1,721 research outputs found
Book Reviews
Reviews of the following books: Dawn Over the Kennebec by Mary R. Calvert; An Honest Woodsman: The Life and Opinions of Dave Priest-Maine Trapper, Guide, and Game Warden by William S. Warner; An Old New England Farm by William Thomson and Kenneth Maclver
A Six-Planet System Around the Star HD 34445
We present a new precision radial velocity dataset that reveals a
multi-planet system orbiting the G0V star HD 34445. Our 18-year span consists
of 333 precision radial velocity observations, 56 of which were previously
published, and 277 which are new data from Keck Observatory, Magellan at Las
Campanas Observatory, and the Automated Planet Finder at Lick Observatory.
These data indicate the presence of six planet candidates in Keplerian motion
about the host star with periods of 1057, 215, 118, 49, 677, and 5700 days, and
minimum masses of 0.63, 0.17, 0.1, 0.05, 0.12 and 0.38 Jupiter masses
respectively. The HD 34445 planetary system, with its high degree of
multiplicity, its long orbital periods, and its induced stellar radial velocity
half-amplitudes in the range is fundamentally unlike either our own solar system (in which only
Jupiter and Saturn induce significant reflex velocities for the Sun), or the
Kepler multiple-transiting systems (which tend to have much more compact
orbital configurations)Comment: 10 pages, 11 figure
The test case of HD26965: difficulties disentangling weak Doppler signals from stellar activity
We report the discovery of a radial velocity signal that can be interpreted
as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital
period of 42.3640.015 days, or alternatively, as the presence of residual,
uncorrected rotational activity in the data. Observations include data from
HIRES, PFS, CHIRON, and HARPS, where 1,111 measurements were made over 16
years. Our best solution for HD26965 is consistent with a super-Earth that
has a minimum mass of 6.920.79 M orbiting at a distance of
0.2150.008 AU from its host star. We have analyzed the correlation between
spectral activity indicators and the radial velocities from each instrument,
showing moderate correlations that we include in our model. From this analysis,
we recover a 38 day signal, which matches some literature values of the
stellar rotation period. However, from independent Mt. Wilson HK data for this
star, we find evidence for a significant 42 day signal after subtraction of
longer period magnetic cycles, casting doubt on the planetary hypothesis for
this period. Although our statistical model strongly suggests that the 42-day
signal is Doppler in origin, we conclude that the residual effects of stellar
rotation are difficult to fully model and remove from this dataset,
highlighting the difficulties to disentangle small planetary signals and
photospheric noise, particularly when the orbital periods are close to the
rotation period of the star. This study serves as an excellent test case for
future works that aim to detect small planets orbiting `Sun-like' stars using
radial velocity measurements.Comment: 16 pages, 10 figures, 13 tables, accepted for publication in A
MagAO Imaging of Long-period Objects (MILO). I. A Benchmark M Dwarf Companion Exciting a Massive Planet around the Sun-like Star HD 7449
We present high-contrast Magellan adaptive optics (MagAO) images of HD 7449,
a Sun-like star with one planet and a long-term radial velocity (RV) trend. We
unambiguously detect the source of the long-term trend from 0.6-2.15 \microns
~at a separation of \about 0\fasec 54. We use the object's colors and spectral
energy distribution to show that it is most likely an M4-M5 dwarf (mass \about
0.1-0.2 \msun) at the same distance as the primary and is therefore likely
bound. We also present new RVs measured with the Magellan/MIKE and PFS
spectrometers and compile these with archival data from CORALIE and HARPS. We
use a new Markov chain Monte Carlo procedure to constrain both the mass ( \msun ~at 99 confidence) and semimajor axis (\about 18 AU) of the M
dwarf companion (HD 7449B). We also refine the parameters of the known massive
planet (HD 7449Ab), finding that its minimum mass is
\mj, its semimajor axis is AU, and its eccentricity is
. We use N-body simulations to constrain the eccentricity
of HD 7449B to 0.5. The M dwarf may be inducing Kozai oscillations
on the planet, explaining its high eccentricity. If this is the case and its
orbit was initially circular, the mass of the planet would need to be
1.5 \mj. This demonstrates that strong constraints on known planets
can be made using direct observations of otherwise undetectable long-period
companions.Comment: Corrected planet mass error (7.8 Mj --> 1.09 Mj, in agreement with
previous studies
Congenital diaphragmatic hernia in the preterm infant.
BACKGROUND: Congenital diaphragmatic hernia (CDH) remains a significant cause of death in newborns. With advances in neonatal critical care and ventilation strategies, survival in the term infant now exceeds 80% in some centers. Although prematurity is a significant risk factor for morbidity and mortality in most neonatal diseases, its associated risk with infants with CDH has been described poorly. We sought to determine the impact of prematurity on survival using data from the Congenital Diaphragmatic Hernia Registry (CDHR).
