions. 19. VV+VS+... when #18 is completed: Revise the 3G system into 4G. VV will already now reintroduce the y-band into 3G, which will then be called 3Gb. 20. CFl by Feb. 2001 : Study the classification of normal giants and clump giants with the proposed phot. systems. APPENDIX ======== ==================================================== GAIA photometry workshop in Copenhagen, in Nov. 2000 ==================================================== Summaries of some of the contributions, especially about the definition of the GAIA photometric systems. ==================================================== Automatic Classification of Stars Based on Simulated GAIA Observations A. Bridzius (1), V. Deveikis (2), V. Vansevicius (1) 1. Institute of Physics, Vilnius, Lithuania 2. Vilnius university astronomical observatory, Lithuania Summary Automatic 4-D {Teff, log g, [Fe/H], E(B-V)} classification of stars based on comparison of simulated "observed" colour indices with corresponding ones from a bank of modeled "standard" stars is presented. The best fitting model is determined by chi-square criterion. Individual weights of the colour indices are defined as: 1/(sigma_CI)^2, where sigma_CI means r.m.s. error of the color index. Theoretical spectra based on Kurucz models, and modified by Lejeune et al. (1997) are used as an input for calculation of the theoretical colors of the "observed" and "standard" stars. The complete set of specific GAIA parameters is used to model telescope, CCD, photon noise etc. effects properly. The standard extinction law (Cardelli et al. 1989) is applied. Analysis of capabilities of two photometric systems proposed for GAIA, i.e., 1F and 3G was performed. Classification results show that an accuracy of the 3G system is better by ~10-20%. However, this question should be addressed again applying the method to the model Galaxy populations in a number of different directions selected by Galactic latitude and longitude. ==================================================== Determination of Interstellar Extinction with GAIA V. Vansevicius (1), A. Bridzius (1), V. Deveikis (2), A. Kucinskas (2,3), J. Sudzius (2) 1. Institute of Physics, Vilnius, Lithuania 2. Vilnius university astronomical observatory, Lithuania 3. Institute of theoretical physics and astronomy, Vilnius, Lithuania Summary 1. Applicability of the diffuse interstellar band (DIB) at 862 nm for the color excess determination was tested for early type stars (Teff > 7300 K). We find a limiting magnitude V ~ 13 for DIB measurement giving E(B-V) precision < 0.05 in case of the GAIA spectral observations. For the B0 V type stars we find a limiting distance (~1.5 kpc) to trace interstellar extinction successfully. 2. Bandwidth effects were investigated for medium and broad band filters of the 3G photometric system proposed for the GAIA. We find significant bandwidth effects and nonlinear excess ratios dependence on color excess itself, even for the medium band filters. This finding implies very careful iterative procedure to be used during classification process. 3. Investigation of capabilities to determine extinction in the range E(B-V) = 0.0 - 3.2 within the photometric system 3G was performed. We find that extinction has reasonably good precision (sigma_E(B-V)~0.05) up to 19 mag for early type stars (O-A), and up to 17 mag for late type stars (F-K). We estimated that presence of strong (E(B-V) > 1.0) interstellar reddening influences the precision of the log(Teff) (~0.02) and [Fe/H] (~0.15 dex) determination at V = 17 mag. 4. The strong effect on the precision of the astrophysical parameter determination by variable extinction law was demonstrated. It is suggested to determine parameter R_BV basing on the parallax measurements provided by GAIA. =========================================================== From Q indices to absolute mag and absorption ---------------------------------------------- Nadia Kalcheva, Jens Knude >From published Vilnius photometry (CDS Catalog) with good quality spectral classification in the literature and Hipparcos parallaxes we have estimated the absolute magnitude and spectral classification from Q -- Q diagrams for G and K type stars. Compared to Hipparcos the absolute magnitudes show very good agreement for KV, GV is estimated too bright, K and GIV even more too bright, but K and GIII too faint. Compared to the literature K stars are classified sligthly too early whereas the G stars are classified slightly too late introducing errors in the intrinsic color (B-V)_0 of about 0.05 and 0.02 mag respectively. So far we have not been able to estimate M_V and spectral type for A and F type stars. Some of the problems may be solved by changing the widths of the U and X bands. =========================================================== Late type stars, K dwarfs, clump giants etc ------------------------------------------- Chris Flynn Dwarfs: A sample of about 30 accurate metallicities by high resolution spectroscopy has been obtained for G5-K5 dwarf stars. Photometric abundance indicators have been developed using broadband R-I and medium band filters in the blue region. It turns out to be very straightforward to make an index with an accuracy of 0.2 in [Fe/H] using either Geneva and Stroemgren filters in the blue region and Cousins R-I, even though the Geneva and Stroemgren filters sample quite different regions in the blue. We consider it therefore likely that the same technique will also work with the proposed GAIA filters in the blue region, as is indeed found by analysis of synthetic spectra by the Vilnius team. Giants: The same will be investigated for giants (expected completion Feb 2000). There is a possible complication which cannot be investigated so easily using spectrum synthesis; the presence of clump giants amongst normal first ascent giants. We will investigate observationally whether these could have an impact on the choice of filter system. This will be done from the red giants in Hipparcos and the (metal rich) open clusters. -------------------------==========================-------------------