15,166 research outputs found
Automated preparation of Kepler time series of planet hosts for asteroseismic analysis
One of the tasks of the Kepler Asteroseismic Science Operations Center
(KASOC) is to provide asteroseismic analyses on Kepler Objects of Interest
(KOIs). However, asteroseismic analysis of planetary host stars presents some
unique complications with respect to data preprocessing, compared to pure
asteroseismic targets. If not accounted for, the presence of planetary transits
in the photometric time series often greatly complicates or even hinders these
asteroseismic analyses. This drives the need for specialised methods of
preprocessing data to make them suitable for asteroseismic analysis. In this
paper we present the KASOC Filter, which is used to automatically prepare data
from the Kepler/K2 mission for asteroseismic analyses of solar-like planet host
stars. The methods are very effective at removing unwanted signals of both
instrumental and planetary origins and produce significantly cleaner
photometric time series than the original data. The methods are automated and
can therefore easily be applied to a large number of stars. The application of
the filter is not restricted to planetary hosts, but can be applied to any
solar-like or red giant stars observed by Kepler/K2.Comment: Accepted for publication in MNRA
The energy dependence of the neon-22 excess in the cosmic radiation
It has been recognized now for some time that the heavy neon isotope, neon-22, is overabundant by a factor of 3 to 4 with respect to neon-22 in the cosmic ray source compared to the ratio of these isotopes in the Solar System. In view of the otherwise remarkable similarity of the chemical composition of the cosmic ray source and the composition of the Solar Energetic Particles, the anomaly regarding the neon isotopes is so much more striking. The observed excess of neon-22 is too large to be explained as a result of the chemical evolution of the Galaxy since the formation of the Solar System. Further information on the origin of the neon-22 excess may come from a comparison of the energy spectra of the two neon isotopes. If the cosmic radiation in the solar neighborhood is a mixture of material from several sources, one of which has an excess of neon-22, then the source energy spectra of neon-20 and neon-22 may differ significantly
K2P: Reduced data from campaigns 0-4 of the K2 mission
Context: After the loss of a second reaction wheel the Kepler mission was
redesigned as the K2 mission, pointing towards the ecliptic and delivering data
for new fields approximately every 80 days. The steady flow of data obtained
with a reduced pointing stability calls for dedicated pipelines for extracting
light curves and correcting these for use in, e.g., asteroseismic analysis.
Aims: We provide corrected light curves for the K2 fields observed until now
(campaigns 0-4), and provide a comparison with other pipelines for K2 data
extraction/correction. Methods: Raw light curves are extracted from K2 pixel
data using the "K2-pixel-photometry" (K2P) pipeline, and corrected using
the KASOC filter. Results: The use of K2P allows for the extraction of the
order of 90.000 targets in addition to 70.000 targets proposed by the community
- for these, other pipelines provide no data. We find that K2P in general
performs as well as, or better than, other pipelines for the tested metrics of
photometric quality. In addition to stars, pixel masks are properly defined
using K2P for extended objects such as galaxies for which light curves are
also extracted.Comment: Accepted for publication in Astronomy and Astrophysic
Search for heavy antinuclei in the cosmic radiation
The existence of significant amounts of antimatter in the Universe is demonstrated through cosmic radiation. The data from the Danish-French Cosmic Ray Spectrometer on the HEAO-3 satellite offers an opportunity to search for heavy antinuclei, since all the relevant parameters (charge, velocity, arrival direction, and satellite position at the time of arrival) are measured for each recorded nucleus. Using the 22676 positive only events in the data seletion corresponding to L 1.5 as a measure of our exposure factor to heavy antinuclei and noting that no corresponding antinuclei were found, an upper limit (95% confidence) is given to the ratio of antinuclei to nuclei as 1.4 x .0001 for particles with Z 9. The upper limit resulting from this work is compared with previous results of searches for heavy antimatter in the cosmic radiation. It is seen that, if one regards only antiparticles heavier than fluorine, then the present result represents a reduced upper limit over previous data. When taken together, all the available experiment data now push the upper limit for the ratio of antiparticles to particles well below .0001
The INTEGRAL Core Observing Programme
The Core Programme of the INTEGRAL mission is defined as the portion of the
scientific programme covering the guaranteed time observations for the INTEGRAL
Science Working Team. This paper describes the current status of the Core
Programme preparations and summarizes the key elements of the observing
programme.Comment: Contributed paper, 3rd INTEGRAL Workshop, Taormina/Sicily, Sep 1998,
to be published in Astrophys. Letters & Communications, 199
A new method to detect solar-like oscillations at very low S/N using statistical significance testing
We introduce a new method to detect solar-like oscillations in frequency
power spectra of stellar observations, under conditions of very low signal to
noise. The Moving-Windowed-Power-Search, or MWPS, searches the power spectrum
for signatures of excess power, over and above slowly varying (in frequency)
background contributions from stellar granulation and shot or instrumental
noise. We adopt a false-alarm approach (Chaplin et al. 2011) to ascertain
whether flagged excess power, which is consistent with the excess expected from
solar-like oscillations, is hard to explain by chance alone (and hence a
candidate detection).
We apply the method to solar photometry data, whose quality was
systematically degraded to test the performance of the MWPS at low
signal-to-noise ratios. We also compare the performance of the MWPS against the
frequently applied power-spectrum-of-power-spectrum (PSxPS) detection method.
The MWPS is found to outperform the PSxPS method.Comment: 10 pages, 7 figures, accepted for publication in MNRAS, Added
reference
Ballerina - Pirouettes in Search of Gamma Bursts
The cosmological origin of gamma ray bursts has now been established with
reasonable certainty. Many more bursts will need to be studied to establish the
typical distance scale, and to map out the large diversity in properties which
have been indicated by the first handful of events. We are proposing Ballerina,
a small satellite to provide accurate positions and new data on the gamma-ray
bursts. We anticipate a detection rate an order of magnitude larger than
obtained from Beppo-SAX.Comment: A&AS in press, proceedings of the Workshop "Gamma Ray Bursts in the
Afterglow Era" in Rome, November 199
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