38 research outputs found
SImMER: A Pipeline for Reducing and Analyzing Images of Stars
We present the first public version of SImMER, an open-source Python
reduction pipeline for astronomical images of point sources. Current
capabilities include dark-subtraction, flat-fielding, sky-subtraction, image
registration, FWHM measurement, contrast curve calculation, and table and plot
generation. SImMER supports observations taken with the ShARCS camera on the
Shane 3-m telescope and the PHARO camera on the Hale 5.1-m telescope. The
modular nature of SImMER allows users to extend the pipeline to accommodate
additional instruments with relative ease. One of the core functions of the
pipeline is its image registration module, which is flexible enough to reduce
saturated images and images of similar-brightness, resolved stellar binaries.
Furthermore, SImMER can compute contrast curves for reduced images and produce
publication-ready plots. The code is developed online at
\url{https://github.com/arjunsavel/SImMER} and is both pip- and
conda-installable. We develop tutorials and documentation alongside the code
and host them online. With SImMER, we aim to provide a community resource for
accurate and reliable data reduction and analysis.Comment: 12 pages, 5 figures. Accepted to PAS
Magnetic Drag and 3-D Effects in Theoretical High-Resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b
Ultrahot Jupiters are ideal candidates to explore with high-resolution
emission spectra. Detailed theoretical studies are necessary to investigate the
range of spectra we can expect to see from these objects throughout their
orbit, because of the extreme temperature and chemical longitudinal gradients
that exist across day and nightside regions. Using previously published 3D GCM
models of WASP-76b with different treatments of magnetic drag, we post-process
the 3D atmospheres to generate high-resolution emission spectra for two
wavelength ranges and throughout the planet's orbit. We find that the
high-resolution emission spectra vary strongly as a function of phase, at times
showing emission features, absorption features, or both, which are a direct
result of the 3D structure of the planet. At phases exhibiting both emission
and absorption features, the Doppler shift differs in direction between the two
spectral features, making them differentiable instead of canceling each other
out. Through the use of cross-correlation, we find different patterns in net
Doppler shift for models with different treatments of drag: the nightside
spectra show opposite signs in their Doppler shift, while the dayside phases
have a reversal in the trend of net shift with phase. Finally, we caution
researchers from using a single spectral template throughout the planet's
orbit; this can bias the corresponding net Doppler shift returned, as it can
pick up on a bright region on the edge of the planet disk that is highly red-
or blue-shifted.Comment: 15 pages, 9 figures (including one animated figure), Accepted to AJ;
Link to animated figure: https://www.youtube.com/watch?v=KnghwJdZxH
A Direct Comparison between the use of Double Gray and Multiwavelength Radiative Transfer in a General Circulation Model with and without Radiatively Active Clouds
Inhomogeneous cloud formation and wavelength-dependent phenomena are expected
to shape hot Jupiter atmospheres. We present a General Circulation Model (GCM)
with multiwavelength "picket fence" radiative transfer and radiatively active,
temperature dependent clouds, and compare the results to a double gray routine.
