24 research outputs found
A Resident-Based Reimbursement System for Intermediate Care Facilities for the Mentally Retarded
In this article, the authors present a resident-based reimbursement system for intermediate care facilities for the mentally retarded (ICFs-MR), which represent a large and growing proportion of the Medicaid budget. The statistical relationship between resident disability level and the expected cost of caring for the individual is estimated, allowing for the prediction of expected resource use across the population of ICF-MR residents. The system incorporates an indirect cost rate, a base direct care rate (constant across all providers), and an individual-specific direct care rate, based on the expected cost of care
Beneficiary Survey-Based Feedback on New Medicare Informational Materials
In response to the Balanced Budget Act (BBA) of 1997, the Center for Medicare & Medicaid Services (CMS) initiated a massive information and education campaign to promote effective health plan decisionmaking. Early results suggest that the pilot version of the Medicare & You handbook and other new Medicare informational materials were viewed favorably overall. Despite their limitations, most beneficiaries found the information useful. The longer, more comprehensive materials were not perceived to be more useful than the shorter, less complicated version. Additional research is needed to determine which subgroups of beneficiaries may need more and, possibly less, information
Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for their Neutron Star Merger Origins
We present the stellar population properties of 69 short gamma-ray burst
(GRB) host galaxies, representing the largest uniformly-modeled sample to-date.
Using the Prospector stellar population inference code, we jointly fit
photometry and/or spectroscopy of each host galaxy. We find a population median
redshift of ( confidence), including 10 new or
revised photometric redshifts at . We further find a median
mass-weighted age of Gyr, stellar mass of
, star formation rate of
SFR=yr, stellar metallicity of
, and dust attenuation of
~mag (68\% confidence). Overall, the majority of
short GRB hosts are star-forming (), with small fractions that are
either transitioning () or quiescent (); however, we
observe a much larger fraction () of quiescent and transitioning
hosts at , commensurate with galaxy evolution. We find that
short GRB hosts populate the star-forming main sequence of normal field
galaxies, but do not include as many high-mass galaxies, implying that their
binary neutron star (BNS) merger progenitors are dependent on a combination of
host star formation and stellar mass. The distribution of ages and redshifts
implies a broad delay-time distribution, with a fast-merging channel at
and a decreased BNS formation efficiency at lower redshifts. If short GRB hosts
are representative of BNS merger hosts within the horizon of current
gravitational wave detectors, these results can inform future searches for
electromagnetic counterparts. All of the data and modeling products are
available on the BRIGHT website.Comment: 32 pages, 15 figures, 3 tables, accepted to Ap
Short GRB Host Galaxies I: Photometric and Spectroscopic Catalogs, Host Associations, and Galactocentric Offsets
We present a comprehensive optical and near-infrared census of the fields of
90 short gamma-ray bursts (GRBs) discovered in 2005-2021, constituting all
short GRBs for which host galaxy associations are feasible ( 60% of
the total Swift short GRB population). We contribute 245 new multi-band imaging
observations across 49 distinct GRBs and 25 spectra of their host galaxies.
Supplemented by literature and archival survey data, the catalog contains 335
photometric and 40 spectroscopic data sets. The photometric catalog reaches
depths of mag and mag for the optical
and near-infrared bands, respectively. We identify host galaxies for 84 bursts,
in which the most robust associations make up 54% (49/90) of events, while only
a small fraction, 6.7%, have inconclusive host associations. Based on new
spectroscopy, we determine 17 host spectroscopic redshifts with a range of
and find that 25-44% of Swift short GRBs
originate from . We also present the galactocentric offset catalog for 83
short GRBs. Taking into account the large range of individual measurement
uncertainties, we find a median of projected offset of kpc, for
which the bursts with the most robust associations have a smaller median of
kpc. Our catalog captures more high-redshift and low-luminosity
hosts, and more highly-offset bursts than previously found, thereby
diversifying the population of known short GRB hosts and properties. In terms
of locations and host luminosities, the populations of short GRBs with and
without detectable extended emission are statistically indistinguishable. This
suggests that they arise from the same progenitors, or from multiple
progenitors which form and evolve in similar environments. All of the data
products are available on the BRIGHT website.Comment: 53 pages, 9 figures, 6 tables, submitte
Multi-Messenger Astronomy with Extremely Large Telescopes
The field of time-domain astrophysics has entered the era of Multi-messenger
Astronomy (MMA). One key science goal for the next decade (and beyond) will be
to characterize gravitational wave (GW) and neutrino sources using the next
generation of Extremely Large Telescopes (ELTs). These studies will have a
broad impact across astrophysics, informing our knowledge of the production and
enrichment history of the heaviest chemical elements, constrain the dense
matter equation of state, provide independent constraints on cosmology,
increase our understanding of particle acceleration in shocks and jets, and
study the lives of black holes in the universe. Future GW detectors will
greatly improve their sensitivity during the coming decade, as will
near-infrared telescopes capable of independently finding kilonovae from
neutron star mergers. However, the electromagnetic counterparts to
high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus
demand ELT capabilities for characterization. ELTs will be important and
necessary contributors to an advanced and complete multi-messenger network.Comment: White paper submitted to the Astro2020 Decadal Surve
The Demographics, Stellar Populations, and Star Formation Histories of Fast Radio Burst Host Galaxies: Implications for the Progenitors
We present a comprehensive catalog of observations and stellar population
properties for 23 highly secure host galaxies of fast radio bursts (FRBs). Our
sample comprises six repeating FRBs and 17 apparent non-repeaters. We present
82 new photometric and eight new spectroscopic observations of these hosts.
Using stellar population synthesis modeling and employing non-parametric star
formation histories (SFHs), we find that FRB hosts have a median stellar mass
of , mass-weighted age Gyr, and
ongoing star formation rate yr but span wide
ranges in all properties. Classifying the hosts by degree of star formation, we
find that 87% (20/23 hosts) are star-forming, two are transitioning, and one is
quiescent. The majority trace the star-forming main sequence of galaxies, but
at least three FRBs in our sample originate in less active environments (two
non-repeaters and one repeater). Across all modeled properties, we find no
statistically significant distinction between the hosts of repeaters and
non-repeaters. However, the hosts of repeating FRBs generally extend to lower
stellar masses, and the hosts of non-repeaters arise in more optically luminous
galaxies. While four of the galaxies with the most clear and prolonged rises in
their SFHs all host repeating FRBs, demonstrating heightened star formation
activity in the last Myr, one non-repeating host shows this SFH
as well. Our results support progenitor models with short delay channels (i.e.,
magnetars formed via core-collapse supernova) for most FRBs, but the presence
of some FRBs in less active environments suggests a fraction form through more
delayed channels.Comment: 52 pages, 32 figures, 6 tables, submitte