Chip 1999 September/Chip_1999-09_cd.bin/sharewar/starclok/SCLOCK20.DOC

Text File | 1996-01-31 | 24.0 KB | 544 lines

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*                   User's Guide To StarClock 2.0                    *
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CONTENTS

1  INTRODUCTION
2  WHAT YOU'LL FIND IN THE DISTRIBUTION PACKET
3  FOR IMPATIENT USERS
4  FULL DESCRIPTION OF THE PROGRAM
5  ACKNOWLEDGEMENTS
6  REFERENCES

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1  INTRODUCTION

Interpolating  in a grid of stellar models computed recently at Geneva
Observatory  by  G.  Schaller  et  al.  (1992), StarClock 2.0 animates
evolution  of stars (0.8 to 25 solar masses, solar metallicity) in the
Hertzsprung-Russell  (H-R) diagram, more exactly in the log(L/L_solar)
vs.  log(T_eff/K)  plane.  The  evolution is followed from the initial
main sequence (also called zero age main sequence, ZAMS) up to the end
of  the  core  carbon burning phase for the most massive stars, to the
early asymptotic giant branch (E-AGB) for the intermediate mass stars,
and to the core helium ignition for the solar-type stars.

The  original grid of stellar models (Schaller et al., 1992; Tab. 5 to
17 and 19 to 22) is available through the following URL:

        http://obswww.unige.ch/~schaerer/evol/Evol_grids.html

The  program  was written in Turbo Pascal 6.0 for PC/DOS machines, VGA
graphics  is required. The executable file SCLOCK20.EXE, compressed by
PKLITE (tm) version 1.05, has 123229 bytes.

StarClock 2.0 (as well as other versions) is freeware. In other words,
it  may  be distributed with no restriction. The standard distribution
packet  (file SCLOCK20.ZIP) can be find at anonymous ftp 147.229.32.10
(psycho.fme.vutbr.cz), cd astronomy/APO.

January 31, 1996                           Leos Ondra
                                           Skretova 6
                                           621 00 Brno
                                           Czech Republic

                                           e-mail: [e-mail]

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2  WHAT YOU'LL FIND IN THE DISTRIBUTION PACKET

   SCLOCK20.DOC

    The file you are reading just now.

   SCLOCK20.EXE

    The program itself. The other files are not necessary to run it.

   GENERAL.DAT, ALGOL.DAT, ECL_BIN.DAT, CEPHEIDS.DAT

    Real  stars  data  (see  section 4 FULL DECRIPTION OF THE PROGRAM,
    Menu "File", for details).

   FILE_ID.DIZ

    Of interest to BBS users only.

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3  FOR IMPATIENT USERS

The  first  thing you see after running the program is the title page.
It isn't of great interest, so press any key (the program doesn't know
mouses)  to  continue.  Now  you  find  yourself  in  the basic regime
"Evolve".  The  right-hand  half  of  the  screen shows a diagram with
logarithm  of  luminosity  on  the  vertical  axis  and  logarithm  of
effective  (or  "surface")  temperature.  Note  that  the  temperature
increases  to  the  left.  The  expression  "Z  = 0.02" tells you that
everything will concern stars with solar chemical composition.

The  other  part  of  the  screen  is  filled  with  menus for setting
parameters  and running various functions. Use arrow or hot keys (case
insensitive)  to navigate between them. The selected (active) menu has
the  brown  frame (it is the case for the menu "Run" now). Stars begin
to  evolve  with the default values of the parameters if you press the
"Enter", "r" or "R" key.

With  increasing  model  time  (in  the  lower left-hand corner of the
diagram,  in  My or millions of years), stars with smaller and smaller
masses  ignite  hydrogen in their cores and appear on the initial main
sequence.  The  number  to  the  left indicates the mass. The evolving
stars  leave  a  color  trace behind them: red codes the core hydrogen
burning  phase, green the core helium burning phase and blue the other
phases  (when  another  or  none  fuel is being consumed in the star's
center).  See section 4 FULL DECRIPTION OF THE PROGRAM, Menu "Define",
to learn how to define these phases.

If  you  are  not  attracted  by what you see on the screen (and what,
hopefully,  reflects real processes in the universe), exit the program
through  menu "Quit" (the hot keys are "q" and "Q"). Otherwise you see
how  the  most massive stars suddenly move to the right, the region of
red giants. After some time, this show becomes boring because stars of
moderate  masses evolve much slower than the heavyweights. But you can
pause  the  evolution (press any key EXCEPT FOR the "Esc" one), select
menu  "Step"  and enter a greater value (in ky or thousands of years).
Then run again the evolution as before. If you decide to break it, use
the "Esc" key.

