127 research outputs found

### Most Sub-Arcsecond Companions of Kepler Exoplanet Candidate Host Stars are Gravitationally Bound

Using the known detection limits for high-resolution imaging observations and
the statistical properties of true binary and line-of-sight companions, we
estimate the binary fraction of {\it Kepler} exoplanet host stars. Our speckle
imaging programs at the WIYN 3.5-m and Gemini North 8.1-m telescopes have
observed over 600 {\it Kepler} objects of interest (KOIs) and detected 49
stellar companions within $\sim$1 arcsecond. Assuming binary stars follow a
log-normal period distribution for an effective temperature range of 3,000 to
10,000 K, then the model predicts that the vast majority of detected
sub-arcsecond companions are long period ($P>50$ years), gravitationally bound
companions. In comparing the model predictions to the number of real detections
in both observational programs, we conclude that the overall binary fraction of
host stars is similar to the 40-50\% rate observed for field stars

### 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 $X_R$, 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 $\langle X_R \rangle \approx 1.5$. If typical
radial velocity and high resolution imaging observations are performed and no
companions are detected, this factor reduces to $\langle X_R \rangle \approx
1.2$. The correction factor $\langle X_R \rangle$ is dependent upon the primary
star properties and ranges from $\langle X_R \rangle \approx 1.6$ for A and F
stars to $\langle X_R \rangle \approx 1.2$ 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 $\langle X_R \rangle \approx 1.1$. 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 $15-20$\%.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

### CCD Speckle Observations of Binary Stars from the Southern Hemisphere. II. Measures from the Lowell-Tololo Telescope During 1999

Speckle observations of 145 double stars and suspected double stars are presented and discussed. On the basis of multiple observations, a total of 280 position angle and separation measures are determined, as well as 23 high-quality nondetections. All observations were taken with the (unintensified) Rochester Institute of Technology fast-readout CCD camera mounted on the Lowell-Tololo 61 cm telescope at the Cerro Tololo Inter-American Observatory during 1999 October. We find that the measures, when judged as a whole against ephemeris positions of binaries with very well-known orbits, have root mean square deviations of (1.8+/- 0.3) degrees in position angle and (13+/-2) mas in separation. Eleven double stars discovered by Hipparcos were also successfully observed, and the change in position angle and/or separation since the Hipparcos observations was substantial in three cases (Refer to PDF file for exact formulas)

### CCD Speckle Observations of Binary Stars from the Southern Hemisphere. III. Differential Photometry

Two hundred seventy-two magnitude difference measures of 135 double star systems are presented. The results are derived from speckle observations using the Bessel V and R passbands and a fast readout CCD camera. Observations were taken at two 60 cm telescopes, namely the Helen Sawyer Hogg Telescope, formerly at Las Campanas, Chile, and the Lowell-Tololo Telescope at the Cerro Tololo Inter- American Observatory, Chile. The data analysis method is presented and, in comparing the results to those of Hipparcos as well as to recent results using adaptive optics, we find very good agreement. Overall, the measurement precision appears to be dependent on seeing and other factors but is generally in the range of 0.10-0.15 mag for single observations under favorable observing conditions. In four cases, multiple observations in both V and R allowed for the derivation of component V-R colors with uncertainties of 0.11 mag or less. Spectral types are assigned and preliminary effective temperatures are estimated in these cases

### 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

### CCD Speckle Observations of Binary Stars from the Southern Hemisphere

We present 119 position angle and separation measures of 86 double stars observed by way of speckle interferometry with the University of Toronto Southern Observatory 60 cm telescope at Las Campanas, Chile. Speckle interferograms are recorded with a bare (unintensified) front-illuminated CCD in a fast subarray-readout mode. Position angles and separations are determined by a weighted least-squares fitting algorithm applied to the binary power spectra, and the 180-degree ambiguity in the position angle inherent in this approach is resolved by bispectral analysis. In this configuration the 60 cm telescope exhibits near-diffraction-limited performance. Initial results indicate that our separation measures have a root-mean-square (rms) deviation of 6.6 +/- 1.0 milliarcsecond (mas) and our position angles have an rms deviation of 1.73 +/- 0.26 degrees when judged against the ephemeris positions of a small sample of binaries with previously well-determined orbits (Refer to PDF file for exact formulas)

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