485 research outputs found
The NN2 Flux Difference Method for Constructing Variable Object Light Curves
We present a new method for optimally extracting point-source time
variability information from a series of images. Differential photometry is
generally best accomplished by subtracting two images separated in time, since
this removes all constant objects in the field. By removing background sources
such as the host galaxies of supernovae, such subtractions make possible the
measurement of the proper flux of point-source objects superimposed on extended
sources. In traditional difference photometry, a single image is designated as
the ``template'' image and subtracted from all other observations. This
procedure does not take all the available information into account and for
sub-optimal template images may produce poor results. Given N total
observations of an object, we show how to obtain an estimate of the vector of
fluxes from the individual images using the antisymmetric matrix of flux
differences formed from the N(N-1)/2 distinct possible subtractions and provide
a prescription for estimating the associated uncertainties. We then demonstrate
how this method improves results over the standard procedure of designating one
image as a ``template'' and differencing against only that image.Comment: Accepted to AJ. To be published in November 2005 issue. 16 page, 2
figures, 2 tables. Source code available at
http://www.ctio.noao.edu/essence/nn2
Redshift-Independent Distances to Type Ia Supernovae
We describe a procedure for accurately determining luminosity distances to
Type Ia supernovae (SNe Ia) without knowledge of redshift. This procedure,
which may be used as an extension of any of the various distance determination
methods currently in use, is based on marginalizing over redshift, removing the
requirement of knowing a priori. We demonstrate that the Hubble diagram
scatter of distances measured with this technique is approximately equal to
that of distances derived from conventional redshift-specific methods for a set
of 60 nearby SNe Ia. This indicates that accurate distances for cosmological
SNe Ia may be determined without the requirement of spectroscopic redshifts,
which are typically the limiting factor for the number of SNe that modern
surveys can collect. Removing this limitation would greatly increase the number
of SNe for which current and future SN surveys will be able to accurately
measure distance. The method may also be able to be used for high- SNe Ia to
determine cosmological density parameters without redshift information.Comment: 12 pages, 3 figures, accepted for publication in Astrophysical
Journal Letter
The Rate of Type Ia Supernovae at High Redshift
We derive the rates of Type Ia supernovae (SNIa) over a wide range of
redshifts using a complete sample from the IfA Deep Survey. This sample of more
than 100 SNIa is the largest set ever collected from a single survey, and
therefore uniquely powerful for a detailed supernova rate (SNR) calculation.
Measurements of the SNR as a function of cosmological time offer a glimpse into
the relationship between the star formation rate (SFR) and Type Ia SNR, and may
provide evidence for the progenitor pathway. We observe a progressively
increasing Type Ia SNR between redshifts z~0.3-0.8. The Type Ia SNR
measurements are consistent with a short time delay (t~1 Gyr) with respect to
the SFR, indicating a fairly prompt evolution of SNIa progenitor systems. We
derive a best-fit value of SFR/SNR 580 h_70^(-2) M_solar/SNIa for the
conversion factor between star formation and SNIa rates, as determined for a
delay time of t~1 Gyr between the SFR and the Type Ia SNR. More complete
measurements of the Type Ia SNR at z>1 are necessary to conclusively determine
the SFR--SNR relationship and constrain SNIa evolutionary pathways.Comment: 37 pages, 9 figures, accepted for publication in Astrophysical
Journal. Figures 7-9 correcte
Cylindrical, periodic surface lattice — theory, dispersion analysis, and experiment
A two-dimensional surface lattice of cylindrical topology obtained via perturbing the inner surface of a cylinder is considered. Periodic perturbations of the surface lead to observation of high-impedance, dielectric-like media and resonant coupling of surface and non-propagating volume fields. This allows synthesis of tailored-for-purpose "coating" material with dispersion suitable, for instance, to mediate a Cherenkov type interaction. An analytical model of the lattice is discussed and coupled-wave equations are derived. Variations of the lattice dispersive properties with variation of parameters are shown, illustrating the tailoring of the structure's electromagnetic properties. Experimental results are presented showing agreement with the theoretical model
A feature-rich transmission spectrum for WASP-127b
WASP-127b is one of the lowest density planets discovered to date. With a
sub-Saturn mass () and super-Jupiter radius
(), it orbits a bright G5 star, which is about to
leave the main-sequence. We aim to explore WASP-127b's atmosphere in order to
retrieve its main atmospheric components, and to find hints for its intriguing
inflation and evolutionary history. We used the ALFOSC spectrograph at the NOT
telescope to observe a low resolution (, seeing limited) long-slit
