78 research outputs found
The Demographics of Terrestrial Planets in the Venus Zone
Understanding the physical characteristics of Venus, including its
atmosphere, interior, and its evolutionary pathway with respect to Earth,
remains a vital component for terrestrial planet evolution models and the
emergence and/or decline of planetary habitability. A statistical strategy for
evaluating the evolutionary pathways of terrestrial planets lies in the
atmospheric characterization of exoplanets, where the sample size provides
sufficient means for determining required runaway greenhouse conditions.
Observations of potential exoVenuses can help confirm hypotheses about Venus'
past, as well as the occurrence rate of Venus-like planets in other systems.
Additionally, the data from future Venus missions, such as DAVINCI, EnVision,
and VERITAS, will provide valuable information regarding Venus, and the study
of exoVenuses will be complimentary to these missions. To facilitate studies of
exoVenus candidates, we provide a catalog of all confirmed terrestrial planets
in the Venus Zone, including transiting and non-transiting cases, and quantify
their potential for follow-up observations. We examine the demographics of the
exoVenus population with relation to stellar and planetary properties, such as
the planetary radius gap. We highlight specific high-priority exoVenus targets
for follow-up observations including: TOI-2285 b, LTT 1445 A c, TOI-1266 c, LHS
1140 c, and L98-59 d. We also discuss follow-up observations that may yield
further insight into the Venus/Earth divergence in atmospheric properties.Comment: 27 pages, 7 figures, accepted for publication in the Astronomical
Journa
The MOSDEF Survey: Kinematic and Structural Evolution of Star-Forming Galaxies at
We present ionized gas kinematics for 681 galaxies at from
the MOSFIRE Deep Evolution Field survey, measured using models which account
for random galaxy-slit misalignments together with structural parameters
derived from CANDELS Hubble Space Telescope (HST) imaging. Kinematics and sizes
are used to derive dynamical masses. Baryonic masses are estimated from stellar
masses and inferred gas masses from dust-corrected star formation rates (SFRs)
and the Kennicutt-Schmidt relation. We measure resolved rotation for 105
galaxies. For the remaining 576 galaxies we use models based on HST imaging
structural parameters together with integrated velocity dispersions and
baryonic masses to statistically constrain the median ratio of intrinsic
ordered to disordered motion, . We find that
increases with increasing stellar mass and decreasing specific SFR (sSFR).
These trends may reflect marginal disk stability, where systems with higher gas
fractions have thicker disks. For galaxies with detected rotation we assess
trends between their kinematics and mass, sSFR, and baryon surface density
(). Intrinsic dispersion correlates most with
and velocity correlates most with mass. By comparing
dynamical and baryonic masses, we find that galaxies at are
baryon dominated within their effective radii (), with Mdyn/Mbaryon
increasing over time. The inferred baryon fractions within ,
, decrease over time, even at fixed mass, size, or surface
density. At fixed redshift, does not appear to vary with
stellar mass but increases with decreasing and increasing
. For galaxies at , the median inferred baryon
fractions generally exceed 100%. We discuss possible explanations and future
avenues to resolve this tension.Comment: Accepted to ApJ. Added Figure 9, corrected sample size (main results
unchanged). 28 pages, 13 figure
Revised Properties and Dynamical History for the HD 17156 System
From the thousands of known exoplanets, those that transit bright host stars
provide the greatest accessibility toward detailed system characterization. The
first known such planets were generally discovered using the radial velocity
technique, then later found to transit. HD 17156b is particularly notable among
these initial discoveries because it diverged from the typical hot Jupiter
population, occupying a 21.2 day eccentric () orbit, offering
preliminary insights into the evolution of planets in extreme orbits. Here we
present new data for this system, including ground and space-based photometry,
radial velocities, and speckle imaging, that further constrain the system
properties and stellar/planetary multiplicity. These data include photometry
from the Transiting Exoplanet Survey Satellite (TESS) that cover five transits
of the known planet. We show that the system does not harbor any additional
giant planets interior to 10 AU. The lack of stellar companions and the age of
the system indicate that the eccentricity of the known planet may have resulted
from a previous planet-planet scattering event. We provide the results from
dynamical simulations that suggest possible properties of an additional planet
that culminated in ejection from the system, leaving a legacy of the observed
high eccentricity for HD 17156b.Comment: 15 pages, 7 figures, accepted for publication in the Astronomical
Journa
Visible-light Phase Curves from the Second Year of the TESS Primary Mission
