10,898 research outputs found
Variable stars in the globular cluster NGC 7492. New discoveries and physical parameters determination
We have performed a photometric V, R, I CCD time-series analysis with a
baseline of ~8 years of the outer-halo globular cluster NGC 7492 with the aim
of searching for new variables and using these (and the previously known
variables) to determine the physical parameters of interest for the cluster
(e.g. metallicity, absolute magnitude of the horizontal branch, distance,
etc.).
We use difference image analysis (DIA) to extract precise light curves in the
relatively crowded star field, especially towards the densely populated central
region. Several approaches are used for variability detection that recover the
known variables and lead to new discoveries. We determine the physical
parameters of the only RR0 star using light curve Fourier decomposition
analysis.
We find one new long period variable and two SX Phe stars in the blue
straggler region. We also present one candidate SX Phe star which requires
follow-up observations. Assuming that the SX Phe stars are cluster members and
using the period-luminosity relation for these stars, we estimate their
distances as ~25.2+-1.8 and 26.8+-1.8 kpc, and identify their possible modes of
oscillation. We refine the periods of the two RR Lyrae stars in our field of
view. We find that the RR1 star V2 is undergoing a period change and possibly
exhibits the Blazhko effect. Fourier decomposition of the light curve of the
RR0 star V1 allows us to estimate the metallicity [Fe/H]_ZW-1.68+-0.10 or
[Fe/H]_UVES-1.64+-0.13, log-luminosity ~1.76+-0.02, absolute magnitude
~0.38+-0.04 mag, and true distance modulus of ~16.93+-0.04 mag, which is
equivalent to a distance of ~24.3+-0.5 kpc. All of these values are consistent
with previous estimates in the literature.Comment: 12 pages, 13 figures, 6 tables, accepted for publication in A&
Proper scoring rules for interval probabilistic forecasts
This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Interval probabilistic forecasts for a binary event are forecasts issued as a range of probabilities for the occurrence of the event, for example, ‘chance of rain: 10-20%’. To verify interval probabilistic forecasts, use can be made of a scoring rule that assigns a score to each forecast-outcome pair. An important requirement for scoring rules, if they are to provide a faithful assessment of a forecaster, is that they be proper, by which is meant that they direct forecasters to issue their true beliefs as their forecasts. Proper scoring rules for probabilistic forecasts issued as precise numbers have been studied extensively. But, applying such a proper scoring rule to, for example, the mid-point of an interval probabilistic forecast, does not, typically, produce a proper scoring rule for interval probabilistic forecasts. Complementing parallel work by other authors, we derive a general characterisation of scoring rules that are proper for interval probabilistic forecasts and from this characterisation we determine particular scoring rules for interval probabilistic forecasts that correspond to the familiar scoring rules used for probabilistic forecasts given as precise probabilities. All the scoring rules we derive apply immediately to rounded probabilistic forecasts, being a special case of interval probabilistic forecasts
Constraining the parameters of globular cluster NGC 1904 from its variable star population
We present the analysis of 11 nights of V and I time-series observations of
the globular cluster NGC 1904 (M 79). Using this we searched for variable stars
in this cluster and attempted to refine the periods of known variables, making
use of a time baseline spanning almost 8 years. We use our data to derive the
metallicity and distance of NGC 1904. We used difference imaging to reduce our
data to obtain high-precision light curves of variable stars. We then estimated
the cluster parameters by performing a Fourier decomposition of the light
curves of RR Lyrae stars for which a good period estimate was possible. We also
derive an estimate for the age of the cluster by fitting theoretical isochrones
to our colour-magnitude diagram (CMD). Out of 13 stars previously classified as
variables, we confirm that 10 are bona fide variables. We cannot detect
variability in one other within the precision of our data, while there are two
which are saturated in our data frames, but we do not find sufficient evidence
in the literature to confirm their variability. We also detect a new RR Lyrae
variable, giving a total number of confirmed variable stars in NGC 1904 of 11.
Using the Fourier parameters, we find a cluster metallicity [Fe/H]_ZW=-1.63 +-
0.14, or [Fe/H]_UVES=-1.57 \pm 0.18, and a distance of 13.3 +- 0.4 kpc (using
RR0 variables) or 12.9 kpc (using the one RR1 variable in our sample for which
Fourier decomposition was possible).Comment: 14 pages, 11 figures, accepted for publication in A&
RR Lyrae Stars In The GCVS Observed By The Qatar Exoplanet Survey
We used the light curve archive of the Qatar Exoplanet Survey (QES) to
investigate the RR Lyrae variable stars listed in the General Catalogue of
Variable Stars (GCVS). Of 588 variables studied, we reclassify 14 as eclipsing
binaries, one as an RS Canum Venaticorum-type variable, one as an irregular
variable, four as classical Cepheids, and one as a type II Cepheid, while also
improving their periods. We also report new RR Lyrae sub-type classifications
for 65 variables and improve on the GCVS period estimates for 135 RR Lyrae
variables. There are seven double-mode RR Lyrae stars in the sample for which
we measured their fundamental and first overtone periods. Finally, we detect
the Blazhko effect in 38 of the RR Lyrae stars for the first time and we
successfully measured the Blazhko period for 26 of them.Comment: Accepted IBV
Towards the Amplituhedron Volume
21 pages; v2: version published in JHEPIt has been recently conjectured that scattering amplitudes in planar N=4 super Yang-Mills are given by the volume of the (dual) amplituhedron. In this paper we show some interesting connections between the tree-level amplituhedron and a special class of differential equations. In particular we demonstrate how the amplituhedron volume for NMHV amplitudes is determined by these differential equations. The new formulation allows for a straightforward geometric description, without any reference to triangulations. Finally we discuss possible implications for volumes related to generic N^kMHV amplitudes.Peer reviewe
Fine-Structure Map of the Histidine Transport Genes in \u3cem\u3eSalmonella typhimurium\u3c/em\u3e
Afine-structure genetic map of the histidine transport region of the Salmonella typhimurium chromosome was constructed. Twenty-five deletion mutants were isolated and used for dividing the hisJ and hisP genes into 8 and 13 regions respectively. A total of 308 mutations, spontaneous and mutagen induced, have been placed in these regions by deletion mapping. The histidine transport operon is presumed to be constituted of genes dhuA, hisJ, and hisP, and the regulation of the hosP and hisJ genes by dhuA is discussed. The orientation of this operon relative to purF has been established by three-point crosses as being: purF duhA hisJ hisP
GeoCLEF 2006: the CLEF 2006 Ccross-language geographic information retrieval track overview
After being a pilot track in 2005, GeoCLEF advanced to be a regular track within CLEF 2006. The
purpose of GeoCLEF is to test and evaluate cross-language geographic information retrieval (GIR): retrieval for
topics with a geographic specification. For GeoCLEF 2006, twenty-five search topics were defined by the
organizing groups for searching English, German, Portuguese and Spanish document collections. Topics were
translated into English, German, Portuguese, Spanish and Japanese. Several topics in 2006 were significantly
more geographically challenging than in 2005. Seventeen groups submitted 149 runs (up from eleven groups and
117 runs in GeoCLEF 2005). The groups used a variety of approaches, including geographic bounding boxes,
named entity extraction and external knowledge bases (geographic thesauri and ontologies and gazetteers)
Testes de translocação e efeito de fungicidas sobre a severidade da antracnose do feijoeiro.
Visto que o controle químico é um dos métodos mais utilizados no manejo da antracnose (Colletotrichum lindemuthianum) do feijoeiro comum, este trabalho objetivou avaliar a translocação e a ação preventiva e curativa de diferentes fungicidas sobre a severidade da doença
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