Recent analyses of data from the NASA Kepler spacecraft have established that planets with radii within 25 per cent of the Earth's (R Earth symbol) are commonplace throughout the Galaxy, orbiting at ...least 16.5 per cent of Sun-like stars. Because these studies were sensitive to the sizes of the planets but not their masses, the question remains whether these Earth-sized planets are indeed similar to the Earth in bulk composition. The smallest planets for which masses have been accurately determined are Kepler-10b (1.42 R Earth symbol) and Kepler-36b (1.49 R Earth symbol), which are both significantly larger than the Earth. Recently, the planet Kepler-78b was discovered and found to have a radius of only 1.16 R Earth symbol. Here we report that the mass of this planet is 1.86 Earth masses. The resulting mean density of the planet is 5.57 g cm(-3), which is similar to that of the Earth and implies a composition of iron and rock.
We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting ...planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple-planet systems orbiting the Kepler target star, but there are likely cases where (1) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (2) the planets orbit different stars within a binary/multiple star system. We use the low overall false-positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets, with periods ranging from 5.67 to 41 days.
We present Doppler tomographic analyses for the spectroscopic transits of KELT-7b and HAT-P-56b, two hot-Jupiters orbiting rapidly rotating F-dwarf host stars. These include analyses of archival ...Tillinghast Reflector Echelle Spectrograph (TRES) observations for KELT-7b, and a new TRES transit observation of HAT-P-56b. We report spin–orbit aligned geometries for KELT-7b (2
$_{.}^{\circ}$
7 ± 0
$_{.}^{\circ}$
6) and HAT-P-56b (8° ± 2°). The host stars KELT-7 and HAT-P-56 are among some of the most rapidly rotating planet-hosting stars known. We examine the tidal re-alignment model for the evolution of the spin–orbit angle in the context of the spin rates of these stars. We find no evidence that the rotation rates of KELT-7 and HAT-P-56 have been modified by star–planet tidal interactions, suggesting that the spin–orbit angle of systems around these hot stars may represent their primordial configuration. In fact, KELT-7 and HAT-P-56 are two of three systems in supersynchronous, spin–orbit aligned states, where the rotation periods of the host stars are faster than the orbital periods of the planets.
We discuss the discovery and characterization of the circumbinary planet Kepler-38b. The stellar binary is single-lined, with a period of 18.8 days, and consists of a moderately evolved main-sequence ...star (MA = 0.949 + or - 0.059 M sub(middot in circle) and RA = 1.757 + or - 0.034 R sub(middot in circle)) paired with a low-mass star (MB = 0.249 + or - 0.010 M sub(middot in circle) and RB = 0.2724 + or - 0.0053 R sub(middot in circle)) in a mildly eccentric (e = 0.103) orbit. A total of eight transits due to a circumbinary planet crossing the primary star were identified in the Kepler light curve (using Kepler Quarters 1-11), from which a planetary period of 105.595 + or - 0.053 days can be established. A photometric dynamical model fit to the radial velocity curve and Kepler light curve yields a planetary radius of 4.35 + or -0.11 R sub(+ in circle), or equivalently 1.12 + or -0.03 R sub(Nep). Since the planet is not sufficiently massive to observably alter the orbit of the binary from Keplerian motion, we can only place an upper limit on the mass of the planet of 122 M sub(+ in circle) (7.11 M sub(Nep) or equivalently 0.384 M sub(Jup)) at 95% confidence. This upper limit should decrease as more Kepler data become available.
