ORCID Profile
0000-0002-3725-3058
Current Organisation
University of Notre Dame
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Publisher: American Astronomical Society
Date: 10-10-2016
Publisher: American Astronomical Society
Date: 25-05-2022
Abstract: Multiplanet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf ( V = 11.6, K = 9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31, 5.90, 18.66, and 37.92 days. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97 ± 0.06 R ⊕ , 2.47 ± 0.08 R ⊕ , 3.46 ± 0.09 R ⊕ , and 3.72 ± 0.16 R ⊕ ) and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1 ± 1.1 M ⊕ , 8.8 ± 1.2 M ⊕ , 5.3 ± 1.7 M ⊕ , and 14.8 ± 2.3 M ⊕ ). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance ( P e / P d = 2.03) and exhibit transit-timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only five systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70 ± 0.24 to 3.21 ± 0.44 g cm −3 , implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 ± 3.6 M ⊕ . This planet candidate is exterior to TOI-1246 e, with a candidate period of 93.8 days, and we discuss the implications if it is confirmed to be planetary in nature.
Publisher: American Astronomical Society
Date: 02-2022
Abstract: We present spectroscopic measurements of the Rossiter–McLaughlin effect for WASP-148b, the only known hot Jupiter with a nearby warm-Jupiter companion, from the WIYN/NEID and Keck/HIRES instruments. This is one of the first scientific results reported from the newly commissioned NEID spectrograph, as well as the second obliquity constraint for a hot Jupiter system with a close-in companion, after WASP-47. WASP-148b is consistent with being in alignment with the sky-projected spin axis of the host star, with λ = − 8 .° 2 − 9 .° 7 + 8 .° 7 . The low obliquity observed in the WASP-148 system is consistent with the orderly-alignment configuration of most compact multi-planet systems around cool stars with obliquity constraints, including our solar system, and may point to an early history for these well-organized systems in which migration and accretion occurred in isolation, with relatively little disturbance. By contrast, previous results have indicated that high-mass and hot stars appear to more commonly host a wide range of misaligned planets: not only single hot Jupiters, but also compact systems with multiple super-Earths. We suggest that, to account for the high rate of spin–orbit misalignments in both compact multi-planet and isolated-hot-Jupiter systems orbiting high-mass and hot stars, spin–orbit misalignments may be caused by distant giant planet perturbers, which are most common around these stellar types.
Publisher: American Astronomical Society
Date: 15-02-2021
Abstract: We measured the Rossiter–McLaughlin effect of WASP-107b during a single transit with Keck/HIRES. We found the sky-projected inclination of WASP-107b’s orbit, relative to its host star’s rotation axis, to be degrees. This confirms the misaligned olar orbit that was previously suggested from spot-crossing events and adds WASP-107b to the growing population of hot Neptunes in polar orbits around cool stars. WASP-107b is also the fourth such planet to have a known distant planetary companion. We examined several dynamical pathways by which this companion could have induced such an obliquity in WASP-107b. We find that nodal precession and disk dispersal-driven tilting can both explain the current orbital geometry while Kozai–Lidov cycles are suppressed by general relativity. While each hypothesis requires a mutual inclination between the two planets, nodal precession requires a much larger angle, which for WASP-107 is on the threshold of detectability with future Gaia astrometric data. As nodal precession has no stellar type dependence, but disk dispersal-driven tilting does, distinguishing between these two models is best done on the population level. Finding and characterizing more extrasolar systems like WASP-107 will additionally help distinguish whether the distribution of hot-Neptune obliquities is a dichotomy of aligned and polar orbits or if we are uniformly s ling obliquities during nodal precession cycles.
Publisher: Springer Science and Business Media LLC
Date: 17-05-2023
Publisher: American Astronomical Society
Date: 05-01-2023
Abstract: Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMRs). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700 ± 150 Myr old G star hosting at least six transiting planets between ∼2 and 5 R ⊕ . The orbital period ratios deviate from exact commensurability by only 10 −4 , smaller than the ∼10 −2 deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3–8 M ⊕ ) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter–McLaughlin measurement of planet d, the star’s rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of a detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar flyby, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMRs. The formation of the delicate 7:5 resonance places strong constraints on the system’s migration history. Short-scale (starting from ∼0.1 au) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density (Σ 1 au ≲ 10 3 g cm −2 lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR.
