12,900 research outputs found
Detecting Unresolved Binaries in TESS Data with Speckle Imaging
The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year
wide-field survey searching for transiting exoplanets around nearby bright
stars that will be ideal for follow-up characterization. To facilitate studies
of planet compositions and atmospheric properties, accurate and precise
planetary radii need to be derived from the transit light curves. Since 40 -
50% of exoplanet host stars are in multiple star systems, however, the observed
transit depth may be diluted by the flux of a companion star, causing the
radius of the planet to be underestimated. High angular resolution imaging can
detect companion stars that are not resolved in the TESS Input Catalog, or by
seeing-limited photometry, to validate exoplanet candidates and derive accurate
planetary radii. We examine the population of stellar companions that will be
detectable around TESS planet candidate host stars, and those that will remain
undetected, by applying the detection limits of speckle imaging to the
simulated host star populations of Sullivan et al. (2015) and Barclay et al.
(2018). By detecting companions with contrasts of delta m < 7 - 9 and
separations of ~0.02 - 1.2'', speckle imaging can detect companion stars as
faint as early M stars around A - F stars and stars as faint as mid-M around G
- M stars, as well as up to 99% of the expected binary star distribution for
systems located within a few hundred parsecs.Comment: Accepted for publication in The Astronomical Journal; 16 pages, 8
figures, 2 table
A Search for Variable Stars and Planetary Occultations in NGC2301 I: Techniques
We observed the young open cluster NGC 2301 for 14 nights in Feb. 2004 using
the orthogonal transfer CCD camera (OPTIC). We used PSF shaping techniques
("square stars") during the observations allowing a larger dynamic range (4.5
magnitudes) of high photometric precision results (2 mmag) to be obtained.
These results are better than similar observing campaigns using standard CCD
imagers. This paper discusses our observational techniques and presents initial
results for the variability statistics found in NGC 2301. Details of the
variability statistics as functions of color, variability type, stellar type,
and cluster location will appear in paper II
Nuclear magnetic octupole moment and the hyperfine structure of the states of the Ba ion
The hyperfine structure of the long-lived and levels of
Ba ion is analyzed. A procedure for extracting relatively unexplored
nuclear magnetic moments is presented. The relevant electronic matrix
elements are computed in the framework of the ab initio relativistic many-body
perturbation theory. Both the first- and the second-order (in the hyperfine
interaction) corrections to the energy levels are analyzed. It is shown that a
simultaneous measurement of the hyperfine structure of the entire
fine-structure manifold allows one to extract without contamination
from the second-order corrections. Measurements to the required accuracy should
be possible with a single trapped barium ion using sensitive techniques already
demonstrated in Ba experiments.Comment: Phys Rev A in pres
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
Discovery of Non-radial pulsations in PQ Andromedae
We have detected pulsations in time-series photometry of the WZ Sge dwarf
nova PQ And. The strongest peak in the power spectrum occurs at a period of
10.5 minutes. Similar periods have been observed in other WZ Sge systems and
are attributed to ZZ Ceti type non-radial pulsations. There is no indication in
the photometry of an approximately 1.7 hour orbital period as reported in
previous spectroscopic observations.Comment: 7 pages, 5 figure
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