1NIGHTFALL(1) Nightfall manual NIGHTFALL(1)
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6 nightfall - binary star astronomy
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9 nightfall -h
10 nightfall -U [more options] [mass_ratio inclination primary_size sec‐
11 ondary_size primary_temperature secondary_temperature]
12 nightfall [-G] [-A] [more options] mass_ratio inclination primary_size
13 secondary_size primary_temperature secondary_temperature
14 nightfall [-G | -U] [-A] [more options] -C file
15
17 nightfall is an interactive astronomy program for fun, education and
18 science. It can generate animated views of eclipsing (or non-eclips‐
19 ing) binary stars, compute light curves and radial velocity curves, and
20 determine best-fit models for observational data.
21 In the simplest case, nightfall computes the light curve for a binary
23 star system with some given mass_ratio (mass of secondary star/mass of
24 primary star), inclination (0 = plane-on view, 90 = edge-on view of the
25 orbital plane), stellar sizes primary_size,secondary_size (dimension‐
26 less, in the range 0 - 1.3), and stellar temperatures primary_tempera‐
27 ture,secondary_temperature (in Kelvin), and writes the light curve to a
28 file NightfallCurve.dat.
29 nightfall is able to show many non-trivial, and sometimes spectacular,
31 physical effecs in binary stars, as it uses a detailed physical model
32 rather than simply assuming the stars to be spherical.
33 The full documentation for nightfall is distributed only in DVI and
35 HTML format, as it is quite big, and thus not very well suited to
36 the 'man' page format. It includes some discussion of binary stars (at
37 a popular science level, hopefully) that you may find helpful in under‐
38 standing what the program does.
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41 -h Print a usage message on standard output and exit successfully.
42 -U Run in interactive mode.
44 -C file
46 Use binary star parameters from a configuration file instead of
47 giving them on the command line. Sample configuration files are
48 in share/nightfall/cfg.
49 -G[P|S|1|2]
51 Plot a graph of the lightcurve after its computation (P|S - zoom
52 on primary/secondary eclipse, 1|2 - plot 1/2 orbits).
53 -A Generate an animated view of the binary star.
55 -V[v|i|c|a]
57 Visualize the geometry of the binary star system (v - view of
58 the stars, i - image of the potential, c - contour plot of the
59 potential, a - all of them).
60 -H Send plot to a postscript file. If the postscript file exists,
62 it will be overwritten.
63 -B[U|B|V|I|R|J|H|K|u|v|b|y|1|2]
65 Select the filter/bandpass for which the lightcurve should be
66 plotted. U-K range from ultraviolett to infrared, best match to
67 the human eye is V. u-y are narrow-band filters. 1|2 will
68 select radial velocity curves instead of a light curve.
69 -fP/-fS value
71 By default, nightfall assumes synchroneous rotation, which
72 means that the stars are rotating with the orbital period, and
73 thus show each other always the same 'side'. With this option,
74 you can set the ratio of stellar rotation frequency to orbital
75 frequency to some value different from one, seperately for the
76 primary P and the secondary S.
77 -e eccentricity periastron_length
79 By default, nightfall assumes the orbit to be circular. With
80 this option, you can set the eccentricity of the orbit (0 is
81 circular, maximum is less than 1), and the periastron length,
82 which is the point of closest approach of the two stars in their
83 orbit (0 - 360 degree).
84 -sP/-sS longitude latitude radius dimfactor
86 Place a spot on the primary (P) or secondary (S). The spot
87 parameters are the location of the spot (longitude,latitude),
88 its radius, and the dimfactor by which the temperature is
89 reduced (or increased) within the spot area.
90 -tP/-tM/-tD value
92 Set the absolute value for the orbital period P (in days), the
93 total mass M (in units of solar masses), and/or the orbital sep‐
94 aration D (in solar radii) of the system. Any two of these are
95 independent, the third is then calculated from Kepler's laws
96 (i.e., you should set only two of these).
97 -I file
99 Read in observational data from a data file. Sample data files
100 are in share/nightfall/data.
101 -D[vwb]
103 Diagnostic output (v - verbose, w - warnings, b - status mes‐
104 sages).
105
107 The definition of primary/secondary is inverse to the usual convention
108 in astronomy.
109 Obviously, the size of a star in a binary system is limited by the
111 orbital separation of the two stars. Instead of having to calculate the
112 maximum useful stellar size herself, the user simply gives the desired
113 stellar size as a fraction (0.001-1.3) of the maximum polar radius of
114 the star (which is calculated by the program). In the output file
115 NightfallCurve.dat, you will then find the 'real' size of the star(s).
116 If no absolute values for total mass and orbital period/separation are
118 given, the program will use some default values (mass = two solar
119 masses, orbital separation = distance earth-sun). In this case,
120 sizes/masses/velocities given in absolute units (e.g. kg, m, m/s, solar
121 masses/radii) are fictuous only - they would be valid only for a system
122 with the assumed default values of total mass and orbital separation.
123 The newest version of nightfall can be found on ftp://meta‐
125 lab.unc.edu/pub/Linux/science/astronomy, and on the homepage
126 http://www.lsw.uni-heidelberg.de/~rwichman/Nightfall.html.
127 To subscribe to the nightfall mailing list, send mail to major‐
129 domo@seul.org with a body of subscribe nightfall-l.
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132 Rainer Wichmann (rwichmann@hs.uni-hamburg.de)
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135 If you find a bug in nightfall, please send electronic mail to rwich‐
136 mann@hs.uni-hamburg.de. Please include your operating system and its
137 revision, the version of nightfall, what C compiler you used to compile
138 it, and the output from 'configure'.
139 28 December 1999 NIGHTFALL(1)