Publisher: Oxford University Press (OUP)
Date: 16-12-2022
Abstract: We report the discovery and confirmation of the planetary system TOI-1288. This late G dwarf harbours two planets: TOI-1288 b and TOI-1288 c. We combine TESS space-borne and ground-based transit photometry with HARPS-N and HIRES high-precision Doppler measurements, which we use to constrain the masses of both planets in the system and the radius of planet b. TOI-1288 b has a period of $2.699835^{+0.000004}_{-0.000003}$ d, a radius of 5.24 ± 0.09 R⊕, and a mass of 42 ± 3 M⊕, making this planet a hot transiting super-Neptune situated right in the Neptunian desert. This desert refers to a paucity of Neptune-sized planets on short period orbits. Our 2.4-yr-long Doppler monitoring of TOI-1288 revealed the presence of a Saturn–mass planet on a moderately eccentric orbit ($0.13^{+0.07}_{-0.09}$) with a minimum mass of 84 ± 7 M⊕ and a period of $443^{+11}_{-13}$ d. The five sectors worth of TESS data do not cover our expected mid-transit time for TOI-1288 c, and we do not detect a transit for this planet in these sectors.
Publisher: American Astronomical Society
Date: 31-01-2022
Abstract: Exoplanet systems with multiple transiting planets are natural laboratories for testing planetary astrophysics. One such system is HD 191939 (TOI 1339), a bright ( V = 9) and Sun-like (G9V) star, which TESS found to host three transiting planets (b, c, and d). The planets have periods of 9, 29, and 38 days each with similar sizes from 3 to 3.4 R ⊕ . To further characterize the system, we measured the radial velocity (RV) of HD 191939 over 415 days with Keck/HIRES and APF/Levy. We find that M b = 10.4 ± 0.9 M ⊕ and M c = 7.2 ± 1.4 M ⊕ , which are low compared to most known planets of comparable radii. The RVs yield only an upper limit on M d ( .8 M ⊕ at 2 σ ). The RVs further reveal a fourth planet (e) with a minimum mass of 0.34 ± 0.01 M Jup and an orbital period of 101.4 ± 0.4 days. Despite its nontransiting geometry, secular interactions between planet e and the inner transiting planets indicate that planet e is coplanar with the transiting planets (Δ i 10°). We identify a second high-mass planet (f) with 95% confidence intervals on mass between 2 and 11 M Jup and period between 1700 and 7200 days, based on a joint analysis of RVs and astrometry from Gaia and Hipparcos. As a bright star hosting multiple planets with well-measured masses, HD 191939 presents many options for comparative planetary astronomy, including characterization with JWST.
Publisher: Springer Science and Business Media LLC
Date: 28-06-2023
Publisher: American Astronomical Society
Date: 04-05-2022
Abstract: The alignment of planetary orbits with respect to the stellar rotation preserves information on their dynamical histories. Measuring this angle for young planets helps illuminate the mechanisms that create misaligned orbits for older planets, as different processes could operate over timescales ranging from a few megayears to a gigayear. We present spectroscopic transit observations of the young exoplanet V1298 Tau b we update the age of V1298 Tau to be 28 ± 4 Myr based on Gaia EDR3 measurements. We observed a partial transit with Keck/HIRES and LBT/PEPSI, and detected the radial velocity anomaly due to the Rossiter–McLaughlin effect. V1298 Tau b has a prograde, well-aligned orbit, with λ = 4 − 10 + 7 deg. By combining the spectroscopically measured v sin i ⋆ and the photometrically measured rotation period of the host star we also find that the orbit is aligned in 3D, ψ = 8 − 7 + 4 deg. Finally, we combine our obliquity constraints with a previous measurement for the interior planet V1298 Tau c to constrain the mutual inclination between the two planets to be i mut = 0° ± 19°. This measurements adds to the growing number of well-aligned planets at young ages, hinting that misalignments may be generated over timescales of longer than tens of megayears. The number of measurements, however, is still small, and this population may not be representative of the older planets that have been observed to date. We also present the derivation of the relationship between i mut , λ , and i for the two planets.
