41 research outputs found
CHARIS Science: Performance Simulations for the Subaru Telescope's Third-Generation of Exoplanet Imaging Instrumentation
We describe the expected scientific capabilities of CHARIS, a high-contrast
integral-field spectrograph (IFS) currently under construction for the Subaru
telescope. CHARIS is part of a new generation of instruments, enabled by
extreme adaptive optics (AO) systems (including SCExAO at Subaru), that promise
greatly improved contrasts at small angular separation thanks to their ability
to use spectral information to distinguish planets from quasistatic speckles in
the stellar point-spread function (PSF). CHARIS is similar in concept to GPI
and SPHERE, on Gemini South and the Very Large Telescope, respectively, but
will be unique in its ability to simultaneously cover the entire near-infrared
, , and bands with a low-resolution mode. This extraordinarily broad
wavelength coverage will enable spectral differential imaging down to angular
separations of a few , corresponding to 0.\!\!''1. SCExAO
will also offer contrast approaching at similar separations,
0.\!\!''1--0.\!\!''2. The discovery yield of a CHARIS survey will
depend on the exoplanet distribution function at around 10 AU. If the
distribution of planets discovered by radial velocity surveys extends unchanged
to 20 AU, observations of 200 mostly young, nearby stars targeted
by existing high-contrast instruments might find 1--3 planets. Carefully
optimizing the target sample could improve this yield by a factor of a few,
while an upturn in frequency at a few AU could also increase the number of
detections. CHARIS, with a higher spectral resolution mode of , will
also be among the best instruments to characterize planets and brown dwarfs
like HR 8799 cde and And b.Comment: 13 pages, 7 figures, proceedings from SPIE Montrea
Supersymmetry breaking induced by radiative corrections
We show that simultaneous gauge and supersymmetry breaking can be induced by
radiative corrections, a la Coleman-Weinberg. When a certain correlation among
the superpotential parameters is present, a local supersymmetry-breaking
minimum is found in the effective potential of a gauge non-singlet field, in a
region where the tree-level potential is almost flat. Supersymmetry breaking is
then transmitted to the MSSM through gauge and chiral messenger loops, thus
avoiding the suppression of gaugino masses characteristic of direct gauge
mediation models. The use of a single field ensures that no dangerous tachyonic
scalar masses are generated at the one-loop level. We illustrate this mechanism
with an explicit example based on an SU(5) model with a single adjoint. An
interesting feature of the scenario is that the GUT scale is increased with
respect to standard unification, thus allowing for a larger colour Higgs
triplet mass, as preferred by the experimental lower bound on the proton
lifetime.Comment: 22 pages, 3 figures. Two references added, small redactional changes,
some discussion improved. Results unchange
Orbital characterization of GJ1108A system, and comparison of dynamical mass with model-derived mass for resolved binaries
We report an orbital characterization of GJ1108Aab that is a low-mass binary
system in pre-main-sequence phase. Via the combination of astrometry using
adaptive optics and radial velocity measurements, an eccentric orbital solution
of =0.63 is obtained, which might be induced by the Kozai-Lidov mechanism
with a widely separated GJ1108B system. Combined with several observed
properties, we confirm the system is indeed young. Columba is the most probable
moving group, to which the GJ1108A system belongs, although its membership to
the group has not been established. If the age of Columba is assumed for
GJ1108A, the dynamical masses of both GJ1108Aa and GJ1108Ab ( and ) are more massive than what an
evolutionary model predicts based on the age and luminosities. We consider the
discrepancy in mass comparison can attribute to an age uncertainty; the system
is likely older than stars in Columba, and effects that are not implemented in
classical models such as accretion history and magnetic activity are not
preferred to explain the mass discrepancy. We also discuss the performance of
the evolutionary model by compiling similar low-mass objects in evolutionary
state based on the literature. Consequently, it is suggested that the current
model on average reproduces the mass of resolved low-mass binaries without any
significant offsets.Comment: Accepted in Ap
