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1. TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to Have Originated from High-eccentricity Migration

   https://doi.org/10.3847/1538-3881/ac5c4f  

   Tran, Quang H. ; Bowler, Brendan P. ; Endl, Michael ; Cochran, William D. ; MacQueen, Phillip J. ; Gandolfi, Davide ; Persson, Carina M. ; Fridlund, Malcolm ; Palle, Enric ; Nowak, Grzegorz ; et al ( April 2022 , The Astronomical Journal)

   We report the discovery of two transiting planets around the bright (V= 9.9 mag) main-sequence F7 star TOI-1670 by the Transiting Exoplanet Survey Satellite. TOI-1670 b is a sub-Neptune ($R_{\mathrm{b}}={2.06}_{-0.15}^{+0.19}$R_⊕) on a 10.9 day orbit, and TOI-1670 c is a warm Jupiter ($R_{\mathrm{c}}={0.987}_{-0.025}^{+0.025}$R_Jup) on a 40.7 day orbit. Using radial velocity observations gathered with the Tull Coudé Spectrograph on the Harlan J. Smith telescope and HARPS-N on the Telescopio Nazionale Galileo, we find a planet mass of$M_{\mathrm{c}}={0.63}_{-0.08}^{+0.09}$M_Jupfor the outer warm Jupiter, implying a mean density of${\rho }_c={0.81}_{-0.11}^{+0.13}$g cm⁻³. The inner sub-Neptune is undetected in our radial velocity data (M_b< 0.13M_Jupat the 99% confidence level). Multiplanet systems like TOI-1670 hosting an outer warm Jupiter on a nearly circular orbit ($e_{\mathrm{c}}={0.09}_{-0.04}^{+0.05}$) and one or more inner coplanar planets are more consistent with “gentle” formation mechanisms such as disk migration or in situ formation rather than high-eccentricity migration. Of the 11 known systems with a warm Jupiter and a smaller inner companion, eight (73%) are near a low-order mean-motion resonance, which can be a signature of migration. TOI-1670 joins two other systems (27% of this subsample) with period commensurabilities greater than 3, a common feature of in situ formation or halted inward migration. TOI-1670 and the handful of similar systems support a diversity of formation pathways for warm Jupiters.

    

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2. Dynamical Mass of the Young Brown Dwarf Companion PZ Tel B

   https://doi.org/10.3847/1538-3881/acca18  

   Franson, Kyle ; Bowler, Brendan P. ( May 2023 , The Astronomical Journal)

   Dynamical masses of giant planets and brown dwarfs are critical tools for empirically validating substellar evolutionary models and their underlying assumptions. We present a measurement of the dynamical mass and an updated orbit of PZ Tel B, a young brown dwarf companion orbiting a late-G member of theβPic moving group. PZ Tel A exhibits an astrometric acceleration between Hipparcos and Gaia EDR3, which enables the direct determination of the companion’s mass. We have also acquired new Keck/NIRC2 adaptive optics imaging of the system, which increases the total baseline of relative astrometry to 15 yr. Our joint orbit fit yields a dynamical mass of${27}_{-9}^{+25}{M}_{\mathrm{Jup}}$, semimajor axis of${27}_{-4}^{+14}\mathrm{au}$, eccentricity of${0.52}_{-0.10}^{+0.08}$, and inclination of${91.73}_{-0.32}^{+0.36}°$. The companion’s mass is consistent within 1.1σof predictions from four grids of hot-start evolutionary models. The joint orbit fit also indicates a more modest eccentricity of PZ Tel B than previous results. PZ Tel joins a small number of young (<200 Myr) systems with benchmark substellar companions that have dynamical masses and precise ages from moving group membership.

    

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3. 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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4. A Tendency Toward Alignment in Single-star Warm-Jupiter Systems

   https://doi.org/10.3847/1538-3881/ac8153  

   Rice, Malena ; Wang, Songhu ; Wang, Xian-Yu ; Stefánsson, Guđmundur ; Isaacson, Howard ; Howard, Andrew W. ; Logsdon, Sarah E. ; Schweiker, Heidi ; Dai, Fei ; Brinkman, Casey ; et al ( August 2022 , The Astronomical Journal)

   The distribution of spin–orbit angles for systems with wide-separation, tidally detached exoplanets offers a unique constraint on the prevalence of dynamically violent planetary evolution histories. Tidally detached planets provide a relatively unbiased view of the primordial stellar obliquity distribution, as they cannot tidally realign within the system lifetime. We present the third result from our Stellar Obliquities in Long-period Exoplanet Systems (SOLES) survey: a measurement of the Rossiter–McLaughlin effect across two transits of the tidally detached warm Jupiter TOI-1478 b with the WIYN/NEID and Keck/HIRES spectrographs, revealing a sky-projected spin–orbit angle$\lambda ={6.2}_{-5.5}^{+5.9}°$. Combining this new measurement with the full set of archival obliquity measurements, including two previous constraints from the SOLES survey, we demonstrate that, in single-star systems, tidally detached warm Jupiters are preferentially more aligned than closer-orbiting hot Jupiters. This finding has two key implications: (1) planets in single-star systems tend to form within aligned protoplanetary disks, and (2) warm Jupiters form more quiescently than hot Jupiters, which, in single-star systems, are likely perturbed into a misaligned state through planet–planet interactions in the post-disk-dispersal phase. We also find that lower-mass Saturns span a wide range of spin–orbit angles, suggesting a prevalence of planet–planet scattering and/or secular mechanisms in these systems.

    

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5. The NANOGrav 12.5-year Data Set: Search for Non-Einsteinian Polarization Modes in the Gravitational-wave Background

   https://doi.org/10.3847/2041-8213/ac401c  

   Arzoumanian, Zaven ; Baker, Paul T. ; Blumer, Harsha ; Bécsy, Bence ; Brazier, Adam ; Brook, Paul R. ; Burke-Spolaor, Sarah ; Charisi, Maria ; Chatterjee, Shami ; Chen, Siyuan ; et al ( December 2021 , The Astrophysical Journal Letters)

   We search NANOGrav’s 12.5 yr data set for evidence of a gravitational-wave background (GWB) with all the spatial correlations allowed by general metric theories of gravity. We find no substantial evidence in favor of the existence of such correlations in our data. We find that scalar-transverse (ST) correlations yield signal-to-noise ratios and Bayes factors that are higher than quadrupolar (tensor-transverse, TT) correlations. Specifically, we find ST correlations with a signal-to-noise ratio of 2.8 that are preferred over TT correlations (Hellings and Downs correlations) with Bayesian odds of about 20:1. However, the significance of ST correlations is reduced dramatically when we include modeling of the solar system ephemeris systematics and/or remove pulsar J0030+0451 entirely from consideration. Even taking the nominal signal-to-noise ratios at face value, analyses of simulated data sets show that such values are not extremely unlikely to be observed in cases where only the usual TT modes are present in the GWB. In the absence of a detection of any polarization mode of gravity, we place upper limits on their amplitudes for a spectral index ofγ= 5 and a reference frequency off_yr= 1 yr⁻¹. Among the upper limits for eight general families of metric theories of gravity, we find the values of$A_{\mathrm{TT}}^{95\%}=(9.7\pm 0.4)\times {10}^{-16}$and$A_{\mathrm{ST}}^{95\%}=(1.4\pm 0.03)\times {10}^{-15}$for the family of metric spacetime theories that contain both TT and ST modes.

    

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