Publisher: American Astronomical Society
Date: 26-05-2010
Publisher: American Astronomical Society
Date: 14-08-2020
Publisher: EDP Sciences
Date: 12-2020
DOI: 10.1051/0004-6361/202038016
Abstract: We report the discovery of a Neptune-like planet (LP 714-47 b, P = 4.05204 d, m b = 30.8 ± 1.5 M ⊕ , R b = 4.7 ± 0.3 R ⊕ ) located in the “hot Neptune desert”. Confirmation of the TESS Object of Interest (TOI 442.01) was achieved with radial-velocity follow-up using CARMENES, ESPRESSO, HIRES, iSHELL, and PFS, as well as from photometric data using TESS, Spitzer , and ground-based photometry from MuSCAT2, TRAPPIST-South, MONET-South, the George Mason University telescope, the Las Cumbres Observatory Global Telescope network, the El Sauce telescope, the TÜBİTAK National Observatory, the University of Louisville Manner Telescope, and WASP-South. We also present high-spatial resolution adaptive optics imaging with the Gemini Near-Infrared Imager. The low uncertainties in the mass and radius determination place LP 714-47 b among physically well-characterised planets, allowing for a meaningful comparison with planet structure models. The host star LP 714-47 is a slowly rotating early M dwarf ( T eff = 3950 ± 51 K) with a mass of 0.59 ± 0.02 M ⊙ and a radius of 0.58 ± 0.02 R ⊙ . From long-term photometric monitoring and spectroscopic activity indicators, we determine a stellar rotation period of about 33 d. The stellar activity is also manifested as correlated noise in the radial-velocity data. In the power spectrum of the radial-velocity data, we detect a second signal with a period of 16 days in addition to the four-day signal of the planet. This could be shown to be a harmonic of the stellar rotation period or the signal of a second planet. It may be possible to tell the difference once more TESS data and radial-velocity data are obtained.
Publisher: American Astronomical Society
Date: 12-08-2020
Publisher: American Astronomical Society
Date: 27-11-2017
Publisher: American Astronomical Society
Date: 08-09-2023
Publisher: SAGE Publications
Date: 08-10-2020
Abstract: This article builds on Games of Empire by centering the experiences of ersity workers in Game Studies of Empire. Our data were gathered through qualitative mixed methods of in-depth surveys and semi-structured interviews. Participants self-identified to be included in the study, all thinking critically through the definitions of “ ersity,” “ ersity work(er),” and “game studies.” Thus, this study reports on a tapestry of knowledge and experiences from the various educators and advocates of ersity across academia and the games industry. Diversity workers in Game Studies of Empire are often exploited by their affective attachment to ersity and perform significant unrecognized and uncompensated affective labor. Empire uses ersity workers to produce a quantifiable and tokenizable product of bodies and lived experiences that can be used to further profits for companies, universities, and other institutions. Diversity work(ers) against Game Studies of Empire unite! We will have nothing to lose when we become unchained.
Publisher: American Astronomical Society
Date: 26-10-2021
Publisher: American Astronomical Society
Date: 25-02-2020
Publisher: American Astronomical Society
Date: 31-12-2020
Abstract: HD 106315 and GJ 9827 are two bright, nearby stars that host multiple super-Earths and sub-Neptunes discovered by K2 that are well suited for atmospheric characterization. We refined the planets’ ephemerides through Spitzer transits, enabling accurate transit prediction required for future atmospheric characterization through transmission spectroscopy. Through a multiyear high-cadence observing c aign with Keck/High Resolution Echelle Spectrometer and Magellan/Planet Finder Spectrograph, we improved the planets’ mass measurements in anticipation of Hubble Space Telescope transmission spectroscopy. For GJ 9827, we modeled activity-induced radial velocity signals with a Gaussian process informed by the Calcium II H& K lines in order to more accurately model the effect of stellar noise on our data. We measured planet masses of M b = 4.87 ± 0.37 M ⊕ , M c = 1.92 ± 0.49 M ⊕ , and M d = 3.42 ± 0.62 M ⊕ . For HD 106315, we found that such activity radial velocity decorrelation was not effective due to the reduced presence of spots and speculate that this may extend to other hot stars as well ( T eff 6200 K). We measured planet masses of M b = 10.5 ± 3.1 M ⊕ and M c = 12.0 ± 3.8 M ⊕ . We investigated all of the planets’ compositions through comparison of their masses and radii to a range of interior models. GJ 9827 b and GJ 9827 c are both consistent with a 50/50 rock-iron composition, GJ 9827 d and HD 106315 b both require additional volatiles and are consistent with moderate amounts of water or hydrogen/helium, and HD 106315 c is consistent with a ∼10% hydrogen/helium envelope surrounding an Earth-like rock and iron core.