SEEDS direct imaging of the RV-detected companion to V450 Andromedae, and characterization of the system
We report the direct imaging detection of a low-mass companion to a young,
moderately active star V450 And, that was previously identified with the radial
velocity method. The companion was found in high-contrast images obtained with
the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics
system. From the public ELODIE and SOPHIE archives we extracted available
high-resolution spectra and radial velocity (RV) measurements, along with RVs
from the Lick planet search program. We combined our multi-epoch astrometry
with these archival, partially unpublished RVs, and found that the companion is
a low-mass star, not a brown dwarf, as previously suggested. We found the
best-fitting dynamical masses to be and
M. We also performed spectral analysis of
the SOPHIE spectra with the iSpec code. The Hipparcos time-series photometry
shows a periodicity of d, which is also seen in SOPHIE spectra as an
RV modulation of the star A. We interpret it as being caused by spots on the
stellar surface, and the star to be rotating with the given period. From the
rotation and level of activity, we found that the system is
Myr old, consistent with an isochrone analysis ( Myr). This
work may serve as a test case for future studies of low-mass stars, brown
dwarfs and exoplanets by combination of RV and direct imaging data.Comment: 15 pages, 9 figures, 7 tables, to appear in Ap
Characterization of the gaseous companion {\kappa} Andromedae b: New Keck and LBTI high-contrast observations
We previously reported the direct detection of a low mass companion at a
projected separation of 55+-2 AU around the B9 type star {\kappa} Andromedae.
The properties of the system (mass ratio, separation) make it a benchmark for
the understanding of the formation and evolution of gas giant planets and brown
dwarfs on wide-orbits. We present new angular differential imaging (ADI) images
of the Kappa Andromedae system at 2.146 (Ks), 3.776 (L'), 4.052 (NB 4.05) and
4.78 {\mu}m (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as more
accurate near-infrared photometry of the star with the MIMIR instrument. We
derive a more accurate J = 15.86 +- 0.21, H = 14.95 +- 0.13, Ks = 14.32 +- 0.09
mag for {\kappa} And b. We redetect the companion in all our high contrast
observations. We confirm previous contrasts obtained at Ks and L' band. We
derive NB 4.05 = 13.0 +- 0.2 and M' = 13.3 +- 0.3 mag and estimate
Log10(L/Lsun) = -3.76 +- 0.06. We build the 1-5 microns spectral energy
distribution of the companion and compare it to seven PHOENIX-based atmospheric
models in order to derive Teff = 1900+100-200 K. Models do not set constrains
on the surface gravity. ``Hot-start" evolutionary models predict masses of
14+25-2 MJup based on the luminosity and temperature estimates, and considering
a conservative age range for the system (30+120-10 Myr). ``warm-start"
evolutionary tracks constrain the mass to M >= 11 MJup. Therefore, the mass of
{\kappa} Andromedae b mostly falls in the brown-dwarf regime, due to remaining
uncertainties in age and mass-luminosity models. According to the formation
models, disk instability in a primordial disk could account for the position
and a wide range of plausible masses of {\kappa} And b.Comment: 20 pages, 16 figures, accepted for publication in Astronomy and
Astrophysics on August 6, 201
A Substellar Companion to Pleiades HII 3441
We find a new substellar companion to the Pleiades member star, Pleiades HII
3441, using the Subaru telescope with adaptive optics. The discovery is made as
part of the high-contrast imaging survey to search for planetary-mass and
substellar companions in the Pleiades and young moving groups. The companion
has a projected separation of 0".49 +/- 0".02 (66 +/- 2 AU) and a mass of 68
+/- 5 M_J based on three observations in the J-, H-, and K_S-band. The spectral
type is estimated to be M7 (~2700 K), and thus no methane absorption is
detected in the H band. Our Pleiades observations result in the detection of
two substellar companions including one previously reported among 20 observed
Pleiades stars, and indicate that the fraction of substellar companions in the
Pleiades is about 10.0 +26.1/-8.8 %. This is consistent with multiplicity
studies of both the Pleiades stars and other open clusters.Comment: Main text (14 pages, 4 figures, 4 tables), and Supplementary data (8
pages, 3 tables). Accepted for Publications of Astronomical Society of Japa