In  addition, StarClock 2.0 offers the other regime "Explore" (use the
menu  of  the same name, the hot keys are "x" and "X"). In it, you can
examine  the  evolution  of  one  selected  mass in close-up. Browsing
through  seven  pages  you can study changes of the star's luminosity,
effective  temperature  or radius, as well as the central composition,
temperature  and  density with time. The current phase of evolution is
indicated by a pointer common to all the pages.

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4  FULL DESCRIPTION OF THE PROGRAM

Contents

4.1  Regime "Evolve"
4.2  Regime "Explore"

     4.21  Basic page ("Page 0")
     4.22  Pages 1 to 6

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4.1  REGIME "EVOLVE"

The  part  of  the  program which simultaneously animates evolution of
selected  masses.  By default, all masses (0.8 to 25) are computed and
displayed,  but you can change this through the column of menus on the
left side (select a menu and press "Enter").

The other menus and functions are as follows:

MENU "Start"          Hot keys: None       Default: 0 My

The model time (age) from which the evolution is animated. The unit is
"My"  or  million  of years. Possible values are integers smaller than
32767.  In  addition,  if  the start time is greater than the end time
(see  the next menu), an attempt to run the animation causes the error
message "End before run!").

MENU "End"            Hot keys: None       Default: 25028 My

The age (in My or millions of years) when the animation stops. It must
be  greater  than the start time (see the previous menu). Only integer
values  smaller  than 32767 are allowed. The default value corresponds
to the last point in the published grid; if the animation reaches this
age, it stops and the message "Out of grid!" is displayed.

MENU "Step"           Hot keys: None       Default: 10 ky

The  step of the animation (in ky or thousands of years). Only integer
values  smaller  than  32767 are allowed. If it is zero, an attempt to
run the evolution leads to the error message "Step = 0!".

MENU "Delay"          Hot keys: None       Default: 0 ms

On  fast  machines,  you  may  want to slow down the animation without
changing  the  step.  Then  add  delay  (in  milliseconds) between two
consecutive cycles of the run. Again, only integer values smaller than
32767 are acceptable.

MENU "Elapsed"

Here StarClock 2.0 informs you how many per cent of the run (given the
start and end time) has already passed.

MENU "Trace"          Hot keys: t,T        Default: Yes

In  this menu, you can press "Enter" to turn on (off) the trace behind
the evolving stars.

MENU "Phases"         Hot keys: p,P        Default: Yes

Determines  if  the  color of the trace behind the stars (or the stars
themselves,  when the trace is not being drawn) codes different phases
of evolution.

The  "Core  hydrogen  burning"  phase  is  coded red, the "Core helium
burning"  phase  green,  and  blue  indicates  all  the  rest  of  the
evolution.  Read the description of the menu "Define" (below) to learn
how to define these phases.

MENU "Eclipse"        Hot keys: e,E        Default: No

The  function  inspired  by  Mirek  Plavec's  (1986) article, where he
writes  that  normal evolution cannot lead to an eclipsing binary with
the  primary  minimum  deeper than about 0.75 magnitude (in this case,
intensity drops to 50 per cent of its normal level). Another his paper
(Plavec 1983) explains why:

   "The  Algol-type  binaries  are  easily recognized by their deep
   primary eclipses, when the light flux may drop to only a few per
   cent  of  the  normal flux. It is impossible to obtain such deep
   eclipses  with  both components on the main sequence. There, the
   luminosity,   surface   brightness,   and  radius  all  increase
   monotonically  with  mass.  So  when  the  less  massive star is
   eclipsed,  less  than half the total light is lost. When, half a
   period  later,  the  more massive star is eclipsed, it cannot be
   eclipsed  totally,  and  again more than 50 per cent of the flux
   remains.  Deep  eclipses also cannot occur when the more massive
   star  is  evolving  away from the main sequence and is expanding
   rapidly.  For  its  luminosity also increases, and, moreover, an
   increasingly smaller fraction of its disk can be eclipsed by the
   other  star.  In  order  to  get  really deep eclipses, the less
   luminous  star  must  be  the larger of the two. For most stars,
   'less  luminous'  implies 'less massive'. But less massive stars
   evolve more slowly. Thus each such deep eclipse signals that the
   binary  system  has  been  evolving  in  violation  of  the laws
   applying  to single star evolution. According to these, the more
   massive star must always be more advanced in its evolution; even
   if  it  is  only  a  few per cent more massive than its mate, it
   should  become  a red giant while its mate is still an unevolved
   main-sequence star."

