664 research outputs found
False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
We present astrophysical false positive probability calculations for every
Kepler Object of Interest (KOI)---the first large-scale demonstration of a
fully automated transiting planet validation procedure. Out of 7056 KOIs, we
determine that 1935 have probabilities <1% to be astrophysical false positives,
and thus may be considered validated planets. 1284 of these have not yet been
validated or confirmed by other methods. In addition, we identify 428 KOIs
likely to be false positives that have not yet been identified as such, though
some of these may be a result of unidentified transit timing variations. A side
product of these calculations is full stellar property posterior samplings for
every host star, modeled as single, binary, and triple systems. These
calculations use 'vespa', a publicly available Python package able to be easily
applied to any transiting exoplanet candidate.Comment: 20 pages, 8 figures. Published in ApJ. Instructions to reproduce
results can be found at https://github.com/timothydmorton/koi-fp
Reunião anual conjunta dos projetos Robin e Amazalert: excursão técnica.
bitstream/item/141586/1/DOCUMENTOS-417-AINFO.pd
Adenosine A(2A) receptor blockade reverts hippocampal stress-induced deficits and restores corticosterone circadian oscillation
Maternal separation (MS) is an early life stress model that induces permanent changes in the central nervous system, impairing hippocampal long-term potentiation (LTP) and spatial working memory. There are compelling evidences for a role of hippocampal adenosine A(2A) receptors in stress-induced modifications related to cognition, thus opening a potential window for therapeutic intervention. Here, we submitted rats to MS and evaluated the long-lasting molecular, electrophysiological and behavioral impairments in adulthood. We then assessed the therapeutic potential of KW6002, a blocker of A(2A) receptors, in stress-impaired animals. We report that the blockade of A(2A) receptors was efficient in reverting the behavior, electrophysiological and morphological impairments induced by MS. In addition, this effect is associated with restoration of the hypothalamic-pituitary-adrenal axis (HPA-axis) activity, as both the plasma corticosterone levels and hippocampal glucocorticoid receptor expression pattern returned to physiological-like status after the treatment. These results reveal the involvement of A(2A) receptors in the stress-associated impairments and directly in the stress response system by showing that the dysfunction of the HPA-axis as well as the long-lasting synaptic and behavioral effects of MS can be reverted by targeting adenosine A(2A) receptors. These findings provide a novel evidence for the use of adenosine A(2A) receptor antagonists as potential therapy against psychopathologiesWe acknowledge Alexandre de Mendonca, David Blum and Rodrigo Cunha for helpful discussions. VLB is thankful to Joao Baiao and Carla Batalha for technical assistance. VLB has been awarded a PhD fellowship from Fundacao para a Ciencia e Tecnologia (BD/63041/2009). LVL is funded by Fundacao para a Ciencia e Tecnologia (PTDC/SAU-NEU/099853/2008) and by EU programme Egide-Pessoa. YB and CEM were funded by the Ministry for Education and Research (BMBF, Grant number 01EW0911) in the frame of ERA-NET NEURON
Predicting the detectability of oscillations in solar-type stars observed by Kepler
Asteroseismology of solar-type stars has an important part to play in the
exoplanet program of the NASA Kepler Mission. Precise and accurate inferences
on the stellar properties that are made possible by the seismic data allow very
tight constraints to be placed on the exoplanetary systems. Here, we outline
how to make an estimate of the detectability of solar-like oscillations in any
given Kepler target, using rough estimates of the temperature and radius, and
the Kepler apparent magnitude.Comment: 21 pages, 6 figures, accepted for publication Astrophysical Journa
Detection of Potential Transit Signals in the First Three Quarters of Kepler Mission Data
We present the results of a search for potential transit signals in the first
three quarters of photometry data acquired by the Kepler Mission. The targets
of the search include 151,722 stars which were observed over the full interval
and an additional 19,132 stars which were observed for only 1 or 2 quarters.
From this set of targets we find a total of 5,392 detections which meet the
Kepler detection criteria: those criteria are periodicity of the signal, an
acceptable signal-to-noise ratio, and a composition test which rejects spurious
detections which contain non-physical combinations of events. The detected
signals are dominated by events with relatively low signal-to-noise ratio and
by events with relatively short periods. The distribution of estimated transit
depths appears to peak in the range between 40 and 100 parts per million, with
a few detections down to fewer than 10 parts per million. The detected signals
are compared to a set of known transit events in the Kepler field of view which
were derived by a different method using a longer data interval; the comparison
shows that the current search correctly identified 88.1% of the known events. A
tabulation of the detected transit signals, examples which illustrate the
analysis and detection process, a discussion of future plans and open,
potentially fruitful, areas of further research are included
Period and light curve fluctuations of the Kepler Cepheid V1154 Cyg
We present a detailed period analysis of the bright Cepheid-type variable
star V1154 Cygni (V =9.1 mag, P~4.9 d) based on almost 600 days of continuous
observations by the Kepler space telescope. The data reveal significant
cycle-to-cycle fluctuations in the pulsation period, indicating that classical
Cepheids may not be as accurate astrophysical clocks as commonly believed:
regardless of the specific points used to determine the O-C values, the cycle
lengths show a scatter of 0.015-0.02 days over the 120 cycles covered by the
observations. A very slight correlation between the individual Fourier
parameters and the O-C values was found, suggesting that the O - C variations
might be due to the instability of the light curve shape. Random fluctuation
tests revealed a linear trend up to a cycle difference 15, but for long term,
the period remains around the mean value. We compare the measurements with
simulated light curves that were constructed to mimic V1154 Cyg as a perfect
pulsator modulated only by the light travel time effect caused by low-mass
companions. We show that the observed period jitter in V1154 Cyg represents a
serious limitation in the search for binary companions. While the Kepler data
