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1. Can the Gravitational Effect of Planet X be Detected in Current-era Tracking of the Known Major and Minor Planets?

   https://doi.org/10.3847/PSJ/acc7a2  

   Gomes, Daniel C. H. ; Murray, Zachary ; Gomes, Rafael C. H. ; Holman, Matthew J. ; Bernstein, Gary M. ( April 2023 , The Planetary Science Journal)

   Using Fisher information matrices, we forecast the uncertaintiesσ_Mon the measurement of a “Planet X” at heliocentric distanced_Xvia its tidal gravitational field’s action on the known planets. Using planetary measurements currently in hand, including ranging from the Juno, Cassini, and Mars-orbiting spacecraft, we forecast a median uncertainty (over all sky positions) of${\sigma }_M=0.22M_{\oplus }{(d_x/400\mathrm{au})}^3.$A 5σdetection of a 5M_⊕Planet X atd_X= 400 au should be possible over the full sky but over only 5% of the sky atd_X= 800 au. The gravity of an undiscovered Earth- or Mars-mass object should be detectable over 90% of the sky to a distance of 260 or 120 au, respectively. Upcoming Mars ranging improves these limits only slightly. We also investigate the power of high-precision astrometry of ≈8000 Jovian Trojans over the 2023–2035 period from the upcoming Legacy Survey of Space and Time (LSST). We find that the dominant systematic errors in optical Trojan astrometry (photocenter motion, nongravitational forces, and differential chromatic refraction) can be solved internally with minimal loss of information. The Trojan data allow cross-checks with Juno/Cassini/Mars ranging, but do not significantly improve the best achievableσ_Mvalues until they are ≳10× more accurate than expected from LSST. The ultimate limiting factor in searches for a Planet X tidal field is confusion with the tidal field created by the fluctuating quadrupole moment of the Kuiper Belt as its members orbit. This background will not, however, become the dominant source of uncertainty until the data get substantially better than they are today.

    

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2. TOI-5126: a hot super-Neptune and warm Neptune pair discovered by TESS and CHEOPS

   https://doi.org/10.1093/mnras/stad3036  

   Fairnington, Tyler R. ; Nabbie, Emma ; Huang, Chelsea X. ; Zhou, George ; Foo, Orion ; Millholland, Sarah ; Wright, Duncan ; Belinski, Alexandre A. ; Bieryla, Allyson ; Ciardi, David R. ; et al ( October 2023 , Monthly Notices of the Royal Astronomical Society)

   We present the confirmation of a hot super-Neptune with an exterior Neptune companion orbiting a bright (V  = 10.1 mag) F-dwarf identified by the Transiting Exoplanet Survey Satellite (TESS). The two planets, observed in sectors 45, 46, and 48 of the TESS extended mission, are $4.74_{-0.14}^{+0.16}$ and $3.86_{-0.16}^{+0.17}$ R⊕ with $5.4588385_{-0.0000072}^{+0.0000070}$ and $17.8999_{-0.0013}^{+0.0018}$ d orbital periods, respectively. We also obtained precise space-based photometric follow-up of the system with ESA’s CHaracterising ExOplanets Satellite to constrain the radius and ephemeris of TOI-5126 b. TOI-5126 b is located in the ‘hot Neptune Desert’ and is an ideal candidate for follow-up transmission spectroscopy due to its high-predicted equilibrium temperature (Teq = ${1442}_{-40}^{+46}$ K) implying a cloud-free atmosphere. TOI-5126 c is a warm Neptune (Teq = $971_{-27}^{+31}$ K) also suitable for follow-up. Tentative transit timing variations have also been identified in analysis, suggesting the presence of at least one additional planet, however this signal may be caused by spot-crossing events, necessitating further precise photometric follow-up to confirm these signals.

