273 research outputs found
Mid-Infrared High-Contrast Imaging of HD 114174 B : An Apparent Age Discrepancy in a "Sirius-Like" Binary System
We present new observations of the faint "Sirius-like" companion discovered
to orbit HD 114174. Previous attempts to image HD 114174 B at mid-infrared
wavelengths using NIRC2 at Keck have resulted in a non-detection. Our new
L'-band observations taken with the Large Binocular Telescope and LMIRCam
recover the companion ( = 10.15 0.15 mag, = 0.675''
0.016'') with a high signal-to-noise ratio (10 ). This
measurement represents the deepest L' high-contrast imaging detection at
sub-arcsecond separations to date, including extrasolar planets. We confirm
that HD 114174 B has near-infrared colors consistent with the interpretation of
a cool white dwarf ( = 0.76 0.19 mag, = 0.64 0.20).
New model fits to the object's spectral energy distribution indicate a
temperature = 4260 360 K, surface gravity log g = 7.94
0.03, a cooling age t 7.8 Gyr, and mass = 0.54
0.01 . We find that the cooling age given by theoretical atmospheric
models do not agree with the age of HD 114174 A derived from both
isochronological and gyrochronological analyses. We speculate on possible
scenarios to explain the apparent age discrepancy between the primary and
secondary. HD 114174 B is a nearby benchmark white dwarf that will ultimately
enable a dynamical mass estimate through continued Doppler and astrometric
monitoring. Efforts to characterize its physical properties in detail will test
theoretical atmospheric models and improve our understanding of white dwarf
evolution, cooling, and progenitor masses.Comment: 6 pages, 3 figures, to be published in the Astrophysical Journal
Letter
Speckle statistics in adaptive optics images at visible wavelengths
Residual speckles in adaptive optics (AO) images represent a well-known
limitation on the achievement of the contrast needed for faint source
detection. Speckles in AO imagery can be the result of either residual
atmospheric aberrations, not corrected by the AO, or slowly evolving
aberrations induced by the optical system. We take advantage of the high
temporal cadence (1 ms) of the data acquired by the System for Coronagraphy
with High-order Adaptive Optics from R to K bands-VIS forerunner experiment at
the Large Binocular Telescope to characterize the AO residual speckles at
visible wavelengths. An accurate knowledge of the speckle pattern and its
dynamics is of paramount importance for the application of methods aimed at
their mitigation. By means of both an automatic identification software and
information theory, we study the main statistical properties of AO residuals
and their dynamics. We therefore provide a speckle characterization that can be
incorporated into numerical simulations to increase their realism and to
optimize the performances of both real-time and postprocessing techniques aimed
at the reduction of the speckle noise
New Extinction and Mass Estimates of the Low-mass Companion 1RXS 1609 B with the Magellan AO System: Evidence of an Inclined Dust Disk
We used the Magellan adaptive optics system to image the 11 Myr substellar
companion 1RXS 1609 B at the bluest wavelengths to date (z' and Ys). Comparison
with synthetic spectra yields a higher temperature than previous studies of
and significant dust extinction of
mag. Mass estimates based on the DUSTY tracks gives
0.012-0.015 Msun, making the companion likely a low-mass brown dwarf surrounded
by a dusty disk. Our study suggests that 1RXS 1609 B is one of the 25% of Upper
Scorpius low-mass members harboring disks, and it may have formed like a star
and not a planet out at 320 AU.Comment: 5 pages, 4 figures; accepted to ApJ
The Multiplicity of M-Dwarfs in Young Moving Groups
We image 104 newly identified low-mass (mostly M-dwarf) pre-main sequence
members of nearby young moving groups with Magellan Adaptive Optics (MagAO) and
identify 27 binaries with instantaneous projected separation as small as 40
mas. 15 were previously unknown. The total number of multiple systems in this
sample including spectroscopic and visual binaries from the literature is 36,
giving a raw multiplicity rate of at least for this
population. In the separation range of roughly 1 - 300 AU in which infrared AO
imaging is most sensitive, the raw multiplicity rate is at least
for binaries resolved by the MagAO infrared camera (Clio). The
M-star sub-sample of 87 stars yields a raw multiplicity of at least
over all separations, for secondary
companions resolved by Clio from 1 to 300 AU ( for all known
binaries in this separation range). A combined analysis with binaries
discovered by the Search for Associations Containing Young stars shows that
multiplicity fraction as a function of mass and age over the range of 0.2 to
1.2 and 10 - 200 Myr appears to be linearly flat in both parameters
and across YMGs. This suggests that multiplicity rates are largely set by 100
Myr without appreciable evolution thereafter. After bias corrections are
applied, the multiplicity fraction of low-mass YMG members () is
in excess of the field.Comment: 25 page
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