128 research outputs found
Dynamical Masses and Ages of Sirius-like Systems
We measure precise orbits and dynamical masses and derive age constraints for
six confirmed and one candidate Sirius-like systems, including the Hyades
member HD 27483. Our orbital analysis incorporates radial velocities, relative
astrometry, and Hipparcos-Gaia astrometric accelerations. We constrain the
main-sequence lifetime of a white dwarf's progenitor from the remnant's
dynamical mass and semi-empirical initial-final mass relations and infer the
cooling age from mass and effective temperature. We present new relative
astrometry of HD 27483 B from Keck/NIRC2 observations and archival HST data,
and obtain the first dynamical mass of ,
and an age of Myr, consistent with previous age estimates
of Hyades. We also measure precise dynamical masses for HD 114174 B ( ) and HD 169889 B ( ),
but their age precisions are limited by their uncertain temperatures. For HD
27786 B, the unusually small mass of suggests a
history of rapid mass loss, possibly due to binary interaction in its
progenitor's AGB phase. The orbits of HD 118475 and HD 136138 from our RV
fitting are overall in good agreement with Gaia DR3 astrometric two-body
solutions, despite moderate differences in the eccentricity and period of HD
136138. The mass of for HD 118475 B and
a speckle imaging non-detection confirms that the companion is a white dwarf.
Our analysis shows examples of a rich number of precise WD dynamical mass
measurements enabled by Gaia DR3 and later releases, which will improve
empirical calibrations of the white dwarf initial-final mass relation.Comment: 21 pages, 7 figures. Submitted to MNRA
Pathology Steered Stratification Network for Subtype Identification in Alzheimer's Disease
Alzheimer's disease (AD) is a heterogeneous, multifactorial neurodegenerative
disorder characterized by beta-amyloid, pathologic tau, and neurodegeneration.
There are no effective treatments for Alzheimer's disease at a late stage,
urging for early intervention. However, existing statistical inference
approaches of AD subtype identification ignore the pathological domain
knowledge, which could lead to ill-posed results that are sometimes
inconsistent with the essential neurological principles. Integrating systems
biology modeling with machine learning, we propose a novel pathology steered
stratification network (PSSN) that incorporates established domain knowledge in
AD pathology through a reaction-diffusion model, where we consider non-linear
interactions between major biomarkers and diffusion along brain structural
network. Trained on longitudinal multimodal neuroimaging data, the biological
model predicts long-term trajectories that capture individual progression
pattern, filling in the gaps between sparse imaging data available. A deep
predictive neural network is then built to exploit spatiotemporal dynamics,
link neurological examinations with clinical profiles, and generate subtype
assignment probability on an individual basis. We further identify an
evolutionary disease graph to quantify subtype transition probabilities through
extensive simulations. Our stratification achieves superior performance in both
inter-cluster heterogeneity and intra-cluster homogeneity of various clinical
scores. Applying our approach to enriched samples of aging populations, we
identify six subtypes spanning AD spectrum, where each subtype exhibits a
distinctive biomarker pattern that is consistent with its clinical outcome.
PSSN provides insights into pre-symptomatic diagnosis and practical guidance on
clinical treatments, which may be further generalized to other
neurodegenerative diseases
Post-processing CHARIS integral field spectrograph data with PyKLIP
We present the pyKLIP-CHARIS post-processing pipeline, a Python library that
reduces high contrast imaging data for the CHARIS integral field spectrograph
used with the SCExAO project on the Subaru Telescope. The pipeline is a part of
the pyKLIP package, a Python library dedicated to the reduction of direct
imaging data of exoplanets, brown dwarfs, and discs. For PSF subtraction, the
pyKLIP-CHARIS post-processing pipeline relies on the core algorithms
implemented in pyKLIP but uses image registration and calibrations that are
unique to CHARIS. We describe the pipeline procedures, calibration results, and
capabilities in processing imaging data acquired via the angular differential
imaging and spectral differential imaging observing techniques. We showcase its
performance on extracting spectra of injected synthetic point sources as well
as compare the extracted spectra from real data sets on HD 33632 and HR 8799 to
results in the literature. The pipeline is a python-based complement to the
SCExAO project supported, widely used (and currently IDL-based) CHARIS data
post-processing pipeline (CHARIS DPP) and provides an additional approach to
reducing CHARIS data and extracting calibrated planet spectra.Comment: 17 pages, 13 figure
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