ORCID Profile
0000-0003-4976-9980
Current Organisation
American Museum of Natural History
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Publisher: American Astronomical Society
Date: 10-10-2016
Publisher: American Astronomical Society
Date: 30-05-2019
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: Oxford University Press (OUP)
Date: 04-08-2017
Publisher: American Astronomical Society
Date: 10-01-2022
Abstract: While the population of confirmed exoplanets continues to grow, the s le of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant ( M ⋆ = 1.53 ± 0.12 M ⊙ , R ⋆ = 2.90 ± 0.14 R ⊙ ) in the Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as a false positive by the TESS Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline to remove background scattered light in TESS Full Frame Image data, we combine space-based TESS photometry, ground-based photometry, and ground-based radial velocity measurements to report a planet radius of R p = 1.017 ± 0.051 R J and mass of M p = 0.65 ± 0.16 M J . For a planet so close to its star, the mass and radius of TOI-2184b are unusually well matched to those of Jupiter. We find that the radius of TOI-2184b is smaller than theoretically predicted based on its mass and incident flux, providing a valuable new constraint on the timescale of post-main-sequence planet inflation. The discovery of TOI-2184b demonstrates the feasibility of detecting planets around faint (TESS magnitude 12) post-main-sequence stars and suggests that many more similar systems are waiting to be detected in the TESS FFIs, whose confirmation may elucidate the final stages of planetary system evolution.
Publisher: American Astronomical Society
Date: 10-01-2023
Abstract: The fate of planets around rapidly evolving stars is not well understood. Previous studies have suggested that, relative to the main-sequence population, planets transiting evolved stars ( P 100 days) tend to have more eccentric orbits. Here we present the discovery of TOI-4582 b, a 0.94 − 0.12 + 0.09 R J , 0.53 ± 0.05 M J planet orbiting an intermediate-mass subgiant star every 31.034 days. We find that this planet is also on a significantly eccentric orbit ( e = 0.51 ± 0.05). We then compare the population of planets found transiting evolved (log g 3.8) stars to the population of planets transiting main-sequence stars. We find that the rate at which median orbital eccentricity grows with period is significantly higher for evolved star systems than for otherwise similar main-sequence systems. In general, we observe that mean planet eccentricity 〈 e 〉 = a + b log 10 ( P ) for the evolved population with significant orbital eccentricity where a = −0.18 ± 0.08 and b = 0.38 ± 0.06, significantly distinct from the main-sequence planetary system population. This trend is seen even after controlling for stellar mass and metallicity. These systems do not appear to represent a steady evolution pathway from eccentric, long-period planetary orbits to circular, short-period orbits, as orbital model comparisons suggest that inspiral timescales are uncorrelated with orbital separation or eccentricity. Characterization of additional evolved planetary systems will distinguish effects of stellar evolution from those of stellar mass and composition.
Publisher: American Astronomical Society
Date: 27-06-2018
Publisher: American Astronomical Society
Date: 12-2022
Abstract: We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet (1.1 R J , 5.9 M J ) orbiting an evolved host star (2.9 R ⊙ , 1.5 M ⊙ ). Using transit timing measurements from Kepler, Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate P ̇ = 131 − 22 + 20 ms yr −1 , corresponding to an infall timescale P / P ̇ ≈ 2.5 Myr . We consider other explanations for the data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed period derivative implies a tidal quality factor Q ⋆ ′ = 2.50 − 0.62 + 0.85 × 10 4 , in good agreement with theoretical predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new benchmark for understanding tidal physics at the end of the planetary life cycle.
