arXiv subjects

Karen A. Collins

Publications and source records attributed to Karen A. Collins.

At least 163 records · Page 9Linked to original sources

arXiv2023

TOI-1695 b: A Water World Orbiting an Early M Dwarf in the Planet Radius Valley

Characterizing the bulk compositions of transiting exoplanets within the M dwarf radius valley offers a unique means to establish whether the radius valley emerges from an atmospheric mass loss process or is imprinted by planet formation itself. We present the confirmation of such a planet orbiting an early M dwarf ($T_{\rm mag} = 11.0294 \pm 0.0074, M_s = 0.513 \pm 0.012\ M_\odot, R_s = 0.515 \pm 0.015\ R_\odot, T_{\rm eff} =3690\pm 50 K$): TOI-1695 b ($P = 3.13$ days, $R_p = 1.90^{+0.16}_{-0.14}\ R_\oplus$). TOI-1695 b's radius and orbital period situate the planet between model predictions from thermally-driven mass loss versus gas depleted formation, offering an important test case for radius valley emergence models around early M dwarfs. We confirm the planetary nature of TOI-1695 b based on five sectors of TESS data and a suite of follow-up observations including 49 precise radial velocity measurements taken with the HARPS-N spectrograph. We measure a planetary mass of $6.36 \pm 1.00\ M_\oplus$, which reveals that TOI-1695 b is inconsistent with a purely terrestrial composition of iron and magnesium silicate, and instead is likely a water-rich planet. Our finding that TOI-1695 b is not terrestrial is inconsistent with the planetary system being sculpted by thermally driven mass loss. We present a statistical analysis of seven well-characterized planets within the M dwarf radius valley demonstrating that a thermally-driven mass loss scenario is unlikely to explain this population.

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arXiv2023

TOI-2525 b and c: A pair of massive warm giant planets with a strong transit timing variations revealed by TESS

TOI-2525 is a K-type star with an estimated mass of M = 0.849$_{-0.033}^{+0.024}$ M$_\odot$ and radius of R = 0.785$_{-0.007}^{+0.007}$ R$_\odot$ observed by the TESS mission in 22 sectors (within sectors 1 and 39). The TESS light curves yield significant transit events of two companions, which show strong transit timing variations (TTVs) with a semi-amplitude of a $\sim$6 hours. We performed TTV dynamical, and photo-dynamical light curve analysis of the TESS data, combined with radial velocity (RV) measurements from FEROS and PFS, and we confirmed the planetary nature of these companions. The TOI-2525 system consists of a transiting pair of planets comparable to Neptune and Jupiter with estimated dynamical masses of $m_{\rm b}$ = 0.088$_{-0.004}^{+0.005}$ M$_{\rm Jup.}$, and $m_{\rm c}$ = 0.709$_{-0.033}^{+0.034}$ M$_{\rm Jup.}$, radius of $r_b$ = 0.88$_{-0.02}^{+0.02}$ R$_{\rm Jup.}$ and $r_c$ = 0.98$_{-0.02}^{+0.02}$ R$_{\rm Jup.}$, and with orbital periods of $P_{\rm b}$ = 23.288$_{-0.002}^{+0.001}$ days and $P_{\rm c}$ = 49.260$_{-0.001}^{+0.001}$ days for the inner and the outer planet, respectively. The period ratio is close to the 2:1 period commensurability, but the dynamical simulations of the system suggest that it is outside the mean motion resonance (MMR) dynamical configuration. TOI-2525 b is among the lowest density Neptune-mass planets known to date, with an estimated median density of $ρ_{\rm b}$ = 0.174$_{-0.015}^{+0.016}$ g\,cm$^{-3}$. The TOI-2525 system is very similar to the other K-dwarf systems discovered by TESS, TOI-2202 and TOI-216, which are composed of almost identical K-dwarf primary and two warm giant planets near the 2:1 MMR.

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arXiv2023

TOI-4562 b: A highly eccentric temperate Jupiter analog orbiting a young field star

