198 research outputs found
A New Planet Around an M Dwarf: Revealing a Correlation Between Exoplanets and Stellar Mass
We report precise Doppler measurements of GJ317 (M3.5V) that reveal the
presence of a planet with a minimum mass Msini = 1.2 Mjup in an eccentric,
692.9 day orbit. GJ317 is only the third M dwarf with a Doppler-detected Jovian
planet. The residuals to a single-Keplerian fit show evidence of a possible
second orbital companion. The inclusion of an additional Jupiter-mass planet (P
= 2700 days, Msini = 0.83 Mjup) improves the quality of fit significantly,
reducing the rms from 12.5 m/s to 6.32 m/s. A false-alarm test yields a 1.1%
probability that the curvature in the residuals of the single-planet fit is due
to random fluctuations, lending additional credibility to the two-planet model.
However, our data only marginally constrain a two-planet fit and further
monitoring is necessary to fully characterize the properties of the second
planet. To study the effect of stellar mass on Jovian planet occurrence we
combine our samples of M stars, Solar-mass dwarfs and intermediate-mass
subgiants. We find a positive correlation between stellar mass and the
occurrence rate of Jovian planets within 2.5 AU; the former A-type stars in our
sample are nearly 5 times more likely than the M dwarfs to harbor a giant
planet. Our analysis shows that the correlation between Jovian planet
occurrence and stellar mass remains even after accounting for the effects of
stellar metallicity.Comment: ApJ accepted, 27 pages, 6 figures, 3 table
Are Estimates of Wind Characteristics Based on Measurements with Pitot Tubes and GNSS Receivers Mounted on Consumer-grade Unmanned Aerial Vehicles Applicable in Meteorological Studies?
The objective of this paper is to empirically show that estimates of wind speed and wind direction based on measurements carried out using the Pitot tubes and GNSS receivers, mounted on consumer-grade unmanned aerial vehicles (UAVs), may accurately approximate true wind parameters. The motivation for the study is that a growing number of commercial and scientific UAV operations may soon become a new source of data on wind speed and wind direction, with unprecedented spatial and temporal resolution. The feasibility study was carried out within an isolated mountain meadow of Polana Izerska located in the Izera Mountains (SW Poland) during an experiment which aimed to compare wind characteristics measured by several instruments: three UAVs (swinglet CAM, eBee, Maja) equipped with the Pitot tubes and GNSS receivers, wind speed and direction meters mounted at 2.5 m and 10 m (mast), conventional weather station and vertical sodar. The three UAVs performed seven missions along spiral-like trajectories, most reaching 130 m above take-off location. The estimates of wind speed and wind direction were found to agree between UAVs. The time series of wind speed measured at 10 m were extrapolated to flight altitudes recorded at a given time so that a comparison was made feasible. It was found that the wind speed estimates provided by the UAVs on a basis of the Pitot tube/GNSS data are in agreement with measurements carried out using dedicated meteorological instruments. The discrepancies were recorded in the first and last phases of UAV flights
Transit timing variation and activity in the WASP-10 planetary system
Transit timing analysis may be an effective method of discovering additional
bodies in extrasolar systems which harbour transiting exoplanets. The
deviations from the Keplerian motion, caused by mutual gravitational
interactions between planets, are expected to generate transit timing
variations of transiting exoplanets. In 2009 we collected 9 light curves of 8
transits of the exoplanet WASP-10b. Combining these data with published ones,
we found that transit timing cannot be explained by a constant period but by a
periodic variation. Simplified three-body models which reproduce the observed
variations of timing residuals were identified by numerical simulations. We
found that the configuration with an additional planet of mass of 0.1
and orbital period of 5.23 d, located close to the outer 5:3
mean motion resonance, is the most likely scenario. If the second planet is a
transiter, the estimated flux drop will be 0.3 per cent and can be
observable with a ground-based telescope. Moreover, we present evidence that
the spots on the stellar surface and rotation of the star affect the radial
velocity curve giving rise to spurious eccentricity of the orbit of the first
planet. We argue that the orbit of WASP-10b is essentially circular. Using the
gyrochronology method, the host star was found to be Myr old. This
young age can explain the large radius reported for WASP-10b.Comment: MNRAS accepte
The barycentric motion of exoplanet host stars: tests of solar spin-orbit coupling
Empirical evidence suggests a tantalising but unproven link between various
indicators of solar activity and the barycentric motion of the Sun. The latter
is exemplified by transitions between regular and more disordered motion
modulated by the motions of the giant planets, and rare periods of retrograde
motion with negative orbital angular momentum. An examination of the
barycentric motion of exoplanet host stars, and their stellar activity cycles,
has the potential of proving or disproving the Sun's motion as an underlying
factor in the complex patterns of short- and long-term solar variability
indices, by establishing whether such correlations exist in other planetary
systems. A variety of complex patterns of barycentric motions of exoplanet host
stars is demonstrated, depending on the number, masses and orbits of the
planets. Each of the behavioural types proposed to correlate with solar
activity are also evident in exoplanet host stars: repetitive patterns
influenced by massive multiple planets, epochs of rapid change in orbital
angular momentum, and intervals of negative orbital angular momentum. The study
provides the basis for independent investigations of the widely-studied but
unproven suggestion that the Sun's motion is somehow linked to various
indicators of solar activity. We show that, because of the nature of their
barycentric motions, the host stars HD168443 and HD74156 offer particularly
powerful tests of this hypothesis.Comment: 7 pages, 3 figures. Accepted for publication in A&
UVSat: a concept of an ultraviolet/optical photometric satellite
Time-series photometry from space in the ultraviolet can be presently done
with only a few platforms, none of which is able to provide wide-field
long-term high-cadence photometry. We present a concept of UVSat, a twin space
telescope which will be capable to perform this kind of photometry, filling an
observational niche. The satellite will host two telescopes, one for
observations in the ultraviolet, the other for observations in the optical
band. We also briefly show what science can be done with UVSat.Comment: 6 pages, 2 figures, accepted for publication in the Proceedings of
the PAS (Proc. of the 2nd BRITE Science conference, Innsbruck
Constraints on a second planet in the WASP-3 system
There have been previous hints that the transiting planet WASP-3 b is
accompanied by a second planet in a nearby orbit, based on small deviations
from strict periodicity of the observed transits. Here we present 17 precise
radial velocity measurements and 32 transit light curves that were acquired
between 2009 and 2011. These data were used to refine the parameters of the
host star and transiting planet. This has resulted in reduced uncertainties for
the radii and masses of the star and planet. The radial-velocity data and the
transit times show no evidence for an additional planet in the system.
Therefore, we have determined the upper limit on the mass of any hypothetical
second planet, as a function of its orbital period.Comment: Accepted for publication in The Astronomical Journa
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