Publisher: American Astronomical Society
Date: 27-11-2017
Publisher: American Astronomical Society
Date: 08-2021
Publisher: American Astronomical Society
Date: 23-11-2016
Publisher: American Astronomical Society
Date: 11-2022
Abstract: In this paper, we report the potential detection of a nonmonotonic radial rotation profile in a low-mass lower-luminosity giant star. For most low- and intermediate-mass stars, the rotation on the main sequence seems to be close to rigid. As these stars evolve into giants, the core contracts and the envelope expands, which should suggest a radial rotation profile with a fast core and a slower envelope and surface. KIC 9267654, however, seems to show a surface rotation rate that is faster than its bulk envelope rotation rate, in conflict with this simple angular momentum conservation argument. We improve the spectroscopic surface constraint, show that the pulsation frequencies are consistent with the previously published core and envelope rotation rates, and demonstrate that the star does not show strong chemical peculiarities. We discuss the evidence against any tidally interacting stellar companion. Finally, we discuss the possible origin of this unusual rotation profile, including the potential ingestion of a giant planet or unusual angular momentum transport by tidal inertial waves triggered by a close substellar companion, and encourage further observational and theoretical efforts.
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: 05-08-2021
Publisher: American Astronomical Society
Date: 13-11-2019
Publisher: Oxford University Press (OUP)
Date: 15-06-2023
Abstract: We report the discovery of three transiting low-mass companions to aged stars: a brown dwarf (TOI-2336b) and two objects near the hydrogen burning mass limit (TOI-1608b and TOI-2521b). These three systems were first identified using data from the Transiting Exoplanet Survey Satellite (TESS). TOI-2336b has a radius of 1.05 ± 0.04 RJ, a mass of 69.9 ± 2.3 MJ and an orbital period of 7.71 d. TOI-1608b has a radius of 1.21 ± 0.06 RJ, a mass of 90.7 ± 3.7 MJ and an orbital period of 2.47 d. TOI-2521b has a radius of 1.01 ± 0.04 RJ, a mass of 77.5 ± 3.3 MJ, and an orbital period of 5.56 d. We found all these low-mass companions are inflated. We fitted a relation between radius, mass, and incident flux using the s le of known transiting brown dwarfs and low-mass M dwarfs. We found a positive correlation between the flux and the radius for brown dwarfs and for low-mass stars that is weaker than the correlation observed for giant planets. We also found that TOI-1608 and TOI-2521 are very likely to be spin-orbit synchronized, leading to the unusually rapid rotation of the primary stars considering their evolutionary stages. Our estimates indicate that both systems have much shorter spin-orbit synchronization time-scales compared to their ages. These systems provide valuable insights into the evolution of stellar systems with brown dwarf and low-mass stellar companions influenced by tidal effects.
Publisher: American Astronomical Society
Date: 09-02-2022
Abstract: Giant planets on short-period orbits are predicted to be inflated and eventually engulfed by their host stars. However, the detailed timescales and stages of these processes are not well known. Here, we present the discovery of three hot Jupiters ( P 10 days) orbiting evolved, intermediate-mass stars ( M ⋆ ≈ 1.5 M ⊙ , 2 R ⊙ R ⋆ 5 R ⊙ ). By combining TESS photometry with ground-based photometry and radial velocity measurements, we report masses and radii for these three planets of between 0.4 and 1.8 M J and 0.8 and 1.8 R J . TOI-2337b has the shortest period ( P = 2.99432 ± 0.00008 days) of any planet discovered around a red giant star to date. Both TOI-4329b and TOI-2669b appear to be inflated, but TOI-2337b does not show any sign of inflation. The large radii and relatively low masses of TOI-4329b and TOI-2669b place them among the lowest density hot Jupiters currently known, while TOI-2337b is conversely one of the highest. All three planets have orbital eccentricities of below 0.2. The large spread in radii for these systems implies that planet inflation has a complex dependence on planet mass, radius, incident flux, and orbital properties. We predict that TOI-2337b has the shortest orbital decay timescale of any planet currently known, but do not detect any orbital decay in this system. Transmission spectroscopy of TOI-4329b would provide a favorable opportunity for the detection of water, carbon dioxide, and carbon monoxide features in the atmosphere of a planet orbiting an evolved star, and could yield new information about planet formation and atmospheric evolution.
Publisher: Oxford University Press (OUP)
Date: 18-04-2018
DOI: 10.1093/MNRAS/STY898
Location: United States of America
No related grants have been discovered for Samuel Grunblatt.