|-h||Print a usage message on standard output and exit successfully.|
|-U||Run in interactive mode.|
|-C file||Use binary star parameters from a configuration file instead of giving them on the command line. Sample configuration files are in share/nightfall/cfg.|
|Plot a graph of the lightcurve after its computation (P|S - zoom on primary/secondary eclipse, 1|2 - plot 1/2 orbits).|
|-A||Generate an animated view of the binary star.|
|Visualize the geometry of the binary star system (v - view of the stars, i - image of the potential, c - contour plot of the potential, a - all of them).|
|-H||Send plot to a postscript file. If the postscript file exists, it will be overwritten.|
|Select the filter/bandpass for which the lightcurve should be plotted. U-K range from ultraviolett to infrared, best match to the human eye is V. u-y are narrow-band filters. 1|2 will select radial velocity curves instead of a light curve.|
|By default, nightfall assumes synchroneous rotation, which means that the stars are rotating with the orbital period, and thus show each other always the same side. With this option, you can set the ratio of stellar rotation frequency to orbital frequency to some value different from one, seperately for the primary P and the secondary S.|
|-e eccentricity periastron_length|
|By default, nightfall assumes the orbit to be circular. With this option, you can set the eccentricity of the orbit (0 is circular, maximum is less than 1), and the periastron length, which is the point of closest approach of the two stars in their orbit (0 - 360 degree).|
|-sP/-sS longitude latitude radius dimfactor|
|Place a spot on the primary (P) or secondary (S). The spot parameters are the location of the spot (longitude,latitude), its radius, and the dimfactor by which the temperature is reduced (or increased) within the spot area.|
|Set the absolute value for the orbital period P (in days), the total mass M (in units of solar masses), and/or the orbital separation D (in solar radii) of the system. Any two of these are independent, the third is then calculated from Keplers laws (i.e., you should set only two of these).|
|-I file||Read in observational data from a data file. Sample data files are in share/nightfall/data.|
|-D[vwb]||Diagnostic output (v - verbose, w - warnings, b - status messages).|
The definition of primary/secondary is inverse to the usual convention in astronomy.
Obviously, the size of a star in a binary system is limited by the orbital separation of the two stars. Instead of having to calculate the maximum useful stellar size herself, the user simply gives the desired stellar size as a fraction (0.001-1.3) of the maximum polar radius of the star (which is calculated by the program). In the output file NightfallCurve.dat, you will then find the real size of the star(s).
If no absolute values for total mass and orbital period/separation are given, the program will use some default values (mass = two solar masses, orbital separation = distance earth-sun). In this case, sizes/masses/velocities given in absolute units (e.g. kg, m, m/s, solar masses/radii) are fictuous only - they would be valid only for a system with the assumed default values of total mass and orbital separation.
The newest version of nightfall can be found on ftp://metalab.unc.edu/pub/Linux/science/astronomy, and on the homepage http://www.lsw.uni-heidelberg.de/~rwichman/Nightfall.html.
To subscribe to the nightfall mailing list, send mail to firstname.lastname@example.org with a body of subscribe nightfall-l.
Rainer Wichmann (email@example.com)
If you find a bug in nightfall, please send electronic mail to firstname.lastname@example.org. Please include your operating system and its revision, the version of nightfall, what C compiler you used to compile it, and the output from configure.
|NIGHTFALL (1)||28 December 1999|