METHODS: Prospectively collected data from live-born infants with CDH were analyzed from the CDHR from January 1995 to July 2009. Preterm infants were defined as \u3c37 weeks estimated gestational age at birth. Univariate and multivariate logistic regression analysis were\u3eperformed.
RESULTS: During the study period, 5,069 infants with CDH were entered in the registry. Of the 5,022 infants with gestational age data, there were 3,895 term infants (77.6%) and 1,127 preterm infants (22.4%). Overall survival was 68.7%. A higher percentage of term infants were treated with extracorporeal membrane oxygenation (ECMO) (33% term vs 25.6% preterm). Preterm infants had a greater percentage of chromosomal abnormalities (4% term vs 8.1% preterm) and major cardiac anomalies (6.1% term vs 11.8% preterm). Also, a significantly higher percentage of term infants had repair of the hernia (86.3% term vs 69.4% preterm). Survival for infants that underwent repair was high in both groups (84.6% term vs 77.2% preterm). Survival decreased with decreasing gestational age (73.1% term vs 53.5% preterm). The odds ratio (OR) for death among preterm infants adjusted for patch repair, ECMO, chromosomal abnormalities, and major cardiac anomalies was OR 1.68 (95% confidence interval [CI], 1.34-2.11).
CONCLUSION: Although outcomes for preterm infants are clearly worse than in the term infant, more than 50% of preterm infants still survived. Preterm infants with CDH remain a high-risk group. Although ECMO may be of limited value in the extremely premature infant with CDH, most preterm infants that live to undergo repair will survive. Prematurity should not be an independent factor in the treatment strategies of infants with CDH
DOPPLER MONITORING OF THE WASP-47 MULTIPLANET SYSTEM
We present precise Doppler observations of WASP-47, a transiting planetary system featuring a hot Jupiter with both inner and outer planetary companions. This system has an unusual architecture and also provides a rare opportunity to measure planet masses in two different ways: the Doppler method, and the analysis of transit-timing variations (TTV). Based on the new Doppler data, obtained with the Planet Finder Spectrograph on the Magellan/Clay 6.5 m telescope, the mass of the hot Jupiter is 370 ± 29[subscript ⊕]. This is consistent with the previous Doppler determination as well as the TTV determination. For the inner planet WASP-47e, the Doppler data lead to a mass of 12.2 ± 3.7[subscript ⊕], in agreement with the TTV-based upper limit of <22 M[subscript ⊕] (95% confidence). For the outer planet WASP-47d, the Doppler mass constraint of 10.4 ± 8.4[subscript ⊕] is consistent with the TTV-based measurement of $15.2[+6.7 over -7.6] M[subscript ⊕].United States. National Aeronautics and Space Administration (Origins Program Grant NNX11AG85G
Doppler monitoring of the WASP-47 multiplanet system
We present precise Doppler observations of WASP-47, a transiting planetary system featuring a hot Jupiter with both inner and outer planetary companions. This system has an unusual architecture and also provides a rare opportunity to measure planet masses in two different ways: the Doppler method, and the analysis of transit-timing variations (TTV). Based on the new Doppler data, obtained with the Planet Finder Spectrograph on the Magellan/Clay 6.5 m telescope, the mass of the hot Jupiter is 370+/- 29M⊕. This is consistent with the previous Doppler determination as well as the TTV determination. For the inner planet WASP-47e, the Doppler data lead to a mass of 12.2 +/-3.7 M⊕ in agreement with the TTV-based upper limit of <22 M⊕ (95% confidence). For the outer planet WASP-47d, the Doppler mass constraint of 10.4 +/- 8.4 M⊕ is consistent with the TTV-based measurement of 15.2 -7.6 to +6.7 M
Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments
We provide evidence that the obliquities of stars with close-in giant planets
were initially nearly random, and that the low obliquities that are often
observed are a consequence of star-planet tidal interactions. The evidence is
based on 14 new measurements of the Rossiter-McLaughlin effect (for the systems
HAT-P-6, HAT-P-7, HAT-P-16, HAT-P-24, HAT-P-32, HAT-P-34, WASP-12, WASP-16,
WASP-18, WASP-19, WASP-26, WASP-31, Gl 436, and Kepler-8), as well as a
critical review of previous observations. The low-obliquity (well-aligned)
systems are those for which the expected tidal timescale is short, and likewise
the high-obliquity (misaligned and retrograde) systems are those for which the
expected timescale is long. At face value, this finding indicates that the
origin of hot Jupiters involves dynamical interactions like planet-planet
interactions or the Kozai effect that tilt their orbits, rather than
inspiraling due to interaction with a protoplanetary disk. We discuss the
status of this hypothesis and the observations that are needed for a more
definitive conclusion.Comment: Accepted for publication in ApJ; typos corrected, 2 broken references
fixed, 26 pages, 25 figure
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