91 research outputs found
Mapping the Planetary Wake in HD 163296 with Kinematics
We map the planetary wake associated with the embedded protoplanet creating
the CO kink in the disk of HD~163296. We show that the wake can be traced by a
series of correlated perturbations in the peak velocity map. The sign change of
the perturbations across the disk major axis confirm that the wake induces
predominantly radial motion, as predicted by models of planet-disk interaction.
These results provide the first direct confirmation of planet wakes generated
by Lindblad resonances. Mapping the wake provides a constraint on the disk
aspect ratio, which is required to measure the mass of the planet.Comment: 10 Pages, 6 figures. Accepted in ApJ
Signatures of an eccentric disc cavity: Dust and gas in IRS 48
We test the hypothesis that the disc cavity in the `transition disc' Oph IRS
48 is carved by an unseen binary companion. We use 3D dust-gas
smoothed-particle hydrodynamics simulations to demonstrate that marginally
coupled dust grains concentrate in the gas over-density that forms in in the
cavity around a low binary mass ratio binary. This produces high contrast ratio
dust asymmetries at the cavity edge similar to those observed in the disc
around IRS 48 and other transition discs. This structure was previously assumed
to be a vortex. However, we show that the observed velocity map of IRS 48
displays a peculiar asymmetry that is not predicted by the vortex hypothesis.
We show the unusual kinematics are naturally explained by the non-Keplerian
flow of gas in an eccentric circumbinary cavity. We further show that
perturbations observed in the isovelocity curves of IRS 48 may be explained as
the product of the dynamical interaction between the companion and the disc.
The presence of a 0.4 M companion at a 10 au separation
can qualitatively explain these observations. High spatial resolution line and
continuum imaging should be able to confirm this hypothesis.Comment: 9 pages, 7 figures, accepted for publication in MNRA
Kinematic and thermal signatures of the directly imaged protoplanet candidate around Elias 2-24
We report kinematic and thermal signatures associated with the directly
imaged protoplanet candidate in the Elias 2-24 disc. Using the DSHARP ALMA
observations of the CO J=2-1 line, we show that the disc kinematics are
perturbed, with a detached CO emission spot at the location of the planet
candidate and traces of spiral wakes, and also that the observed CO emission
intensities require local heating. While the foreground extinction hides the
velocity channels associated with the planet, preventing a planet mass
estimate, the level of gas heating implied by the CO emission indicates the
presence of a warm, embedded giant planet. Comparison with models show this
could either be a M, or a lower mass ( M) but accreting proto-planet.Comment: 6 pages, 3 figures, accepted for publication in MNRAS Letter
Quasar accretion disk sizes from continuum reverberation mapping in the DES standard-star fields
Measurements of the physical properties of accretion disks in active galactic
nuclei are important for better understanding the growth and evolution of
supermassive black holes. We present the accretion disk sizes of 22 quasars
from continuum reverberation mapping with data from the Dark Energy Survey
(DES) standard star fields and the supernova C fields. We construct continuum
lightcurves with the \textit{griz} photometry that span five seasons of DES
observations. These data sample the time variability of the quasars with a
cadence as short as one day, which corresponds to a rest frame cadence that is
a factor of a few higher than most previous work. We derive time lags between
bands with both JAVELIN and the interpolated cross-correlation function method,
and fit for accretion disk sizes using the JAVELIN Thin Disk model. These new
measurements include disks around black holes with masses as small as
, which have equivalent sizes at 2500\AA \, as small as
light days in the rest frame. We find that most objects have
accretion disk sizes consistent with the prediction of the standard thin disk
model when we take disk variability into account. We have also simulated the
expected yield of accretion disk measurements under various observational
scenarios for the Large Synoptic Survey Telescope Deep Drilling Fields. We find
that the number of disk measurements would increase significantly if the
default cadence is changed from three days to two days or one day.Comment: 33 pages, 24 figure
Cardiovascular risk factors and evolution of patients attended with COVID-19 in a National Reference Hospital from Lima, Peru
Introduction: Coronavirus disease 2019 (COVID-19) fatal outcomes have been associated with multiple cardiovascular risk factors. In new epidemic areas, such as Latin America, there is a lack of studies about this. Objectives: To evaluate demographic data, signs and symptoms during emergency arrival, prevalence of cardiovascular risk factors, laboratory and ECG findings and their influence in mortality, in a retrospective cohort of patients in a national reference hospital of Lima, Peru. Methods: Review the clinical records of the patients attended at Hospital Rebagliati Hospital during March 6th and April 30th, 2020, using rRT-PCR was used for the detection of the RNA of SARS-CoV-2 following the protocol Charité, Berlin, Germany, from nasopharyngeal swabs at the National Institute of Health. Bivariate analysis and multivariate analysis using logistic regression was done. Values of p < 0.05 were considered significant for all analyses. Results: One hundred six hospitalized patients were evaluated. The mean age of patients was 61.58 years (SD 16.81). Cardiovascular risk factors among them were hypertension (46.2%), diabetes (28.3%), and obesity (28.3%), among others. Fifty-six patients died (52.8%). Mortality associated factors at the multivariate analysis were arterial hypertension (OR=1.343, 95% 1.089-1.667), myocardial injury (OR=1.303, 95% 1.031-1.642), and mechanical ventilation (OR 1.262, 95% 1.034-1.665), as associated factors. Conclusion: Cardiovascular risk factors and cardiovascular signs or symptoms are common during emergency arrival in patients with COVID-19. Arterial