We report the discovery of TOI-4562 b (TIC-349576261), a Jovian planet orbiting a young F7V-type star, younger than the Praesepe/Hyades clusters (< $700$ Myr). This planet stands out because of its unusually long orbital period for transiting planets with known masses ($P_{\mathrm{orb}}$ = $225.11781^{+0.00025}_{-0.00022}$ days), and because it has a substantial eccentricity ($e$ = $0.76^{+0.02}_{-0.02}$). The location of TOI-4562 near the southern continuous viewing zone of TESS allowed observations throughout 25 sectors, enabling an unambiguous period measurement from TESS alone. Alongside the four available TESS transits, we performed follow-up photometry using the South African Astronomical Observatory node of the Las Cumbres Observatory, and spectroscopy with the CHIRON spectrograph on the 1.5 m SMARTS telescope. We measure a radius of $1.118_{+0.013}^{-0.014}$ $R_{\mathrm{J}}$ and a mass of $2.30^{+0.48}_{-0.47}$ $M_{\mathrm{J}}$ for TOI-4562 b. The radius of the planet is consistent with contraction models describing the early evolution of the size of giant planets. We detect tentative transit timing variations at the $\sim$ 20 min level from five transit events, favouring the presence of a companion that could explain the dynamical history of this system if confirmed by future follow-up observations. With its current orbital configuration, tidal timescales are too long for TOI-4562 b to become a hot-Jupiter via high eccentricity migration, though it is not excluded that interactions with the possible companion could modify TOI-4562 b eccentricity and trigger circularization. The characterisation of more such young systems is essential to set constraints on models describing giant planet evolution.

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arXiv2023

HIP 33609 b: An Eccentric Brown Dwarf Transiting a V=7.3 Rapidly Rotating B-Star

We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite TESS as TOI-588 b. HIP 33609 b is a large (R$_{b}$ = 1.580$_{-0.070}^{+0.074}$ R$_{J}$) brown dwarf on a highly eccentric (e = 0.560$_{-0.031}^{+0.029}$) orbit with a 39-day period. The host star is a bright (V = 7.3 mag), T$_{eff}$ = 10,400$_{-660}^{+800}$ K star with a mass of M$_{*}$ = 2.383$_{-0.095}^{+0.10}$ M$_{\odot}$ and radius of R$_{*}$ = 1.863$_{-0.082}^{+0.087}$ R$_{\odot}$, making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M$_{b}$ = 68.0$_{-7.1}^{+7.4}$ M$_{J}$ as well as the host star's rotation rate ($vsini_{*} = 55.6 \pm 1.8$ km/s). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 $\pm$ 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.

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arXiv2023

The K2 & TESS Synergy II: Revisiting 26 systems in the TESS Primary Mission

The legacy of NASA's K2 mission has provided hundreds of transiting exoplanets that can be revisited by new and future facilities for further characterization, with a particular focus on studying the atmospheres of these systems. However, the majority of K2-discovered exoplanets have typical uncertainties on future times of transit within the next decade of greater than four hours, making observations less practical for many upcoming facilities. Fortunately, NASA's Transiting exoplanet Survey Satellite (TESS) mission is reobserving most of the sky, providing the opportunity to update the ephemerides for $\sim$300 K2 systems. In the second paper of this series, we reanalyze 26 single-planet, K2-discovered systems that were observed in the TESS primary mission by globally fitting their K2 and TESS lightcurves (including extended mission data where available), along with any archival radial velocity measurements. As a result of the faintness of the K2 sample, 13 systems studied here do not have transits detectable by TESS. In those cases, we re-fit the K2 lightcurve and provide updated system parameters. For the 23 systems with $M_* \gtrsim 0.6 M_\odot$, we determine the host star parameters using a combination of Gaia parallaxes, Spectral Energy Distribution (SED) fits, and MESA Isochrones and Stellar Tracks (MIST) stellar evolution models. Given the expectation of future TESS extended missions, efforts like the K2 & TESS Synergy project will ensure the accessibility of transiting planets for future characterization while leading to a self-consistent catalog of stellar and planetary parameters for future population efforts.

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arXiv2023

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 ($T_{mag}=11.032$, $M_* = 0.63 M_\odot$, $R_* = 0.60 R_\odot$, $T_{eff} = 3900$ K, $d = 61.54$ 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 ($R_b = 2.266_{-0.038}^{+0.038} R_\oplus$ and $R_c = 2.415_{-0.040}^{+0.043} R_\oplus$; $P_b$ = 5.538 days and $P_c$ = 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.

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arXiv2022

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{ü}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 $300\pm50$ 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 $2.6\pm0.2$ \rearth\ radius planet on a 13.8-day orbit around its 300 Myr-old host star.