The double gray method inherently fails to model polychromatic effects in hot
Jupiter atmospheres, while picket fence captures these non-gray aspects and
performs well compared to fully wavelength-dependent methods. We compare both
methods with radiatively active clouds and cloud-free models, assessing the
limitations of the double gray method. Although there are broad similarities,
the picket fence models have larger day-night side temperature differences,
non-isothermal upper atmospheres, and multiwavelength effects in the presence
of radiatively active clouds. We model the well-known hot Jupiters HD 189733 b
and HD 209458 b. For the hotter HD 209458 b, the picket fence method prevents
clouds from thermostating dayside temperatures, resulting in hotter upper
atmospheres and the dissipation of dayside clouds. Differences in the
temperature structures are then associated with nuanced differences in the
circulation patterns and clouds. Models of the cooler HD 189733 b have global
cloud coverage, regardless of radiative transfer scheme, whereas there are
larger differences in the models of HD 209458 b, particularly in the extent of
the partial cloud coverage on its dayside. This results in minor changes to the
thermal and reflected light phase curves of HD 189733 b, but more significant
differences for the picket fence and double gray versions of HD 209458 b.Comment: Submitted to ApJ, 31 page
A Closer Look at Exoplanet Occurrence Rates: Considering the Multiplicity of Stars without Detected Planets
One core goal of the Kepler mission was to determine the frequency of Earth-like planets that orbit Sun-like stars. Accurately estimating this planet occurrence rate requires both a well-vetted list of planets and a clear understanding of the stars searched for planets. Previous ground-based follow-up observations have, through a variety of methods, sought to improve our knowledge of stars that are known to host planets. Kepler targets without detected planets, however, have not been subjected to the same intensity of follow-up observations. In this paper, we constrain better the stellar multiplicity for stars around which Kepler could have theoretically detected a transiting Earth-sized planet in the habitable zone. We subsequently aim to improve estimates of the exoplanet search completeness—the fraction of exoplanets that were detected by Kepler—with our analysis. By obtaining adaptive optics observations of 71 Kepler target stars from the Shane 3 m telescope at Lick Observatory, we detected 14 candidate stellar companions within 4'' of 13 target stars. Of these 14 candidate stellar companions, we determine through multiple independent methods that 3 are likely to be bound to their corresponding target star. We then assess the impact of our observations on exoplanet occurrence rate calculations, finding an increase in occurrence of 6% (0.9σ) for various estimates of the frequency of Earth-like planets and an increase of 26% (4.5σ) for super-Earths and sub-Neptunes. These occurrence increases are not entirely commensurate with theoretical predictions, though this discrepancy may be due to differences in the treatment of stellar binarity
Global Chemical Transport on Hot Jupiters: Insights from 2D VULCAN photochemical model
The atmospheric dynamics of tidally-locked hot Jupiters is dominated by the
equatorial winds. Understanding the interaction between global circulation and
chemistry is crucial in atmospheric studies and interpreting observations.
Two-dimensional (2D) photochemical transport models shed light on how the
atmospheric composition depends on circulation. In this paper, we introduce the
2D photochemical transport model, VULCAN 2D, which improves on the pseudo-2D
approaches by allowing for non-uniform zonal winds. We extensively validate our
VULCAN 2D with analytical solutions and benchmark comparisons. Applications to
HD 189733 b and HD 209458 b reveal distinct characteristics in horizontal
transport-dominated and vertical mixing-dominated regimes. Motivated by the
inferred carbon-rich atmosphere by Giacobbe et al. (2021), we find that HD
209458 b with super-solar carbon-to-oxygen ratio (C/O) exhibits pronounced C2H4
absorption on the morning limb but not on the evening limb, owing to horizontal
transport from the nightside. We discuss when a pseudo-2D approach is a valid
assumption and its inherent limitations. Finally, we demonstrate the effect of
horizontal transport in transmission observations and its impact on the
morning-evening limb asymmetry with synthetic spectra, highlighting the need to
consider global transport when interpreting exoplanet atmospheres.Comment: 18 pages, 20 figures, submitted to Ap
exoplanet : gradient-based probabilistic inference for exoplanet data & other astronomical time series
Funding: This research was partially conducted during the Exostar19 program at the Kavli Institute for Theoretical Physics at UC Santa Barbara, which was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958."exoplanet" is a toolkit for probabilistic modeling of astronomical time series data, with a focus on observations of exoplanets, using PyMC3 (Salvatier et al., 2016). PyMC3 is a flexible and high-performance model-building language and inference engine that scales well to problems with a large number of parameters. "exoplanet" extends PyMC3's modeling language to support many of the custom functions and probability distributions required when fitting exoplanet datasets or other astronomical time series. While it has been used for other applications, such as the study of stellar variability, the primary purpose of "exoplanet" is the characterization of exoplanets or multiple star systems using time-series photometry, astrometry, and/or radial velocity. In particular, the typical use case would be to use one or more of these datasets to place constraints on the physical and orbital parameters of the system, such as planet mass or orbital period, while simultaneously taking into account the effects of stellar variability.Publisher PDFPeer reviewe
A Non-Detection of Iron in the First High-Resolution Emission Study of the Lava Planet 55 Cnc e
Close-in lava planets represent an extreme example of terrestrial worlds, but
their high temperatures may allow us to probe a diversity of crustal
compositions. The brightest and most well-studied of these objects is 55 Cancri
e, a nearby super-Earth with a remarkably short 17-hour orbit. However, despite
numerous studies, debate remains about the existence and composition of its
atmosphere. We present upper limits on the atmospheric pressure of 55 Cnc e
derived from high-resolution time-series spectra taken with Gemini-N/MAROON-X.
