docs: def dRV(self,dt,com=False):
          """Change in RV of star 1 for time separation dt (default=days)
  
          :param dt:
              Time separation for which to compute RV change.  If not a ``Quantity``,
              then assumed to be in days.
          :type dt:
              float, array-like, or ``Quantity``
  
          :param com: (``bool``, optional)
              If ``True``, then return dRV of star 1 in center-of-mass frame.
  
          :return dRV:
              Change in radial velocity over time ``dt``.
  
          """
          if type(dt) != Quantity:
              dt *= u.day
  
          mean_motions = np.sqrt(G*(self.mred)*MSUN/(self.semimajor*AU)**3)
          mean_motions = np.sqrt(const.G*(self.mred)/(self.semimajor)**3)
  
          newM = self.M + mean_motions * dt
          pos,vel = orbit_posvel(newM,self.ecc,self.semimajor.value,
                                 self.mred.value,
                                 self.obspos)
  
          if com:
              return (vel.z - self.RV) * (self.M2 / (self.M1 + self.M2))
          else:
              return vel.z-self.RV