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arXiv2022

A Low-mass, Pre-main-sequence Eclipsing Binary in the 40 Myr Columba Association -- Fundamental Stellar Parameters and Modeling the Effect of Star Spots

Young eclipsing binaries (EBs) are powerful probes of early stellar evolution. Current models are unable to simultaneously reproduce the measured and derived properties that are accessible for EB systems (e.g., mass, radius, temperature, luminosity). In this study we add a benchmark EB to the pre-main-sequence population with our characterization of TOI 450 (TIC 77951245). Using Gaia astrometry to identify its comoving, coeval companions, we confirm TOI 450 is a member of the $\sim$40 Myr Columba association. This eccentric ($e=0.2969$), equal-mass ($q=1.000$) system provides only one grazing eclipse. Despite this, our analysis achieves the precision of a double-eclipsing system by leveraging information in our high-resolution spectra to place priors on the surface-brightness and radius ratios. We also introduce a framework to include the effect of star spots on the observed eclipse depths. Multicolor eclipse light curves play a critical role in breaking degeneracies between the effects of star spots and limb-darkening. Including star spots reduces the derived radii by $\sim$2\% from an unspotted model ($>2σ$) and inflates the formal uncertainty in accordance with our lack of knowledge regarding the star spot orientation. We derive masses of 0.1768($\pm$0.0004) and 0.1767($\pm$0.0003) $M_\odot$, and radii of 0.345($\pm$0.006) and 0.346($\pm$0.006) $R_\odot$ for the primary and secondary, respectively. We compare these measurements to multiple stellar evolution isochones, finding good agreement with the association age. The MESA MIST and SPOTS ($f_{\rm s}=0.17$) isochrones perform the best across our comparisons, but detailed agreement depends heavily on the quantities being compared.

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arXiv2022

The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets

NASA's Transiting Exoplanet Survey Satellite (TESS) mission promises to improve our understanding of hot Jupiters by providing an all-sky, magnitude-limited sample of transiting hot Jupiters suitable for population studies. Assembling such a sample requires confirming hundreds of planet candidates with additional follow-up observations. Here, we present twenty hot Jupiters that were detected using TESS data and confirmed to be planets through photometric, spectroscopic, and imaging observations coordinated by the TESS Follow-up Observing Program (TFOP). These twenty planets have orbital periods shorter than 7 days and orbit relatively bright FGK stars ($10.9 < G < 13.0$). Most of the planets are comparable in mass to Jupiter, although there are four planets with masses less than that of Saturn. TOI-3976 b, the longest period planet in our sample ($P = 6.6$ days), may be on a moderately eccentric orbit ($e = 0.18\pm0.06$), while observations of the other targets are consistent with them being on circular orbits. We measured the projected stellar obliquity of TOI-1937A b, a hot Jupiter on a 22.4 hour orbit with the Rossiter-McLaughlin effect, finding the planet's orbit to be well-aligned with the stellar spin axis ($|λ| = 4.0\pm3.5^\circ$). We also investigated the possibility that TOI-1937 is a member of the NGC 2516 open cluster, but ultimately found the evidence for cluster membership to be ambiguous. These objects are part of a larger effort to build a complete sample of hot Jupiters to be used for future demographic and detailed characterization work.

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arXiv2022

TOI-1075 b: A Dense, Massive, Ultra-Short Period Hot Super-Earth Straddling the Radius Gap

Populating the exoplanet mass-radius diagram in order to identify the underlying relationship that governs planet composition is driving an interdisciplinary effort within the exoplanet community. The discovery of hot super-Earths - a high temperature, short-period subset of the super-Earth planet population - has presented many unresolved questions concerning the formation, evolution, and composition of rocky planets. We report the discovery of a transiting, ultra-short period hot super-Earth orbiting TOI-1075 (TIC 351601843), a nearby ($d$ = 61.4 pc) late K-/early M-dwarf star, using data from the Transiting Exoplanet Survey Satellite (TESS). The newly discovered planet has a radius of $1.791^{+0.116}_{-0.081}$ $R_{\oplus}$, and an orbital period of 0.605 days (14.5 hours). We precisely measure the planet mass to be $9.95^{+1.36}_{-1.30}$ $M_{\oplus}$ using radial velocity measurements obtained with the Planet Finder Spectrograph (PFS), mounted on the Magellan II telescope. Our radial velocity data also show a long-term trend, suggesting an additional planet in the system. While TOI-1075 b is expected to have a substantial H/He atmosphere given its size relative to the radius gap, its high density ($9.32^{+2.05}_{-1.85}$ $\rm{g/cm^3}$) is likely inconsistent with this possibility. We explore TOI-1075 b's location relative to the M-dwarf radius valley, evaluate the planet's prospects for atmospheric characterization, and discuss potential planet formation mechanisms. Studying the TOI-1075 system in the broader context of ultra-short period planetary systems is necessary for testing planet formation and evolution theories, density enhancing mechanisms, and for future atmospheric and surface characterization studies via emission spectroscopy with JWST.

