摘要：ϵ Eridani is
one of the nearest solar-type stars. Its proximity and relatively young age allow
high-contrast imaging observations to achieve sensitivities to planets at narrow
separations down to an inner radius of ~5 AU. Previous observational studies of the system report a dust
disk with asymmetric morphology as well as a giant planet with large orbital eccentricity,
which may require another massive companion to induce the peculiar morphology and to
enhance the large orbital eccentricity. In this paper, we report results from deep
high-contrastimaging observations to detect the previously reported planet and search for
other unseen less massive companions with Subaru/HiCIAO, Gemini-South/NICI, and VLT/NACO.
No positive detection was made, but high-contrast measurements with the CH4S
narrow-band filter of HiCIAO achieved sensitivities at 14.7 mag differential magnitude
level, at an angular separation of 1.0″. In terms of planetary mass, as determined by cooling
evolutionary models, the highest sensitivities were achieved by the Lp broad-band filter of
NACO, resulting in sensitivities corresponding to 1.8, 2.8, and 4.5 Mjup at the
projected separation of 3 AU, if 200, 400, and 800 Myr is assumed for the age of the
system, respectively. We also discuss origins of the dust disk from the detection
sensitivity in the planetary mass and find that a less massive eccentric planet is
preferred for disk stirring, which is consistent with the orbital parameters of
ϵ Eri b
claimed from the previous long-term radial velocity monitoring.
关键词：planets and satellites: general;stars: individual:ϵEridani;instrumentation: adaptive optics;techniques: image processing
