37 research outputs found
Kepler-730: A hot Jupiter system with a close-in, transiting, Earth-sized planet
Kepler-730 is a planetary system hosting a statistically validated hot
Jupiter in a 6.49-day orbit and an additional transiting candidate in a
2.85-day orbit. We use spectroscopic radial velocities from the APOGEE-2N
instrument, Robo-AO contrast curves, and Gaia distance estimates to
statistically validate the planetary nature of the additional Earth-sized
candidate. We perform astrophysical false positive probability calculations for
the candidate using the available Kepler data and bolster the statistical
validation by using radial velocity data to exclude a family of possible binary
star solutions. Using a radius estimate for the primary star derived from
stellar models, we compute radii of and
() for Kepler-730b and
Kepler-730c, respectively. Kepler-730 is only the second compact system hosting
a hot Jupiter with an inner, transiting planet.Comment: 13 pages, 2 figures, 3 tables, published in ApJ
A Green Bank Telescope search for narrowband technosignatures between 1.1-1.9 GHz during 12 Kepler planetary transits
A growing avenue for determining the prevalence of life beyond Earth is to
search for "technosignatures" from extraterrestrial intelligences/agents.
Technosignatures require significant energy to be visible across interstellar
space and thus intentional signals might be concentrated in frequency, in time,
or in space, to be found in mutually obvious places. Therefore, it could be
advantageous to search for technosignatures in parts of parameter space that
are mutually-derivable to an observer on Earth and a distant transmitter. In
this work, we used the L-band (1.1-1.9 GHz) receiver on the Robert C. Byrd
Green Bank Telescope (GBT) to perform the first technosignature search
pre-synchronized with exoplanet transits, covering 12 Kepler systems. We used
the Breakthrough Listen turboSETI pipeline to flag narrowband hits (3 Hz)
using a maximum drift rate of 614.4 Hz/s and a signal-to-noise threshold
of 5 - the pipeline returned apparently-localized
features. Visual inspection by a team of citizen scientists ruled out 99.6% of
them. Further analysis found 2 signals-of-interest that warrant follow-up, but
no technosignatures. If the signals-of-interest are not re-detected in future
work, it will imply that the 12 targets in the search are not producing
transit-aligned signals from 1.1-1.9 GHz with transmitter powers 60 times
that of the former Arecibo radar. This search debuts a range of innovative
technosignature techniques: citizen science vetting of potential
signals-of-interest, a sensitivity-aware search out to extremely high drift
rates, a more flexible method of analyzing on-off cadences, and an extremely
low signal-to-noise threshold.Comment: 18 pages, 11 figure
Characterization of low-mass companions to objects of interest observed with APOGEE-N
We report the characterization of 28 low-mass
() companions
to objects of interest (KOIs), eight of which were previously
designated confirmed planets. These objects were detected as transiting
companions to Sun-like stars (G and F dwarfs) by the mission
and are confirmed as single-lined spectroscopic binaries in the current work
using the northern multiplexed Apache Point Observatory Galactic Evolution
Experiment near-infrared spectrograph (APOGEE-N) as part of the third and
fourth Sloan Digital Sky Surveys. We have observed hundreds of KOIs using
APOGEE-N and collected a total of 43,175 spectra with a median of 19 visits and
a median baseline of years per target. We jointly model the
photometry and APOGEE-N radial velocities to derive
fundamental parameters for this subset of 28 transiting companions. The radii
for most of these low-mass companions are over-inflated (by ) when
compared to theoretical models. Tidally locked M dwarfs on short period orbits
show the largest amount of inflation, but inflation is also evident for
companions that are well separated from the host star. We demonstrate that
APOGEE-N data provides reliable radial velocities when compared to precise
high-resolution spectrographs that enable detailed characterization of
individual systems and the inference of orbital elements for faint ()
KOIs. The data from the entire APOGEE-KOI program is public and presents an
opportunity to characterize an extensive subset of the binary population
observed by .Comment: 98 pages (include 56 for the figure sets), 10 tables, 7 figures, 2
