179 research outputs found
Discovery of the Transiting Planet Kepler-5B
We present 44 days of high duty cycle, ultra precise photometry of the 13th magnitude star Kepler-5 (KIC 8191672, T(eff) = 6300 K, log g = 4.1), which exhibits periodic transits with a depth of 0.7%. Detailed modeling of the transit is consistent with a planetary companion with an orbital period of 3.548460 +/- 0.000032 days and a radius of 1.431(-0.052)(+0.041) R(J). Follow-up radial velocity measurements with the Keck HIRES spectrograph on nine separate nights demonstrate that the planet is more than twice as massive as Jupiter with a mass of 2.114(-0.059)(+0.056) M(J) and a mean density of 0.894 +/- 0.079 g cm(-3).NASA's Science Mission DirectorateAstronom
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Kepler-4B: A Hot Neptune-Like Planet of A G0 Star Near Main-Sequence Turnoff
Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19(h)02(m)27.(s)68, delta = +50 degrees 08'08 '' 7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10(-3) and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3(-1.9)(+1.1) m s(-1), consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223(-0.091)(+0.053) M(circle dot) and 1.487(-0.084)(+0.071) R(circle dot).We estimate the planet mass and radius to be {M(P), R(P)} = {24.5 +/- 3.8 M(circle plus), 3.99 +/- 0.21 R(circle plus)}. The planet's density is near 1.9 g cm(-3); it is thus slightly denser and more massive than Neptune, but about the same size.W. M. Keck FoundationNASA's Science Mission DirectorateAstronom
Kepler-7b: A Transiting Planet with Unusually Low Density
We report the discovery and confirmation of Kepler-7b, a transiting planet
with unusually low density. The mass is less than half that of Jupiter, Mp =
0.43 Mj, but the radius is fifty percent larger, Rp = 1.48 Rj. The resulting
density, 0.17 g/cc, is the second lowest reported so far for an extrasolar
planet. The orbital period is fairly long, P = 4.886 days, and the host star is
not much hotter than the Sun, Teff = 6000 K. However, it is more massive and
considerably larger than the sun, Mstar = 1.35 Msun and Rstar = 1.84 Rsun, and
must be near the end of its life on the Main Sequence.Comment: 19 pages, 3 figure
A Transiting Hot Jupiter Orbiting a Metal-Rich Star
We announce the discovery of Kepler-6b, a transiting hot Jupiter orbiting a
star with unusually high metallicity, [Fe/H] = +0.34 +/- 0.04. The planet's
mass is about 2/3 that of Jupiter, Mp = 0.67 Mj, and the radius is thirty
percent larger than that of Jupiter, Rp = 1.32 Rj, resulting in a density of
0.35 g/cc, a fairly typical value for such a planet. The orbital period is P =
3.235 days. The host star is both more massive than the Sun, Mstar = 1.21 Msun,
and larger than the Sun, Rstar = 1.39 Rsun.Comment: 12 pages, 2 figures, submitted to the Astrophysical Journal Letter
Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
The Kepler mission has discovered over 2500 exoplanet candidates in the first
two years of spacecraft data, with approximately 40% of them in candidate
multi-planet systems. The high rate of multiplicity combined with the low rate
of identified false-positives indicates that the multiplanet systems contain
very few false-positive signals due to other systems not gravitationally bound
to the target star (Lissauer, J. J., et al., 2012, ApJ 750, 131). False
positives in the multi- planet systems are identified and removed, leaving
behind a residual population of candidate multi-planet transiting systems
expected to have a false-positive rate less than 1%. We present a sample of 340
planetary systems that contain 851 planets that are validated to substantially
better than the 99% confidence level; the vast majority of these have not been
previously verified as planets. We expect ~2 unidentified false-positives
making our sample of planet very reliable. We present fundamental planetary
properties of our sample based on a comprehensive analysis of Kepler light
curves and ground-based spectroscopy and high-resolution imaging. Since we do
not require spectroscopy or high-resolution imaging for validation, some of our
derived parameters for a planetary system may be systematically incorrect due
to dilution from light due to additional stars in the photometric aperture.
None the less, our result nearly doubles the number of verified exoplanets.Comment: 138 pages, 8 Figures, 5 Tables. Accepted for publications in the
Astrophysical Journa
Kepler Observations of Transiting Hot Compact Objects
Kepler photometry has revealed two unusual transiting companions orbiting an
early A-star and a late B-star. In both cases the occultation of the companion
is deeper than the transit. The occultation and transit with follow-up optical
spectroscopy reveal a 9400 K early A-star, KOI-74 (KIC 6889235), with a
companion in a 5.2 day orbit with a radius of 0.08 Rsun and a 10000 K late
B-star KOI-81 (KIC 8823868) that has a companion in a 24 day orbit with a
radius of 0.2 Rsun. We infer a temperature of 12250 K for KOI-74b and 13500 K
for KOI-81b.