are accurate enough to allow the detection of planetary bodies in close orbits
around a Cepheid, the astrophysical noise can easily hide the signal of the
light-time effect.Comment: published in MNRAS: 8 pages, 7 figure
TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics
The nearest accreting T Tauri star, TW Hya was observed with spectroscopic
and photometric measurements simultaneous with a long se gmented exposure using
the CHANDRA satellite. Contemporaneous optical photometry from WASP-S indicates
a 4.74 day period was present during this time. Absence of a similar
periodicity in the H-alpha flux and the total X-ray flux points to a different
source of photometric variations. The H-alpha emission line appears
intrinsically broad and symmetric, and both the profile and its variability
suggest an origin in the post-shock cooling region. An accretion event,
signaled by soft X-rays, is traced spectroscopically for the first time through
the optical emission line profiles. After the accretion event, downflowing
turbulent material observed in the H-alpha and H-beta lines is followed by He I
(5876A) broadening. Optical veiling increases with a delay of about 2 hours
after the X-ray accretion event. The response of the stellar coronal emission
to an increase in the veiling follows about 2.4 hours later, giving direct
evidence that the stellar corona is heated in part by accretion. Subsequently,
the stellar wind becomes re-established. We suggest a model that incorporates
this sequential series of events: an accretion shock, a cooling downflow in a
supersonically turbulent region, followed by photospheric and later, coronal
heating. This model naturally explains the presence of broad optical and
ultraviolet lines, and affects the mass accretion rates determined from
emission line profiles.Comment: 61 pages; 22 figures; to appear in The Astrophysical Journa
Qatar-2: A K dwarf orbited by a transiting hot Jupiter and a more massive companion in an outer orbit
We report the discovery and initial characterization of Qatar-2b, a hot
Jupiter transiting a V = 13.3 mag K dwarf in a circular orbit with a short
period, P_ b = 1.34 days. The mass and radius of Qatar-2b are M_p = 2.49 M_j
and R_p = 1.14 R_j, respectively. Radial-velocity monitoring of Qatar-2 over a
span of 153 days revealed the presence of a second companion in an outer orbit.
The Systemic Console yielded plausible orbits for the outer companion, with
periods on the order of a year and a companion mass of at least several M_j.
Thus Qatar-2 joins the short but growing list of systems with a transiting hot
Jupiter and an outer companion with a much longer period. This system
architecture is in sharp contrast to that found by Kepler for multi-transiting
systems, which are dominated by objects smaller than Neptune, usually with
tightly spaced orbits that must be nearly coplanar
Asteroseismology of red giants from the first four months of Kepler data: Global oscillation parameters for 800 stars
We have studied solar-like oscillations in ~800 red-giant stars using Kepler
long-cadence photometry. The sample includes stars ranging in evolution from
the lower part of the red-giant branch to the Helium main sequence. We
investigate the relation between the large frequency separation (Delta nu) and
the frequency of maximum power (nu_max) and show that it is different for red
giants than for main-sequence stars, which is consistent with evolutionary
models and scaling relations. The distributions of nu_max and Delta nu are in
qualitative agreement with a simple stellar population model of the Kepler
field, including the first evidence for a secondary clump population
characterized by M ~> 2 M_sun and nu_max ~ 40-110 muHz. We measured the small
frequency separations delta nu_02 and delta nu_01 in over 400 stars and delta
nu_03 in over 40. We present C-D diagrams for l=1, 2 and 3 and show that the
frequency separation ratios delta nu_02/Delta nu and delta nu_01/Delta nu have
opposite trends as a function of Delta nu. The data show a narrowing of the l=1
ridge towards lower nu_max, in agreement with models predicting more efficient
mode trapping in stars with higher luminosity. We investigate the offset
epsilon in the asymptotic relation and find a clear correlation with Delta nu,
demonstrating that it is related to fundamental stellar parameters. Finally, we
present the first amplitude-nu_max relation for Kepler red giants. We observe a
lack of low-amplitude stars for nu_max ~> 110 muHz and find that, for a given
nu_max between 40-110 muHz, stars with lower Delta nu (and consequently higher
mass) tend to show lower amplitudes than stars with higher Delta nu.Comment: 12 pages, 12 figures, accepted for publication in Ap
Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
New transiting planet candidates are identified in sixteen months (May 2009 -
September 2010) of data from the Kepler spacecraft. Nearly five thousand
periodic transit-like signals are vetted against astrophysical and instrumental
false positives yielding 1,091 viable new planet candidates, bringing the total
count up to over 2,300. Improved vetting metrics are employed, contributing to
higher catalog reliability. Most notable is the noise-weighted robust averaging
of multi-quarter photo-center offsets derived from difference image analysis
which identifies likely background eclipsing binaries. Twenty-two months of
photometry are used for the purpose of characterizing each of the new
candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are
tabulated as well as the products of light curve modeling: reduced radius
(Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest
fractional increases are seen for the smallest planet candidates (197% for
candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and
those at longer orbital periods (123% for candidates outside of 50-day orbits
versus 85% for candidates inside of 50-day orbits). The gains are larger than
expected from increasing the observing window from thirteen months (Quarter 1--
Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the
benefit of continued development of pipeline analysis software. The fraction of
all host stars with multiple candidates has grown from 17% to 20%, and the
paucity of short-period giant planets in multiple systems is still evident. The
progression toward smaller planets at longer orbital periods with each new
catalog release suggests that Earth-size planets in the Habitable Zone are
forthcoming if, indeed, such planets are abundant.Comment: Submitted to ApJS. Machine-readable tables are available at
http://kepler.nasa.gov, http://archive.stsci.edu/kepler/results.html, and the
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