figure sets, accepted for publication in ApJ
Kepler-503b: An Object at the Hydrogen Burning Mass Limit Orbiting a Subgiant Star
Using spectroscopic radial velocities with the APOGEE instrument and Gaia
distance estimates, we demonstrate that Kepler-503b, currently considered a
validated Kepler planet, is in fact a brown-dwarf/low-mass star in a nearly
circular 7.2-day orbit around a subgiant star. Using a mass estimate for the
primary star derived from stellar models, we derive a companion mass and radius
of () and
(),
respectively. Assuming the system is coeval, the evolutionary state of the
primary indicates the age is Gyr. Kepler-503b sits right at the
hydrogen burning mass limit, straddling the boundary between brown dwarfs and
very low-mass stars. More precise radial velocities and secondary eclipse
spectroscopy with James Webb Space Telescope will provide improved measurements
of the physical parameters and age of this important system to better constrain
and understand the physics of these objects and their spectra. This system
emphasizes the value of radial velocity observations to distinguish a genuine
planet from astrophysical false positives, and is the first result from the
SDSS-IV monitoring of Kepler planet candidates with the multi-object APOGEE
instrument.Comment: Accepted for publication in ApJL, 12 pages, 3 figures, 2 table
TOI-150: A transiting hot Jupiter in the TESS southern CVZ
We report the detection of a hot Jupiter ($M_{p}=1.75_{-0.17}^{+0.14}\
M_{J}R_{p}=1.38\pm0.04\ R_{J}\log
g=4.152^{+0.030}_{-0.043}\beta=-79.59^{\circ}$). We confirm the
planetary nature of the candidate TOI-150.01 using radial velocity observations
from the APOGEE-2 South spectrograph and the Carnegie Planet Finder
Spectrograph, ground-based photometric observations from the robotic
Three-hundred MilliMeter Telescope at Las Campanas Observatory, and Gaia
distance estimates. Large-scale spectroscopic surveys, such as APOGEE/APOGEE-2,
now have sufficient radial velocity precision to directly confirm the signature
of giant exoplanets, making such data sets valuable tools in the TESS era.
Continual monitoring of TOI-150 by TESS can reveal additional planets and
subsequent observations can provide insights into planetary system
architectures involving a hot Jupiter around a star about halfway through its
main-sequence life.Comment: 13 pages, 3 figures, 2 tables, accepted to ApJ
TOI-5375 B: A Very Low Mass Star at the Hydrogen-Burning Limit Orbiting an Early M-type Star
The TESS mission detected a companion orbiting TIC 71268730, categorized it
as a planet candidate, and designated the system TOI-5375. Our follow-up
analysis using radial velocity data from the Habitable-zone Planet Finder
(HPF), photometric data from Red Buttes Observatory (RBO), and speckle imaging
with NN-EXPLORE Exoplanet Stellar Speckle Imager (NESSI) determined that the
companion is a very low mass star (VLMS) near the hydrogen-burning mass limit
with a mass of 0.080\pm{0.002} M_{\Sun} (), a radius of
0.1114^{+0.0048}_{-0.0050} R_{\Sun} (1.0841), and
brightness temperature of K. This object orbits with a period of
1.721553 days around an early M dwarf star
(0.62\pm{0.016}M_{\Sun}). TESS photometry shows regular variations in the
host star's TESS light curve, which we interpreted as activity-induced
variation of 2\%, and used this variability to measure the host star's
stellar rotation period of 1.9716 days. The TOI-5375
system provides tight constraints on stellar models of low-mass stars at the
hydrogen-burning limit and adds to the population in this important region.Comment: 15 pages, 8 figures, Accepted to the Astronomical Journa
TOI-3785 b: A Low-Density Neptune Orbiting an M2-Dwarf Star
Using both ground-based transit photometry and high-precision radial velocity
(RV) spectroscopy, we confirm the planetary nature of TOI-3785 b. This
transiting Neptune orbits an M2-Dwarf star with a period of ~4.67 days, a
planetary radius of 5.14 +/- 0.16 Earth Radii, a mass of 14.95 +4.10, -3.92
Earth Masses, and a density of 0.61 +0.18, -0.17 g/cm^3. TOI-3785 b belongs to
a rare population of Neptunes (4 Earth Radii < Rp < 7 Earth Radii) orbiting
cooler, smaller M-dwarf host stars, of which only ~10 have been confirmed. By
increasing the number of confirmed planets, TOI-3785 b offers an opportunity to
compare similar planets across varying planetary and stellar parameter spaces.
