ORCID Profile
0000-0001-6416-1274
Current Organisations
Trinity College Dublin
,
University of Hawai'i
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Publisher: American Astronomical Society
Date: 29-01-2021
Abstract: We report the discovery of two transiting brown dwarfs (BDs), TOI-811b and TOI-852b, from NASA’s Transiting Exoplanet Survey Satellite mission. These two transiting BDs have similar masses but very different radii and ages. Their host stars have similar masses, effective temperatures, and metallicities. The younger and larger transiting BD is TOI-811b at a mass of M b = 59.9 ± 13.0 M J and radius of R b = 1.26 ± 0.06 R J , and it orbits its host star in a period of P = 25.16551 ± 0.00004 days. We derive the host star’s age of Myr from an application of gyrochronology. The youth of this system, rather than external heating from its host star, is why this BD’s radius is relatively large. This constraint on the youth of TOI-811b allows us to test substellar mass–radius evolutionary models at young ages where the radius of BDs changes rapidly. TOI-852b has a similar mass at M b = 53.7 ± 1.4 M J but is much older (4 or 8 Gyr, based on bimodal isochrone results of the host star) and is also smaller with a radius of R b = 0.83 ± 0.04 R J . TOI-852b’s orbital period is P = 4.94561 ± 0.00008 days. TOI-852b joins the likes of other old transiting BDs that trace out the oldest substellar mass–radius evolutionary models where contraction of the BD’s radius slows and approaches a constant value. Both host stars have a mass of M ⋆ = 1.32 M ⊙ ± 0.05 and differ in their radii, T eff , and [Fe/H], with TOI-811 having R ⋆ = 1.27 ± 0.09 R ⊙ , T eff = 6107 ± 77 K, and [Fe/H] = + 0.40 ± 0.09 and TOI-852 having R ⋆ = 1.71 ± 0.04 R ⊙ , T eff = 5768 ± 84 K, and [Fe/H] = + 0.33 ± 0.09. We take this opportunity to examine how TOI-811b and TOI-852b serve as test points for young and old substellar isochrones, respectively.
Publisher: Springer Science and Business Media LLC
Date: 26-07-2021
Publisher: American Astronomical Society
Date: 06-2023
Abstract: 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 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 days 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 ⊙ and radius of R * = 1.863 − 0.082 + 0.087 R ⊙ , 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 ( v sin i * = 55.6 ± 1.8 km s −1 ). 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 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.
Publisher: American Astronomical Society
Date: 28-06-2021
Publisher: American Astronomical Society
Date: 02-07-2020
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.
Publisher: American Astronomical Society
Date: 30-03-2020
Location: United Kingdom of Great Britain and Northern Ireland
Location: India
No related grants have been discovered for Theron Carmichael.