We carried out a systematic study of full-orbit phase curves for known transiting systems in the northern ecliptic sky that were observed during Year 2 of the TESS primary mission. We applied the same methodology for target selection, data processing, and light-curve fitting as we did in our Year 1 study. Out of the 15 transiting systems selected for analysis, seven—HAT-P-7, KELT-1, KELT-9, KELT-16, KELT-20, Kepler-13A, and WASP-12—show statistically significant secondary eclipses and day–night atmospheric brightness modulations. Small eastward dayside hot-spot offsets were measured for KELT-9b and WASP-12b. KELT-1, Kepler-13A, and WASP-12 show additional phase-curve variability attributed to the tidal distortion of the host star; the amplitudes of these signals are consistent with theoretical predictions. We combined occultation measurements from TESS and Spitzer to compute dayside brightness temperatures, TESS-band geometric albedos, Bond albedos, and phase integrals for several systems. The new albedo values solidify the previously reported trend between dayside temperature and geometric albedo for planets with 1500 K < Tday < 3000 K. For Kepler-13Ab, we carried out an atmospheric retrieval of the full secondary eclipse spectrum, which revealed a noninverted temperature–pressure profile, significant H2O and K absorption in the near-infrared, evidence for strong optical atmospheric opacity due to sodium, and a confirmation of the high geometric albedo inferred from our simpler analysis. We explore the implications of the phase integrals (ratios of Bond to geometric albedos) for understanding exoplanet clouds. We also report updated transit ephemerides for all of the systems studied in this work
The MOSDEF Survey: An Improved Voronoi Binning Technique on Spatially Resolved Stellar Populations at z~2
We use a sample of 350 star-forming galaxies at from the
MOSFIRE Deep Evolution Field survey to demonstrate an improved Voronoi binning
technique that we use to study the properties of resolved stellar populations
in galaxies. Stellar population and dust maps are constructed from the
high-resolution CANDELS/3D-HST multi-band imaging. Rather than constructing the
layout of resolved elements (i.e., Voronoi bins) from the S/N distribution of
the -band alone, we introduce a modified Voronoi binning method that
additionally incorporates the S/N distribution of several resolved filters. The
SED-derived resolved E(B-V), stellar population ages, SFRs,
and stellar masses that are inferred from the Voronoi bins constructed from
multiple filters are generally consistent with the properties inferred from the
integrated photometry within the uncertainties, with the exception of the
inferred E(B-V) from our sample due to their UV
slopes being unconstrained by the resolved photometry. The results from our
multi-filter Voronoi binning technique are compared to those derived from a
"traditional" single-filter Voronoi binning approach. We find that
single-filter binning produces inferred E(B-V) that are
systematically redder by 0.02 mag on average, but could differ by up to 0.20
mag, and could be attributed to poorly constrained resolved photometry covering
the UV slope. Overall, we advocate that our methodology produces more reliable
SED-derived parameters due to the best-fit resolved SEDs being better
constrained at all resolved wavelengths--particularly those covering the UV
slope.Comment: 23 pages, 15 figures, accepted for publication in MNRA
Variability Catalog of Stars Observed During the TESS Prime Mission
During its 2-year Prime Mission, TESS observed over 232,000 stars at a 2-min
cadence across ~70% of the sky. These data provide a record of photometric
variability across a range of astrophysically interesting time scales, probing
stellar rotation, stellar binarity, and pulsations. We have analyzed the TESS
2-min light curves to identify periodic variability on timescales 0.01-13 days,
and explored the results across various stellar properties. We have identified
over 46,000 periodic variables with high confidence, and another 38,000 with
moderate confidence. These light curves show differences in variability type
across the HR diagram, with distinct groupings of rotational, eclipsing, and
pulsational variables. We also see interesting patterns across
period-luminosity space, with clear correlations between period and luminosity
for high-mass pulsators, evolved stars, and contact binary systems, a
discontinuity corresponding to the Kraft break, and a lower occurrence of
periodic variability in main-sequence stars on timescales of 1.5 to 2 days. The
variable stars identified in this work are cross-identified with several other
variability catalogs, from which we find good agreement between the measured
periods of variability. There are ~65,000 variable stars that are newly
identified in this work, which includes rotation rates of low-mass stars,
high-frequency pulsation periods for high-mass stars, and a variety of giant
star variability.Comment: 29 pages, 17 figures, accepted to ApJS, catalog available:
https://archive.stsci.edu/hlsp/tess-svc, data visualization tool:
https://filtergraph.com/tessvariabilit
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