133 research outputs found
KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star
We present the discovery of KELT-1b, the first transiting low-mass companion
from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North)
survey. The V=10.7 primary is a mildly evolved, solar-metallicity, mid-F star.
The companion is a low-mass brown dwarf or super-massive planet with mass of
27.23+/-0.50 MJ and radius of 1.110+0.037-0.024 RJ, on a very short period
(P=1.21750007) circular orbit. KELT-1b receives a large amount of stellar
insolation, with an equilibrium temperature assuming zero albedo and perfect
redistribution of 2422 K. Upper limits on the secondary eclipse depth indicate
that either the companion must have a non-zero albedo, or it must experience
some energy redistribution. Comparison with standard evolutionary models for
brown dwarfs suggests that the radius of KELT-1b is significantly inflated.
Adaptive optics imaging reveals a candidate stellar companion to KELT-1, which
is consistent with an M dwarf if bound. The projected spin-orbit alignment
angle is consistent with zero stellar obliquity, and the vsini of the primary
is consistent with tidal synchronization. Given the extreme parameters of the
KELT-1 system, we expect it to provide an important testbed for theories of the
emplacement and evolution of short-period companions, and theories of tidal
dissipation and irradiated brown dwarf atmospheres.Comment: 30 pages, 19 figures. Submitted to Ap
KELT-2Ab: A Hot Jupiter Transiting the Bright (V=8.77) Primary Star of a Binary System
We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright
(V=8.77) primary star of the HD 42176 binary system. The host is a slightly
evolved late F-star likely in the very short-lived "blue-hook" stage of
evolution, with \teff=6148\pm48{\rm K}, and
\feh=0.034\pm0.78. The inferred stellar mass is
\msun\ and the star has a relatively large radius
of \rsun. The planet is a typical hot Jupiter with
period days and a mass of \mj\ and
radius of \rj. This is mildly inflated as compared
to models of irradiated giant planets at the 4 Gyr age of the system.
KELT-2A is the third brightest star with a transiting planet identified by
ground-based transit surveys, and the ninth brightest star overall with a
transiting planet. KELT-2Ab's mass and radius are unique among the subset of
planets with host stars, and therefore increases the diversity of bright
benchmark systems. We also measure the relative motion of KELT-2A and -2B over
a baseline of 38 years, robustly demonstrating for the first time that the
stars are bound. This allows us to infer that KELT-2B is an early K-dwarf. We
hypothesize that through the eccentric Kozai mechanism KELT-2B may have
emplaced KELT-2Ab in its current orbit. This scenario is potentially testable
with Rossiter-McLaughlin measurements, which should have an amplitude of
44 m s.Comment: 9 pages, 2 tables, 4 figures. A short video describing this paper is
available at http://www.youtube.com/watch?v=wVS8lnkXXlE. Revised to reflect
the ApJL version. Note that figure 4 is not in the ApJL versio
Spitzer observations of a 24 micron shadow: Bok Globule CB190
We present Spitzer observations of the dark globule CB190 (L771). We observe
a roughly circular 24 micron shadow with a 70 arcsec radius. The extinction
profile of this shadow matches the profile derived from 2MASS photometry at the
outer edges of the globule and reaches a maximum of ~32 visual magnitudes at
the center. The corresponding mass of CB190 is ~10 Msun. Our 12CO and 13CO J =
2-1 data over a 10 arcmin X 10 arcmin region centered on the shadow show a
temperature ~10 K. The thermal continuum indicates a similar temperature for
the dust. The molecular data also show evidence of freezeout onto dust grains.
We estimate a distance to CB190 of 400 pc using the spectroscopic parallax of a
star associated with the globule. Bonnor-Ebert fits to the density profile, in
conjunction with this distance, yield xi_max = 7.2, indicating that CB190 may
be unstable. The high temperature (56 K) of the best fit Bonnor-Ebert model is
in contradiction with the CO and thermal continuum data, leading to the
conclusion that the thermal pressure is not enough to prevent free-fall
collapse. We also find that the turbulence in the cloud is inadequate to
support it. However, the cloud may be supported by the magnetic field, if this
field is at the average level for dark globules. Since the magnetic field will
eventually leak out through ambipolar diffusion, it is likely that CB190 is
collapsing or in a late pre-collapse stage.Comment: 16 pages, 13 figures, accepted for publication in Ap
The transcriptional and functional properties of mouse epiblast stem cells resemble the anterior primitive streak.