Publisher: American Astronomical Society
Date: 30-05-2022
Abstract: The Kepler and TESS missions have demonstrated that planets are ubiquitous. However, the success of these missions heavily depends on ground-based radial velocity (RV) surveys, which combined with transit photometry can yield bulk densities and orbital properties. While most Kepler host stars are too faint for detailed follow-up observations, TESS is detecting planets orbiting nearby bright stars that are more amenable to RV characterization. Here, we introduce the TESS-Keck Survey (TKS), an RV program using ∼100 nights on Keck/HIRES to study exoplanets identified by TESS. The primary survey aims are investigating the link between stellar properties and the compositions of small planets studying how the ersity of system architectures depends on dynamical configurations or planet multiplicity identifying prime candidates for atmospheric studies with JWST and understanding the role of stellar evolution in shaping planetary systems. We present a fully automated target selection algorithm, which yielded 103 planets in 86 systems for the final TKS s le. Most TKS hosts are inactive, solar-like, main-sequence stars (4500 K ≤ T eff K) at a wide range of metallicities. The selected TKS s le contains 71 small planets ( R p ≤ 4 R ⊕ ), 11 systems with multiple transiting candidates, six sub-day-period planets and three planets that are in or near the habitable zone ( S inc ≤ 10 S ⊕ ) of their host star. The target selection described here will facilitate the comparison of measured planet masses, densities, and eccentricities to predictions from planet population models. Our target selection software is publicly available and can be adapted for any survey that requires a balance of multiple science interests within a given telescope allocation.
Publisher: American Astronomical Society
Date: 06-09-2022
Abstract: We present a transmission spectrum for the Neptune-sized exoplanet HD 106315c from optical to infrared wavelengths based on transit observations from the Hubble Space Telescope/Wide Field Camera 3, K2, and Spitzer. The spectrum shows tentative evidence for a water absorption feature in the 1.1–1.7 μ m wavelength range with a small litude of 30 ppm (corresponding to just 0.8 ± 0.04 atmospheric scale heights). Based on an atmospheric retrieval analysis, the presence of water vapor is tentatively favored with a Bayes factor of 1.7–2.6 (depending on prior assumptions). The spectrum is most consistent with either an enhanced metallicity or high-altitude condensates, or both. Cloud-free solar composition atmospheres are ruled out at σ confidence. We compare the spectrum to grids of cloudy and hazy forward models and find that the spectrum is fit well by models with moderate cloud lofting or haze formation efficiency over a wide range of metallicities (1–100× solar). We combine the constraints on the envelope composition with an interior structure model and estimate that the core mass fraction is ≳0.3. With a bulk composition reminiscent of that of Neptune and an orbital distance of 0.15 au, HD 106315c hints that planets may form out of broadly similar material and arrive at vastly different orbits later in their evolution.
Publisher: American Astronomical Society
Date: 16-07-2021
Abstract: We report the discovery of TOI-1444b, a 1.4 R ⊕ super-Earth on a 0.47 day orbit around a Sun-like star discovered by TESS. Precise radial velocities from Keck/HIRES confirmed the planet and constrained the mass to be 3.87 ± 0.71 M ⊕ . The RV data set also indicates a possible nontransiting, 16 day planet (11.8 ± 2.9 M ⊕ ). We report a tentative detection of phase-curve variation and a secondary eclipse of TOI-1444b in the TESS bandpass. TOI-1444b joins the growing s le of 17 ultra-short-period planets (USPs) with well-measured masses and sizes, most of which are compatible with an Earth-like composition. We take this opportunity to examine the expanding s le of ultra-short-period planets ( R ⊕ ) and contrast them with the newly discovered sub-day ultrahot Neptunes ( R ⊕ , F ⊕ TOI-849 b, LTT9779 b, and K2-100). We find that (1) USPs have predominately Earth-like compositions with inferred iron core mass fractions of 0.32 ± 0.04 and have masses below the threshold of runaway accretion (∼10 M ⊕ ), while ultrahot Neptunes are above the threshold and have H/He or other volatile envelopes. (2) USPs are almost always found in multi-planet systems consistent with a secular interaction formation scenario ultrahot Neptunes ( P orb ≲1 day) tend to be “lonely,” similar to longer-period hot Neptunes ( P orb 1–10 days) and hot Jupiters. (3) USPs occur around solar-metallicity stars while hot Neptunes prefer higher metallicity hosts. (4) In all these respects, ultrahot Neptunes show more resemblance to hot Jupiters than the smaller USP planets, although ultrahot Neptunes are rarer than both USPs and hot Jupiters by 1–2 orders of magnitude.
