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1. Three short-period Jupiters from TESS: HIP 65Ab, TOI-157b, and TOI-169b

   https://doi.org/10.1051/0004-6361/202037941  

   Nielsen, L. D. ; Brahm, R. ; Bouchy, F. ; Espinoza, N. ; Turner, O. ; Rappaport, S. ; Pearce, L. ; Ricker, G. ; Vanderspek, R. ; Latham, D. W. ; et al ( July 2020 , Astronomy & Astrophysics)

   We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period Jupiter orbiting a bright ( V = 11.1 mag) K4-dwarf every 0.98 days. It is a massive 3.213 ± 0.078  M J planet in a grazing transit configuration with an impact parameter of b = 1.17 −0.08 +0.10 . As a result the radius is poorly constrained, 2.03 −0.49 +0.61 R J . The planet’s distance to its host star is less than twice the separation at which it would be destroyed bymore »Roche lobe overflow. It is expected to spiral into HIP 65A on a timescale ranging from 80 Myr to a few gigayears, assuming a reduced tidal dissipation quality factor of Q s ′ = 10 7 − 10 9 . We performed a full phase-curve analysis of the TESS data and detected both illumination- and ellipsoidal variations as well as Doppler boosting. HIP 65A is part of a binary stellar system, with HIP 65B separated by 269 AU (3.95 arcsec on sky). TOI-157b (TIC 140691463) is a typical hot Jupiter with a mass of 1.18 ± 0.13  M J and a radius of 1.29 ± 0.02  R J . It has a period of 2.08 days, which corresponds to a separation of just 0.03 AU. This makes TOI-157 an interesting system, as the host star is an evolved G9 sub-giant star ( V = 12.7). TOI-169b (TIC 183120439) is a bloated Jupiter orbiting a V = 12.4 G-type star. It has a mass of 0.79 ±0.06  M J and a radius of 1.09 −0.05 +0.08 R J . Despite having the longest orbital period ( P = 2.26 days) of the three planets, TOI-169b receives the most irradiation and is situated on the edge of the Neptune desert. All three host stars are metal rich with [Fe / H] ranging from 0.18 to0.24.« less
2. TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in its Atmosphere

   Cabot, Samuel H. ; Bello-Arufe, Aaron ; Mendonça, João M. ; Tronsgaard, René ; Wong, Ian ; Zhou, George ; Buchhave, Lars A. ; Fischer, Debra A. ; Stassun, Keivan G. ; Antoci, Victoria ; et al ( January 2021 , Astronomical Journal)

   We present the discovery of TOI-1518b -- an ultra-hot Jupiter orbiting a bright star $V = 8.95$. The transiting planet is confirmed using high-resolution optical transmission spectra from EXPRES. It is inflated, with $R_p = 1.875\pm0.053\,R_{\rm J}$, and exhibits several interesting properties, including a misaligned orbit (${240.34^{+0.93}_{-0.98}}$ degrees) and nearly grazing transit ($b =0.9036^{+0.0061}_{-0.0053}$). The planet orbits a fast-rotating F0 host star ($T_{\mathrm{eff}} \simeq 7300$ K) in 1.9 days and experiences intense irradiation. Notably, the TESS data show a clear secondary eclipse with a depth of $364\pm28$ ppm and a significant phase curve signal, from which we obtain a relativemore »day-night planetary flux difference of roughly 320 ppm and a 5.2$\sigma$ detection of ellipsoidal distortion on the host star. Prompted by recent detections of atomic and ionized species in ultra-hot Jupiter atmospheres, we conduct an atmospheric cross-correlation analysis. We detect neutral iron (${5.2\sigma}$), at $K_p = 157^{+68}_{-44}$ km s$^{-1}$ and $V_{\rm sys} = -16^{+2}_{-4}$ km s$^{-1}$, adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission. Detections so far favor particularly inflated gas giants with radii $rsim 1.78\,R_{\rm J}$; although this may be due to observational bias. With an equilibrium temperature of $T_{\rm eq}=2492\pm38$ K and a measured dayside brightness temperature of $3237\pm59$ K (assuming zero geometric albedo), TOI-1518b is a promising candidate for future emission spectroscopy to probe for a thermal inversion.« less
3. TOI-1696 and TOI-2136: Constraining the Masses of Two Mini-Neptunes with the Habitable-Zone Planet Finder

   https://doi.org/10.3847/1538-3881/ac69ec  

   Beard, Corey ; Robertson, Paul ; Kanodia, Shubham ; Libby-Roberts, Jessica ; Cañas, Caleb I. ; Gupta, Arvind F. ; Holcomb, Rae ; Jones, Sinclaire ; Kobulnicky, Henry A. ; Lin, Andrea S. ; et al ( May 2022 , The Astronomical Journal)

