Hubble space telescope imaging and spectroscopy of the sirius-like triple star system HD 217411

Abstract

We present Hubble Space Telescope imaging and spectroscopy of HD 217411, a G3 V star associated with the extreme ultraviolet (UV) excess source (EUV 2RE J2300-07.0). This star is revealed to be a triple system with a G 3V primary (HD 217411 A) separated by ~1.1 arcsec from a secondary that is in turn composed of an unresolved K0 V star (HD 217411 Ba) and a hot DA white dwarf (HD 217411 Bb). The hot white dwarf dominates the UV flux of the system. However, it is in turn dominated by the K0 V component beyond 3000 Å. A revised distance of 143 pc is estimated for the system. A low level photometric modulation having a period of 0.61 d has also been observed in this system along with a rotational velocity of the order of 60 km s-1 in the K0 V star. Together both observations point to a possible wind induced spin-up of the K0 V star during the AGB phase of the white dwarf. The nature of all three components is discussed as are constraints on the orbits, system age and evolution.