Luminosity Calibration


Research lines

Luminosity calibration from maximum likelihood method

The determination of the luminosity calibration for a given stellar population from a limited sample of stars is always affected by some bias. Maximum likelihood method allows to modelize the sample’s selection process to obtain an unbiased luminosity calibration for the population. Furthermore, the method takes into account all the available information (for instance, in the case of the luminosity calibration, not only the parallax, but also the proper motion), in such a way that the final uncertainty is reduced.

From the work of Luri (1996) our team have applied these methods with different purposes, as the study of the luminosity-period relationship of cepheids (Luri, 1998), the characterization of the stellar population in our Galaxy (Masana et al. 2000) or, more recently, the study of the open clusters (Palmer et al., in press).

Eclipsing binaries as stellar laboratories for distance determination

We collaborated in a project aimed to determine the first direct distance to the Andromeda Galaxy (M31) from Eclipsing binaries. A photometric survey was carried out in the North-Eastern part of M31, providing light curves for almost 4000 variable stars, with over 400 EBs and 400 Cepheids. After a preliminary selection, four EBs were selected for spectroscopic follow up with the Gemini-North telescope. The analysis performed revealed the fundamental properties of several massive stars. Two of these EBs were used to determine the first direct distance to M31 of (m-M)0=24.36±0.08 mag, which yields and error of only 4% (see Vilardell et al., 2010; Vilardell, 2009 PhD thesis). The study also yielded probably the detection of the most massive star in an eclipsing binary with apsidal motion, and is under investigation.

Exploitation of the Gaia Simulator: The fundamental distance scale

The data generated by the Gaia Simulator, in particular the Gaia Universe Model Snapshot (GUMS), allow to estimate some final results of the Gaia mission. In particular we have analised the Gaia expectations for the derivation of the distance scale from data in SMC and LMC galaxies. The work was presented at the “The Fundamental Distance Scale: state of the art and the Gaia perspectives” meeting (Naples, Italy, 2011) and published on Turon et al., 2012.

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