If  you activate the menu "Eclipse" (by using the hot keys or pressing
"Enter"  if  the  menu  is  selected  and brown), a small cross-shaped
pointer  appears  in the H-R diagram. Press the "Esc" key to remove it
and  thus  cancel  the  operation, or use arrow keys to move it to the
target position (the arrow keys of the numerical keyboard, effectively
the  keys  "6",  "4",  "8"  and  "2",  move  it faster). The pointer's
position  corresponds  to  the effective temperature and luminosity of
one  component  of  an  eclipsing  binary.  Now, if you press "Enter",
StarClock 2.0 colors a part of the diagram light cyan [*]. In order to
get  the  primary  minimum  deeper  than  0.75  magnitude,  the  other
component  of  the  binary  has to be situated within this highlighted
area.

The  function  calculates  changes  of  bolometric  magnitude  on  the
supposition  that  both  the  components  of  the eclipsing binary are
spherical and radiate like a black body with no limb darkening.

[*]  Warning:  Note  that  before  doing  this StarClock 2.0 saves the
current  status  of  the diagram's area in the memory, and restores it
when  you  exit  the  function. If you run the paused animation in the
meantime, the model time (age) will not correspond to the situation in
the diagram.

MENU "Stars"          Hot keys: s,S        Default: No

Plots  real  stars from a data file, whose name (without the extension
".dat")  is  displayed  in  the menu "File". The warning labeled "[*]"
(see the description of the menu "Eclipse" above) is applicable.

The  function  generates  two  error messages. The first one, "No data
file!",  signals  that no file "*.dat" is available (in this case, the
menu  "File"  is empty). The second message, "Bad data file!", appears
when StarClock 2.0 comes across data with an incorrect format.

MENU "Define"         Hot keys: d,D        Default: see below

This function opens a new page where you can modify definitions of the
core  hydrogen  and  helium  burning  phases  (coded in red and green,
respectively,  during the animation). The definitions are based on the
conception  of  the authors of the grid (Schaller et al. 1992) and use
mass fractions of hydrogen (H) and helium (He) in the star's center.

The  beginning  of  the core hydrogen burning phase begins simply with
the  first  point  of  the  published grid of stellar models (the star
arrives  the  initial  main  sequence).  This  cannot  be  changed  in
StarClock 2.0.

The  core  hydrogen  burning  phase  ends  (according  to the accepted
conception)  when  the mass fraction of hydrogen H in the center drops
to the level "H/end". The common and default value is 0.

The mass fraction of helium He at the end of the core hydrogen burning
phase  reaches  its  maximum,  He_max.  The  core helium burning phase
starts  when  He drops to the value He = He_max - dHe/beg. The authors
of  the  grid  favor  the  value  dHe/beg = 0.002. For example, He_max
0.98065  for  the star of 15 solar masses implies that the core helium
burning  phase  begins when He equals 0.97865. The value "dHe/beg" can
be however modified in the relevant menu.

The end of the core helium burning phase is defined by condition that
He drops to the level "He/end". The common and default value is 0.

MENU "File"           Hot keys: f,F        Default: see below

Immediately  after  you run it, StarClock 2.0 searches through its own
(sub)directory  for  files with the extension ".dat" (ascii text files
with  real stars data) and creates a list of them. The function "File"
allows  you  to select one of them to be used in the function "Stars".
Simply  press  "Enter"  repeatedly  until  you  find  the file you are
looking  for.  A slight drawback of the current version of the program
is  that the files are sorted by DOS rather than alphabetically. If no
files "*.dat" are available, the menu remains empty and any attempt to
browse  through  the  blank  list generates the error message "Mo data
file!".

The  standard  distribution  packet  of  StarClock  2.0  includes  the
following data files:

  GENERAL.DAT

Contains  data for some well-known stars (Spica, Regulus or Arcturus),
used  by  Mirek  Plavec  (1994)  in  his  basic  courses at UCLA as an
illustration   of  terms  like  main  sequence,  red  giants  or  blue
supergiants.   Note  that  the  luminosities  of  some  distant  stars
(Betelgeuse) are uncertain.

  CEPHEIDS.DAT

Data   for   the  well-calibrated  Cepheids  (Population  I)  and  the
non-variable   yellow   supergiants   which  are  situated  along  the
instability  strip  in  the  H-R diagram (Evans 1995). They are either
members  of  binaries  with  a  hot  companion, calibrated by Nancy R.
Evans,  or  members  of  open  clusters  (Schmidt 1984). The stars are
identical  with  those  plotted  in  the  Fig.  3 of Evans (1993). The
Cepheids  are  yellow,  the  non-variable  supergiants  magenta in the
diagram.

