543 research outputs found
Extrasolar Planets in the Classroom
The field of extrasolar planets is still, in comparison with other
astrophysical topics, in its infancy. There have been about 300 or so
extrasolar planets detected and their detection has been accomplished by
various different techniques. Here we present a simple laboratory experiment to
show how planets are detected using the transit technique. Following the simple
analysis procedure describe we are able to determine the planetary radius to be
1.27 +/- 0.20 R_{J} which, within errors agrees with the establish value of
1.32 +/- 0.25 R_{J}.Comment: 7 pages, 2 figures, published in Physics Educatio
Homozygous disruption of P450 side-chain cleavage (CYP11A1) is associated with prematurity, complete 46,XY sex reversal, and severe adrenal failure
Disruption of the P450 side-chain cleavage cytochrome (P450scc) enzyme due to deleterious mutations of the CYP11A1 gene is thought to be incompatible with fetal survival because of impaired progesterone production by the fetoplacental unit. We present a 46, XY patient with a homozygous disruption of CYP11A1.The child was born prematurely with complete sex reversal and severe adrenal insufficiency. Laboratory data showed diminished or absent steroidogenesis in all pathways. Molecular genetic analysis of the CYP11A1 gene revealed a homozygous single nucleotide deletion leading to a premature termination at codon position 288. This mutation will delete highly conserved regions of the P450scc enzyme and thus is predicted to lead to a nonfunctional protein. Both healthy parents were heterozygous for this mutation.Our report demonstrates that severe disruption of P450scc can be compatible with survival in rare instances. Furthermore, defects in this enzyme are inherited in an autosomal-recessive fashion, and heterozygote carriers can be healthy and fertile. The possibility of P450scc-independent pathways of steroid synthesis in addition to the current concept of luteoplacental shift of progesterone synthesis in humans has to be questioned
The EXPLORE Project I: A Deep Search for Transiting Extrasolar Planets
(Abridged) We discuss the design considerations of the EXPLORE (EXtra-solar
PLanet Occultation REsearch) project, a series of transiting planet searches
using 4-m-class telescopes to continuously monitor a single field of stars in
the Galactic Plane in each ~2 week observing campaign. We discuss the general
factors which determine the efficiency and the number of planets found by a
transit search, including time sampling strategy and field selection. The
primary goal is to select the most promising planet candidates for radial
velocity follow-up observations. We show that with very high photometric
precision light curves that have frequent time sampling and at least two
detected transits, it is possible to uniquely solve for the main parameters of
the eclipsing system (including planet radius) based on several important
assumptions about the central star. Together with a measured spectral type for
the star, this unique solution for orbital parameters provides a powerful
method for ruling out most contaminants to transiting planet candidates. For
the EXPLORE project, radial velocity follow-up observations for companion mass
determination of the best candidates are done on 8-m-class telescopes within
two or three months of the photometric campaigns. This same-season follow-up is
made possible by the use of efficient pipelines to produce high quality light
curves within weeks of the observations. We conclude by presenting early
results from our first search, EXPLORE I, in which we reached <1% rms
photometric precision (measured over a full night) on ~37,000 stars to I <=
18.2.Comment: accepted by ApJ. Main points unchanged but more thorough discussion
of some issues. 36 pages, including 14 figure
The statistics of the photometric accuracy based on MASS data and the evaluation of high-altitude wind
The effect of stellar scintillation on the accuracy of photometric
measurements is analyzed. We obtain a convenient form of estimaton of this
effect in the long exposure regime, when the turbulence shift produced by the
wind is much larger than the aperture of the telescope. A simple method is
proposed to determine index introduced by perture of the Kenyon et al.
(2006), directly from the measurements with the Multi Aperture Scintillation
Sensor (MASS) without information on vertical profile of the wind. The
statistics resulting from our campaign of 2005 -- 2007 at Maidanak
observatory is presented. It is shown that these data can be used to estimate
high-altitude winds at pressure level 70 -- 100 mbar. Comparison with the wind
speed retrieved from the NCEP/NCAR global models shows a good agreement. Some
prospects for retrieval of the wind speed profile from the MASS measurements
are outlined.Comment: 11 pages, 9 figures, accepted for publication in Astronomy Letter
New ground-based observational methods and instrumentation for asteroseismology
Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being
built to attain very high precision data to be used for asteroseismic analysis.
