def transit_sec(in_sec, start_sec, end_sec, transit_list):
    """
    determine in what sectors the marked transit are.
    
    Parameters
    ----------
    in_sec : list
        the sectors that we are looking at.
    start_sec : list
        the start time of these sectors
    end_sec : list
        the end time of these sectors
    transit_list : list
        list of the marked peaks

    Returns
    -------
    transit_sec  : list
        list of the sectors in which the peaks appear.

    """
    transit_sec = []
    for peak in transit_list:
        for n, start in enumerate(start_sec):
            if peak >= start[0] and peak <= end_sec[n][0]:
                transit_sec.append(in_sec[n])
    return list(set(transit_sec))
