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0.08truecm       a detailed discussion of expected gaia performances will necessarily be postponed to the end of the present series , when enough stars will be investigated to cover the span of spectral types and kinds of interaction ( detached , semi - detached , contact ) .
this will provide us with a representative sample of the huge zoo of eclipsing binary stars within the observational capabilities of the coming esa cornerstone  6 mission .    nevertheless , a few brief statements are in order to comment on the promising results on well detached , double - lined eclipsing binaries of a , f spectral types of a few days orbital period obtained here .      in this paper we used a mean of 23 spectra per star , spread over a wide range of s / n .
table  2 ) .
orbital separations and individual masses are constrained to @xmath30.7% and @xmath31.5% , respectively .
thus the selected @xmath4250   wavelength range between 8490 and 8740   is working fine for spectral types a and f , even though it was optimized for cooler stars ( the vast majority of field stars in the range of magnitude of interest to gaia are g and k stars ) .
gaia will record the majority of its spectra at s / n lower than obtained for this paper , but this will be compensated by a much larger number of spectra per star , typically 150 .
it is therefore quite possible that a sizeable fraction of the well detached , double - lined eclipsing binaries of a - f spectral type observed by gaia will have their orbital separation and masses of both components determined to an accuracy of @xmath31% provided that the spectral dispersion and resolution will be not too far from 0.25  / pix and 0.5  , respectively .
the baricentric velocities are constrained to better than 0.5 km sec@xmath5 , which is fine in comparison to the accuracy of gaia tangential motions , and also adequate to resolve the internal kinematics of stellar aggregates ( clusters , associations , etc . )        for the program stars we adopted @xmath6 because modeling excluded any eccentricity larger than 0.01 , which can be taken as a rough indication of the accuracy to which eccentricity could be determined by gaia observations .
periods for the three program stars have been determined to such an accuracy that it would take @xmath7170 years ( on the average ) to bring the ephemeris out of phase for more than 10%  of the orbital period .
the 5 years of gaia operation ( compared to the time span of 3.36 years for hipparcos data or 1.38 years for the spectral data used here ) , should expand the 10% accuracy horizon of the ephemeris to @xmath7250 years .
hipparcos has collected about 110 measurements per star .
if eclipses last for 1/10 or less of the orbital period , one has to expect 10 or less photometric points to be distributed over the eclipse phases .
gaia will have three lines of view ( at @xmath3120 deg ) .
if the same set of core photometric bands is present in _ all _ the three channels ( a feature yet to be optimized in the currently baselined gaia design ) , the number of collected photometric points will proportionally increase with great benefit not only to the study of eclipsing binaries but also to variable stars in general .
effective temperatures and surface gravities are in fact two of the basic output of spectral synthesis analysis ( e.g.  based on kurucz model atmospheres ) .
the 0.25  / pix dispersion and 0.5   resolution gaia spectra used here are quite adequate to derive temperatures to @xmath830  k and gravities to 0.1 dex ( cf .
munari and castelli 2000 ) .
the analysis of gaia spectra of eclipsing binaries ( mainly those obtained at quadratures when spectra of both components are better observed ) would therefore provide these quantities directly .    the effective temperature and surface gravity determined directly from gaia spectra
could then be used to check _ a posteriori _ the results of modeling or used as inputs in the modeling process to decrease the number of variables .
a natural check about the goodness of the orbital solution and modeling is to compare the distance to the program stars computed from the modeling parameters in table  4 with the trigonometric parallaxes measured by hipparcos .
this is done in table  5 , together with the distance to v505  per from the modeling of marshall et al .
