gw_final_period.f90

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!> \file gw_final_period.f90  Calculates the orbital period of a detached stellar binary after a given time of GW evolution

!   
!   GWtool:       Simple tools for working with gravitational waves
!                 http://gwtool.sourceforge.net/
!   
!   
!   Copyright 2007-2013 AstroFloyd - astrofloyd.org
!   
!   
!   This file is part of GWtool.
!   
!   GWtool is free software: you can redistribute it and/or modify
!   it under the terms of the GNU General Public License as published by
!   the Free Software Foundation, either version 3 of the License, or
!   (at your option) any later version.
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!   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!   GNU General Public License for more details.
!   
!   You should have received a copy of the GNU General Public License
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!***********************************************************************************************************************************
!> \brief  Calculates the orbital period of a detached stellar binary after a given time of GW evolution

program gw_final_period
  use sufr_kinds, only: double
  use sufr_system, only: syntax_quit
  use sufr_constants, only: set_sufr_constants, c3rd,pi2, pc_g,pc_c, msun, solday,julyear
  
  implicit none
  real(double) :: m1,m2,time,cst,pin,pf83,pf
  character :: tmpstr*(99)
  
  if(command_argument_count().eq.4) then
     call get_command_argument(1, tmpstr)
     read(tmpstr,*) m1
     call get_command_argument(2, tmpstr)
     read(tmpstr,*) m2
     call get_command_argument(3, tmpstr)
     read(tmpstr,*) pin
     call get_command_argument(4, tmpstr)
     read(tmpstr,*) time
  else
     call syntax_quit('<M1> <M2> <Pi> <t>  (Mo, days and yr)', 0, &
          'This program calculates the orbital period of a detached stellar binary after a given time of GW evolution')
  end if
  
  call set_sufr_constants()
  
  cst = 5.d0/256.d0 * pi2**(-8.d0*c3rd) * pc_c**5 / pc_g**(5.d0*c3rd) * (m1+m2)**c3rd / (m1*m2*msun**(5.d0*c3rd))
  pf83 = (pin*solday)**(8.d0*c3rd) - time*julyear/cst  ! Pf^8/3
  
  
  write(*,*)
  if(pf83.lt.0.d0) then
     write(*,'(2x,A,ES11.3,A)') 'System has already merged after ',time,' yr.'
     pf83 = 0.d0
  end if
  
  pf = pf83 ** 0.375d0 / solday
  
  write(*,'(2x,A,ES20.9,A5)') 'Pf:    ',pf,' days'
  write(*,'(2x,A,ES20.9,A5)') 'Pf/Pi: ',pf/pin,''
  write(*,*)
  
end program gw_final_period
!***********************************************************************************************************************************