hypertension, myocardial injury and mechanical ventilation were associated with mortality in multivariate analysis, as observed in other regions of the world.Introducción: Los desenlaces fatales de la enfermedad por coronavirus 2019 (COVID-19) se han asociado con múltiples factores de riesgo cardiovascular. En nuevas áreas epidémicas, como América Latina, faltan estudios al respecto. Objetivos: Evaluar datos demográficos, signos y sÃntomas durante la ingreso a emergencia, prevalencia de factores de riesgo cardiovascular, hallazgos de laboratorio y ECG y su influencia en la mortalidad, en una cohorte retrospectiva de pacientes en un hospital nacional de referencia de Lima, Perú. Métodos: Se revisaron las historias clÃnicas de los pacientes atendidos en el Hospital Nacional Edgardo Rebagliati durante los dÃas 6 de marzo y 30 de abril de 2020, se utilizó rRT-PCR para la detección del ARN del SARS-CoV-2 siguiendo el protocolo Charité, BerlÃn, Alemania de hisopos nasofarÃngeos en el Instituto Nacional de Salud. Se realizó análisis bivariado y análisis multivariado mediante regresión logÃstica. Los valores de p <0,05 se consideraron significativos para todos los análisis. Resultados: Se evaluaron ciento seis pacientes hospitalizados. La edad media de los pacientes fue de 61,58 años (DE 16,81). Los factores de riesgo cardiovascular entre ellos fueron hipertensión (46,2%), diabetes (28,3%) y obesidad (28,3%), entre otros. Fallecieron 56 pacientes (52,8%). Los factores asociados a la mortalidad en el análisis multivariado fueron hipertensión arterial (OR = 1.343, 95% 1.089-1.667), lesión miocárdica (OR = 1.303, 95% 1.031-1.642) y ventilación mecánica (OR 1.262, 95% 1.034-1.665), como factores asociados. Conclusión: Los factores de riesgo cardiovascular y los signos o sÃntomas cardiovasculares son comunes durante la llegada de emergencia en pacientes con COVID-19. La hipertensión arterial, la lesión miocárdica y la ventilación mecánica se asociaron con la mortalidad en el análisis multivariado, como se observó en otras regiones del mundo
Recreating the OSIRIS-REx Slingshot Manoeuvre from a Network of Ground-Based Sensors
Optical tracking systems typically trade-off between astrometric precision
and field-of-view. In this work, we showcase a networked approach to optical
tracking using very wide field-of-view imagers that have relatively low
astrometric precision on the scheduled OSIRIS-REx slingshot manoeuvre around
Earth on September 22nd, 2017. As part of a trajectory designed to get
OSIRIS-REx to NEO 101955 Bennu, this flyby event was viewed from 13 remote
sensors spread across Australia and New Zealand to promote triangulatable
observations. Each observatory in this portable network was constructed to be
as lightweight and portable as possible, with hardware based off the successful
design of the Desert Fireball Network.
Over a 4 hour collection window, we gathered 15,439 images of the night sky
in the predicted direction of the OSIRIS-REx spacecraft. Using a specially
developed streak detection and orbit determination data pipeline, we detected
2,090 line-of-sight observations. Our fitted orbit was determined to be within
about 10~km of orbital telemetry along the observed 109,262~km length of
OSIRIS-REx trajectory, and thus demonstrating the impressive capability of a
networked approach to SSA
Rapidly evolving transients in the Dark Energy Survey
We present the results of a search for rapidly evolving transients in the Dark Energy Survey Supernova Programme. These events are characterized by fast light-curve evolution (rise to peak in≲10 d and exponential decline in≲30 d after peak).We discovered 72 events, including 37 transients with a spectroscopic redshift from host galaxy spectral features. The 37 events increase the total number of rapid optical transients by more than a factor of two. They are found at a wide range of redshifts (0.05 Mg > -22.25). The multiband photometry is well fit by a blackbody up to few weeks after peak. The events appear to be hot (T ≈ 10 000-30 000 K) and large (R ≈ 1014 - 2 × 1015 cm) at peak, and generally expand and cool in time, though some events show evidence for a receding photosphere with roughly constant temperature. Spectra taken around peak are dominated by a blue featureless continuum consistent with hot, optically thick ejecta. We compare our events with a previously suggested physical scenario involving shock breakout in an optically thick wind surrounding a core-collapse supernova, we conclude that current models for such a scenario might need an additional power source to describe the exponential decline. We find that these transients tend to favour star-forming host galaxies, which could be consistent with a core-collapse origin. However, more detailed modelling of the light curves is necessary to determine their physical origin
OzDES reverberation mapping program: Lag recovery reliability for 6-yr C iv analysis
We present the statistical methods that have been developed to analyse the OzDES reverberation mapping sample. To perform this statistical analysis we have created a suite of customizable simulations that mimic the characteristics of each source in the OzDES sample. These characteristics include: the variability in the photometric and spectroscopic light curves, the measurement uncertainties, and the observational cadence. By simulating the sources in the OzDES sample that contain the C iv emission line, we developed a set of criteria that rank the reliability of a recovered time-lag depending on the agreement between different recovery methods, the magnitude of the uncertainties, and the rate at which false positives were found in the simulations. These criteria were applied to simulated light curves and these results used to estimate the quality of the resulting Radius-Luminosity relation. We grade the results using three quality levels (gold, silver, and bronze). The input slope of the R-L relation was recovered within 1σ for each of the three quality samples, with the gold standard having the lowest dispersion with a recovered a R-L relation slope of 0.454 ± 0.016 with an input slope of 0.47. Future work will apply these methods to the entire OzDES sample of 771 AGN
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