ORCID Profile
0000-0002-5034-9476
Current Organisation
University of California, Irvine
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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: 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: American Astronomical Society
Date: 30-08-2022
Abstract: We detail the follow-up and characterization of a transiting exo-Venus identified by TESS, GJ 3929b (TOI-2013b), and its nontransiting companion planet, GJ 3929c (TOI-2013c). GJ 3929b is an Earth-sized exoplanet in its star’s Venus zone ( P b = 2.616272 ± 0.000005 days S b = 17.3 − 0.7 + 0.8 S ⊕ ) orbiting a nearby M dwarf. GJ 3929c is most likely a nontransiting sub-Neptune. Using the new, ultraprecise NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak National Observatory, we are able to modify the mass constraints of planet b reported in previous works and consequently improve the significance of the mass measurement to almost 4 σ confidence ( M b = 1.75 ± 0.45 M ⊕ ). We further adjust the orbital period of planet c from its alias at 14.30 ± 0.03 days to the likely true period of 15.04 ± 0.03 days, and we adjust its minimum mass to m sin i = 5.71 ± 0.92 M ⊕ . Using the diffuser-assisted ARCTIC imager on the ARC 3.5 m telescope at Apache Point Observatory, in addition to publicly available TESS and LCOGT photometry, we are able to constrain the radius of planet b to R p = 1.09 ± 0.04 R ⊕ . GJ 3929b is a top candidate for transmission spectroscopy in its size regime (TSM = 14 ± 4), and future atmospheric studies of GJ 3929b stand to shed light on the nature of small planets orbiting M dwarfs.
Publisher: American Astronomical Society
Date: 23-05-2022
Abstract: We present the validation of two planets orbiting M dwarfs, TOI-1696b and TOI-2136b. Both planets are mini-Neptunes orbiting nearby stars, making them promising prospects for atmospheric characterization with the James Webb Space Telescope (JWST). We validated the planetary nature of both candidates using high-contrast imaging, ground-based photometry, and near-infrared radial velocities. Adaptive optics images were taken using the ShARCS camera on the 3 m Shane Telescope. Speckle images were taken using the NN-Explore Exoplanet Stellar Speckle Imager on the WIYN 3.5 m telescope. Radii and orbital ephemerides were refined using a combination of the Transiting Exoplanet Survey Satellite, the diffuser-assisted Astrophysical Research Consortium (ARC) Telescope Imaging Camera (ARCTIC) imager on the 3.5 m ARC telescope at Apache Point Observatory, and the 0.6 m telescope at Red Buttes Observatory. We obtained radial velocities using the Habitable-Zone Planet Finder on the 10 m Hobby–Eberly Telescope, which enabled us to place upper limits on the masses of both transiting planets. TOI-1696b ( P = 2.5 days R p = 3.24 R ⊕ M p 56.6 M ⊕ ) falls into a sparsely populated region of parameter space considering its host star’s temperature ( T eff = 3168 K, M4.5), as planets of its size are quite rare around mid- to late-M dwarfs. On the other hand, TOI-2136b ( P = 7.85 days R p = 2.09 R ⊕ M p 15.0 M ⊕ ) is an excellent candidate for atmospheric follow-up with the JWST.
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: 08-09-2023
Publisher: American Astronomical Society
Date: 09-07-2020
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: 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: 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: 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.
No related grants have been discovered for Rae Holcomb.