Publisher: American Astronomical Society
Date: 07-12-2022
Abstract: We validate the presence of a two-planet system orbiting the 0.15–1.4 Gyr K4 dwarf TOI 560 (HD 73583). The system consists of an inner moderately eccentric transiting mini-Neptune (TOI 560 b, P = 6.3980661 − 0.0000097 + 0.0000095 days, e = 0.294 − 0.062 + 0.13 , M = 0.94 − 0.23 + 0.31 M Nep ) initially discovered in the Sector 8 Transiting Exoplanet Survey Satellite (TESS) mission observations, and a transiting mini-Neptune (TOI 560 c, P = 18.8805 − 0.0011 + 0.0024 days, M = 1.32 − 0.32 + 0.29 M Nep ) discovered in the Sector 34 observations, in a rare near-1:3 orbital resonance. We utilize photometric data from TESS Spitzer, and ground-based follow-up observations to confirm the ephemerides and period of the transiting planets, vet false-positive scenarios, and detect the photoeccentric effect for TOI 560 b. We obtain follow-up spectroscopy and corresponding precise radial velocities (RVs) with the iSHELL spectrograph at the NASA Infrared Telescope Facility and the HIRES Spectrograph at Keck Observatory to validate the planetary nature of these signals, which we combine with published Planet Finder Spectrograph RVs from the Magellan Observatory. We detect the masses of both planets at σ significance. We apply a Gaussian process (GP) model to the TESS light curves to place priors on a chromatic RV GP model to constrain the stellar activity of the TOI 560 host star, and confirm a strong wavelength dependence for the stellar activity demonstrating the ability of near-IR RVs to mitigate stellar activity for young K dwarfs. TOI 560 is a nearby moderately young multiplanet system with two planets suitable for atmospheric characterization with the James Webb Space Telescope and other upcoming missions. In particular, it will undergo six transit pairs separated by hr before 2027 June.
Publisher: American Astronomical Society
Date: 29-04-2020
Publisher: American Astronomical Society
Date: 09-05-2022
Abstract: The NASA K2 mission, salvaged from the hardware failures of the Kepler telescope, has continued Kepler’s planet-hunting success. It has revealed nearly 500 transiting planets around the ecliptic plane, many of which are the subject of further study, and over 1000 additional candidates. Here we present the results of an ongoing project to follow-up and statistically validate new K2 planets, in particular to identify promising new targets for further characterization. By analyzing the reconnaissance spectra, high-resolution imaging, centroid variations, and statistical likelihood of the signals of 91 candidates, we validate 60 new planets in 46 systems. These include a number of planets amenable to transmission spectroscopy (K2-384 f, K2-387 b, K2-390 b, K2-403 b, and K2-398 c), emission spectroscopy (K2-371 b, K2-370 b, and K2-399 b), and both (K2-405 b and K2-406 b) several systems with planets in or close to mean motion resonances (K2-381 and K2-398) including a compact, TRAPPIST-1-like system of five small planets orbiting a mid-M dwarf (K2-384) an ultra-short-period sub-Saturn in the hot Saturn desert (K2-399 b) and a super-Earth orbiting a moderately bright ( V = 11.93), metal-poor ([Fe/H] = −0.579 ± 0.080) host star (K2-408 b). In total we validate planets around four F stars, 26 G stars, 13 K stars, and three M dwarfs. In addition, we provide a list of 37 vetted planet candidates that should be prioritized for future follow-up observation in order to be confirmed or validated.
Publisher: American Astronomical Society
Date: 30-05-2019
Publisher: American Astronomical Society
Date: 19-01-2023
Abstract: We present the Distant Giants Survey, a three-year radial velocity c aign to measure P(DG∣CS), the conditional occurrence of distant giant planets (DG M p ∼ 0.3–13 M J , P 1 yr) in systems hosting a close-in small planet (CS R p 10 R ⊕ ). For the past two years, we have monitored 47 Sun-like stars hosting small transiting planets detected by TESS. We present the selection criteria used to assemble our s le and report the discovery of two distant giant planets, TOI-1669 b and TOI-1694 c. For TOI-1669 b we find that M sin i = 0.573 ± 0.074 M J , P = 502 ± 16 days, and e 0.27, while for TOI-1694 c, M sin i = 1.05 ± 0.05 M J , P = 389.2 ± 3.9 days, and e = 0.18 ± 0.05. We also confirmed the 3.8 days transiting planet TOI-1694 b by measuring a true mass of M = 26.1 ± 2.2 M ⊕ . At the end of the Distant Giants Survey, we will incorporate TOI-1669 b and TOI-1694 c into our calculation of P(DG∣CS), a crucial statistic for understanding the relationship between outer giants and small inner companions.