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arXiv2022

A sub-Neptune transiting the young field star HD 18599 at 40 pc

Transiting exoplanets orbiting young nearby stars are ideal laboratories for testing theories of planet formation and evolution. However, to date only a handful of stars with age <1 Gyr have been found to host transiting exoplanets. Here we present the discovery and validation of a sub-Neptune around HD 18599, a young (300 Myr), nearby (d=40 pc) K star. We validate the transiting planet candidate as a bona fide planet using data from the TESS, Spitzer, and Gaia missions, ground-based photometry from IRSF, LCO, PEST, and NGTS, speckle imaging from Gemini, and spectroscopy from CHIRON, NRES, FEROS, and Minerva-Australis. The planet has an orbital period of 4.13 d, and a radius of 2.7Rearth. The RV data yields a 3-sigma mass upper limit of 30.5Mearth which is explained by either a massive companion or the large observed jitter typical for a young star. The brightness of the host star (V~9 mag) makes it conducive to detailed characterization via Doppler mass measurement which will provide a rare view into the interior structure of young planets.

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arXiv2022

Occurrence rate of hot Jupiters around early-type M dwarfs based on TESS data

We present an estimate of the occurrence rate of hot Jupiters ($7\ R_{\oplus}\leq R_{p}\leq 2\ R_{J}$, $0.8 \leq P_{b}\leq 10$ days) around early-type M dwarfs based on stars observed by TESS during its Primary Mission. We adopt stellar parameters from the TESS Input Catalog, and construct a sample of 60,819 M dwarfs with $10.5 \leq T_{\rm mag}\leq 13.5$, effective temperature $2900 \leq T_{\rm eff}\leq 4000\ K$ and stellar mass $0.45\leq M_{\ast}\leq 0.65\ M_{\odot}$. We conduct a uninformed transit search using a detection pipeline based on the box least square search and characterize the searching completeness through an injection and recovery experiment. We combine a series of vetting steps including light centroid measurement, odd/even and secondary eclipse analysis, rotation and transit period synchronization tests as well as inspecting the ground-based photometric, spectroscopic and imaging observations. Finally, we find a total of nine planet candidates, all of which are known TESS objects of interest. We obtain an occurrence rate of $0.27\pm0.09\%$ for hot Jupiters around early-type M dwarfs that satisfy our selection criteria. Compared with previous studies, the occurrence rate of hot Jupiters around early-type M dwarfs is smaller than all measurements for FGK stars, although they are consistent within 1--2$σ$. Combining results from transit, radial velocity and microlensing surveys, we find that hot Jupiters around early-type M dwarfs possibly show a steeper decrease in occurrence rate per logarithmic semi-major axis bin (${{\rm d}N}/{\rm d}\log_{10} a$) when compared with FGK stars.

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arXiv2022

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 $c$) and 411.02 (planet $b$), 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$1.157\pm0.025R_\odot$. Adopting this value, we determined the radii for the three exoplanet candidates and found that planet $b$ is a super-Earth, with a radius of $1.72\pm0.10R_\oplus$, while planet $c$ and $d$ are sub-Neptunian planets, with radii of$2.74\pm0.14R_\oplus$ and $3.23\pm0.19R_\oplus$ 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 $c$ and $d$.(Abridged)

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arXiv2022

Gaia-TESS synergy: Improving the identification of transit candidates

Context: The TESS team periodically issues a new list of transiting exoplanet candidates based on the analysis of the accumulating light curves obtained by the satellite. The list includes the estimated epochs, periods, and durations of the potential transits. As the point spread function (PSF) of TESS is relatively wide, follow-up photometric observations at higher spatial resolution are required in order to exclude apparent transits that are actually blended background eclipsing binaries (BEBs). Aims: The Gaia space mission, with its growing database of epoch photometry and high angular resolution, enables the production of distinct light curves for all sources included in the TESS PSF, up to the limiting magnitude of Gaia. This paper reports the results of an ongoing Gaia-TESS collaboration that uses the Gaia photometry to facilitate the identification of BEB candidates and even to confirm on-target candidates in some cases. Methods: We inspected the Gaia photometry of the individual sources included in the TESS PSF, searching for periodic dimming events compatible with their ephemerides and uncertainties, as published by TESS. The performance of the search depends mainly on the number of Gaia measurements during transit and their precision. Results: Since February 2021, the collaboration has been able to confirm 126 on-target candidates and exclude 124 as BEBs. Since June 2021, when our search methodology matured, we have been able to identify on the order of 5% as on-target candidates and another 5% as BEBs. Conclusions: This synergistic approach is combining the complementary capabilities of two of the astronomical space missions of NASA and ESA. It serves to optimize the process of detecting new planets by making better use of the resources of the astronomical community.