Nonetheless, there is a very strong need for providing additional information,
especially on mode identification. With this contribution I will review the
efforts been put on new ground-based instrumentation and the methodology that
can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and
Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar
Pulsation Conference Series: Impact of new instrumentation and new insights
in stellar pulsations", 5-9 September 2011, Granada, Spai
Ornamental plants, 1985: a summary of research
Field transplant survival of Amelanchier liners produced by tissue culture / Daniel K. Struve and R. Daniel Lineberger -- An evaluation of strawdust - an alternative growing media / Elton M. Smith and Sharon A. Treaster -- Growth of container grown nursery stock produced in composted municipal sludge amended media / Elton M. Smith and Sharon A. Treaster -- Soil temperature effects on root regeneration of scarlet oak seedlings / Daniel K. Struve arid Bruno C. Moser -- Lighting Viburnum opulus 'Nanum' cuttings to increase winter survival / Elton M. Smith and Sharon A. Treaster -- Treatments of etiolated dormant rose shoots / Elton M. Smith and Sharon A. Treaster -- Evaluation of flowering crabapple susceptibility to apple scab in Ohio â 1984 / Elton M. Smith and Sharon A. Treaster -- Tolerance of azalea, cotoneaster, and euonymus to Devrinol, Goal, and Goal Combinations / Elton M. Smith and Sharon A. Treaster -- Micropropagation of chimeral african violets / R. Daniel Lineberger and Mark Druckenbrod -- capital requirements of overwintering structures for nurseries in Ohio - 1984 / Reed D. Taylor, Daryl T. Gillette, and Elton M. Smith -- annual fixed costs of overwintering plants in nurseries differentiated by type of structure for Ohio - 1984 / Daryl T. Gillette, Reed D. Taylor, and Elton M. Smith -- Comparative costs of overwintering plants in nurseries differentiated by system for Ohio - 1984 / Reed D. Taylor, Daryl T. Gillette, and Elton M. Smit
Sub-milliarcsecond precision spectro-astrometry of Be stars
The origin of the disks around Be stars is still not known. Further progress
requires a proper parametrization of their structure, both spatially and
kinematically. This is challenging as the disks are very small. Here we assess
whether a novel method is capable of providing these data. We obtained spectro
astrometry around the Pa beta line of two bright Be stars, alpha Col and zeta
Tau, to search for disk signatures. The data, with a pixel to pixel precision
of the centroid position of 0.3..0.4 milliarcsecond is the most accurate such
data to date. Artefacts at the 0.85 mas level are present in the data, but
these are readily identified as they were non-repeatable in our redundant
datasets. This does illustrate the need of taking multiple data to avoid
spurious detections. The data are compared with simple model simulations of the
spectro astrometric signatures due to rotating disks around Be stars. The upper
limits we find for the disk radii correspond to disk sizes of a few dozen
stellar radii if they rotate Keplerian. This is very close to observationally
measured and theoretically expected disk sizes, and this paper therefore
demonstrates that spectro-astrometry, of which we present the first such
attempt, has the potential to resolve the disks around Be stars.Comment: 6 pages, A&A accepte
Orbital parameters, masses and distance to Beta Centauri determined with the Sydney University Stellar Interferometer and high resolution spectroscopy
The bright southern binary star beta Centauri (HR 5267) has been observed
with the Sydney University Stellar Interferometer (SUSI) and spectroscopically
with the ESO CAT and Swiss Euler telescopes at La Silla. The interferometric
observations have confirmed the binary nature of the primary component and have
enabled the determination of the orbital parameters of the system. At the
observing wavelength of 442 nm the two components of the binary system have a
magnitude difference of 0.15. The combination of interferometric and
spectroscopic data gives the following results: orbital period 357 days,
semi-major axis 25.30 mas, inclination 67.4 degrees, eccentricity 0.821,
distance 102.3 pc, primary and secondary masses M1 = M2 = 9.1 solar masses and
absolute visual magnitudes of the primary and secondary M1V = -3.85 and M2V =
-3.70. The high accuracy of the results offers a fruitful starting point for
future asteroseismic modelling of the pulsating binary components.Comment: 10 pages, 4 figures. Accepted for publication in MNRA
A Method for the Detection of Planetary Transits in Large Time-Series Datasets
We present a fast, efficient and easy to apply computational method for the
detection of planetary transits in large photometric datasets. The code has
been specifically produced to analyse an ensemble of 21,950 stars in the
globular cluster 47 Tucanae, the results of which are the subject of a separate
paper. Using cross correlation techniques and Monte Carlo tested detection
criteria, each time-series is compared with a large database of appropriate
transit models. The algorithm recovers transit signatures with high efficiency
while maintaining a low false detection probability, even in noisy data.
This is illustrated by describing its application to our 47 Tuc dataset, for
which the algorithm produced a weighted mean transit recoverabilty spanning 85%
to 25% for orbital periods of 1-16 days despite gaps in the time series caused
by weather and observing duty cycle. The code is easily adaptable and is
currently designed to accept time-series produced using Difference Imaging
Analysis.Comment: 28 pages, 12 figures. Accepted and 'in press' for ApJ. Higher
resolution versions for both this paper and astro-ph/0411233 are available at
http://www.mso.anu.edu.au/~dtf
Abundance and Occurrence of Common Bottlenose Dolphins (Tursiops truncatus) in Three Estuaries of the Northwestern Gulf of Mexico
Current abundance estimates for populations of common bottlenose dolphins (Tursiops truncatus, Montagu, 1821) in bays, sounds, and estuaries are lacking throughout most of the northwestern Gulf of Mexico, including areas of Texas and western Louisiana. To address this issue, we conducted 92 small-boat photographic identification surveys covering ~2000 km2 and comprising ~11,000 km of track-line in winter and summer seasons in West Bay, TX (2014 â 2015, n = 25), the Galveston Bay, TX system (2016, n = 50), Sabine Lake, TX (2017, n = 17), and adjacent coastal waters. Individual dolphin encounter histories were constrained by spatiotemporal parameters to approximately represent 1) a âBayâ estimate of individuals limited to the interior of each embayment, and 2) a âSelectiveâ estimate of the number of individuals in each survey area (including nearshore coastal waters), filtered for potential transient dolphins. Using the Selective dataset, estimated dolphins (95% CI) were (winter and summer, respectively) 38 (29 â 47) and 37 (33 â 40) for West Bay, 842 (694 â 990) and 1132 (846 â 1417) for Galveston Bay, and 122 (73 â 170) and 162 (114 â 210) for Sabine Lake. A range of 4-15% of marked individuals in each study area were identified as inter-bay matches. These results provide new insights on the potential spatial range of each population, update previous abundance estimates for West Bay and Galveston Bay, and contribute novel population information for Sabine Lake and adjacent coastal waters of the northwestern Gulf of Mexico
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