spectroscopic time series during a planetary transit, and present here the
first transmission spectrum for WASP-127b. We find the presence of a strong
Rayleigh slope at blue wavelengths and a hint of Na absorption, although the
quality of the data does not allow us to claim a detection. At redder
wavelengths the absorption features of TiO and VO are the best explanation to
fit the data. Although higher signal-to-noise ratio observations are needed to
conclusively confirm the absorption features, WASP-127b seems to posses a
cloud-free atmosphere and is one of the best targets to perform further
characterization studies in the near future.Comment: Accepted for Publication A&A Letters, May 22nd, 201
Na I and H absorption features in the atmosphere of MASCARA-2b/KELT-20b
We have used the HARPS-North high resolution spectrograph (=115
000) at TNG to observe one transit of the highly irradiated planet
MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly
resolve the spectral features of the atomic sodium (Na I) doublet and the
H line in its atmosphere, measuring absorption depths of
0.170.03 and 0.590.08 for a 0.75 passband,
respectively. These absorptions are corroborated with the transmission measured
from their respective transmission light curves, which show a large
Rossiter-McLaughlin effect. In case of H, this absorption corresponds
to an effective radius of =1.200.04. While the S/N of the
final transmission spectrum is not sufficient to adjust different temperature
profiles to the lines, we find that higher temperatures than the equilibrium
are needed to explain the lines contrast. Particularly, we find that the Na I
lines core require a temperature of T=4210180K and that H requires
T=4330520K. MASCARA-2b, like other planets orbiting A-type stars, receives
a large amount of UV energy from its host star. This energy excites the atomic
hydrogen and produces H absorption, leading to the expansion and
abrasion of the atmosphere. The study of other Balmer lines in the transmission
spectrum would allow the determination of the atmospheric temperature profile
and the calculation of the lifetime of the atmosphere. In the case of
MASCARA-2b, residual features are observed in the H and H lines,
but they are not statistically significant. More transit observations are
needed to confirm our findings in Na I and H, and to build up enough
S/N to explore the presence of H and H planetary absorptions.Comment: 14 pages, 12 figure
Iniciación a la metodología Dáder de seguimiento farmacoterapéutico en una farmacia comunitaria
The objectives of this study were to analyse drug related problems (DRP) detected in patients at a community pharmacy,to classify them in accordance with the categories of necessity, effectiveness and safety, and to evaluate the communicationchannel used to solve the problem. The Dáder Program methodology for pharmacotherapy following at communitypharmacies, was proposed by the Research Group for Pharmaceutical Care at the University of Granada.A total of 44 DRPs were detected over a period of 16 months, of which 75% were successfully resolved. The distributionof DRPs in accordance with the three basic categories of drug therapy were as follows: indication 31.8% (DRP 1 & 2),effectiveness 34.1% (DRP 3 & 4) and safety 34.1% (DRP 5 & 6). A successful outcome was achieved in 72.4% of theDRPs when a physician was contacted in order to resolve the problem, while 66.7% of the cases were resolved successfullythrough direct pharmacist intervention with the patient. The main therapeutic groups predominating in DRPs were:antihypertensives, lipid-lowering drugs and antidiabetics. New strategies are necessary in order to overcome barriers andin so doing, increase the number of patients receiving pharmacotherapy following service. This may be achieved throughan improvement in communication techniques with the patient and a greater integration of the community pharmacywithin the health system.Los objetivos del estudio han sido analizar los Problemas Relacionados con Medicamentos (PRM) detectados enpacientes de una farmacia comunitaria, clasificar los PRM en sus distintas categorías y valorar las vías de comunicaciónutilizadas para su resolución. La metodología utilizada en el seguimiento del tratamiento farmacológico enuna farmacia comunitaria ha sido la propuesta por el grupo de Investigación en Atención Farmacéutica de laUniversidad de Granada (Programa Dáder). En el período de estudio (16 meses) se han detectado un total de 44PRM, de los que se han resuelto positivamente el 70,5%. La distribución de los PRM basada en las tres necesidadesde la farmacoterapia ha sido: necesidad 31,8% (PRM 1 y 2), efectividad 34,1% (PRM 3 y 4) y seguridad 34,1%(PRM 5 y 6). Se ha resuelto de forma positiva el 72,4% de los PRM en que ha habido que contactar con el médico,mientras que se ha solucionado el 66,7% de los casos en la intervención farmacéutica directa con los pacientes. Losprincipales grupos de medicamentos implicados en los PRM han sido los antihipertensivos, antiasmáticos e hipolipemiantes.Es necesario solventar determinadas barreras con el objetivo de aplicar el servicio de seguimiento farmacoterapéuticoa un mayor número de pacientes: mejora en técnicas de comunicación y mayor integración de la farmacia comunitariaen la sistemática de la asistencia sanitaria
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