Browsing by Author "Lucero, Jennifer P."

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    HATS-38 b and WASP-139 b Join a Growing Group of Hot Neptunes on Polar Orbits
    (2024) Espinoza-Retamal, Juan I.; Stefansson, Gudmundur; Petrovich, Cristobal; Brahm, Rafael; Jordan, Andres; Sedaghati, Elyar; Lucero, Jennifer P.; Pinto, Marcelo Tala; Munoz, Diego J.; Boyle, Gavin; Leiva, Rodrigo; Suc, Vincent
    We constrain the sky-projected obliquities of two low-density hot Neptune planets, HATS-38 b and WASP-139 b, orbiting nearby G and K stars using Rossiter-McLaughlin (RM) observations with VLT/ESPRESSO, yielding lambda=-108(-16)(+11) deg and -85.6(-4.2)(+7.7) deg, respectively. To model the RM effect, we use a new publicly available code, ironman, which is capable of jointly fitting transit photometry, Keplerian radial velocities, and RM effects. WASP-139 b has a residual eccentricity e=0.103(-0.041)(+0.050) while HATS-38 b has an eccentricity of e=0.112(-0.070)(+0.072), which is compatible with a circular orbit given our data. Using the obliquity constraints, we show that they join a growing group of hot and low-density Neptunes on polar orbits. We use long-term radial velocities to rule out companions with masses similar to 0.3-50 M-J within similar to 10 au. We show that the orbital architectures of the two Neptunes can be explained with high-eccentricity migration from greater than or similar to 2 au driven by an unseen distant companion. If HATS-38b has no residual eccentricity, its polar and circular orbit can also be consistent with a primordial misalignment. Finally, we performed a hierarchical Bayesian modeling of the true obliquity distribution of Neptunes and found suggestive evidence for a higher preponderance of polar orbits of hot Neptunes compared to Jupiters. However, we note that the exact distribution is sensitive to the choice of priors, highlighting the need for additional obliquity measurements of Neptunes to robustly compare the hot Neptune obliquity distribution to Jupiters.
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    VaTEST I: validation of sub-Saturn exoplanet TOI-181b in narrow orbit from its host star
    (2023) Mistry, Priyashkumar; Pathak, Kamlesh; Lekkas, Georgios; Prasad, Aniket; Bhattarai, Surendra; Maity, Mousam; Beichman, Charles A.; Ciardi, David R.; Evans, Phil; Bieryla, Allyson; Eastman, Jason D.; Esquerdo, Gilbert A.; Lucero, Jennifer P.
    We present here a validation of sub-Saturn exoplanet TOI-181b orbiting a K spectral type star TOI-181 (mass: 0.822 +/- 0.04 M-circle dot, radius: 0.745 +/- 0.02 R-circle dot, temperature: 4994 +/- 50 K) as a part of Validation of Transiting Exoplanets using Statistical Tools (VaTEST) project. TOI-181b is a planet with radius 6.95 +/- 0.08 R-circle plus, mass 46.16 +/- 2.71 M-circle plus, orbiting in a slightly eccentric orbit with eccentricity 0.15 +/- 0.06 and semimajor axis of 0.054 +/- 0.004 au, with an orbital period of 4.5320 +/- 0.000002 d. The transit photometry data were collected using Transiting Exoplanet Survey Satellite (TESS) and spectroscopic data for radial velocity analysis were collected using The European Southern Observatory's (ESO) High Accuracy Radial Velocity Planet Searcher (HARPS) telescope. Based on the radial velocity best-fit model we measured RV semi-amplitude to be 20.56 +/- 2.37 m s(-1). Additionally, we used VESPA and TRICERATOPS to compute the False Positive Probability (FPP), and the findings were FPP values of 1.68 x 10(-14) and 3.81 x 10(-04), respectively, which are significantly lower than the 1 per cent threshold. The finding of TOI-181b is significant in the perspective of future work on the formation and migration history of analogous planetary systems since warm sub-Saturns are uncommon in the known sample of exoplanets.