39 research outputs found
Searching for exoplanets using the transit method.
Master of Science in Applied Mathematics, University of KwaZulu-Natal, Westville, 2017.We present a study designed to detect transiting exoplanets in Kepler
light curve data. We developed an exoplanet detection algorithm based on
modelling transit light curves and fitting the models to light curve data using a chi-square minimization approach in order to identify exoplanets and
estimate their properties such as orbital period, planetary radius and semi-
major axis (orbital radius) from the best t parameters of the model. We
applied our algorithm to a blind sample of Kepler mission data consisting of
approximately 4500 stars. The selection criteria for the blind sample were
Tstar < 6000 K, Rstar < 1R and 13:5 < Kepler Magnitude < 14. The blind
sample contained 70 known exoplanets. Our algorithm detected 50 of the
70 known exoplanets in the blind sample. We found that our algorithm was
effective in detecting exoplanets with planet-star radius ratios greater than
0.01 (k > 0:01) and/or exoplanets with radii greater than 2:5R , as well as
short-period exoplanets (p < 90 days). Twenty four of the exoplanets in the
blind sample were from multi-planetary systems and, in these cases, we found
our algorithm first fits for the largest transit depth and/or (subsequently) for
the shortest orbital period. We did not find any potentially habitable exo-
planets in our blind sample. This is not unexpected as, of more than 3400
exoplanets found to date after surveying upward of 500 000 stars, only 52
exoplanets are considered potentially habitable to varying degrees i.e. 1.5%
of all exoplanets found to date are considered potentially habitable
Low Albedo Surfaces of Lava Worlds
Hot super Earths are exoplanets with short orbital periods ( 10 days),
heated by their host stars to temperatures high enough for their rocky surfaces
to become molten. A few hot super Earths exhibit high geometric albedos (
0.4) in the Kepler band (420-900 nm). We are motivated to determine whether
reflection from molten lava and quenched glasses (a product of rapidly cooled
lava) on the surfaces of hot super Earths contributes to the observationally
inferred high geometric albedos. We experimentally measure reflection from
rough and smooth textured quenched glasses of both basalt and feldspar melts.
For lava reflectance values, we use specular reflectance values of molten
silicates from non-crystalline solids literature. Integrating the empirical
glass reflectance function and non-crystalline solids reflectance values over
the dayside surface of the exoplanet at secondary eclipse yields an upper limit
for the albedo of a lava-quenched glass planet surface of 0.1. We
conclude that lava planets with solid (quenched glass) or liquid (lava)
surfaces have low albedos. The high albedos of some hot super Earths are most
likely explained by atmospheres with reflective clouds (or, for a narrow range
of parameter space, possibly Ca/Al oxide melt surfaces). Lava planet candidates
in TESS data can be identified for follow-up observations and future
characterization.Comment: 18 pages, 14 figures, 4 tables, published in Ap
Exploring the atmospheric dynamics of the extreme ultra-hot Jupiter KELT-9b using TESS photometry
We carry out a phase-curve analysis of the KELT-9 system using photometric
observations from NASA's Transiting Exoplanet Survey Satellite (TESS). The
measured secondary eclipse depth and peak-to-peak atmospheric brightness
modulation are ppm and ppm, respectively. The
planet's brightness variation reaches maximum minutes before the
midpoint of the secondary eclipse, indicating a
eastward shift in the dayside hot
spot from the substellar point. We also detect stellar pulsations on KELT-9
with a period of hours. The dayside emission of KELT-9b in
the TESS bandpass is consistent with a blackbody brightness temperature of
K. The corresponding nightside brightness temperature is
K, comparable to the dayside temperatures of the hottest known
exoplanets. In addition, we detect a significant phase-curve signal at the
first harmonic of the orbital frequency and a marginal signal at the second
harmonic. While the amplitude of the first harmonic component is consistent
with the predicted ellipsoidal distortion modulation assuming equilibrium
tides, the phase of this photometric variation is shifted relative to the
expectation. Placing KELT-9b in the context of other exoplanets with