    

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3. Cometary Activity Discovered on Vacationing Centaur 2019 OE31

   https://doi.org/10.3847/2515-5172/ad14f5  

   Oldroyd, William J. ; Chandler, Colin Orion ; Trujillo, Chadwick A. ; Deen, Sam ; Hsieh, Henry H. ; Farrell, Kennedy A. ; DeSpain, Jarod A. ; Kueny, Jay K. ; Burris, William A. ; Sheppard, Scott S. ; et al ( December 2023 , Research Notes of the AAS)

   We have detected cometary activity on minor planet 2019 OE₃₁through both theActive AsteroidsCitizen Science program and an independent archival search. Before 2013, 2019 OE₃₁was on a Centaur orbit, between the orbits of Jupiter and Neptune. Centaurs are objects in transition from the outer solar system to the inner solar system. They play a vital role in the understanding of the Kuiper Belt and comets. In 2013 October, following a close encounter with Jupiter, 2019 OE₃₁moved to an orbit entirely interior to that of Jupiter. This reduced orbital distance and, hence, increased temperature is likely the cause of the observed activity. Through a suite of orbital dynamics simulations, we find that 2019 OE₃₁will experience many more similar encounters and is statistically likely to return to a Centaur orbit, potentially within the next 80 yr, from its current “vacation.”

    

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4. Radial velocity confirmation of a hot super-Neptune discovered by TESS with a warm Saturn–mass companion

   https://doi.org/10.1093/mnras/stac3684  

   Knudstrup, E. ; Gandolfi, D. ; Nowak, G. ; Persson, C. M. ; Furlan, E. ; Livingston, J. ; Matthews, E. ; Lundkvist, M. S. ; Winther, M. L. ; Rørsted, J. L. ; et al ( December 2022 , Monthly Notices of the Royal Astronomical Society)

   We report the discovery and confirmation of the planetary system TOI-1288. This late G dwarf harbours two planets: TOI-1288 b and TOI-1288 c. We combine TESS space-borne and ground-based transit photometry with HARPS-N and HIRES high-precision Doppler measurements, which we use to constrain the masses of both planets in the system and the radius of planet b. TOI-1288 b has a period of $2.699835^{+0.000004}_{-0.000003}$ d, a radius of 5.24 ± 0.09 R⊕, and a mass of 42 ± 3 M⊕, making this planet a hot transiting super-Neptune situated right in the Neptunian desert. This desert refers to a paucity of Neptune-sized planets on short period orbits. Our 2.4-yr-long Doppler monitoring of TOI-1288 revealed the presence of a Saturn–mass planet on a moderately eccentric orbit ($0.13^{+0.07}_{-0.09}$) with a minimum mass of 84 ± 7 M⊕ and a period of $443^{+11}_{-13}$ d. The five sectors worth of TESS data do not cover our expected mid-transit time for TOI-1288 c, and we do not detect a transit for this planet in these sectors.

    

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5. The Warm Neptune GJ 3470b Has a Polar Orbit

   https://doi.org/10.3847/2041-8213/ac6e3c  

   Stefànsson, Guđmundur ; Mahadevan, Suvrath ; Petrovich, Cristobal ; Winn, Joshua N. ; Kanodia, Shubham ; Millholland, Sarah C. ; Maney, Marissa ; Cañas, Caleb I. ; Wisniewski, John ; Robertson, Paul ; et al ( May 2022 , The Astrophysical Journal Letters)

   The warm Neptune GJ 3470b transits a nearby (d= 29 pc) bright slowly rotating M1.5-dwarf star. Using spectroscopic observations during two transits with the newly commissioned NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the classical Rossiter–McLaughlin effect, yielding a sky-projected obliquity of$\lambda ={98}_{-12}^{+15◦}$and a$v\sin i={0.85}_{-0.33}^{+0.27}\mathrm{km}{\mathrm{s}}^{-1}$. Leveraging information about the rotation period and size of the host star, our analysis yields a true obliquity of$\psi ={95}_{-8}^{+9◦}$, revealing that GJ 3470b is on a polar orbit. Using radial velocities from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that the data are compatible with a long-term radial velocity (RV) slope of$\dot{\gamma }=-0.0022\pm 0.0011\mathrm{m}{\mathrm{s}}^{-1}{\mathrm{day}}^{-1}$over a baseline of 12.9 yr. If the RV slope is due to acceleration from another companion in the system, we show that such a companion is capable of explaining the polar and mildly eccentric orbit of GJ 3470b using two different secular excitation models. The existence of an outer companion can be further constrained with additional RV observations, Gaia astrometry, and future high-contrast imaging observations. Lastly, we show that tidal heating from GJ 3470b’s mild eccentricity has most likely inflated the radius of GJ 3470b by a factor of ∼1.5–1.7, which could help account for its evaporating atmosphere.

    

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