The mass-radius relationship for very low mass stars: Four new discoveries from the HATSouth Survey

Development of the HATSouth project was funded by NSF MRI grant NSF/AST-0723074, operations are supported by NASA grant NNX09AB29G and follow-up observations receive partial support from grant NSF/AST-1108686. Work at the Australian National University is supported by ARC Laureate Fellowship Grant FL0992131. Follow-up observations with the ESO 2.2 m/FEROS instrument were performed under MPI guaranteed time [P087.A9014(A), P088.A-9008(A), P089.A-9008(A)]. AJ acknowledges support from FONDECYT project 1130857, BASAL CATA PFB06 and the Millenium Science Initiative, Chilean Ministry of Economy (Nuclei: P10-022-F, P07-021-F). RB and NE are supported by CONICYT-PCHA/Doctorado Nacional and MR is supported by FONDECYT postdoctoral fellowship 3120097. We acknowledge the use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund, and the SIMBAD data base, operated at CDS, Strasbourg, France. Operations at the MPG/ESO 2.2 m telescope are jointly performed by the Max Planck Gesellschaft and the European Southern Observatory.