phase-curve observations, we find that the elevated nightside temperature and
relatively low day-night temperature contrast agree with the predictions of
atmospheric models that include H dissociation and recombination. The
nightside temperature of KELT-9b implies an atmospheric composition containing
about 50% molecular and 50% atomic hydrogen at 0.1 bar, a nightside emission
spectrum that deviates significantly from a blackbody, and a 0.5-2.0 m
transmission spectrum that is featureless at low resolution.Comment: Published in AJ, updated with proof corrections. 17 pages, 8 figure
Exploring the Atmospheric Dynamics of the Extreme Ultrahot Jupiter KELT-9b Using TESS Photometry
We carry out a phase-curve analysis of the KELT-9 system using photometric observations from NASA's Transiting Exoplanet Survey Satellite (TESS). The measured secondary eclipse depth and peak-to-peak atmospheric brightness modulation are 650⁺¹⁴₋₁₅ and 566 ± 16 ppm, respectively. The planet's brightness variation reaches maximum 31 ± 5 minutes before the midpoint of the secondary eclipse, indicating a 5.°2 ± 0.°9 eastward shift in the dayside hot spot from the substellar point. We also detect stellar pulsations on KELT-9 with a period of 7.58695 ± 0.00091 hr. The dayside emission of KELT-9b in the TESS bandpass is consistent with a blackbody brightness temperature of 4600 ± 100 K. The corresponding nightside brightness temperature is 3040 ± 100 K, comparable to the dayside temperatures of the hottest known exoplanets. In addition, we detect a significant phase-curve signal at the first harmonic of the orbital frequency and a marginal signal at the second harmonic. While the amplitude of the first harmonic component is consistent with the predicted ellipsoidal distortion modulation assuming equilibrium tides, the phase of this photometric variation is shifted relative to the expectation. Placing KELT-9b in the context of other exoplanets with phase-curve observations, we find that the elevated nightside temperature and relatively low day–night temperature contrast agree with the predictions of atmospheric models that include H₂ dissociation and recombination. The nightside temperature of KELT-9b implies an atmospheric composition containing about 50% molecular and 50% atomic hydrogen at 0.1 bar, a nightside emission spectrum that deviates significantly from a blackbody, and a 0.5–2.0 μm transmission spectrum that is featureless at low resolution
TESS Discovery of Twin Planets near 2:1 Resonance around Early M-Dwarf TOI 4342
With data from the Transiting Exoplanet Survey Satellite (TESS), we showcase
improvements to the MIT Quick-Look Pipeline (QLP) through the discovery and
validation of a multi-planet system around M-dwarf TOI 4342 (,
, , K,
pc). With updates to QLP, including a new multi-planet search, as well as
faster cadence data from TESS' First Extended Mission, we discovered two
sub-Neptunes ( and ; = 5.538 days and = 10.689 days)
and validated them with ground-based photometry, spectra, and speckle imaging.
Both planets notably have high transmission spectroscopy metrics (TSMs) of 36
and 32, making TOI 4342 one of the best systems for comparative atmospheric
studies. This system demonstrates how improvements to QLP, along with faster
cadence Full-Frame Images (FFIs), can lead to the discovery of new multi-planet
systems.Comment: accepted for publication in A
TESS discovery of a super-Earth and two sub-Neptunes orbiting the bright, nearby, Sun-like star HD 22946
We report the Transiting Exoplanet Survey Satellite (TESS) discovery of a
three-planet system around the bright Sun-like star HD~22946(V=8.3 mag),also
known as TIC~100990000, located 63 parsecs away.The system was observed by TESS
in Sectors 3, 4, 30 and 31 and two planet candidates, labelled TESS Objects of
Interest (TOIs) 411.01 (planet ) and 411.02 (planet ), were identified on
orbits of 9.57 and 4.04 days, respectively. In this work, we validate the two
planets and recover an additional single transit-like signal in the light
curve, which suggests the presence of a third transiting planet with a longer
period of about 46 days.We assess the veracity of the TESS transit signals and
use follow-up imaging and time series photometry to rule out false positive
scenarios, including unresolved binary systems, nearby eclipsing binaries or
background/foreground stars contaminating the light curves. Parallax
measurements from Gaia EDR3, together with broad-band photometry and