  ALGOL.DAT

The   luminosities   and  effective  temperatures  of  all  the  three
components  of  Algol (Beta Persei), taken from Richards (1992). To be
used in the function "Eclipse".

  ECL_BIN.DAT

The  data  for  components  of  eclipsing binaries from the catalog by
Brancewicz   and   Dworak   (1980).  Selected  were  the  semidetached
Algol-type  binaries  with  the Roche lobe filling-up factor 95 to 105
per cent for the secondary component (loser) and less than 50 per cent
for  the primary component (gainer). The parameters of the gainers are
at  the  odd  lines  of the file and these components are magenta when
plotted in the diagram (losers are yellow). To be used in the function
"Eclipse".

Being plain text, real stars data files can be modified and created by
any text editor as long as you keep to the proper format apparent from
the following example (the first line of the file GENERAL.DAT):

1        4.461  4.856  7  7  14 Mimosa

Each  line  contains  data  for  one  star. The first item is a string
(maximum  7  characters)  which  appears  in the diagram as the star's
label.  The  next two items are logarithm of the effective temperature
and  logarithm  of  the  luminosity  (real  type  variables).  The two
integers  which  follow  describe the relative position (in pixels) of
the  star's  symbol  and  label  in  the diagram. They are followed by
another  integer number which codes the color of the star's symbol and
label  (values  0  to 15 are allowed, the gray background has the code
7). Finally, the rest of the line (up to the 256th column) may contain
your  notes  (other  names  of  the star, the reference,...) in a free
format. Neighboring items must be separated by at least one space.

MENU "Run"            Hot keys: r,R

Runs  the  animation of the stellar evolution. Erroneous values of the
parameters may cause error messages (see individual menus).

Press the "Esc" key to break the animation (the prompt "Break (y/n)?")
is  offered.  Press  another  key to pause it (this does not reset the
model  time and allows you to change some parameters, like the step or
delay).

MENU "Quit"           Hot keys: q,Q

Exits the program (the prompt "Quit (y/n)?" is offered).

MENU "Explore"        Hot keys: x,X

Opens pages of the other part of StarClock 2.0, the regime "Explore".

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4.1  REGIME "EXPLORE"

This  new  part  of  StarClock  offers  you possibility to explore the
evolution  of  one  selected  mass in close-up. The default is 5 solar
masses,  change  the  mass  using the column of menus on the left side
(select a menu and press "Enter"). The regime "Explore" shows not only
the  evolutionary  track  in the Hertzsprung-Russell diagram, but also
plots  changes  of  the  star's  luminosity, effective temperature and
radius,  as  well  as  central  temperature,  chemical composition and
density  with age. A movable pointer which indicates the current phase
of evolution is at disposal in all these diagrams.

Note:  In  the  regime "Explore" the arrow keys EITHER allows the menu
selection  OR  moves  the pointer. Use the "Tab" key to toggle between
these possibilities.

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4.21  BASIC PAGE ("PAGE 0")

MENU "Number"         Hot keys: n,N        Default: 2400

Number of steps in computing the evolutionary track. Press "Enter" (if
the  menu is selected and brown) or the hot keys to browse through the
available values (2400 to 24000).

MENU "Stars"          Hot keys: s,S        Default: No
MENU "File"           Hot keys: f,F        Default: see above

See the description of the regime "Evolve" above.

MENU "Run"            Hot keys: r,R

Computes and draws the evolutionary track for the star of the selected
mass. Having done this, StarClock 2.0 puts a cross-shape pointer on it
and displays the corresponding age (in My or millions of years) in the
lower  left-hand  corner  of  the diagram. Use the left or right arrow
keys, the "Home" or "End" keys to move the cursor along the track (the
arrow  keys  of  the  numerical keyboard, effectively the keys "6" and
"4",  move  it  faster).  The  trick is that the pointers at the other
available pages (see below, 4.22 PAGES 1 TO 6) move correspondingly.

MENU "Quit"           Hot keys: q,Q

Exits the program (the prompt "Quit (y/n)?" is offered).

MENU "Explore"        Hot keys: x,X

Opens pages of the other part of StarClock 2.0, the regime "Evolve".

MENU "PgDn"           Hot keys: Page Down

Opens the other pages (1 to 6) of the regime "Explore". See below.

