742 research outputs found
Understanding The Effects Of Stellar Multiplicity On The Derived Planet Radii From Transit Surveys: Implications for Kepler, K2, and TESS
We present a study on the effect of undetected stellar companions on the
derived planetary radii for the Kepler Objects of Interest (KOIs). The current
production of the KOI list assumes that the each KOI is a single star. Not
accounting for stellar multiplicity statistically biases the planets towards
smaller radii. The bias towards smaller radii depends on the properties of the
companion stars and whether the planets orbit the primary or the companion
stars. Defining a planetary radius correction factor , we find that if the
KOIs are assumed to be single, then, {\it on average}, the planetary radii may
be underestimated by a factor of . If typical
radial velocity and high resolution imaging observations are performed and no
companions are detected, this factor reduces to . The correction factor is dependent upon the primary
star properties and ranges from for A and F
stars to for K and M stars. For missions like
K2 and TESS where the stars may be closer than the stars in the Kepler target
sample, observational vetting (primary imaging) reduces the radius correction
factor to . Finally, we show that if the
stellar multiplicity rates are not accounted for correctly, occurrence rate
calculations for Earth-sized planets may overestimate the frequency of small
planets by as much as \%.Comment: 10 pages, 6 Figures, Accepted for publication in The Astrophysical
Journal (Fix typo in Equation 6 of original astroph submission; correction
also submitted to Journal
Speckle interferometry at SOAR in 2019
The results of speckle interferometric observations at the 4.1 m Southern
Astrophysical Research Telescope (SOAR) in 2019 are given, totaling 2555
measurements of 1972 resolved pairs with separations from 15 mas (median 0.21")
and magnitude difference up to 6 mag, and non-resolutions of 684 targets. We
resolved for the first time 90 new pairs or subsystems in known binaries. This
work continues our long-term speckle program. Its main goal is to monitor
orbital motion of close binaries, including members of high-order hierarchies
and Hipparcos pairs in the solar neighborhood. We give a list of 127 orbits
computed using our latest measurements. Their quality varies from excellent (25
orbits of grades 1 and 2) to provisional (47 orbits of grades 4 and 5).Comment: Accepted by The Astronomical Journal. 10 pages, 5 Figures.
Measurements and non-resolutions, published electronically, are available
from the first author. arXiv admin note: substantial text overlap with
arXiv:1905.1043
Speckle interferometry at SOAR in 2015
The results of speckle interferometric observations at the SOAR telescope in
2015 are given, totalling 1303 measurements of 924 resolved binary and multiple
stars and non-resolutions of 260 targets. The separations range from 12 mas to
3.37" (median 0.17"); the maximum measured magnitude difference is 6.7 mag. We
resolved 27 pairs for the first time, including 10 as inner or outer subsystems
in previously known binaries, e.g. the 50-mas pair in Epsilon Cha. Newly
resolved pairs are commented upon. We discuss three apparently non-hierarchical
systems discovered in this series, arguing that their unusual configuration
results from projection. The resolved quadruple system HIP 71510 is studied as
well.Comment: 10 pages, 8 figures. Accepted for publication in AJ. The online
tables are not included, available from Tokovinin on request. arXiv admin
note: text overlap with arXiv:1506.0571
Unusual explosive growth of a squamous cell carcinoma of the scalp after electrical burn injury and subsequent coverage by sequential free flap vascular connection – a case report
BACKGROUND: Squamous cell carcinomos may arise from chronic ulcerating wounds in scars, most commonly postburn scars. Tumour growth usually takes place over months to years. Localization on the scalp is a relatively rare condition. CASE PRESENTATION: This report presents the case of a 63-year-old man with chronic ulceration of a postburn scar of the scalp due to an electrical burn 58 years ago. Sudden tumour growth started within weeks and on presentation already had extended through the skull into frontal cortex. After radical tumour resection, defect was covered with a free radial forearm flap. Local recurrence occurred 6 weeks later. Subsequent wide excision including discard of the flap and preservation of the radial vessels was followed by transfer of a free latissimus dorsi muscle flap, using the radial vessels of the first flap as recipient vessels. The patient received radiotherapy post-operatively. There were no problems with flap survivals or wound healing. Due to rapidly growing recurrence the patient died 2 months later. CONCLUSION: Explosive SCC tumour growth might occur in post-burn scars after more than 50 years. As a treatment option the use of sequential free flap connections might serve in repeated extensive tumour resections, especially in the scalp region, where suitable donor vessels are often located in distance to the defect
On the Occurrence Rate of Hot Jupiters in Different Stellar Environments
Many Hot Jupiters (HJs) are detected by the Doppler and the transit
techniques. From surveys using these two techniques, however, the measured HJ
occurrence rates differ by a factor of two or more. Using the California Planet
Survey sample and the Kepler sample, we investigate the causes for the
difference of HJ occurrence rate. First, we find that of HJs
are misidentified in the Kepler mission because of photometric dilution and
subgiant contamination. Second, we explore the differences between the Doppler
sample and the Kepler sample that can account for the different HJ occurrence
rate. Third, we discuss how to measure the fundamental HJ occurrence rates by
synthesizing the results from the Doppler and Kepler surveys. The fundamental
HJ occurrence rates are a measure of HJ occurrence rate as a function of
stellar multiplicity and evolutionary stage, e.g., the HJ occurrence rate for
single and multiple stars or for main sequence and subgiant stars. While we
find qualitative evidence that HJs occur less frequently in subgiants and
multiple stellar systems, we conclude that our current knowledge of stellar
properties and stellar multiplicity rate is too limited for us to reach any
quantitative result for the fundamental HJ occurrence rates. This concern
extends to , the occurrence rate of Earth-like planets.Comment: 10 pages, 3 figures, 1 table, submitted to Ap
Masses, Luminosities, and Orbital Coplanarities of the mu Orionis Quadruple Star System from PHASES Differential Astrometry
mu Orionis was identified by spectroscopic studies as a quadruple star
system. Seventeen high precision differential astrometry measurements of mu Ori
have been collected by the Palomar High-precision Astrometric Search for
Exoplanet Systems (PHASES). These show both the motion of the long period
binary orbit and short period perturbations superimposed on that caused by each
of the components in the long period system being themselves binaries. The new
measurements enable the orientations of the long period binary and short period
subsystems to be determined. Recent theoretical work predicts the distribution
of relative inclinations between inner and outer orbits of hierarchical systems
to peak near 40 and 140 degrees. The degree of coplanarity of this complex
system is determined, and the angle between the planes of the A-B and Aa-Ab
orbits is found to be 136.7 +/- 8.3 degrees, near the predicted distribution
peak at 140 degrees; this result is discussed in the context of the handful of
systems with established mutual inclinations. The system distance and masses
for each component are obtained from a combined fit of the PHASES astrometry
and archival radial velocity observations. The component masses have relative
precisions of 5% (component Aa), 15% (Ab), and 1.4% (each of Ba and Bb). The
median size of the minor axes of the uncertainty ellipses for the new
measurements is 20 micro-arcseconds. Updated orbits for delta Equulei, kappa
Pegasi, and V819 Herculis are also presented.Comment: 12 Pages, Accepted for publication in A
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