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Full list of authors: Turtelboom, Emma V.; Weiss, Lauren M.; Dressing, Courtney D.; Nowak, Grzegorz; Pallé, Enric; Beard, Corey; Blunt, Sarah; Brinkman, Casey; Chontos, Ashley; Claytor, Zachary R.; Dai, Fei; Dalba, Paul A.; Giacalone, Steven; Gonzales, Erica; Harada, Caleb K.; Hill, Michelle L.; Holcomb, Rae; Korth, Judith; Lubin, Jack; Masseron, Thomas; MacDougall, Mason; Mayo, Andrew W.; Močnik, Teo; Akana Murphy, Joseph M.; Polanski, Alex S.; Rice, Malena; Rubenzahl, Ryan A.; Scarsdale, Nicholas; Stassun, Keivan G.; Tyler, Dakotah B.; Zandt, Judah Van; Crossfield, Ian J. M.; Deeg, Hans J.; Fulton, Benjamin; Gandolfi, Davide; Howard, Andrew W.; Huber, Dan; Isaacson, Howard; Kane, Stephen R.; Lam, Kristine W. F.; Luque, Rafael; Martín, Eduardo L.; Morello, Giuseppe; Orell-Miquel, Jaume; Petigura, Erik A.; Robertson, Paul; Roy, Arpita; Van Eylen, Vincent; Baker, David; Belinski, Alexander A.; Bieryla, Allyson; Ciardi, David R.; Collins, Karen A.; Cutting, Neil; Della-Rose, Devin J.; Ellingsen, Taylor B.; Furlan, E.; Gan, Tianjun; Gnilka, Crystal L.; Guerra, Pere; Howell, Steve B.; Jimenez, Mary; Latham, David W.; Larivière, Maude; Lester, Kathryn V.; Lillo-Box, Jorge; Luker, Lindy; Mann, Christopher R.; Plavchan, Peter P.; Safonov, Boris; Skinner, Brett; Strakhov, Ivan A.; Wittrock, Justin M.; Caldwell, Douglas A.; Essack, Zahra; Jenkins, Jon M.; Quintana, Elisa V.; Ricker, George R.; Vanderspek, Roland; Seager, S.; Winn, Joshua N.-- This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., Multiplanet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V = 11.6, K = 9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31, 5.90, 18.66, and 37.92 days. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97 ± 0.06 R⊕, 2.47 ± 0.08 R⊕, 3.46 ± 0.09 R⊕, and 3.72 ± 0.16 R⊕) and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1 ± 1.1 M⊕, 8.8 ± 1.2 M⊕, 5.3 ± 1.7 M⊕, and 14.8 ± 2.3 M⊕). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (Pe/Pd = 2.03) and exhibit transit-timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only five systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70 ± 0.24 to 3.21 ± 0.44 g cm−3, implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 ± 3.6 M⊕. This planet candidate is exterior to TOI-1246 e, with a candidate period of 93.8 days, and we discuss the implications if it is confirmed to be planetary in nature. © 2022. The Author(s). Published by the American Astronomical Society., We thank the time assignment committees of the University of California, the California Institute of Technology, NASA, and the University of Hawaii for supporting the TESS-Keck Survey with observing time at Keck Observatory. We thank NASA for funding associated with our Key Strategic Mission Support project. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff for support of HIRES and remote observing. We recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has within the indigenous Hawaiian community. We are deeply grateful to have the opportunity to conduct observations from this mountain. We thank Ken and Gloria Levy, who supported the construction of the Levy Spectrometer on the Automated Planet Finder. We thank the University of California and Google for supporting Lick Observatory, and the UCO staff for their dedicated work scheduling and operating the telescopes of Lick Observatory. This paper is based on data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. C.D. gratefully acknowledges support from the David & Lucile Packard Foundation and the Alfred P. Sloan Foundation. A.A.B., B.S.S., and I.A.S. acknowledge the support of the Ministry of Science and Higher Education of the Russian Federation under the grant 075-15-2020-780(N13.1902.21.0039). J.K. gratefully acknowledges the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). A.W.M. is supported by the NSF Graduate Research Fellowship grant No. DGE 1752814. J.M.A.M. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1842400. J.M.A.M. acknowledges the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant No. 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. C.K.H. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant No. DGE 2146752. M.R. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1752134. R.A.R. is supported by an NSF Graduate Research Fellowship, grant No. DGE 1745301. P.D. is supported by a National Science Foundation (NSF) Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. R.L. acknowledges financial support from the Centre of Excellence "Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). D.H. acknowledges support from the Alfred P. Sloan Foundation and the National Aeronautics and Space Administration (80NSSC20K0593, 80NSSC21K0652). T.M. acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) through the Spanish State Research Agency, under the Severo Ochoa Program 2020-2023 (CEX2019-000920-S). K.W.F.L. acknowledges support by DFG grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, "Exploring the Diversity of Extrasolar Planets."