Publisher: EDP Sciences
Date: 02-2022
DOI: 10.1051/0004-6361/202141429
Abstract: We present the discovery and characterization of a transiting sub-Neptune that orbits the nearby (28 pc) and bright ( V = 8.37) K0V star HD 207897 (TOI-1611) with a 16.20-day period. This discovery is based on photometric measurements from the Transiting Exoplanet Survey Satellite mission and radial velocity (RV) observations from the SOPHIE, Automated Planet Finder, and HIRES high-precision spectrographs. We used EXOFASTv2 to model the parameters of the planet and its host star simultaneously, combining photometric and RV data to determine the planetary system parameters. We show that the planet has a radius of 2.50 ± 0.08 R E and a mass of either 14.4 ± 1.6 M E or 15.9 ± 1.6 M E with nearly equal probability. The two solutions correspond to two possibilities for the stellar activity period. The density accordingly is either 5.1 ± 0.7 g cm −3 or 5.5 −0.7 +0.8 g cm −3 , making it one of the relatively rare dense sub-Neptunes. The existence of this dense planet at only 0.12 AU from its host star is unusual in the currently observed sub-Neptune (2 R E 4) population. The most likely scenario is that this planet has migrated to its current position.
Publisher: American Astronomical Society
Date: 14-03-2022
Abstract: LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 pc. The primary star LTT 1445A (0.257 M ⊙ ) is known to host the transiting planet LTT 1445Ab with an orbital period of 5.36 days, making it the second-closest known transiting exoplanet system, and the closest one for which the host is an M dwarf. Using Transiting Exoplanet Survey Satellite data, we present the discovery of a second planet in the LTT 1445 system, with an orbital period of 3.12 days. We combine radial-velocity measurements obtained from the five spectrographs, Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, High Accuracy Radial Velocity Planet Searcher, High-Resolution Echelle Spectrometer, MAROON-X, and Planet Finder Spectrograph to establish that the new world also orbits LTT 1445A. We determine the mass and radius of LTT 1445Ab to be 2.87 ± 0.25 M ⊕ and 1.304 − 0.060 + 0.067 R ⊕ , consistent with an Earth-like composition. For the newly discovered LTT 1445Ac, we measure a mass of 1.54 − 0.19 + 0.20 M ⊕ and a minimum radius of 1.15 R ⊕ , but we cannot determine the radius directly as the signal-to-noise ratio of our light curve permits both grazing and nongrazing configurations. Using MEarth photometry and ground-based spectroscopy, we establish that star C (0.161 M ⊙ ) is likely the source of the 1.4 day rotation period, and star B (0.215 M ⊙ ) has a likely rotation period of 6.7 days. We estimate a probable rotation period of 85 days for LTT 1445A. Thus, this triple M-dwarf system appears to be in a special evolutionary stage where the most massive M dwarf has spun down, the intermediate mass M dwarf is in the process of spinning down, while the least massive stellar component has not yet begun to spin down.
Publisher: American Astronomical Society
Date: 12-08-2022
Abstract: We report the discovery of an eccentric hot Neptune and a non-transiting outer planet around TOI-1272. We identified the eccentricity of the inner planet, with an orbital period of 3.3 days and R p,b = 4.1 ± 0.2 R ⊕ , based on a mismatch between the observed transit duration and the expected duration for a circular orbit. Using ground-based radial velocity (RV) measurements from the HIRES instrument at the Keck Observatory, we measured the mass of TOI-1272b to be M p,b = 25 ± 2 M ⊕ . We also confirmed a high eccentricity of e b = 0.34 ± 0.06, placing TOI-1272b among the most eccentric well-characterized sub-Jovians. We used these RV measurements to also identify a non-transiting outer companion on an 8.7 day orbit with a similar mass of M p,c sin i = 27 ± 3 M ⊕ and e c ≲ 0.35. Dynamically stable planet–planet interactions have likely allowed TOI-1272b to avoid tidal eccentricity decay despite the short circularization timescale expected for a close-in eccentric Neptune. TOI-1272b also maintains an envelope mass fraction of f env ≈ 11% despite its high equilibrium temperature, implying that it may currently be undergoing photoevaporation. This planet joins a small population of short-period Neptune-like planets within the “Hot Neptune Desert” with a poorly understood formation pathway.
Publisher: American Astronomical Society
Date: 13-02-2023
Abstract: NASA’s Transiting Exoplanet Survey Satellite (TESS) mission promises to improve our understanding of hot Jupiters by providing an all-sky, magnitude-limited s le of transiting hot Jupiters suitable for population studies. Assembling such a s le requires confirming hundreds of planet candidates with additional follow-up observations. Here we present 20 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. These 20 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-3976b, the longest-period planet in our s le ( P = 6.6 days), may be on a moderately eccentric orbit ( e = 0.18 ± 0.06), 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 hr orbit with the Rossiter–McLaughlin effect, finding the planet’s orbit to be well aligned with the stellar spin axis (∣ λ ∣ = 4.°0 ± 3.°5). 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 s le of hot Jupiters to be used for future demographic and detailed characterization work.
