252 research outputs found
Concern for the patientâs experience comes of age
In this special guest editorial for the inaugural issue of Patient Experience Journal. Dr. Press reflects on how the focus on patient experience has evolved. He starts with a reflection, A journal devoted exclusively to the patientâs experience? A patient satisfaction survey mandated by CMS for all hospitals and a portion of reimbursement dependent upon the scores? An Institute and an âAssociationâ addressing Patient Experience? A new hospital administrative position labeled âChief Experience Officerâ? Some 30 years ago no one would have predicted any of these.
Dr. Press helps us explore and review how the patient experience movement has evolved and the implications of both our history and current state on how we address patient and family needs moving forward. He aptly offers in closing, Concern for the patientâs experience is coming of age
The SuperCOSMOS Sky Survey. Paper III: Astrometry
In this, the third in a series of three papers concerning the SuperCOSMOS Sky
Survey, we describe the astrometric properties of the database. We describe the
algorithms employed in the derivation of the astrometric parameters of the
data, and demonstrate their accuracies by comparison with external datasets
using the first release of data, the South Galactic Cap survey. We show that
the celestial coordinates, which are tied to the International Celestial
Reference Frame via the Tycho-2 reference catalogue, are accurate to better
than +/- 0.2 arcsec at J,R=19,18 rising to +/- 0.3 arcsec at J,R=22,21 with
positional dependent systematic effects from bright to faint magnitudes at the
+/- 0.1 arcsec level. The proper motion measurements are shown to be accurate
to typically +/- 10 mas/yr at J,R=19,18 rising to +/- 50 mas/yr at J,R=22,21
and are tied to zero using the extragalactic reference frame. We show that the
zeropoint errors in the proper motions are 17 and are no
larger than 10 mas/yr for R < 17 mas/yr.Comment: 15 pages, 12 figures; accepted for publication in MNRA
Correcting the influence of an asymmetric line spread function in 2-degree Field spectrograph data
We investigate the role of asymmetries in the line spread function of the
2-degree field spectrograph and the variations in these asymmetries with the
CCD, the plate, the time of observation and the fibre. A data-reduction
pipeline is developed that takes these deformations into account for the
calibration and cross-correlation of the spectra. We show that, using the
emission lines of calibration lamp observations, we can fit the line spread
function with the sum of two Gaussian functions representing the theoretical
signal and a perturbation of the system. This model is then used to calibrate
the spectra and generate templates by downgrading high resolution spectra.
Thus, we can cross-correlate the observed spectra with templates degraded in
the same way. Our reduction pipeline is tested on real observations and
provides a significant improvement in the accuracy of the radial velocities
obtained. In particular, the systematic errors that were as high as ~20 km/s
when applying the AAO reduction package 2dfDR are now reduced to ~5 km/s. Even
though the 2-degree Field spectrograph is to be decommissioned at the end of
2005, the analysis of archival data and previous studies could be improved by
the reduction procedure we propose here.Comment: 9 pages, 9 figures, accepted to PASA, minor change
Transit Detection in the MEarth Survey of Nearby M Dwarfs: Bridging the Clean-First, Search-Later Divide
In the effort to characterize the masses, radii, and atmospheres of
potentially habitable exoplanets, there is an urgent need to find examples of
such planets transiting nearby M dwarfs. The MEarth Project is an ongoing
effort to do so, as a ground-based photometric survey designed to detect
exoplanets as small as 2 Earth radii transiting mid-to-late M dwarfs within 33
pc of the Sun. Unfortunately, identifying transits of such planets in
photometric monitoring is complicated both by the intrinsic stellar variability
that is common among these stars and by the nocturnal cadence, atmospheric
variations, and instrumental systematics that often plague Earth-bound
observatories. Here we summarize the properties of MEarth data gathered so far,
and we present a new framework to detect shallow exoplanet transits in wiggly
and irregularly-spaced light curves. In contrast to previous methods that clean
trends from light curves before searching for transits, this framework assesses
the significance of individual transits simultaneously while modeling
variability, systematics, and the photometric quality of individual nights. Our
Method for Including Starspots and Systematics in the Marginalized Probability
of a Lone Eclipse (MISS MarPLE) uses a computationally efficient semi-Bayesian
approach to explore the vast probability space spanned by the many parameters
of this model, naturally incorporating the uncertainties in these parameters
into its evaluation of candidate events. We show how to combine individual
transits processed by MISS MarPLE into periodic transiting planet candidates
and compare our results to the popular Box-fitting Least Squares (BLS) method
with simulations. By applying MISS MarPLE to observations from the MEarth
Project, we demonstrate the utility of this framework for robustly assessing
the false alarm probability of transit signals in real data. [slightly
abridged]Comment: accepted to the Astronomical Journal, 21 pages, 12 figure
Stellar Photometry and Astrometry with Discrete Point Spread Functions
The key features of the MATPHOT algorithm for precise and accurate stellar
photometry and astrometry using discrete Point Spread Functions are described.
