ORCID Profile
0000-0003-1286-5231
Current Organisation
Space Telescope Science Institute
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Publisher: Oxford University Press (OUP)
Date: 05-11-2019
Abstract: The past two decades have seen dramatic progress in our knowledge of the population of young stars of age $\\lt \\!200\\,$ Myr that lie within $150\\,$ pc of the Sun. These nearby, young stars, most of which are found in loose, comoving groups, provide the opportunity to explore (among many other things) the dissolution of stellar clusters and their diffusion into the field star population. Here, we exploit the combination of astrometric and photometric data from Gaia and photometric data from GALEX (UV) and 2MASS (near-IR) in an attempt to identify additional nearby, young, late-type stars. Specifically, we present a s le of 146 GALEX UV-selected late-type (predominantly K-type) field stars with Gaia-based distances $\\lt \\!125\\,$ pc (based on Gaia Data Release 1) that have isochronal ages $\\lt \\!80\\,$ Myr even if equal-components binaries. We investigate the spectroscopic and kinematic properties of this s le. Despite their young isochronal ages, only ∼10 per cent of stars among this s le can be confidently associated with established nearby, young moving groups (MGs). These candidate MG members include five stars newly identified in this study. The vast majority of our s le of 146 nearby young star candidates have anomalous kinematics relative to the known MGs. These stars may hence represent a previously unrecognized population of young stars that has recently mixed into the older field star population. We discuss the implications and caveats of such a hypothesis – including the intriguing fact that, in addition to their non-young-star-like kinematics, the majority of the UV-selected, isochronally young field stars within $50\\,$ pc appear surprisingly X-ray faint.
Publisher: IOP Publishing
Date: 09-2021
Publisher: Oxford University Press (OUP)
Date: 18-10-2014
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: 21-08-2013
Publisher: EDP Sciences
Date: 07-2010
Publisher: American Astronomical Society
Date: 08-2022
Abstract: We report the discovery in TESS data and validation of HD 56414 b (a.k.a. TOI-1228 b), a Neptune-size ( R p = 3.71 ± 0.20 R ⊕ ) planet with a 29 day orbital period transiting a young (age = 420 ± 140 Myr) A-type star in the TESS southern continuous-viewing zone. HD 56414 is one of the hottest stars ( T eff = 8500 ± 150 K) to host a known sub-Jovian planet. HD 56414 b lies on the boundary of the hot Neptune desert in the planet radius–bolometric insolation flux space, suggesting that the planet may be experiencing mass loss. To explore this, we apply a photoevaporation model that incorporates the high near-ultraviolet continuum emission of A-type stars. We find that the planet can retain most of its atmosphere over the typical 1 Gyr main-sequence lifetime of an A-type star if its mass is ≥8 M ⊕ . Our model also predicts that close-in Neptune-size planets with masses M ⊕ are susceptible to total atmospheric stripping over 1 Gyr, hinting that the hot Neptune desert, which has been previously observed around FGKM-type stars, likely extends to A-type stars.
Publisher: American Astronomical Society
Date: 22-02-2023
Abstract: We report the discovery of TOI-4562b (TIC-349576261), a Jovian planet orbiting a young F7V-type star, younger than the Praesepe/Hyades clusters ( Myr). This planet stands out because of its unusually long orbital period for transiting planets with known masses ( P orb = 225.11781 − 0.00022 + 0.00025 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 J and a mass of 2.30 − 0.47 + 0.48 M J for TOI-4562b. 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 ∼20 minutes level from five transit events, favoring 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-4562b to become a hot Jupiter via high-eccentricity migration though it is not excluded that interactions with the possible companion could modify TOI-4562b’s eccentricity and trigger circularization. The characterization of more such young systems is essential to set constraints on models describing giant-planet evolution.
Publisher: American Astronomical Society
Date: 06-2021
Publisher: American Astronomical Society
Date: 12-03-2015
Publisher: American Astronomical Society
Date: 21-01-2022
Abstract: The imminent launch of space telescopes designed to probe the atmospheres of exoplanets has prompted new efforts to prioritize the thousands of transiting planet candidates for follow-up characterization. We report the detection and confirmation of TOI-1842b, a warm Saturn identified by TESS and confirmed with ground-based observations from M inerva -Australis, NRES, and the Las Cumbres Observatory Global Telescope. This planet has a radius of 1.04 − 0.05 + 0.06 R J , a mass of 0.214 − 0.038 + 0.040 M J , an orbital period of 9.5739 − 0.0001 + 0.0002 days, and an extremely low density ( ρ = 0.252 ± 0.091 g cm −3 ). TOI-1842b has among the best known combinations of large atmospheric scale height (893 km) and host-star brightness ( J = 8.747 mag), making it an attractive target for atmospheric characterization. As the host star is beginning to evolve off the main sequence, TOI-1842b presents an excellent opportunity to test models of gas giant reinflation. The primary transit duration of only 4.3 hr also makes TOI-1842b an easily-schedulable target for further ground-based atmospheric characterization.
Publisher: EDP Sciences
Date: 27-11-2012
Publisher: American Astronomical Society
Date: 13-12-2021
Abstract: We report the discovery of two short-period massive giant planets from NASA’s Transiting Exoplanet Survey Satellite (TESS). Both systems, TOI-558 (TIC 207110080) and TOI-559 (TIC 209459275), were identified from the 30 minute cadence full-frame images and confirmed using ground-based photometric and spectroscopic follow-up observations from TESS’s follow-up observing program working group. We find that TOI-558 b, which transits an F-dwarf ( M * = 1.349 − 0.065 + 0.064 M ⊙ , R * = 1.496 − 0.040 + 0.042 R ⊙ , T eff = 6466 − 93 + 95 K, age 1.79 − 0.73 + 0.91 Gyr) with an orbital period of 14.574 days, has a mass of 3.61 ± 0.15 M J , a radius of 1.086 − 0.038 + 0.041 R J , and an eccentric ( e = 0.300 − 0.020 + 0.022 ) orbit. TOI-559 b transits a G dwarf ( M * = 1.026 ± 0.057 M ⊙ , R * = 1.233 − 0.026 + 0.028 R ⊙ , T eff = 5925 − 76 + 85 K, age 6.8 − 2.0 + 2.5 Gyr) in an eccentric ( e = 0.151 ± 0.011) 6.984 days orbit with a mass of 6.01 − 0.23 + 0.24 M J and a radius of 1.091 − 0.025 + 0.028 R J . Our spectroscopic follow up also reveals a long-term radial velocity trend for TOI-559, indicating a long-period companion. The statistically significant orbital eccentricity measured for each system suggests that these planets migrated to their current location through dynamical interactions. Interestingly, both planets are also massive ( M J ), adding to the population of massive giant planets identified by TESS. Prompted by these new detections of high-mass planets, we analyzed the known mass distribution of hot and warm Jupiters but find no significant evidence for multiple populations. TESS should provide a near magnitude-limited s le of transiting hot Jupiters, allowing for future detailed population studies.
Location: United States of America
Location: United States of America
No related grants have been discovered for David Rodriguez.