Mouse epiblast stem cells (EpiSCs) can be derived from a wide range of developmental stages. To characterize and compare EpiSCs with different origins, we derived a series of EpiSC lines from pregastrula stage to late-bud-stage mouse embryos. We found that the transcriptomes of these cells are hierarchically distinct from those of the embryonic stem cells, induced pluripotent stem cells (iPSCs), and epiblast/ectoderm. The EpiSCs display globally similar gene expression profiles irrespective of the original developmental stage of the source tissue. They are developmentally similar to the ectoderm of the late-gastrula-stage embryo and behave like anterior primitive streak cells when differentiated in vitro and in vivo. The EpiSC lines that we derived can also be categorized based on a correlation between gene expression signature and predisposition to differentiate into particular germ-layer derivatives. Our findings therefore highlight distinct identifying characteristics of EpiSCs and provide a foundation for further examination of EpiSC properties and potential
The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. I. Identifying and Characterizing the Protostellar Content of the OMC-2 FIR4 and OMC-2 FIR3 Regions
We present ALMA (0.87~mm) and VLA (9~mm) observations toward OMC2-FIR4 and
OMC2-FIR3 within the Orion integral-shaped filament that are thought to be the
nearest regions of intermediate mass star formation. We characterize the
continuum sources within these regions on 40~AU (0\farcs1) scales and
associated molecular line emission at a factor of 30 better resolution
than previous observations at similar wavelengths. We identify six compact
continuum sources within OMC2-FIR4, four in OMC2-FIR3, and one additional
source just outside OMC2-FIR4. This continuum emission is tracing the inner
envelope and/or disk emission on less than 100~AU scales. HOPS-108 is the only
protostar in OMC2-FIR4 that exhibits emission from high-excitation transitions
of complex organic molecules (e.g., methanol and other lines) coincident with
the continuum emission. HOPS-370 in OMC2-FIR3 with L~~360~\lsun, also
exhibits emission from high-excitation methanol and other lines. The methanol
emission toward these two protostars is indicative of temperatures high enough
to thermally evaporate methanol from icy dust grains; overall these protostars
have characteristics similar to hot corinos. We do not identify a clear outflow
from HOPS-108 in \twco, but find evidence of interaction between the
outflow/jet from HOPS-370 and the OMC2-FIR4 region. The multitude of
observational constraints indicate that HOPS-108 is likely a low to
intermediate-mass protostar in its main mass accretion phase and it is the most
luminous protostar in OMC2-FIR4. The high resolution data presented here are
essential for disentangling the embedded protostars from their surrounding
dusty environments and characterizing them
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy
We measure the energy emitted by extensive air showers in the form of radio
emission in the frequency range from 30 to 80 MHz. Exploiting the accurate
energy scale of the Pierre Auger Observatory, we obtain a radiation energy of
15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV
arriving perpendicularly to a geomagnetic field of 0.24 G, scaling
quadratically with the cosmic-ray energy. A comparison with predictions from
state-of-the-art first-principle calculations shows agreement with our
measurement. The radiation energy provides direct access to the calorimetric
energy in the electromagnetic cascade of extensive air showers. Comparison with
our result thus allows the direct calibration of any cosmic-ray radio detector
against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI.
Supplemental material in the ancillary file
The interplay of landscape composition and configuration: new pathways to manage functional biodiversity and agroecosystem services across Europe
Managing agricultural landscapes to support biodiversity and ecosystem services is a key aim of a sustainable agriculture. However, how the spatial arrangement of crop fields and other habitats in landscapes impacts arthropods and their functions is poorly known. Synthesising data from 49 studies (1515 landscapes) across Europe, we examined effects of landscape composition (% habitats) and configuration (edge density) on arthropods in fields and their margins, pest control, pollination and yields. Configuration effects interacted with the proportions of crop and nonâcrop habitats, and speciesâ dietary, dispersal and overwintering traits led to contrasting responses to landscape variables. Overall, however, in landscapes with high edge density, 70% of pollinator and 44% of natural enemy species reached highest abundances and pollination and pest control improved 1.7â and 1.4âfold respectively. Arableâdominated landscapes with high edge densities achieved high yields. This suggests that enhancing edge density in European agroecosystems can promote functional biodiversity and yieldâenhancing ecosystem services
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