A discrete Point Spread Function (PSF) is a sampled version of a continuous PSF
which describes the two-dimensional probability distribution of photons from a
point source (star) just above the detector. The shape information about the
photon scattering pattern of a discrete PSF is typically encoded using a
numerical table (matrix) or a FITS image file. Discrete PSFs are shifted within
an observational model using a 21-pixel-wide damped sinc function and position
partial derivatives are computed using a five-point numerical differentiation
formula. Precise and accurate stellar photometry and astrometry is achieved
with undersampled CCD observations by using supersampled discrete PSFs that are
sampled 2, 3, or more times more finely than the observational data. The
precision and accuracy of the MATPHOT algorithm is demonstrated by using the
C-language MPD code to analyze simulated CCD stellar observations; measured
performance is compared with a theoretical performance model. Detailed analysis
of simulated Next Generation Space Telescope observations demonstrate that
millipixel relative astrometry and millimag photometric precision is achievable
with complicated space-based discrete PSFs. For further information about
MATPHOT and MPD, including source code and documentation, see
http://www.noao.edu/staff/mighell/matphotComment: 19 pages, 22 figures, accepted for publication in MNRA
Microlensing induced spectral variability in Q2237+0305
We present both photometry and spectra of the individual images of the
quadruple gravitational lens system Q2237+0305. Comparison of spectra obtained
at two epochs, separated by years, shows evidence for significant
changes in the emission line to continuum ratio of the strong ultraviolet
CIV~1549, CIII]~1909 and MgII~2798 lines. The short,
day, light--travel time differences between the sight lines to the
four individual quasar images rule out any explanation based on intrinsic
variability of the source. The spectroscopic differences thus represent direct
detection of microlensing--induced spectroscopic differences in a quasar. The
observations allow constraints to be placed on the relative spatial scales in
the nucleus of the quasar, with the ultra--violet continuum arising in a region
of \la~0.05~{\rm pc} in extent, while the broad emission line material is
distributed on scales much greater than this.Comment: Accepted for Publication in MNRAS. Paper with 11 figure
Unambiguous quasar microlensing
Microlensing studies of quasars can reveal dark matter lumps over a broad
mass spectrum; we highlight the importance of monitoring quasars which are seen
through the halos of low-redshift galaxies. For these configurations
microlensing by planetary-mass objects will manifest itself as isolated events
which are only weakly chromatic. Statistical comparison of the observed optical
depths with their theoretical counterparts provides a strong test for a
microlensing origin of such events. If microlensing is detected, the
light-curves can reveal not only the characteristic microlens masses, and their
corresponding contribution to dark halos, but also how compact the individual
objects are. In this way we can decisively test the possibility that the dark
matter associated with galaxies is composed principally of planetary-mass gas
clouds.Comment: Revised version; 5 pages, 4 figures, to appear in MNRA
The Upper Atmosphere of HD17156b
HD17156b is a newly-found transiting extrasolar giant planet (EGP) that
orbits its G-type host star in a highly eccentric orbit (e~0.67) with an
orbital semi-major axis of 0.16 AU. Its period, 21.2 Earth days, is the longest
among the known transiting planets. The atmosphere of the planet undergoes a
27-fold variation in stellar irradiation during each orbit, making it an
interesting subject for atmospheric modelling. We have used a three-dimensional
model of the upper atmosphere and ionosphere for extrasolar gas giants in order
to simulate the progress of HD17156b along its eccentric orbit. Here we present
the results of these simulations and discuss the stability, circulation, and
composition in its upper atmosphere. Contrary to the well-known transiting
planet HD209458b, we find that the atmosphere of HD17156b is unlikely to escape
hydrodynamically at any point along the orbit, even if the upper atmosphere is
almost entirely composed of atomic hydrogen and H+, and infrared cooling by H3+
ions is negligible. The nature of the upper atmosphere is sensitive to to the
composition of the thermosphere, and in particular to the mixing ratio of H2,
as the availability of H2 regulates radiative cooling. In light of different
simulations we make specific predictions about the thermosphere-ionosphere
system of HD17156b that can potentially be verified by observations.Comment: 31 pages, 42 eps figure
The Binary Fraction of Low Mass White Dwarfs
We describe spectroscopic observations of 21 low-mass (<0.45 M_sun) white
dwarfs (WDs) from the Palomar-Green Survey obtained over four years. We use
both radial velocities and infrared photometry to identify binary systems, and
find that the fraction of single, low-mass WDs is <30%. We discuss the
potential formation channels for these single stars including binary mergers of
lower-mass objects. However, binary mergers are not likely to explain the
observed number of single low-mass WDs. Thus additional formation channels,
such as enhanced mass loss due to winds or interactions with substellar
companions, are likely.Comment: 9 pages, accepted to Ap
A catalogue of rotation and activity in early-M stars
We present a catalogue of rotation and chromospheric activity in a sample of
334 M dwarfs of spectral types M0--M4.5 populating the parameter space around
the boundary to full convection. We obtained high-resolution optical spectra
for 206 targets and determined projected rotational velocity, vsini, and Halpha
emission. The data are combined with measurements of vsini in field stars of
the same spectral type from the literature. Our sample adds 157 new rotation
measurements to the existing literature and almost doubles the sample of
available vsini. The final sample provides a statistically meaningful picture
of rotation and activity at the transition to full convection in the solar
neighborhood. We confirm the steep rise in the fraction of active stars at the
transition to full convection known from earlier work. In addition, we see a
clear rise in rotational velocity in the same stars. In very few stars, no
chromospheric activity but a detection of rotational broadening was reported.
We argue that all of them are probably spurious detections; we conclude that in
our sample all significantly rotating stars are active, and all active stars
are significantly rotating. The rotation-activity relation is valid in
partially and in fully convective stars. Thus, we do not observe any evidence
for a transition from a rotationally dominated dynamo in partially convective
stars to a rotation-independent turbulent dynamo in fully convective stars;
turbulent dynamos in fully convective stars of spectral types around M4 are
still driven by rotation. Finally, we compare projected rotational velocities
of 33 stars to rotational periods derived from photometry in the literature and
determine inclinations for a few of them.Comment: accepted for publication in A
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