565 research outputs found
A Search for Lost Planets in the Kepler Multi-planet Systems and the Discovery of the Long-period, Neptune-sized Exoplanet Kepler-150 f
The vast majority of the 4700 confirmed planets and planet candidates
discovered by the Kepler mission were first found by the Kepler pipeline. In
the pipeline, after a transit signal is found, all data points associated with
those transits are removed, creating a "Swiss cheese"-like light curve full of
holes, which is then used for subsequent transit searches. These holes could
render an additional planet undetectable (or "lost"). We examine a sample of
114 stars with confirmed planets to evaluate the effect of this "Swiss
cheesing". A simulation determines that the probability that a transiting
planet is lost due to the transit masking is low, but non-negligible, reaching
a plateau at lost in the period range of days. We then
model all planet transits and subtract out the transit signals for each star,
restoring the in-transit data points, and use the Kepler pipeline to search the
transit-subtracted (i.e., transit-cleaned) light curves. However, the pipeline
did not discover any credible new transit signals. This demonstrates the
validity and robustness of the Kepler pipeline's choice to use transit masking
over transit subtraction. However, a follow-up visual search through all the
transit-subtracted data, which allows for easier visual identification of new
transits, revealed the existence of a new, Neptune-sized exoplanet (Kepler-150
f) and a potential single transit of a likely false positive (Kepler-208).
Kepler-150 f ( days, R)
is confirmed with confidence using a combination of the planet
multiplicity argument, a false positive probability analysis, and a transit
duration analysis.Comment: 11 pages, 5 figures, 2 tables. Accepted into A
Chromospheric Activity and Jitter Measurements for 2630 Stars on the California Planet Search
We present time series measurements of chromospheric activity for more than
2600 main sequence and subgiant stars on the California Planet Search (CPS)
program with spectral types ranging from about F5V to M4V for main sequence
stars and from G0IV to about K5IV for subgiants. The large data set of more
than 44,000 spectra allows us to identify an empirical baseline floor for
chromospheric activity as a function of color and height above the main
sequence. We define as an excess in emission in the Ca II H\&K lines
above the baseline activity floor and define radial velocity jitter as a
function of and \bv\ for main sequence and subgiant stars. Although
the jitter for any individual star can always exceed the baseline level, we
find that K dwarfs have the lowest level of jitter. The lack of correlation
between observed jitter and chromospheric activity in K dwarfs suggests that
the observed jitter is dominated by instrumental or analysis errors and not
astrophysical noise sources. Thus, given the long-term precision for the CPS
program, radial velocities are not correlated with astrophysical noise for
chromospherically quiet K dwarf stars, making these stars particularly
well-suited for the highest precision Doppler surveys. Chromospherically quiet
F and G dwarfs and subgiants exhibit higher baseline levels of astrophysical
jitter than K dwarfs. Despite the fact that the \rms\ in Doppler velocities is
correlated with the mean chromospheric activity, it is rare to see one-to-one
correlations between the individual time series activity and Doppler
measurements, diminishing the prospects for correcting activity-induced
velocity variations.Comment: 17 figures, two large tex tables, accepted Ap
TWO SUNS IN THE SKY: STELLAR MULTIPLICITY INFLUENCE ON PLANET FORMATION
We found that a planet is less likely to exist around a binary star, and thus Tatooine may be just a dream
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