We present 43 days of high duty cycle, 30 minute cadence photometry, with
models demonstrating the intriguing properties of these object, and speculate
on their nature.Comment: 12 pages, 3 figures, submitted to ApJL (updated to correct KOI74
lightcurve
A First Comparison of Kepler Planet Candidates in Single and Multiple Systems
In this letter we present an overview of the rich population of systems with
multiple candidate transiting planets found in the first four months of Kepler
data. The census of multiples includes 115 targets that show 2 candidate
planets, 45 with 3, 8 with 4, and 1 each with 5 and 6, for a total of 170
systems with 408 candidates. When compared to the 827 systems with only one
candidate, the multiples account for 17 percent of the total number of systems,
and a third of all the planet candidates. We compare the characteristics of
candidates found in multiples with those found in singles. False positives due
to eclipsing binaries are much less common for the multiples, as expected.
Singles and multiples are both dominated by planets smaller than Neptune; 69
+2/-3 percent for singles and 86 +2/-5 percent for multiples. This result, that
systems with multiple transiting planets are less likely to include a
transiting giant planet, suggests that close-in giant planets tend to disrupt
the orbital inclinations of small planets in flat systems, or maybe even to
prevent the formation of such systems in the first place.Comment: 13 pages, 13 figures, submitted to ApJ Letter
PHAT Stellar Cluster Survey I. Year 1 Catalog and Integrated Photometry
The Panchromatic Hubble Andromeda Treasury (PHAT) survey is an on-going
Hubble Space Telescope (HST) multi-cycle program to obtain high spatial
resolution imaging of one-third of the M31 disk at ultraviolet through
near-infrared wavelengths. In this paper, we present the first installment of
the PHAT stellar cluster catalog. When completed, the PHAT cluster catalog will
be among the largest and most comprehensive surveys of resolved star clusters
in any galaxy. The exquisite spatial resolution achieved with HST has allowed
us to identify hundreds of new clusters that were previously inaccessible with
existing ground-based surveys. We identify 601 clusters in the Year 1 sample,
representing more than a factor of four increase over previous catalogs within
the current survey area (390 arcmin^2). This work presents results derived from
the first \sim25% of the survey data; we estimate that the final sample will
include \sim2500 clusters. For the Year 1 objects, we present a catalog with
positions, radii, and six-band integrated photometry. Along with a general
characterization of the cluster luminosities and colors, we discuss the cluster
luminosity function, the cluster size distributions, and highlight a number of
individually interesting clusters found in the Year 1 search.Comment: 26 pages, 22 figures, Accepted by Ap
Discovery and Validation of Kepler-452b: A 1.6-Re Super Earth Exoplanet in the Habitable Zone of a G2 Star
We report on the discovery and validation of Kepler-452b, a transiting planet
identified by a search through the 4 years of data collected by NASA's Kepler
Mission. This possibly rocky 1.63 R planet orbits
its G2 host star every 384.843 days, the longest orbital
period for a small (R < 2 R) transiting exoplanet to date. The
likelihood that this planet has a rocky composition lies between 49% and 62%.
The star has an effective temperature of 575785 K and a log g of
4.320.09. At a mean orbital separation of 1.046 AU,
this small planet is well within the optimistic habitable zone of its star
(recent Venus/early Mars), experiencing only 10% more flux than Earth receives
from the Sun today, and slightly outside the conservative habitable zone
(runaway greenhouse/maximum greenhouse). The star is slightly larger and older
than the Sun, with a present radius of 1.11 R and an
estimated age of 6 Gyr. Thus, Kepler-452b has likely always been in the
habitable zone and should remain there for another 3 Gyr.Comment: 19 pages, 16 figure
Characteristics of Kepler Planetary Candidates Based on the First Data Set: The Majority are Found to be Neptune-Size and Smaller
In the spring of 2009, the Kepler Mission commenced high-precision photometry
on nearly 156,000 stars to determine the frequency and characteristics of small
exoplanets, conduct a guest observer program, and obtain asteroseismic data on
a wide variety of stars. On 15 June 2010 the Kepler Mission released data from
the first quarter of observations. At the time of this publication, 706 stars
from this first data set have exoplanet candidates with sizes from as small as
that of the Earth to larger than that of Jupiter. Here we give the identity and
characteristics of 306 released stars with planetary candidates. Data for the
remaining 400 stars with planetary candidates will be released in February
2011. Over half the candidates on the released list have radii less than half
that of Jupiter. The released stars include five possible multi-planet systems.
One of these has two Neptune-size (2.3 and 2.5 Earth-radius) candidates with
near-resonant periods.Comment: Paper to accompany Kepler's June 15, 2010 data release; submitted to
Astrophysical Journal Figures 1,2,& 3 revised. Improved labeling on all
figures. Slight changes to planet frequencies in result
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