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4.22  PAGES 1 TO 6

For  the  star  of  the  selected  mass plots changes of the following
quantities with age:

  Page 1  "Luminosity"

  Logarithm of the luminosity (unit of the latter: solar luminosity).

  Page 2  "Surface temperature"

  Logarithm of the effective temperature (expressed in kelvins).

  Page 3  "Radius"

  Logarithm of the star's radius (computed from the luminosity and the
  effective temperature) expressed in solar radii.

  Page 4  "Central chemical composition"

  Chemical  composition,  more  exactly  the mass fraction of hydrogen
  (H),  helium  (He), carbon (C12), oxygen (O16) and nitrogen (N14) at
  the  star's  center.  In  the  diagram,  the  mass  fractions of the
  individual  elements  are graphically added. For example, during the
  main-sequence  evolution,  total mass fraction of H and He is nearly
  constant  and  equals  to  0.98  (the  rest, 0.02, is the metal mass
  fraction Z). Note that the diagram has nothing to do with the star's
  radial structure!

  Page 5  "Central temperature"

  Logarithm of the central temperature expressed in kelvins.

  Page 6  "Central density"

  Logarithm of the central density expressed in grams per cubic
  centimeter.

On  the  time  (horizontal)  axis  is  relative  age  of  the  star (0
corresponds  to  the  first point of evolutionary track, 1 to the last
one). The absolute age is displayed at the basic page (see above).

Note  that  at  these  pages  the  arrow  keys  EITHER allows the menu
selection  OR  moves  the pointer (the left or right arrows, including
those  of  the  numerical  keyboard,  and  "Home"  or  "End"  keys are
applicable). Use the "Tab" key to toggle between these possibilities.

The mass of the evolving star can be changed by the column of menus on
the left side (select a menu and press "Enter").

MENU "Zoom"           Hot keys: z,Z        Default: No

Displays  in  close-up the last 20 per cent of the evolution (from 0.8
to 1.0 on the time axis). If the pointer indicates a phase out of this
range,  it  does  not  appear  in  the zoomed diagram. Nevertheless it
reappears at the position 0.8 or 1.0 once you try to move it.

MENU "Main"           Hot keys: m,M

Goes to the basic page ("page 0") of the regime "Explore".

MENU "PgUp"           Hot keys: Page Up

Opens the previous page of the regime "Explore".

MENU "PgDn"           Hot keys: Page Down

Opens the next page of the regime "Explore".

MENU "Quit"           Hot keys: q,Q

Exits the program (the prompt "Quit (y/n)?" is offered).

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5  ACKNOWLEDGEMENTS

StarClock  2.0  could  have  never been created if it were not for the
grid of stellar models computed by G. Schaller, D. Schaerer, G. Meynet
and  A.  Maeder  (Geneva  Observatory)  and  published in a form which
called for writting the program. I am grateful to Nancy R. Evans (York
University) and Mirek J. Plavec (University of California Los Angeles)
for  providing  me with the real stars data. My thanks go to all users
(mainly  teachers of astronomy or physics) who shared their experience
with  StarClock  1.0.  Their  responses  encouraged  me to finish this
second, much extended and hopefully better version. I acknowledge help
of  Rudolf Novak, Jenik Hollan and Jan Janca with the code. The online
services  of  CDS  (Strasbourg,  France)  proved  to  be quite useful.
StarClock  2.0  was  developed  on  computers  of  the  Department  Of
Theoretical  Physics And Astrophysics (DTPA) of the Masaryk University
Brno,  and the Nicholas Copernicus Observatory and Planetarium Brno. I
thank  both  the  institutions  and especially Jarek Kucera (DTPA) for
hospitality.

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6  REFERENCES

Brancewicz, H. K. & Dworak, T. Z. 1980, Acta Astron., 30, 501
Evans, N. R. 1993, Astron. J., 105, 1956
Evans, N. R. 1995, Private communication
Meynet, G.,  Mermilliod,  J.-C. & Maeder, A. 1993,  Astron. Astrophys.
   Suppl. Ser., 98, 477
Plavec, M. J. 1983, J. Roy. Astron. Soc. Can., 77, 283
Plavec, M. J. 1986, In  Instrumentation and  Research  Programmes  for
   Small Telescopes (IAU Symposium No. 118), ed. B. Hearnshaw &  P. L.
   Cottrell (Reidel, Dordrecht), 173
Plavec, M. J. 1994, Private communication
Richards, M. T. 1992, Astrophys. J., 387, 329
Schaller, G. et al. 1992, Astron. Astrophys. Suppl. Ser., 96, 269
Schmidt, E. G. 1984, Astrophys. J., 287, 261

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