Cool Stars 14 - Submitted Abstract # 7
This version created on 05 October 2006

Multiplicity study of Exoplanet host Stars


Markus Mugrauer, AIU Jena 
Ralph Neuhaeuser, AIU Jena 
Tsevi Mazeh, Tel Aviv University 
Eike Guenther, TLS Tautenburg

We present new results from our ongoing multiplicity study of
exoplanet host stars.  We found new stellar companions of the
exoplanet host stars GJ3021 and HD40979 and present our imaging and
spectroscopic data of the wide companion of the exoplanet host star
HD27442.  GJ3021 is a new close planet hosting binary system with a
M3-M5 stellar companion (~0.125Msun) which is separated from its
primary by only 70AU.  In contrast, HD40979 is one of the widest
planet hosting stellar systems known today with a projected separation
of ~6400AU.  We present our observations of the wide companion
HD40979B, which turned out to be a stellar pair composed of a ~0.8Msun
and a ~0.4Msun dwarf with a projected separation of ~130AU.  Hence,
HD40979 is a new member of the small group of planet hosting triple
star systems known today.  Finally, we present our observations of the
planet hosting subgiant HD27442, which has a co-moving companion with
a projected separation of ~240AU.  The V- and H-band magnitudes of
this faint companion are fully consistent with a relatively young, hot
white dwarf, with an effective temperature of ~14400K, and cooling age
of ~220Myr.  With follow-up spectroscopy which shows Hydrogen
absorption features in its optical and infrared spectra, we confirm
the white dwarf nature of this companion.  With the subgiant exoplanet
host star and its white-dwarf companion, HD27442AB is the most evolved
planet hosting stellar system presently known.

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