Penev, Kaloyan
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/6247
Kaloyan Penev joined the UTD faculty as an Assistant Professor of Physics in 2017. His research interests include:
- Extrasolar planet detection and orbital dynamics
- Searching for transiting extrasolar planets using small robotic telescopes
- High precision photometry from space and from the ground
- Orbital dynamics of extrasolar planetary systems
- Astrophysical probes of tidal dissipation in giant planets and low mass stars
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Browsing Penev, Kaloyan by Subject "Planets"
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Item Hats-70b: A 13 MJ Brown Dwarf Transiting an A Star(IOP Publishing Ltd, 2019-01-02) Zhou, G.; Bakos, G. A.; Bayliss, D.; Bento, J.; Bhatti, W.; Brahm, R.; Csubry, Z.; Espinoza, N.; Hartman, J. D.; Henning, T.; Jordan, A.; Mancini, L.; Penev, Kaloyan; Rabus, M.; Sarkis, P.; Suc, V.; de Val-Borro, M.; Rodriguez, J. E.; Osip, D.; Kedziora-Chudczer, L.; Bailey, J.; Tinney, C. G.; Durkan, S.; Lazar, J.; Papp, I.; Sari, P.; 0000-0003-4464-1371 (Penev, K); Penev, KaloyanWe report the discovery of HATS-70b, a transiting brown dwarf at the deuterium burning limit. HATS-70b has a mass of M_{p} = 12.9{{-1.6}^{+1.8} M_{Jup} and a radius of R_{p} = 1.384_{{-0.074} {+0.079}} R_{Jup}, residing in a close-in orbit with a period of 1.89 days. The host star is a M⁎ = 1.78 ± 0.12 M_⊙ A star rotating at v sin I⁎ = 40.61{_{-0.35}}^{+0.32}} km s⁻¹ , enabling us to characterize the spectroscopic transit of the brown dwarf via Doppler tomography. We find that HATS-70b, like other massive planets and brown dwarfs previously sampled, orbits in a low projected-obliquity orbit with λ = {_{8.9}^{5.6°}}. The low obliquities of these systems is surprising given all brown dwarf and massive planets with obliquities measured orbit stars hotter than the Kraft break. This trend is tentatively inconsistent with dynamically chaotic migration for systems with massive companions, though the stronger tidal influence of these companions makes it difficult to draw conclusions on the primordial obliquity distribution of this population. We also introduce a modeling scheme for planets around rapidly rotating stars, accounting for the influence of gravity darkening on the derived stellar and planetary parameters.Item KELT-22Ab: A Massive, Short-Period Hot Jupiter Transiting a Near-Solar Twin(IOP Publishing Ltd, 2019-01-21) Labadie-Bartz, Jonathan; Rodriguez, Joseph E.; Stassun, Keivan G.; Ciardi, David R.; Penev, Kaloyan; Johnson, Marshall C.; Gaudi, B. Scott; 0000-0003-4464-1371 (Penev, K); Penev, KaloyanWe present the discovery of KELT-22Ab, a hot Jupiter from the KELT-South survey. KELT-22Ab transits the moderately bright (V ~ 11.1) Sun-like G2V star TYC 7518-468-1. The planet has an orbital period of P = 1.3866529 ± 0.0000027 days, a radius of R_{P} = 1.285{_{-0.071}^{+0.12}} R_{J}, and a relatively large mass of M_{P} = 3.47{_{-0.14}^{+0.15}}, M_{J}. The star has R_{⋆} = 1.099{_{-0.046}^{0.079}} R_{⊙}, M_{⋆} = 1.092{_{-0.041}^{+0.045}} M_{⊙}, T_{eff} = 5767{_{-49}^{+50}} K, log g_{⋆} = 4.393{_{-0.060}^{+0.039}} (cgs), and [m/H] = +0.259{_{-0.083}^{+0.085}}; thus other than its slightly super-solar metallicity, it appears to be a near-solar twin. Surprisingly, KELT-22A exhibits kinematics and a Galactic orbit that are somewhat atypical for thin-disk stars. Nevertheless, the star is rotating rapidly for its estimated age, and shows evidence of chromospheric activity. Imaging reveals a slightly fainter companion to KELT-22A that is likely bound, with a projected separation of 6 '' (similar to 1400 au). In addition to the orbital motion caused by the transiting planet, we detect a possible linear trend in the radial velocity of KELT-22A, suggesting the presence of another relatively nearby body that is perhaps non-stellar. KELT-22Ab is highly irradiated (as a consequence of the small semimajor axis of a/R_{⋆}, and is mildly inflated. At such small separations, tidal forces become significant. The configuration of this system is optimal for measuring the rate of tidal dissipation within the host star. Our models predict that, due to tidal forces, the semimajor axis is decreasing rapidly, and KELT-22Ab is predicted to spiral into the star within the next Gyr.