Transit model function

gistfile1.py

def trend(p,t):
    """
    Fit the local transit shape with the following function.

    """
    domain = [t.min(),t.max()]
    return Legendre(p,domain=domain)(t)
    
def P051T(p,t):
    """
    Protopapas single transit

    Single transit + trend

    Parameters
    ----------

    p : List of parameters.
        p[0]   epoch
        p[1]   df
        p[2]   tdur 
        p[3:]  passed to trend

    P : period

    Period is held fixed since for a single transit, it doesnot make
    sense to specify period and epoch

    """
    P = 100
    pP05 = [P , p[0] , p[1] , p[2] ]
    sig = P05(pP05,t)

    ptrend = p[3:]
    tr     = trend(ptrend,t)

    return sig + tr

def P05(p,t):
    """
    Analytic model of Protopapas 2005.
    """
    P     = p[0]
    epoch = p[1]
    df    = p[2]
    tdur  = p[3]

    tp = tprime(P,epoch,tdur,t)

    return df * ( 0.5*( 2. - tanh(c*(tp + 0.5)) + tanh(c*(tp - 0.5)) ) - 1.)

def tprime(P,epoch,tdur,t):
    """
    t' in Protopapas
    """
    return  ( P*sin( pi*(t - epoch) / P ) ) / (pi*tdur)