Kepler-10b was the first rocky planet detected by the Kepler satellite and confirmed with radial velocity follow-up observations from Keck-HIRES. The mass of the planet was measured with a precision ...of around 30%, which was insufficient to constrain models of its internal structure and composition in detail. In addition to Kepler-10b, a second planet transiting the same star with a period of 45 days was statistically validated, but the radial velocities were only good enough to set an upper limit of 20 M sub(+ in circle) for the mass of Kepler-10c. To improve the precision on the mass for planet b, the HARPS-N Collaboration decided to observe Kepler-10 intensively with the HARPS-N spectrograph on the Telescopio Nazionale Galileo on La Palma. In total, 148 high-quality radial-velocity measurements were obtained over two observing seasons. These new data allow us to improve the precision of the mass determination for Kepler-10b to 15%. With a mass of 3.33 + or - 0.49 M sub(+ in circle) and an updated radius of 1.47 super(+0.03) sub(-0.02) R sub(+ in circle), Kepler-10b has a density of 5.8 + or - 0.8 g cm super(-3), very close to the value predicted by models with the same internal structure and composition as the Earth. We were also able to determine a mass for the 45-day period planet Kepler-10c, with an even better precision of 11%. With a mass of 17.2 + or - 1.9 M sub(+ in circle) and radius of 2.35 super(+0.09) sub(-0.04) R sub(+ in circle), Kepler-10c has a density of 7.1 + or - 1.0 g cm super(-3). Kepler-10c appears to be the first strong evidence of a class of more massive solid planets with longer orbital periods.
Abstract
As part of the Panchromatic Exoplanet Treasury program, we have conducted a spectroscopic study of WASP-79b, an inflated hot Jupiter orbiting an F-type star in Eridanus with a period of 3.66 ...days. Building on the original WASP and TRAPPIST photometry of Smalley et al., we examine
Hubble Space Telescope
(
HST
)/Wide Field Camera 3 (WFC3) (1.125–1.650
μ
m), Magellan/Low Dispersion Survey Spectrograph (LDSS)-3C (0.6–1
μ
m) data, and
Spitzer
data (3.6 and 4.5
μ
m). Using data from all three instruments, we constrain the water abundance to be −2.20 ≤ log(H
2
O) ≤ −1.55. We present these results along with the results of an atmospheric retrieval analysis, which favor inclusion of FeH and H
−
in the atmospheric model. We also provide an updated ephemeris based on the Smalley,
HST
/WFC3, LDSS-3C,
Spitzer
, and
Transiting Exoplanet Survey Satellite
(
TESS
) transit times. With the detectable water feature and its occupation of the clear/cloudy transition region of the temperature/gravity phase space, WASP-79b is a target of interest for the approved
James Webb Space Telescope
(
JWST
) Director’s Discretionary Early Release Science (ERS) program, with ERS observations planned to be the first to execute in Cycle 1. Transiting exoplanets have been approved for 78.1 hr of data collection, and with the delay in the
JWST
launch, WASP-79b is now a target for the Panchromatic Transmission program. This program will observe WASP-79b for 42 hr in four different instrument modes, providing substantially more data by which to investigate this hot Jupiter.
We establish the three-dimensional architecture of the Kepler-419 (previously KOI-1474) system to be eccentric yet with a low mutual inclination. Kepler-419b is a warm Jupiter at semi-major axis a = ...0.370 super(+0.007) sub(-0.006) AU with a large eccentricity (e = 0.85 super(+0.08) sub(-0.07)) measured via the "photoeccentric effect." It exhibits transit timing variations (TTVs) induced by the non-transiting Kepler-419c, which we uniquely constrain to be a moderately eccentric (e = 0.184 + or - 0.002), hierarchically separated (a = 1.68 + or - 0.03 AU) giant planet (7.3 + or - 0.4 M sub(Jup)). We combine 16 quarters of Kepler photometry, radial-velocity (RV) measurements from the HIgh Resolution Echelle Spectrometer on Keck, and improved stellar parameters that we derive from spectroscopy and asteroseismology. From the RVs, we measure the mass of the inner planet to be 2.5 + or - 0.3 M sub(Jup) and confirm its photometrically measured eccentricity, refining the value to e = 0.83 + or - 0.01. The RV acceleration is consistent with the properties of the outer planet derived from TTVs. We find that despite their sizable eccentricities, the planets are coplanar to within 9 super(+8) sub(-6) degrees, and therefore the inner planet's large eccentricity and close-in orbit are unlikely to be the result of Kozai migration. Moreover, even over many secular cycles, the inner planet's periapse is most likely never small enough for tidal circularization. Finally, we present and measure a transit time and impact parameter from four simultaneous ground-based light curves from 1 m class telescopes, demonstrating the feasibility of ground-based follow-up of Kepler giant planets exhibiting large TTVs.
