Talk:Atmospheric parameters of VSOP M stars

Overview
Team: Gaspare (lead), Thomas

Goal: obtain Teff, logg, [Fe/H] for all M stars to be treated in VSOP-1. Obtain abundance estimates of other elements in case of non-solar metallicity. (Depends on cross-correlation of FEROS spectra!)

Methods:
 * Since most targets have visible Ca II H+K emission cores, the Wilson-Bappu calibration can be used to infer the luminosity class.
 * Teff (and logg, [Fe/H]??) can be infered from fitting synthetic spectra made with MOOG, using ATLAS9 atmospheric models, in a chi^2 minimization.
 * In case of binaries, the spectral subtraction technique of Montes at al. (2000; A&AS 146, 103 + 1995; A&A 294, 165) may be tried in order to simultaneously fit and separate the spectra of the two components. Alternatively, smaller regions may be fit in order to estimate Teff, logg of the components.

Deadlines:


 * 1) Wilson-Bappu calibration defined, ready to use
 * 2) Alternative luminosity indicators defined
 * 3) Wilson-Bappu calibration done
 * 4) Define spectral regions to fit
 * 5) Procedures for iterative analysis defined
 * 6) All singles done.
 * 7) Binaries procedures defined...

Remember that the team leader should organize the work, and make sure dates are assigned to the deadlines. These should be published on this Team-page before May 24 (for Paper1)

Categories:
 * M stars

Update 2006-06-03
I discovered that SYNTHE (by Kurucz) may be doing a better job in modelling molecular lines and bands, so instead of using MOOG, I'd like to use SYNTHE (distribution is the Linux port by L. Sbordone et al.). I have now installed and tested this tool, plus downloaded a grid of ATLAS9 model atmospheres to use with it. We still need to define which regions would be the most sensible ones to fit, and we need a good chi^2 iteration scheme. -- Tdall 03:41, 3 June 2006 (CLT)

Update 2006-06-04
For the Wilson-Bappu calibration: The original paper by Wilson & Bappu (1957) is not directly applicable, since they use measurements on photographic plates. The best objective definition of what exactly to measure, is the one given by Pace et al. (2003). Thus, we will use their W_o - M_v relation, and their definition of W_o. I will think about how to do this measurement automatically. As for alternative luminosity indicators, we may fit synthetic spectra to the strong Ca I 4227 line. -- Tdall 02:05, 4 June 2006 (CLT)