Moreover, with a high transmission spectroscopy metric (TSM) of ~150 combined
with a relatively cool equilibrium temperature of 582 +/- 16 K and an inactive
host star, TOI-3785 b is one of the more promising low-density M-dwarf Neptune
targets for atmospheric follow-up. Future investigation into atmospheric mass
loss rates of TOI-3785 b may yield new insights into the atmospheric evolution
of these low-mass gas planets around M-dwarfs.Comment: 22 pages, 6 figures, 6 tables, Submitted to A
TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm Super-Neptune Orbiting an M-dwarf Host
We confirm the planetary nature of TOI-1728b using a combination of ground-based photometry, near-infrared Doppler velocimetry and spectroscopy with the Habitable-zone Planet Finder. TOI-1728 is an old, inactive M0 star with T_(eff) = 3980⁺³¹₋₃₂ K, which hosts a transiting super-Neptune at an orbital period of ~3.49 days. Joint fitting of the radial velocities and TESS and ground-based transits yields a planetary radius of 5.05^(+0.16)_(-0.17) R_⊕, mass 26.78^(+5.43)_(-5.13) M_⊕, and eccentricity 0.057^(+0.054)_(-0.039). We estimate the stellar properties, and perform a search for He 10830 Å absorption during the transit of this planet and claim a null detection with an upper limit of 1.1% with 90% confidence. A deeper level of He 10830 Å absorption has been detected in the planet atmosphere of GJ 3470b, a comparable gaseous planet. TOI-1728b is the largest super-Neptune—the intermediate subclass of planets between Neptune and the more massive gas-giant planets—discovered around an M dwarf. With its relatively large mass and radius, TOI-1728 represents a valuable data point in the M-dwarf exoplanet mass–radius diagram, bridging the gap between the lighter Neptune-sized planets and the heavier Jovian planets known to orbit M dwarfs. With a low bulk density of 1.14^(+0.26)_(-0.24) g cm⁻³, and orbiting a bright host star (J ~ 9.6, V ~ 12.4), TOI-1728b is also a promising candidate for transmission spectroscopy both from the ground and from space, which can be used to constrain planet formation and evolutionary models
The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b
Using radial velocity data from the Habitable Zone Planet Finder, we have measured the mass of the Neptune-sized planet K2-25b, as well as the obliquity of its M4.5 dwarf host star in the 600–800 Myr Hyades cluster. This is one of the youngest planetary systems for which both of these quantities have been measured and one of the very few M dwarfs with a measured obliquity. Based on a joint analysis of the radial velocity data, time-series photometry from the K2 mission, and new transit light curves obtained with diffuser-assisted photometry, the planet's radius and mass are 3.44 ± 0.12 R_⊕ and 24.5_(-5.2)^(+5.7) M_⊕. These properties are compatible with a rocky core enshrouded by a thin hydrogen–helium atmosphere (5% by mass). We measure an orbital eccentricity of e = 0.43 ± 0.05. The sky-projected stellar obliquity is λ = 3° ± 16°, compatible with spin–orbit alignment, in contrast to other "hot Neptunes" that have been studied around older stars