spectroscopic follow-up by TFOP allowed us to constrain the stellar parameters
of TOI-411, including its radius of. Adopting this value,
we determined the radii for the three exoplanet candidates and found that
planet is a super-Earth, with a radius of , while
planet and are sub-Neptunian planets, with radii
of and respectively. By using
dynamical simulations, we assessed the stability of the system and evaluated
the possibility of the presence of other undetected, non-transiting planets by
investigating its dynamical packing. We find that the system is dynamically
stable and potentially unpacked, with enough space to host at least one more
planet between and .(Abridged)Comment: 21 pages, 12 figures. Accepted for publication on A&
TOI-4010: A System of Three Large Short-Period Planets With a Massive Long-Period Companion
We report the confirmation of three exoplanets transiting TOI-4010
(TIC-352682207), a metal-rich K dwarf observed by TESS in Sectors 24, 25, 52,
and 58. We confirm these planets with HARPS-N radial velocity observations and
measure their masses with 8 - 12% precision. TOI-4010 b is a sub-Neptune ( days, , ) in the hot Neptune desert, and is one of the
few such planets with known companions. Meanwhile, TOI-4010 c ( days,
, ) and TOI-4010 d ( days, , )
are similarly-sized sub-Saturns on short-period orbits. Radial velocity
observations also reveal a super-Jupiter-mass companion called TOI-4010 e in a
long-period, eccentric orbit ( days and based on
available observations). TOI-4010 is one of the few systems with multiple
short-period sub-Saturns to be discovered so far.Comment: 26 pages, 16 figures, published in A
An Eccentric Massive Jupiter Orbiting a Subgiant on a 9.5-day Period Discovered in the <i>Transiting Exoplanet Survey Satellite</i> Full Frame Images
We report the discovery of TOI-172 b from the Transiting Exoplanet Survey Satellite (TESS) mission, a massive hot Jupiter transiting a slightly evolved G star with a 9.48-day orbital period. This is the first planet to be confirmed from analysis of only the TESS full frame images, because the host star was not chosen as a two-minute cadence target. From a global analysis of the TESS photometry and follow-up observations carried out by the TESS Follow-up Observing Program Working Group, TOI-172 (TIC 29857954) is a slightly evolved star with an effective temperature of T eff = 5645 ± 50 K, a mass of M ⋆ = {1.128}-0.061+0.065 M ⊙, radius of R ⋆ = {1.777}-0.044+0.047 R ⊙, a surface gravity of log g ⋆ = {3.993}-0.028+0.027, and an age of {7.4}-1.5+1.6 {Gyr}. Its planetary companion (TOI-172 b) has a radius of R P = {0.965}-0.029+0.032 R J, a mass of M P = {5.42}-0.20+0.22 M J, and is on an eccentric orbit (e={0.3806}-0.0090+0.0093). TOI-172 b is one of the few known massive giant planets on a highly eccentric short-period orbit. Future study of the atmosphere of this planet and its system architecture offer opportunities to understand the formation and evolution of similar systems
The TESS Grand Unified Hot Jupiter Survey. I. Ten TESS Planets
We report the discovery of ten short-period giant planets (TOI-2193A b,
TOI-2207 b, TOI-2236 b, TOI-2421 b, TOI-2567 b, TOI-2570 b, TOI-3331 b,
TOI-3540A b, TOI-3693 b, TOI-4137 b). All of the planets were identified as
planet candidates based on periodic flux dips observed by NASA's Transiting
Exoplanet Survey Satellite (TESS). The signals were confirmed to be from
transiting planets using ground-based time-series photometry, high angular
resolution imaging, and high-resolution spectroscopy coordinated with the TESS
Follow-up Observing Program. The ten newly discovered planets orbit relatively
bright F and G stars (,~ between 4800 and 6200 K).
The planets' orbital periods range from 2 to 10~days, and their masses range
from 0.2 to 2.2 Jupiter masses. TOI-2421 b is notable for being a Saturn-mass
planet and TOI-2567 b for being a ``sub-Saturn'', with masses of and Jupiter masses, respectively. In most cases, we
have little information about the orbital eccentricities. Two exceptions are
TOI-2207 b, which has an 8-day period and a detectably eccentric orbit (), and TOI-3693 b, a 9-day planet for which we can set an upper
limit of . The ten planets described here are the first new planets
resulting from an effort to use TESS data to unify and expand on the work of
previous ground-based transit surveys in order to create a large and
statistically useful sample of hot Jupiters.Comment: 44 pages, 15 tables, 21 figures; revised version submitted to A