   Abstract We present the validation of two planets orbiting M dwarfs, TOI-1696b and TOI-2136b. Both planets are mini-Neptunes orbiting nearby stars, making them promising prospects for atmospheric characterization with the James Webb Space Telescope (JWST). We validated the planetary nature of both candidates using high-contrast imaging, ground-based photometry, and near-infrared radial velocities. Adaptive optics images were taken using the ShARCS camera on the 3 m Shane Telescope. Speckle images were taken using the NN-Explore Exoplanet Stellar Speckle Imager on the WIYN 3.5 m telescope. Radii and orbital ephemerides were refined using a combination of the Transiting Exoplanet Survey Satellite, themore »diffuser-assisted Astrophysical Research Consortium (ARC) Telescope Imaging Camera (ARCTIC) imager on the 3.5 m ARC telescope at Apache Point Observatory, and the 0.6 m telescope at Red Buttes Observatory. We obtained radial velocities using the Habitable-Zone Planet Finder on the 10 m Hobby–Eberly Telescope, which enabled us to place upper limits on the masses of both transiting planets. TOI-1696b ( P = 2.5 days; R p = 3.24 R ⊕ ; M p < 56.6 M ⊕ ) falls into a sparsely populated region of parameter space considering its host star’s temperature ( T eff = 3168 K, M4.5), as planets of its size are quite rare around mid- to late-M dwarfs. On the other hand, TOI-2136b ( P = 7.85 days; R p = 2.09 R ⊕ ; M p < 15.0 M ⊕ ) is an excellent candidate for atmospheric follow-up with the JWST.« less
4. TOI-257b (HD 19916b): a warm sub-saturn orbiting an evolved F-type star

   https://doi.org/10.1093/mnras/staa3960  

   Addison, Brett C ; Wright, Duncan J ; Nicholson, Belinda A ; Cale, Bryson ; Mocnik, Teo ; Huber, Daniel ; Plavchan, Peter ; Wittenmyer, Robert A ; Vanderburg, Andrew ; Chaplin, William J ; et al ( February 2021 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the Minerva-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of MP = 0.138 ± 0.023 $\rm {M_J}$ (43.9 ± 7.3 $\, M_{\rm \oplus}$), a radius of RP = 0.639 ± 0.013 $\rm {R_J}$ (7.16 ± 0.15 $\, \mathrm{ R}_{\rm \oplus}$), bulk density of $0.65^{+0.12}_{-0.11}$ (cgs), and period $18.38818^{+0.00085}_{-0.00084}$ $\rm {days}$. TOI-257b orbits a bright (V = 7.612 mag)more »somewhat evolved late F-type star with M* = 1.390 ± 0.046 $\rm {M_{sun}}$, R* = 1.888 ± 0.033 $\rm {R_{sun}}$, Teff = 6075 ± 90 $\rm {K}$, and vsin i = 11.3 ± 0.5 km s−1. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.« less
5. The CARMENES search for exoplanets around M dwarfs: LP 714-47 b (TOI 442.01): populating the Neptune desert

   https://doi.org/10.1051/0004-6361/202038016  

   Dreizler, S. ; Crossfield, I. J. ; Kossakowski, D. ; Plavchan, P. ; Jeffers, S. V. ; Kemmer, J. ; Luque, R. ; Espinoza, N. ; Pallé, E. ; Stassun, K. ; et al ( December 2020 , Astronomy & Astrophysics)

   We report the discovery of a Neptune-like planet (LP 714-47 b, P = 4.05204 d, m b = 30.8 ± 1.5 M ⊕ , R b = 4.7 ± 0.3 R ⊕ ) located in the “hot Neptune desert”. Confirmation of the TESS Object of Interest (TOI 442.01) was achieved with radial-velocity follow-up using CARMENES, ESPRESSO, HIRES, iSHELL, and PFS, as well as from photometric data using TESS, Spitzer , and ground-based photometry from MuSCAT2, TRAPPIST-South, MONET-South, the George Mason University telescope, the Las Cumbres Observatory Global Telescope network, the El Sauce telescope, the TÜBİTAK National Observatory, the University ofmore »Louisville Manner Telescope, and WASP-South. We also present high-spatial resolution adaptive optics imaging with the Gemini Near-Infrared Imager. The low uncertainties in the mass and radius determination place LP 714-47 b among physically well-characterised planets, allowing for a meaningful comparison with planet structure models. The host star LP 714-47 is a slowly rotating early M dwarf ( T eff = 3950 ± 51 K) with a mass of 0.59 ± 0.02 M ⊙ and a radius of 0.58 ± 0.02 R ⊙ . From long-term photometric monitoring and spectroscopic activity indicators, we determine a stellar rotation period of about 33 d. The stellar activity is also manifested as correlated noise in the radial-velocity data. In the power spectrum of the radial-velocity data, we detect a second signal with a period of 16 days in addition to the four-day signal of the planet. This could be shown to be a harmonic of the stellar rotation period or the signal of a second planet. It may be possible to tell the difference once more TESS data and radial-velocity data are obtained.« less