17 research outputs found
The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
Kepler-454 (KOI-273) is a relatively bright (V = 11.69 mag), Sun-like star that hosts a transiting planet candidate in a 10.6 day orbit. From spectroscopy, we estimate the stellar temperature to be 5687 ± 50 K, its metallicity to be [m/H] = 0.32 ± 0.08, and the projected rotational velocity to be v sin i 10 years and mass >12.1 MJ. The 12 exoplanets with radii <2.7 R_⊕ and precise mass measurements appear to fall into two populations, with those <1.6 R_⊕ following an Earth-like composition curve and larger planets requiring a significant fraction of volatiles. With a density of 2.76 ± 0.73 g cm^(−3), Kepler-454b lies near the mass transition between these two populations and requires the presence of volatiles and/or H/He gas
Non-Detection of the Putative Substellar Companion to HD 149382
It has been argued that a substellar companion may significantly influence
the evolution of the progenitors of sdB stars. Recently, the bright sdB star HD
149382 has been claimed to host a substellar (possibly planetary) companion
with a period of 2.391 days. This has important implications for the evolution
of the progenitors of sdB stars as well as the source of the UV-excess seen in
elliptical galaxies. In order to verify this putative planet, we made 10 radial
velocity measurements of HD 149382 over 17 days with the High Resolution
Spectrograph at the Hobby-Eberly Telescope. Our data conclusively demonstrate
that the putative substellar companion does not exist, and they exclude the
presence of almost any substellar companion with P ~ 1
Mjup.Comment: 5 figures, 6 pages, 2 table
The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet
Kepler-10b was the first rocky planet detected by the Kepler satellite and
con- firmed 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 sta- tistically validated, but the radial
velocities were only good enough to set an upper limit of 20 Mearth 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 to- tal, 148
high-quality radial-velocity measurements were obtained over two observing
seasons. These new data allow us to improve the precision of the mass
determina- tion for Kepler-10b to 15%. With a mass of 3.33 +/- 0.49 Mearth and
an updated radius of 1.47 +0.03 -0.02 Rearth, Kepler-10b has a density of 5.8
+/- 0.8 g cm-3, very close to the value -0.02 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 +/- 1.9 Mearth and radius of 2.35 +0.09 -0.04
Rearth, -0.04 Kepler-10c has a density of 7.1 +/- 1.0 g cm-3. Kepler-10c
appears to be the first strong evidence of a class of more massive solid
planets with longer orbital periods.Comment: 44 pages, 8 figures, accepted for publication in Ap
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The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet.
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 ⊕ 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 ± 0.49 M ⊕ and an updated radius of R ⊕, Kepler-10b has a density of 5.8 ± 0.8 g cm–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 ± 1.9 M ⊕ and radius of R ⊕, Kepler-10c has a density of 7.1 ± 1.0 g cm–3. Kepler-10c appears to be the first strong evidence of a class of more massive solid planets with longer orbital periods.Astronom
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An Earth-sized planet with an Earth-like density
Recent analyses1–4 of data from the NASA Kepler spacecraft5 have established that planets with radii within 25 per cent of Earth’s (R⊕) are commonplace throughout the Galaxy, orbiting at least 16.5 per cent of Sun-like stars1. 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 determined6,7 are Kepler-10b (1.42R⊕) and Kepler-36b (1.49R⊕), which are both significantly larger than the Earth. Recently, the planet Kepler-78b was discovered8 and found to have a radius of only 1.16R⊕. 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.Astronom
The Mass of Kepler-93b and The Composition of Terrestrial Planets
Kepler-93b is a 1.478 +/- 0.019 Earth radius planet with a 4.7 day period
around a bright (V=10.2), astroseismically-characterized host star with a mass
of 0.911+/-0.033 solar masses and a radius of 0.919+/-0.011 solar radii. Based
on 86 radial velocity observations obtained with the HARPS-N spectrograph on
the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we
present a precise mass estimate of 4.02+/-0.68 Earth masses. The corresponding
high density of 6.88+/-1.18 g/cc is consistent with a rocky composition of
primarily iron and magnesium silicate. We compare Kepler-93b to other dense
planets with well-constrained parameters and find that between 1-6 Earth
masses, all dense planets including the Earth and Venus are well-described by
the same fixed ratio of iron to magnesium silicate. There are as of yet no
examples of such planets with masses > 6 Earth masses: All known planets in
this mass regime have lower densities requiring significant fractions of
volatiles or H/He gas. We also constrain the mass and period of the outer
companion in the Kepler-93 system from the long-term radial velocity trend and
archival adaptive optics images. As the sample of dense planets with
well-constrained masses and radii continues to grow, we will be able to test
whether the fixed compositional model found for the seven dense planets
considered in this paper extends to the full population of 1-6 Earth mass
planets.Comment: 8 pages, 4 figures. Accepted for publication in Ap
The Kepler-10 Planetary System Revisited by HARPS-N: A Hot Rocky World and a Solid Neptune-Mass Planet
Kepler-10b was the first rocky planet detected by the Kepler satellite and
con- firmed 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 sta- tistically validated, but the radial
velocities were only good enough to set an upper limit of 20 Mearth 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 to- tal, 148
high-quality radial-velocity measurements were obtained over two observing
seasons. These new data allow us to improve the precision of the mass
determina- tion for Kepler-10b to 15%. With a mass of 3.33 +/- 0.49 Mearth and
an updated radius of 1.47 +0.03 -0.02 Rearth, Kepler-10b has a density of 5.8
+/- 0.8 g cm-3, very close to the value -0.02 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 +/- 1.9 Mearth and radius of 2.35 +0.09 -0.04
Rearth, -0.04 Kepler-10c has a density of 7.1 +/- 1.0 g cm-3. Kepler-10c
appears to be the first strong evidence of a class of more massive solid
planets with longer orbital periods.Comment: 44 pages, 8 figures, accepted for publication in Ap