Publisher: American Astronomical Society
Date: 26-11-2021
Abstract: We report the discovery of HIP-97166b (TOI-1255b), a transiting sub-Neptune on a 10.3 day orbit around a K0 dwarf 68 pc from Earth. This planet was identified in a systematic search of TESS Objects of Interest for planets with eccentric orbits, based on a mismatch between the observed transit duration and the expected duration for a circular orbit. We confirmed the planetary nature of HIP-97166b with ground-based radial-velocity measurements and measured a mass of M b = 20 ± 2 M ⊕ along with a radius of R b = 2.7 ± 0.1 R ⊕ from photometry. We detected an additional nontransiting planetary companion with M c sin i = 10 ± 2 M ⊕ on a 16.8 day orbit. While the short transit duration of the inner planet initially suggested a high eccentricity, a joint RV-photometry analysis revealed a high impact parameter b = 0.84 ± 0.03 and a moderate eccentricity. Modeling the dynamics with the condition that the system remain stable over 5 orbits yielded eccentricity constraints e b = 0.16 ± 0.03 and e c 0.25. The eccentricity we find for planet b is above average for the small population of sub-Neptunes with well-measured eccentricities. We explored the plausible formation pathways of this system, proposing an early instability and merger event to explain the high density of the inner planet at 5.3 ± 0.9 g cc −1 as well as its moderate eccentricity and proximity to a 5:3 mean-motion resonance.
Publisher: American Astronomical Society
Date: 29-04-2020
Publisher: American Astronomical Society
Date: 30-09-2020
Publisher: American Astronomical Society
Date: 13-01-2022
Abstract: We report the discovery of TOI-2180 b, a 2.8 M J giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring c aign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8 ± 0.6 days, revealed an orbital eccentricity of 0.368 ± 0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method.
Publisher: American Astronomical Society
Date: 03-01-2019
Publisher: American Astronomical Society
Date: 10-12-2019
Publisher: Wiley
Date: 03-01-2023
DOI: 10.1111/IJFS.16269
Abstract: Adipogenesis is a complex physiological process involving the formation of adipocytes and accumulation as adipose tissues. It is one of the contributors for the development of obesity. This study assessed the potential of phenolic extracts and potassium hydroxycitrate, obtained from Hibiscus sabdariffa , to inhibit adipogenesis. The phenolic extracts were obtained using organic solvents (methanol, ethanol and ethyl acetate) and water in idually. Human adipose‐derived stem cells (hADSCs) were selected to study the impact of these extracts on adipogenesis. Results showed that phenolic extracts were able to reduce lipid accumulation by about 95% in hADSCs, while potassium hydroxycitrate did not show any reduction. All the phenolic extracts downregulated the gene expression of two key adipogenic markers (PPAR‐γ and aP2). Ethanol extracts exhibited the highest downregulation of PPAR‐γ and aP2 by 3 and 10 times, respectively. There was no improvement in the anti‐adipogenic potential when the phenolic extract was combined with potassium hydroxycitrate confirming that phenolic compounds were responsible for the inhibition of adipogenesis. These results indicate that phenolic extracts from H. sabdariffa have potential to regulate the expression of adipogenic genes and restrict the lipid accumulation in mature adipocytes. Thus, phenolic extracts can be used in formulations intended to manage obesity.
Publisher: American Astronomical Society
Date: 22-12-2020
Abstract: We present the occurrence rates for rocky planets in the habitable zones (HZs) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define η ⊕ as the HZ occurrence of planets with radii between 0.5 and 1.5 R ⊕ orbiting stars with effective temperatures between 4800 and 6300 K. We find that η ⊕ for the conservative HZ is between (errors reflect 68% credible intervals) and planets per star, while the optimistic HZ occurrence is between and planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates between using Poisson likelihood Bayesian analysis and using Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is ∼6 pc away and there are ∼4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun.
