107 research outputs found
The "missing link": a 4-day period transiting exoplanet around OGLE-TR-111
We report the discovery of a transiting hot Jupiter around OGLE-TR-111, from
our radial velocity follow-up of OGLE transiting candidates in Carina. The
planet has a mass of 0.53 +- 0.11 M_J and a radius of 1.0 +0.13-0.06 R_J. Three
transiting exoplanets have already been found among OGLE candidates, all with
periods near 1.5 days. The planet presented here, with P=4.0 days, is the first
exoplanet detected by transits with the characteristics of a "normal" hot
Jupiter, as found in abundance by radial velocity surveys The radius of
OGLE-TR-111b and the scarcity of hot Jupiters detected among OGLE transit
candidates tend to indicate that the case of HD209458b, with a radius of 1.4
R_J, is exceptional, with most hot Jupiters being smaller.Comment: 4 pages, 4 figures, to be published in A&A Letter
A new yield simulator for transiting planets and false positives: application to the Next Generation Transit Survey
We present a yield simulator to predict the number and characteristics of planets, false positives and false alarms in transit surveys. The simulator is based on a galactic model and the planet occurrence rates measured by the Kepler mission. It takes into account the observation window function and measured noise levels of the investigated survey. Additionally, it includes vetting criteria to identify false positives. We apply this simulator to the Next Generation Transit Survey (NGTS), a wide-field survey designed to detect transiting Neptune-sized exoplanets. We find that red noise is the main limitation of NGTS up to 14 mag, and that its obtained level determines the expected yield. Assuming a red noise level of 1âmmag, the simulation predicts the following for a 4-yr survey: 4 ± 3 Super-Earths, 19 ± 5 Small Neptunes, 16 ± 4 Large Neptunes, 55 ± 8 Saturn-sized planets and 150 ± 10 Jupiter-sized planets, along with 4688 ± 45 eclipsing binaries and 843 ± 75 background eclipsing binaries. We characterize the properties of these objects to enhance the early identification of false positives and discuss follow-up strategies for transiting candidates
The HARPS search for southern extra-solar planets. IX. Exoplanets orbiting HD 100777, HD 190647, and HD 221287
The HARPS high-resolution high-accuracy spectrograph is offered to the
astronomical community since the second half of 2003. Since then, we have been
using this instrument for monitoring radial velocities of a large sample of
Solar-type stars (~1400 stars) in order to search for their possible low-mass
companions. Amongst the goals of our survey, one is to significantly increase
the number of detected extra-solar planets in a volume-limited sample to
improve our knowledge of their orbital elements distributions and thus obtain
better constraints for planet-formation models.
In this paper, we present the HARPS radial-velocity data and orbital
solutions for 3 Solar-type stars: HD 100777, HD 190647, and HD 221287. The
radial-velocity data of HD 100777 is best explained by the presence of a 1.1
M_Jup planetary companion on a 384--day eccentric orbit (e=0.36). The orbital
fit obtained for the slightly evolved star HD 190647 reveals the presence of a
long-period (P=1038 d) 1.9 M_Jup planetary companion on a moderately eccentric
orbit (e=0.18). HD 221287 is hosting a 3.1 M_Jup planet on a 456--day orbit.
The shape of this orbit is not very well constrained because of our non-optimal
temporal coverage and because of the presence of abnormally large residuals. We
find clues for these large residuals to result from spectral line profile
variations probably induced by stellar activity related processes.Comment: 7 pages, 4 figures, RV data added in paper. A&A in pres
ELODIE metallicity-biased search for transiting Hot Jupiters II. A very hot Jupiter transiting the bright K star HD189733
Among the 160 known exoplanets, mainly detected in large radial-velocity
surveys, only 8 have a characterization of their actual mass and radius thanks
to the two complementary methods of detection: radial velocities and
photometric transit. We started in March 2004 an exoplanet-search programme
biased toward high-metallicity stars which are more frequently host extra-solar
planets. This survey aims to detect close-in giant planets, which are most
likely to transit their host star. For this programme, high-precision radial
velocities are measured with the ELODIE fiber-fed spectrograph on the 1.93-m
telescope, and high-precision photometry is obtained with the CCD Camera on the
1.20-m telescope, both at the Haute-Provence Observatory. We report here the
discovery of a new transiting hot Jupiter orbiting the star HD189733. The
planetary nature of this object is confirmed by the observation of both the
spectroscopic and photometric transits. The exoplanet HD189733b, with an
orbital period of 2.219 days, has one of the shortest orbital periods detected
by radial velocities, and presents the largest photometric depth in the light
curve (~ 3%) observed to date. We estimate for the planet a mass of 1.15 +-
