Calculate the mass and semi-major axis of a planet, from its orbital period, semi-amplitude and eccentricity

planet.py

from astropy.constants import G
import astropy.units as u

# we assume m_planet << m_star

def get_planet_mass(P, K, e, star_mass=1.0):
    """ 
    P in days, K in m/s, star_mass in solar masses 
    output is planet mass in Jupiter masses
    """
    m_mj = 4.919e-3 * star_mass**(2./3) * P**(1./3) * K * np.sqrt(1-e**2)
    return m_mj

def get_planet_semimajor_axis(P, K, star_mass=1.0):
  """ 
  P in days, K in m/s, star_mass in solar masses 
  output is semimajor axis (of planet orbit) in AU
  """
  f = (G.to(u.AU**3 / (u.solMass * u.day**2))**(1./3)).value
  a = f * star_mass**(1./3) * (P/(2*np.pi))**(2./3)
  return a