The stellar composition of the star formation region CMa R1 – III. A new outburst of the Be star component in Z CMa     

M. E. van den Ancker  P. F. C. Blondel  H. R. E. Tjin A Djie  K. N. Grankin  O. V. Ezhkova  V. S. Shevchenko  E. Guenther  B. Acke 《Monthly notices of the Royal Astronomical Society》2004,349(4):1516-1536

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Astrometric confirmation of a wide low‐mass companion to the planet host star HD 89744     

M. Mugrauer  R. Neuhuser  T. Mazeh  E. Guenther  M. Fernndez 《Astronomische Nachrichten》2004,325(9):718-722

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Deep infrared imaging and spectroscopy of the nearby late M‐dwarf DENIS‐P J104814 –395606     

R. Neuhuser  E.W. Guenther  J. Alves  N. Grosso  Ch. Leinert  Th. Ratzka  Th. Ott  M. Mugrauer  F. Comern  A. Eckart  W. Brandner 《Astronomische Nachrichten》2002,323(5):447-452

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An infrared imaging search for low‐mass companions to members of the young nearby β Pic and Tucana/Horologium associations     

R. Neuhuser  E.W. Guenther  J. Alves  N. Hulamo  Th. Ott  A. Eckart 《Astronomische Nachrichten》2003,324(6):535-542

We present deep high dynamic range infrared images of young nearby stars in the Tucana/Horologium and β Pic associations, all ∼10 to 35 Myrs young and at ∼10 to 60 pc distance. Such young nearby stars are well‐suited for direct imaging searches for brown dwarf and even planetary companions, because young sub‐stellar objects are still self‐luminous due to contraction and accretion. We performed our observations at the ESO 3.5m NTT with the normal infrared imaging detector SofI and the MPE speckle camera Sharp‐I. Three arc sec north of GSC 8047‐0232 in Horologium a promising brown dwarf companion candidate is detected, which needs to be confirmed by proper motion and/or spectroscopy. Several other faint companion candidates are already rejected by second epoch imaging. Among 21 stars observed in Tucana/Horologium, there are not more than one to five brown dwarf companions outside of 75 AU (1.5″ at 50 pc); most certainly only ≤5% of the Tuc/HorA stars have brown dwarf companions (13 to 78 Jupiter masses) outside of 75 AU. For the first time, we can report an upper limit for the frequency of massive planets (∼10 M_jup) at wide separations (∼100 AU) using a meaningfull and homogeneous sample: Of 11 stars observed sufficiently deep in β Pic (12 Myrs), not more than one has a massive planet outside of ∼100 AU, i.e. massive planets at large separations are rare (≤9%). (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献