0.04 Mjup and a radius of 1.26 +- 0.03 RJup. Considering that HD189733 has the
same visual magnitude as the well known exoplanet host star HD209458, further
ground-based and space-based follow-up observations are very promising and will
permit a characterization of the atmosphere and exosphere of this giant
exoplanet.Comment: 5 pages, submitted to Astronomy & Astrophysic
HAT-P-9b: A Low Density Planet Transiting a Moderately Faint F star
We report the discovery of a planet transiting a moderately faint (V=12.3
mag) late F star, with an orbital period of 3.92289 +/- 0.00004 days. From the
transit light curve and radial velocity measurements we determine that the
radius of the planet is R_p = 1.40 +/- 0.06 R_Jup and that the mass is M_p =
0.78 +/- 0.09 M_Jup. The density of the new planet, rho = 0.35 +/- 0.06 g
cm^{-3}, fits to the low-density tail of the currently known transiting
planets. We find that the center of transit is at T_c = 2454417.9077 +/- 0.0003
(HJD), and the total transit duration is 0.143 +/- 0.004 days. The host star
has M_s = 1.28 +/- 0.13 M_Sun and R_s = 1.32 +/- 0.07 R_Sun.Comment: Submitted to ApJ; V2: Replaced with accepted versio
The HARPS search for southern extra-solar planets: XXVIII. Two giant planets around M0 dwarfs
Fewer giants planets are found around M dwarfs than around more massive
stars, and this dependence of planetary characteristics on the mass of the
central star is an important observational diagnostic of planetary formation
theories. In part to improve on those statistics, we are monitoring the radial
velocities of nearby M dwarfs with the HARPS spectrograph on the ESO 3.6 m
telescope. We present here the detection of giant planets around two nearby M0
dwarfs: planets, with minimum masses of respectively 5 Jupiter masses and 1
Saturn mass, orbit around Gl 676A and HIP 12961. The latter is, by over a
factor of two, the most massive planet found by radial velocity monitoring of
an M dwarf, but its being found around an early M-dwarf is in approximate line
with the upper envelope of the planetary vs stellar mass diagram. HIP 12961
([Fe/H]=-0.07) is slightly more metal-rich than the average solar neighborhood
([Fe/H]=-0.17), and Gl 676A ([Fe/H=0.18) significantly so. The two stars
together therefore reinforce the growing trend for giant planets being more
frequent around more metal-rich M dwarfs, and the 5~Jupiter mass Gl 676Ab being
found around a metal-rich star is consistent with the expectation that the most
massive planets preferentially form in disks with large condensate masses.Comment: Corrected an error in the labelling of one line in Table
Solar-like oscillations in the G2 subgiant beta Hydri from dual-site observations
We have observed oscillations in the nearby G2 subgiant star beta Hyi using
high-precision velocity observations obtained over more than a week with the
HARPS and UCLES spectrographs. The oscillation frequencies show a regular comb
structure, as expected for solar-like oscillations, but with several l=1 modes
being strongly affected by avoided crossings. The data, combined with those we
obtained five years earlier, allow us to identify 28 oscillation modes. By
scaling the large frequency separation from the Sun, we measure the mean
density of beta Hyi to an accuracy of 0.6%. The amplitudes of the oscillations
are about 2.5 times solar and the mode lifetime is 2.3 d. A detailed comparison
of the mixed l=1 modes with theoretical models should allow a precise estimate
of the age of the star.Comment: 13 pages, 14 figures, accepted by ApJ. Fixed minor typo (ref to Fig
14
Elliptic and hyperelliptic magnetohydrodynamic equilibria
The present study is a continuation of a previous one on "hyperelliptic"
axisymmetric equilibria started in [Tasso and Throumoulopoulos, Phys. Plasmas
5, 2378 (1998)].
Specifically, some equilibria with incompressible flow nonaligned with the
magnetic field and restricted by appropriate side conditions like "isothermal"
magnetic surfaces, "isodynamicity" or P + B^2/2 constant on magnetic surfaces
are found to be reducible to elliptic integrals. The third class recovers
recent equilibria found in [Schief, Phys. Plasmas 10, 2677 (2003)]. In contrast
to field aligned flows, all solutions found here have nonzero toroidal magnetic
field on and elliptic surfaces near the magnetic axis.Comment: 9 page
Solar-like oscillations in the metal-poor subgiant nu Indi: constraining the mass and age using asteroseismology
Asteroseismology is a powerful method for determining fundamental properties
of stars. We report the first application to a metal-poor object, namely the
subgiant star nu Ind. We measured precise velocities from two sites, allowing
us to detect oscillations and infer a large frequency separation of Delta_nu =
24.25 +/- 0.25 microHz. Combining this value with the location of the star in
the H-R diagram and comparing with standard evolutionary models, we were able
to place constraints on the stellar parameters. In particular, our results
indicate that nu Ind has a low mass (0.85 +/- 0.04 M_sun) and is at least 9 Gyr
old.Comment: accpted for publication in Ap
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