code: def sigOmega(self,dangle):
          
          dOmin= dangle/self._tdisrupt
          meandO= self._meandO
          sO1D2= ((numpy.sqrt(2./numpy.pi)*numpy.sqrt(self._sortedSigOEig[2])\
                       *(meandO+dOmin)\
                       *numpy.exp(-0.5*(meandO-dOmin)**2.\
                                     /self._sortedSigOEig[2])/
                  (1.+special.erf((meandO-dOmin)\
                                      /numpy.sqrt(2.*self._sortedSigOEig[2]))))\
                     +meandO**2.+self._sortedSigOEig[2])
          mO= self.meanOmega(dangle,oned=True,use_physical=False)
          return numpy.sqrt(sO1D2-mO**2.)
docs: NAME:
  
             sigmaOmega
  
          PURPOSE:
  
             calculate the 1D sigma in frequency as a function of angle, assuming a uniform time distribution up to a maximum time
  
          INPUT:
  
             dangle - angle offset
  
          OUTPUT:
  
             sigma Omega
  
          HISTORY:
  
             2013-12-05 - Written - Bovy (IAS)