Our results are consistent with current crustal evaporation models for this
planet which predict a thin 100 mbar atmosphere. We conclude that, if a
mineral atmosphere is present on 55 Cnc e, the atmospheric pressure is below
100 mbar.Comment: Accepted to the AJ. 7 pages, 5 figure
Spitzer phase curve observations and circulation models of the inflated ultra-hot Jupiter WASP-76b
The large radii of many hot Jupiters can only be matched by models that have
hot interior adiabats, and recent theoretical work has shown that the interior
evolution of hot Jupiters has a significant impact on their atmospheric
structure. Due to its inflated radius, low gravity, and ultra-hot equilibrium
temperature, WASP-76b is an ideal case study for the impact of internal
evolution on observable properties. Hot interiors should most strongly affect
the non-irradiated side of the planet, and thus full phase curve observations
are critical to ascertain the effect of the interior on the atmospheres of hot
Jupiters. In this work, we present the first Spitzer phase curve observations
of WASP-76b. We find that WASP-76b has an ultra-hot day side and relatively
cold nightside with brightness temperatures of / at 3.6~\micron and / at 4.5~\micron, respectively. These results provide evidence
for a dayside thermal inversion. Both channels exhibit small phase offsets of
at 3.6~\micron and at
. We compare our observations to a suite of general
circulation models that consider two end-members of interior temperature along
with a broad range of frictional drag strengths. Strong frictional drag is
necessary to match the small phase offsets and cold nightside temperatures
observed. From our suite of cloud-free GCMs, we find that only cases with a
cold interior can reproduce the cold nightsides and large phase curve amplitude
at 4.5~\micron, hinting that the hot interior adiabat of WASP-76b does not
significantly impact its atmospheric dynamics or that clouds blanket its
nightside.Comment: 24 pages, 10 Figures, 5 Tables. Accepted to AJ. Co-First Author
TESS Hunt for Young and Maturing Exoplanets (THYME) VII : Membership, rotation, and lithium in the young cluster Group-X and a new young exoplanet
The public, all-sky surveys Gaia and TESS provide the ability to identify new
young associations and determine their ages. These associations enable study of
planetary evolution by providing new opportunities to discover young
exoplanets. A young association was recently identified by Tang et al. and
F{\"u}rnkranz et al. using astrometry from Gaia (called "Group-X" by the
former). In this work, we investigate the age and membership of this
association; and we validate the exoplanet TOI 2048 b, which was identified to
transit a young, late G dwarf in Group-X using photometry from TESS. We first
identified new candidate members of Group-X using Gaia EDR3 data. To infer the
age of the association, we measured rotation periods for candidate members
using TESS data. The clear color--period sequence indicates that the
association is the same age as the Myr-old NGC 3532. We obtained
optical spectra for candidate members that show lithium absorption consistent
with this young age. Further, we serendipitously identify a new, small
association nearby Group-X, which we call MELANGE-2. Lastly, we statistically
validate TOI 2048 b, which is \rearth\ radius planet on a 13.8-day
orbit around its 300 Myr-old host star.Comment: Revised to correct error in reported planet radius (original: 2.1
Earth radii, corrected: 2.6 Earth radii) and units for planetary radius ratio
entries in Table 8. All data tables available open-access with the AJ articl
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