def get_src_names(gta):
    """Build and return a list of source name

    Parameters
    ----------

    gta : `fermipy.GTAnalysis`
        The analysis object


    Returns
    -------

    l : list
       Names of the source

    """
    o = []
    for s in gta.roi.sources:
        o += [s.name]
    return sorted(o)