56 research outputs found
TEE, a simple estimator for the precision of eclipse and transit minimum times
Context: Transit or eclipse timing variations have proven to be a valuable
tool in exoplanet research. However, no simple way to estimate the potential
precision of such timing measures has been presented yet, nor are guidelines
available regarding the relation between timing errors and sampling rate.
Aims: A `timing error estimator' (TEE) equation is presented that requires
only basic transit parameters as input. With the TEE, it is straightforward to
estimate timing precisions both for actual data as well as for future
instruments, such as the TESS and PLATO space missions.
Methods: A derivation of the timing error based on a trapezoidal transit
shape is given. We also verify the TEE on realistically modeled transits using
Monte Carlo simulations and determine its validity range, exploring in
particular the interplay between ingress/egress times and sampling rates.
Results: The simulations show that the TEE gives timing errors very close to
the correct value, as long as the temporal sampling is faster than transit
ingress/egress durations and transits with very low S/N are avoided.
Conclusions: The TEE is a useful tool to estimate eclipse or transit timing
errors in actual and future data-sets. In combination with an equation to
estimate period errors (Deeg 2015), predictions for the ephemeris precision of
long-coverage observations are possible as well. The tests for the TEE's
validity-range led also to implications for instrumental design: Temporal
sampling has to be faster than transit in- or egress durations, or a loss in
timing-precision will occur. An application to the TESS mission shows that
transits close to its detection limit will have timing uncertainties that
exceed 1 hour within a few months after their acquisition. Prompt follow-up
observations will be needed to avoid a `loosing' of their ephemeris.Comment: Accepted by A&A. Version 2 with updated timing uncertainties of TESS
mission due to correction of a figure in Sullivan et al. 201
Using Stellar Densities to Evaluate Transiting Exoplanetary Candidates
One of the persistent complications in searches for transiting exoplanets is
the low percentage of the detected candidates that ultimately prove to be
planets, which significantly increases the load on the telescopes used for the
follow-up observations to confirm or reject candidates. Several attempts have
been made at creating techniques that can pare down candidate lists without the
need of additional observations. Some of these techniques involve a detailed
analysis of light curve characteristics; others estimate the stellar density or
some proxy thereof. In this paper, we extend upon this second approach,
exploring the use of independently-calculated stellar densities to identify the
most promising transiting exoplanet candidates. We use a set of CoRoT
candidates and the set of known transiting exoplanets to examine the potential
of this approach. In particular, we note the possibilities inherent in the
high-precision photometry from space missions, which can detect stellar
asteroseismic pulsations from which accurate stellar densities can be extracted
without additional observations.Comment: 33 pages, 9 figure
stm: An R Package for Structural Topic Models
This paper demonstrates how to use the R package stm for structural topic modeling. The structural topic model allows researchers to flexibly estimate a topic model that includes document-level metadata. Estimation is accomplished through a fast variational approximation. The stm package provides many useful features, including rich ways to explore topics, estimate uncertainty, and visualize quantities of interest
Transits against Fainter Stars: The Power of Image Deconvolution
Compared to bright star searches, surveys for transiting planets against fainter (V = 12-18) stars have the advantage of much higher sky densities of dwarf star primaries, which afford easier detection of small transiting bodies. Furthermore, deep searches are capable of probing a wider range of stellar environments. On the other hand, for a given spatial resolution and transit depth, deep searches are more prone to confusion from blended eclipsing binaries. We present a powerful mitigation strategy for the blending problem that includes the use of image deconvolution and high-resolution imaging. The techniques are illustrated with Lupus-TR-3 and very recent IR imaging with PANIC on Magellan. The results are likely to have implications for the CoRoT and KEPLER missions designed to detect transiting planets of terrestrial siz
Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?
We present a strong case for a transiting Hot Jupiter planet identified
during a single-field transit survey towards the Lupus Galactic plane. The
object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d.
Spectroscopy and stellar colors indicate a host star with effective temperature
5000 +/- 150K, with a stellar mass and radius of 0.87 +/- 0.04M_sun and 0.82
+/- 0.05R_sun, respectively. Limb-darkened transit fitting yields a companion
radius of 0.89 +/- 0.07R_J and an orbital inclination of 88.3 +1.3/-0.8 deg.
Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 +/-
25m/s sinusoidal variation in phase with the transit ephemeris. The resulting
mass is 0.81 +/- 0.18M_J and density 1.4 +/- 0.4g/cm^3. Y-band PANIC image
deconvolution reveal a V>=21 red neighbor 0.4'' away which, although highly
unlikely, we cannot conclusively rule out as a blended binary with current
data. However, blend simulations show that only the most unusual binary system
can reproduce our observations. This object is very likely a planet, detected
from a highly efficient observational strategy. Lupus-TR-3b constitutes the
faintest ground-based detection to date, and one of the lowest mass Hot
Jupiters known.Comment: 4 pages, 4 figures, accepted for publication in ApJ
The impact of stellar jitter on the confirmation of transiting exoplanet candidates around Solar-like stars
A Photometric Diagnostic to Aid in the Identification of Transiting Extra-Solar Planets
One of the obstacles in the search for exoplanets via transits is the large
number of candidates that must be followed up, few of which ultimately prove to
be exoplanets. Any method that could make this process more efficient by
somehow identifying the best candidates and eliminating the worst would
therefore be very useful. Seager and Mallen-Ornelas (2003) demonstrated that it
was possible to discern between blends and exoplanets using only the
photometric characteristics of the transits. However, these techniques are
critically dependent on the shape of the transit, characterization of which
requires very high precision photometry of a sort that is atypical for
candidates identified from transit searches. We present a method relying only
on transit duration, depth, and period, which require much less precise
photometry to determine accurately. The numerical tool we derive, the exoplanet
diagnostic \eta, is intended to identify the subset of candidates from a
transit search that is most likely to contain exoplanets, and thus most worthy
of subsequent follow-up studies. The effectiveness of the diagnostic is
demonstrated with its success in separating modeled exoplanetary transits and
interlopers, and by applying it to actual OGLE transit candidates.Comment: accepted to Ap
- …