We present new Spitzer transit observations of four K2 transiting sub-Neptunes: K2-36c, K2-79b, K2-167b, and K2-212b. We derive updated orbital ephemerides and radii for these planets based on a joint analysis of the Spitzer, TESS, and K2 photometry. We use the EVEREST pipeline to provide improved K2 photometry, by detrending instrumental noise and K2's pointing jitter. We used a pixel level decorrelation method on the Spitzer observations to reduce instrumental systematic effects. We modeled the effect of possible blended eclipsing binaries, seeking to validate these planets via the achromaticity of the transits (K2 versus Spitzer). However, we find that Spitzer's signal-to-noise ratio for these small planets is insufficient to validate them via achromaticity. Nevertheless, by jointly fitting radii between K2 and Spitzer observations, we were able to independently confirm the K2 radius measurements. Due to the long time baseline between the K2 and Spitzer observations, we were also able to increase the precision of the orbital periods compared to K2 observations alone. The improvement is a factor of 3 for K2-36c, and more than an order of magnitude for the remaining planets. Considering possible JWST observations in 1/2023, previous 1 sigma uncertainties in transit times for these planets range from 74 to 434 minutes, but we have reduced them to the range of 8 to 23 minutes., Comment: 18 pages, 11 Figures, Accepted by The Astronomical Journal

Using a general circulation model (GCM), we investigate trends in simulated hot Jupiter atmospheres for a range of irradiation temperatures (1,500 - 4,000 K), surface gravities (10 and 40 m s-2), and cloud conditions. Our models include simplified temperature-dependent clouds with radiative feedback and show how different cloud compositions, vertical thicknesses, and opacities shape hot Jupiters atmospheres by potentially increasing planetary albedos, decreasing photospheric pressures and nightside temperatures, and in some cases producing strong dayside thermal inversions. With decreasing irradiation, clouds progressively form on the nightside and cooler western limb followed by the eastern limb and central dayside. We find that clouds significantly modify the radiative transport and affect the observable properties of planets colder than T_irr ~ 3,000~K (T_eq~2,100 K) depending on the clouds' vertical extent. The precise strength of expected effects depends on the assumed parameters, but trends in predicted phase curves emerge from an ensemble of simulations. Clouds lead to larger phase curve amplitudes and smaller phase curve offsets at IR wavelengths, compared to cloud-free models. At optical wavelengths, we predict mostly westward phase curve offsets at intermediate temperatures (T_irr ~ 2,000 - 3,500 K) with clouds confined to the nightside and western limb. If clouds are vertically compact (i.e. on order of a pressure scale height in thickness), their distributions and effects become more complicated as different condensates form at different heights -- some too deep to significantly affect the observable atmosphere. Our results have implications for interpreting the diversity of phase curve observations of planets with T_irr, Comment: Accepted to ApJ. 34 pages, 16 figures

Infrared observations of metastable 2$^3$S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass loss rate of an exoplanet's upper atmosphere. Here, we present a new photometric technique to measure metastable 2$^3$S helium absorption using an ultra-narrowband filter (full-width at half-maximum of 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera (WIRC) on the 200-inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of $0.498\pm0.045$% (11.1$\sigma$), consistent with previous measurements after considering our bandpass. Then, we use this method to study the inflated gas giant WASP-52b and place a 95th-percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass loss rate for WASP-69b to be $5.25^{+0.65}_{-0.46}\times10^{-4}~M_\mathrm{J}/\mathrm{Gyr}$ ($3.32^{+0.67}_{-0.56}\times10^{-3}~M_\mathrm{J}/\mathrm{Gyr}$) at 7,000 K (12,000 K). Additionally, we set an upper limit on the mass loss rate of WASP-52b at these temperatures of $2.1\times10^{-4}~M_\mathrm{J}/\mathrm{Gyr}$ ($2.1\times10^{-3}~M_\mathrm{J}/\mathrm{Gyr}$). These results show that ultra-narrowband photometry can reliably quantify absorption in the metastable helium feature., Comment: 17 pages, 8 figures (figures 1 and 2 are rasterized for arXiv file size compliance), accepted to AJ

Observations of scattered light and thermal emission from hot Jupiter exoplanets have suggested the presence of inhomogeneous aerosols in their atmospheres. 3D general circulation models (GCMs) that attempt to model the effects of aerosols have been developed to understand the physical processes that underlie their dynamical structures. In this work, we investigate how different approaches to aerosol modeling in GCMs of hot Jupiters affect high-resolution thermal emission spectra throughout the duration of the planet's orbit. Using results from a GCM with temperature-dependent cloud formation, we calculate spectra of a representative hot Jupiter with different assumptions regarding the vertical extent and thickness of clouds. We then compare these spectra to models in which clouds are absent or simply post-processed (i.e., added subsequently to the completed clear model). We show that the temperature-dependent treatment of clouds in the GCM produces high-resolution emission spectra that are markedly different from the clear and post-processed cases -- both in the continuum flux levels and line profiles -- and that increasing the vertical extent and thickness of clouds leads to bigger changes in these features. We evaluate the net Doppler shifts of the spectra induced by global winds and the planet's rotation and show that they are strongly phase-dependent, especially for models with thicker and more extended clouds. This work further demonstrates the importance of radiative feedback in cloudy atmospheric models of hot Jupiters, as this can have a significant impact on interpreting spectroscopic observations of exoplanet atmospheres., 23 pages, 10 figures, 2 tables, 1 animation (Fig. 6: https://tinyurl.com/v69ljww), ApJ accepted

The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey for transiting planets orbiting bright stars for over ten years. The KELT images have a pixel scale of ~23"/pixel---very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS)---as well as a large point spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3'. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with higher spatial resolution, cadence, and photometric precision than the KELT telescopes, as well as spectroscopic observations of the candidate host stars. The KELT-FUN team has followed-up over 1,600 planet candidates since 2011, resulting in more than 20 planet discoveries. Excluding ~450 false alarms of non-astrophysical origin (i.e., instrumental noise or systematics), we present an all-sky catalog of the 1,128 bright stars (6, Comment: Accepted for publication in AJ, 21 pages, 12 figures, 7 tables