JKTABSDIM - for calculating the absolute dimensions and distance of an eclipsing binary system


This code calculates the absolute dimensions, related quantities, and distance of a detached eclipsing binary from the results of a radial velocity and light curve analysis. Careful attention is paid to correctly propagating errors, and an error budget is printed for each output quantity (expressed in percentages of the total error).

Several distance measurements are included, using both theoretical and empirical bolometric corrections or surface brightness relations, and for each passband with an available apparent magnitude.

Input quantities (with uncertainties)

Velocity semiamplitudes (km/s), orbital eccentricity, periastron longitude (degrees), period (days), orbital inclination (degrees), fractional stellar radii (i.e. in units of the orbital semimajor axis), apparent magnitudes and light ratios in the UBVRIJHKL passbands, effective temperatures of the stars (K) and the interstellar reddening E(B-V) (mag).

Output quantities (each with an error budget)

Among other things, the absolute masses (Msun) and radii (Rsun) of the two stars, their luminosities (Lsun) and absolute bolometric magnitudes, their surface gravities (cm/s) and synchronous rotational velocities (km/s), and the theoretical tidal synchronisation and circularisation timescales from Zahn (1975, 1977). The distance calculations are optional (put sub-zero Teff to avoid entering any magnitudes or light ratios for distance calculation).

Distances are calculated in essentially two ways. The first is using the surface brightness method introduced by Southworth et al. (2005A&A...429..645), which is an excellent semi-empirical method for stars with temperatures below 10000 K.

The second distance method uses bolometric corrections to transform the absolute bolometric magnitudes to passband-dependent magnitudes, which give distance when compared to the apparent magnitudes (the equations are given in Southworth et al. (2005tvnv.conf..361S). For this method, separate distances are quoted using empirical bolometric corrections from Code et al (1975) and Flower (1996), and theoretical ones from Bessell et al (1998) and Girardi et al (2001). Remember that different people use different zeropoints for their bolometric correction scales: the absolute bolometric magnitudes of the stars are recalculated each time in the code to ensure consistency.

Running the code

Download the Fortran code or the tarfile. Example input and output files are in the tar file. The tarball also contains the datafiles needed to run the code (which contain the bolometric corrections). The datafiles are assumed to be in the directory /home/jkt/tabs/ so this must be changed in the code if they are not (which is easy to do).

Once you have a compiled executable program then (on Unix machines) just type on the terminal line:

jktabsdim < [inputfile] > [outputfile]

or just type jktabsdim and enter the data as it is prompted for (a bit less convenient).


Last modified: 05/05/2010           John Southworth   (Keele University, UK)