32 research outputs found
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
Finding the most variable stars in the Orion Belt with the All Sky Automated Survey
We look for high-amplitude variable young stars in the open clusters and
associations of the Orion Belt. We use public data from the ASAS-3 Photometric
V-band Catalogue of the All Sky Automated Survey, infrared photometry from the
2MASS and IRAS catalogues, proper motions, and the Aladin sky atlas to obtain a
list of the most variable stars in a survey area of side 5 deg centred on the
bright star Alnilam (eps Ori) in the centre of the Orion Belt. We identify 32
highly-variable stars, of which 16 had not been reported to vary before. They
are mostly variable young stars and candidates (16) and background giants (8),
but there are also field cataclysmic variables, contact binaries, and eclipsing
binary candidates. Of the young stars, which typically are active Herbig Ae/Be
and T Tauri stars with Halpha emission and infrared flux excess, we discover
four new variables and confirm the variability status of another two. Some of
them belong to the well known sigma Orionis cluster. Besides, six of the eight
giants are new variables, and three are new periodic variables.Comment: Astronomische Nachrichten, in pres
A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-Transiting Planet in the Kepler-20 System*
Kepler-20 is a solar-type star (V = 12.5) hosting a compact system of five transiting planets, all packed within the orbital distance of Mercury in our own Solar System. A transition from rocky to gaseous planets with a planetary transition radius of ∼ 1.6 R⊕ has recently been proposed by several publications in the literature (Rogers 2015; Weiss& Marcy 2014). Kepler-20b (Rp ∼ 1.9 R⊕) has a size beyond this transition radius, however previous mass measurements were not sufficiently precise to allow definite conclusions to be drawn regarding its composition. We present new mass measurements of Kepler-20 three of the planets in the Kepler-20 system facilitated by 104 radial velocity measurements from the HARPS-N spectrograph and 30 archival Keck/HIRES observations, as well as an updated photometric analysis of the Kepler data and an asteroseismic analysis of the host star (M* = 0.948 ± 0.051 M☉ and R* = 0.964 ± 0.018 R☉).Kepler-20b is a 1.868+0.066 −0.034 R⊕ planet in a 3.7 day period with amass of 9.70+1.41 −1.44 M⊕ resulting in a mean density of 8.2 +1.5 −1.3 g cm−3 indicating a rocky composition with an iron to silicate ratio consistent with that of the Earth. This makes Kepler-20b the most massive planet with a rocky composition found to date. Furthermore, we report the discovery of an additional non-transiting planet with a minimum mass of 19.96+3.08 −3.61 M⊕ and an orbital period of ∼ 34 days in the gap between Kepler-20f (P ∼ 11 days) and Kepler-20d (P ∼78 days).PostprintPeer reviewe
Recommended from our members
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
An Accurate Mass Determination for Kepler-1655b, a Moderately Irradiated World with a Significant Volatile Envelope
Funding: A.C.C. acknowledges support from STFC consolidated grant number ST/M001296/1. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 313014 (ETAEARTH).We present the confirmation of a small, moderately-irradiated (F= 155±7 F⊕) Neptune with a substantial gas envelope in a P=11.8728787±0.0000085-day orbit about a quiet, Sun-like G0V star Kepler-1655. Based on our analysis of the Kepler light curve, we determined Kepler-1655b’s radius to be 2.213±0.082 R⊕. We acquired 95 high-resolution spectra with TNG/HARPS-N, enabling us to characterize the host star and determine an accurate mass for Kepler-1655b of 5.0±^3.1_2.8 M⊕ via Gaussian-process regression. Our mass determination excludes an Earth-like composition with 98% confidence. Kepler-1655b falls on the upper edge of the evaporation valley, in the relatively sparsely occupied transition region between rocky and gas-rich planets. It is therefore part of a population of planets that we should actively seek to characterize further.PostprintPeer reviewe
Recommended from our members
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
VizieR Online Data Catalog: A transiting rocky planet at 6.5pc from the Sun (Motalebi+ 2015)
We obtained 98 spectra of HD219134 using the HARPS-N spectrograph. Our RV data are provided online. spitzer.dat contains the photometric time-series presented in the paper for HD219134 and gathered by the IRAC instrument aboard the Spitzer telescope in its channel 2 (4.5 microns) on 2015-04-14
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
Characterization of the planetary system Kepler-101 with HARPS-N. A hot super-Neptune with an Earth-sized low-mass companion
We report on the characterization of the Kepler-101 planetary system, thanks
to a combined DE-MCMC analysis of Kepler data and forty radial velocities
obtained with the HARPS-N spectrograph. This system was previously validated by
Rowe et al. (2014) and is composed of a hot super-Neptune, Kepler-101b, and an
Earth-sized planet, Kepler-101c. These two planets orbit the slightly evolved
and metal-rich G-type star in 3.49 and 6.03 days, respectively. With mass
, radius , and density , Kepler-101b is the first
fully-characterized super-Neptune, and its density suggests that heavy elements
make up a significant fraction of its interior; more than of its total
mass. Kepler-101c has a radius of , which
implies the absence of any H/He envelope, but its mass could not be determined
due to the relative faintness of the parent star for highly precise
radial-velocity measurements () and the limited number of
radial velocities. The upper limit, ,
excludes a pure iron composition with a probability. The architecture
of the Kepler-101 planetary system - containing a close-in giant planet and an
outer Earth-sized planet with a period ratio slightly larger than the 3:2
resonance - is certainly of interest for planet formation and evolution
scenarios. This system does not follow the trend, seen by Ciardi et al. (2013),
that in the majority of Kepler systems of planet pairs with at least one
Neptune-size or larger planet, the larger planet has the longer period.Comment: 7 pages, 3 figures, accepted in A&