We report the detection of eclipses in LSPM J1112+7626, which we find to be a moderately bright (IC = 12.14 ? 0.05) very low mass binary system with an orbital period of 41.03236 ? 0.00002 days, and ...component masses M 1 = 0.395 ? 0.002 M and M 2 = 0.275 ? 0.001 M in an eccentric (e = 0.239 ? 0.002) orbit. A 65 day out-of-eclipse modulation of approximately 2% peak-to-peak amplitude is seen in I-band, which is probably due to rotational modulation of photospheric spots on one of the binary components. This paper presents the discovery and characterization of the object, including radial velocities sufficient to determine both component masses to better than 1% precision, and a photometric solution. We find that the sum of the component radii, which is much better determined than the individual radii, is inflated by 3.8+0.9 --0.5% compared to the theoretical model predictions, depending on the age and metallicity assumed. These results demonstrate that the difficulties in reproducing observed M-dwarf eclipsing binary radii with theoretical models are not confined to systems with very short orbital periods. This object promises to be a fruitful testing ground for the hypothesized link between inflated radii in M-dwarfs and activity.
We report the discovery of Qatar-3b, Qatar-4b, and Qatar-5b, three new transiting planets identified by the Qatar Exoplanet Survey. The three planets belong to the hot Jupiter family, with orbital ...periods of = 2.50792 days, = 1.80539 days, and = 2.87923 days. Follow-up spectroscopic observations reveal the masses of the planets to be = 4.31 0.47 , = 6.10 0.54 , and = 4.32 0.18 , while model fits to the transit light curves yield radii of = 1.096 0.14 , = 1.135 0.11 , and = 1.107 0.064 . The host stars are low-mass main sequence stars with masses and radii MQ3 = 1.145 0.064 M , MQ4 = 0.896 0.048 M , MQ5 = 1.128 0.056 M and RQ3 = 1.272 0.14 R , RQ4 = 0.849 0.063 R , and RQ5 = 1.076 0.051 R for Qatar-3, 4, and 5 respectively. The V magnitudes of the three host stars are VQ3 = 12.88, VQ4 = 13.60, and VQ5 = 12.82. All three new planets can be classified as heavy hot Jupiters (M > 4 MJ).
Abstract
Giant planets on short-period orbits are predicted to be inflated and eventually engulfed by their host stars. However, the detailed timescales and stages of these processes are not well ...known. Here, we present the discovery of three hot Jupiters (
P
< 10 days) orbiting evolved, intermediate-mass stars (
M
⋆
≈ 1.5
M
⊙
, 2
R
⊙
<
R
⋆
< 5
R
⊙
). By combining TESS photometry with ground-based photometry and radial velocity measurements, we report masses and radii for these three planets of between 0.4 and 1.8
M
J
and 0.8 and 1.8
R
J
. TOI-2337b has the shortest period (
P
= 2.99432 ± 0.00008 days) of any planet discovered around a red giant star to date. Both TOI-4329b and TOI-2669b appear to be inflated, but TOI-2337b does not show any sign of inflation. The large radii and relatively low masses of TOI-4329b and TOI-2669b place them among the lowest density hot Jupiters currently known, while TOI-2337b is conversely one of the highest. All three planets have orbital eccentricities of below 0.2. The large spread in radii for these systems implies that planet inflation has a complex dependence on planet mass, radius, incident flux, and orbital properties. We predict that TOI-2337b has the shortest orbital decay timescale of any planet currently known, but do not detect any orbital decay in this system. Transmission spectroscopy of TOI-4329b would provide a favorable opportunity for the detection of water, carbon dioxide, and carbon monoxide features in the atmosphere of a planet orbiting an evolved star, and could yield new information about planet formation and atmospheric evolution.
PDF