( 1997 ) .
the high expected performances of gaia observations are confirmed : ( @xmath1 ) the modeling of photometric lightcurves and radial velocity curves for the three program stars constrains the distance to a better accuracy than hipparcos trigonometric parallax , and ( @xmath2 ) modeling distances and hipparcos parallaxes agree inside the respective errors .    as for the effective temperature and surface gravity , trigonometric parallaxes determined directly by gaia ( at an average 200@xmath9 better precision than hipparcos )
could then be used to check _ a posteriori _ the results of modeling or used as an input value in the modeling process itself .
the unique characteristic of gaia as a single mission which combines astrometry , spectroscopy and photometry appears to offer special advantages compared to the classical ground - based approach to eclipsing binaries .
the possibility to use effective temperatures , surface gravities and trigonometric parallaxes as fixed input values to the modeling of lightcurves and radial velocities should allow more confident derivation of other parameters , both stimulating a new modeling approach to eclipsing binaries and also granting lower errors to the solution .    by probing all constituents of the galaxy ( halo , disk , bulge ) and detecting eclipsing binaries there
, gaia can foster an epochal leap in our knowledge of the basic stellar parameters and how they vary with mass , age and chemical abundance .
this will be true not only on statistical grounds ( given the huge number of observable eclipsing systems ) but also for an object by object approach .
this paper has in fact shown that an accuracy of 1% in the derived stellar parameters can be achieved by gaia on a fraction of the detached eclipsing binaries observed during the mission .
andersen j. 1991 , a&a review 3 , 91 carquillat j.m . , nadal r. , ginestet n. , pedoussaut a. 1982 , a&a 115 , 23 castelli , f. , munari u. , 2001 , 366 , 1003 gilmore g. , perryman m. , lindegren l. favata f. , hoeg e. , lattanzi m. , luri x. , mignard f. , roeser s. , de zeeuw p.t . , 1998 , proc spie conference 3350 , p. 541 kallrath , j. , milone , e.f . 1999 , _ eclipsing binary stars : modeling and analysis
, springer - verlag kallrath , j. , milone , e.f . , terrell , d. , young , a.t .
1998 , apj 508 , 308 marschall , l.a . ,
stefanik , r.p . ,
lacy , c.h . , torres , g. , williams , d.b . , and agerer , f. 1997 , aj 114 , 793 mrat p. , safa f. , camus j.p . , pace o. , perryman m.a.c . 1999 , in proceedings of the esa leiden workshop on gaia , 23 - 27 nov 1998 , baltic astronomy , 8 , 1 munari u. 1999a , in proceedings of the esa leiden workshop on gaia , 23 - 27 nov 1998 , baltic astronomy , 8 , 73 munari u. 1999b , in proceedings of the esa leiden workshop on gaia , 23 - 27 nov 1998 , baltic astronomy , 8 , 123 munari u. , castelli f. 2000 , a&as 141 , 141 munari u. , lattanzi m.g .
1992 , pasp 104 , 121 munari u. , tomasella l. 1999a , a&a 343 , 806 munari u. , tomasella l. 1999b , a&as 137 , 521 perryman , m.a.c .
, de boer , k.s . , gilmore , g. , hoeg , e. , lattanzi , m.g . ,
lindegren , l. , luri , x. , mignard , f. , pace , o. , de zeeuw , p.t .
2001 , a&a 369 , 339 popper , d. m. 1980 , ara&a 18 , 115 wilson , r. e. 1998 , _ computing binary star observables _ , univ . of florida astronomy dept
the orbits and physical parameters of three detached , double - lined a - f eclipsing binaries have been derived combining @xmath0 photometry from the hipparcos / tycho mission with 8500 - 8750   ground - based spectroscopy , mimicking the photometric+spectroscopic observations that should be obtained by gaia , the approved cornerstone 6 mission by esa . 
 this study has two main objectives , namely ( @xmath1 ) to derive reasonable orbits for a number of new eclipsing binaries and ( @xmath2 ) to evaluate the expected performances by gaia on eclipsing binaries and the accuracy achievable on the determination of fundamental stellar parameters like masses and radii . 
 it is shown that a 1% precision in the basic stellar parameters can be achieved by gaia on well observed detached eclipsing binaries provided that the spectroscopic observations are performed at high enough resolution . 
 other types of eclipsing binaries ( including semi - detached and contact types ) and different spectral types will be investigated in following papers along this series .