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arXiv2022

TOI-2196 b: Rare planet in the hot Neptune desert transiting a G-type star

Highly irradiated planets in the hot Neptune desert are usually either small (R < 2 Rearth) and rocky or they are gas giants with radii of >1 Rjup. Here, we report on the intermediate-sized planet TOI-2196 on a 1.2 day orbit around a G-type star discovered by TESS in sector 27. We collected 42 radial velocity measurements with the HARPS spectrograph to determine the mass. The radius of TOI-2196 b is 3.51 +/- 0.15 Rearth, which, combined with the mass of 26.0 +/- 1.3 Mearth, results in a bulk density of 3.31+0.51-0.43 g/cm3. Hence, the radius implies that this planet is a sub-Neptune, although the density is twice than that of Neptune. A significant trend in the HARPS radial velocities points to the presence of a distant companion with a lower limit on the period and mass of 220 days and 0.65 Mjup, respectively, assuming zero eccentricity. The short period of planet b implies a high equilibrium temperature of 1860 +/- 20 K, for zero albedo and isotropic emission. This places the planet in the hot Neptune desert, joining a group of very few planets in this parameter space discovered in recent years. These planets suggest that the hot Neptune desert may be divided in two parts for planets with equilibrium temperatures of > 1800 K: a hot sub-Neptune desert devoid of planets with radii of 1.8-3 Rearth and a sub-Jovian desert for radii of 5-12 Rearth. More planets in this parameter space are needed to further investigate this finding. Planetary interior structure models of TOI-2196 b are consistent with a H/He atmosphere mass fraction between 0.4 % and 3 %, with a mean value of 0.7 % on top of a rocky interior. We estimated the amount of mass this planet might have lost at a young age, and we find that while the mass loss could have been significant, the planet had not changed in terms of character: it was born as a small volatile-rich planet, and it remains one at present.

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arXiv2022

TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf

We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright ($T = 8.5$ mag), high proper motion ($\sim\,200$ mas yr$^{-1}$), low metallicity ([Fe/H]$\approx\,-0.28$) K-dwarf with a mass of $0.68\pm0.05$ M$_{\odot}$ and a radius of $0.67\pm0.01$ R$_{\odot}$. We obtain photometric follow-up observations with a variety of facilities, and we use these data-sets to determine that the inner planet, TOI-836 b, is a $1.70\pm0.07$ R$_{\oplus}$ super-Earth in a 3.82 day orbit, placing it directly within the so-called 'radius valley'. The outer planet, TOI-836 c, is a $2.59\pm0.09$ R$_{\oplus}$ mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that TOI-836 b has a mass of $4.5\pm0.9$ M$_{\oplus}$ , while TOI-836 c has a mass of $9.6\pm2.6$ M$_{\oplus}$. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.

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arXiv2022

TOI-2119: A transiting brown dwarf orbiting an active M-dwarf from NASA's TESS mission

We report the discovery of TOI-2119b, a transiting brown dwarf (BD) that orbits and is completely eclipsed by an active M-dwarf star. Using light curve data from the Transiting Exoplanet Survey Satellite mission and follow-up high-resolution Doppler spectroscopic observations, we find the BD has a radius of $R_b = 1.08 \pm 0.03{\rm R_J}$, a mass of $M_b = 64.4 \pm 2.3{\rm M_J}$, an orbital period of $P = 7.200865 \pm 0.00002$ days, and an eccentricity of $e=0.337\pm 0.002$. The host star has a mass of $M_\star = 0.53 \pm 0.02{\rm M_\odot}$, a radius of $R_\star= 0.50 \pm 0.01{\rm R_\odot}$, an effective temperature of $T_{\rm eff} = 3621 \pm 48$K, and a metallicity of $\rm [Fe/H]=+0.06\pm 0.08$. TOI-2119b joins an emerging population of transiting BDs around M-dwarf host stars, with TOI-2119 being the ninth such system. These M-dwarf--brown dwarf systems typically occupy mass ratios near $q = M_b/M_\star \approx 0.1-0.2$, which separates them from the typical mass ratios for systems with transiting substellar objects and giant exoplanets that orbit more massive stars. The nature of the secondary eclipse of the BD by the star enables us to estimate the effective temperature of the substellar object to be $2030\pm 84$K, which is consistent with predictions by substellar evolutionary models.

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arXiv2022

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 ($G < 12.5$,~$T_\mathrm{eff}$ 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 $0.322\pm 0.073$ and $0.195\pm 0.030$ 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 ($e = 0.17\pm0.05$), and TOI-3693 b, a 9-day planet for which we can set an upper limit of $e < 0.052$. 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.

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