Publisher: American Astronomical Society
Date: 11-01-2021
Abstract: We report the discovery of TOI-561, a multiplanet system in the galactic thick disk that contains a rocky, ultra-short-period planet. This bright ( V = 10.2) star hosts three small transiting planets identified in photometry from the NASA TESS mission: TOI-561 b (TOI-561.02, P = 0.44 days, R p = 1.45 ± 0.11 R ⊕ ), c (TOI-561.01, P = 10.8 days, R p = 2.90 ± 0.13 R ⊕ ), and d (TOI-561.03, P = 16.3 days, R p = 2.32 ± 0.16 R ⊕ ). The star is chemically ([Fe/H] = −0.41 ± 0.05, [ α /Fe] = +0.23 ± 0.05) and kinematically consistent with the galactic thick-disk population, making TOI-561 one of the oldest (10 ± 3 Gyr) and most metal-poor planetary systems discovered yet. We dynamically confirm planets b and c with radial velocities from the W. M. Keck Observatory High Resolution Echelle Spectrometer. Planet b has a mass and density of 3.2 ± 0.8 M ⊕ and g cm −3 , consistent with a rocky composition. Its lower-than-average density is consistent with an iron-poor composition, although an Earth-like iron-to-silicates ratio is not ruled out. Planet c is 7.0 ± 2.3 M ⊕ and 1.6 ± 0.6 g cm −3 , consistent with an interior rocky core overlaid with a low-mass volatile envelope. Several attributes of the photometry for planet d (which we did not detect dynamically) complicate the analysis, but we vet the planet with high-contrast imaging, ground-based photometric follow-up, and radial velocities. TOI-561 b is the first rocky world around a galactic thick-disk star confirmed with radial velocities and one of the best rocky planets for thermal emission studies.
Publisher: American Astronomical Society
Date: 27-01-2023
Abstract: Radial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the solar system. Kepler-102, which consists of five tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using RVs. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and Telescopio Nazionale Galileo/HARPS-N and modeled Kepler-102's activity using quasiperiodic Gaussian process regression. For Kepler-102d, we report a mass upper limit M d 5.3 M ⊕ (95% confidence), a best-fit mass M d = 2.5 ± 1.4 M ⊕ , and a density ρ d = 5.6 ± 3.2 g cm −3 , which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a mass M e = 4.7 ± 1.7 M ⊕ and a density ρ e = 1.8 ± 0.7 g cm −3 . These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2%–4% of the planet mass and 16%–50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors.
Publisher: American Astronomical Society
Date: 05-08-2021
Publisher: American Astronomical Society
Date: 07-02-2023
Abstract: TOI-561 is a galactic thick-disk star hosting an ultra-short-period (0.45-day-orbit) planet with a radius of 1.37 R ⊕ , making it one of the most metal-poor ([Fe/H] = −0.41) and oldest (≈10 Gyr) sites where an Earth-sized planet has been found. We present new simultaneous radial velocity (RV) measurements from Gemini-N/MAROON-X and Keck/HIRES, which we combined with literature RVs to derive a mass of M b = 2.24 ± 0.20 M ⊕ . We also used two new sectors of TESS photometry to improve the radius determination, finding R b = 1.37 ± 0.04 R ⊕ and confirming that TOI-561 b is one of the lowest-density super-Earths measured to date ( ρ b = 4.8 ± 0.5 g cm −3 ). This density is consistent with an iron-poor rocky composition reflective of the host star’s iron and rock-building element abundances however, it is also consistent with a low-density planet with a volatile envelope. The equilibrium temperature of the planet (∼2300 K) suggests that this envelope would likely be composed of high mean molecular weight species, such as water vapor, carbon dioxide, or silicate vapor, and is likely not primordial. We also demonstrate that the composition determination is sensitive to the choice of stellar parameters and that further measurements are needed to determine whether TOI-561 b is a bare rocky planet, a rocky planet with an optically thin atmosphere, or a rare ex le of a nonprimordial envelope on a planet with a radius smaller than 1.5 R ⊕ .
Publisher: American Astronomical Society
Date: 27-06-2023
Abstract: We present the stellar and planetary properties for 85 TESS Objects of Interest (TOIs) hosting 108 planet candidates that compose the TESS-Keck Survey (TKS) s le. We combine photometry, high-resolution spectroscopy, and Gaia parallaxes to measure precise and accurate stellar properties. We then use these parameters as inputs to a light-curve processing pipeline to recover planetary signals and homogeneously fit their transit properties. Among these transit fits, we detect significant transit-timing variations among at least three multiplanet systems (TOI-1136, TOI-1246, TOI-1339) and at least one single-planet system (TOI-1279). We also reduce the uncertainties on planet-to-star radius ratios R p / R ⋆ across our s le, from a median fractional uncertainty of 8.8% among the original TOI Catalog values to 3.0% among our updated results. With this improvement, we are able to recover the Radius Gap among small TKS planets and find that the topology of the Radius Gap among our s le is broadly consistent with that measured among Kepler planets. The stellar and planetary properties presented here will facilitate follow-up investigations of both in idual TOIs and broader trends in planet properties, system dynamics, and the evolution of planetary systems.
Publisher: American Astronomical Society
Date: 19-05-2017
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Lauren Weiss.