We present a validation of the long-period (\(91.68278^{+0.00032}_{-0.00041}\) days) transiting sub-Neptune planet TOI-1221 b (TIC 349095149.01) around a Sun-like (m\(_{\rm V}\)=10.5) star. This is ...one of the few known exoplanets with period >50 days, and belongs to the even smaller subset of which have bright enough hosts for detailed spectroscopic follow-up. We combine TESS light curves and ground-based time-series photometry from PEST (0.3~m) and LCOGT (1.0~m) to analyze the transit signals and rule out nearby stars as potential false positive sources. High-contrast imaging from SOAR and Gemini/Zorro rule out nearby stellar contaminants. Reconnaissance spectroscopy from CHIRON sets a planetary scale upper mass limit on the transiting object (1.1 and 3.5 M\(_{\rm Jup}\) at 1\(\sigma\) and 3\(\sigma\), respectively) and shows no sign of a spectroscopic binary companion. We determine a planetary radius of \(R_{\rm p} = 2.91^{+0.13}_{-0.12} R_{\oplus}\), placing it in the sub-Neptune regime. With a stellar insolation of \(S = 6.06^{+0.85}_{-0.77}\ S_{\oplus}\), we calculate a moderate equilibrium temperature of \(T_{\rm eq} =\) 440 K, assuming no albedo and perfect heat redistribution. We find a false positive probability from TRICERATOPS of FPP \( = 0.0014 \pm 0.0003\) as well as other qualitative and quantitative evidence to support the statistical validation of TOI-1221 b. We find significant evidence (>\(5\sigma\)) of oscillatory transit timing variations, likely indicative of an additional non-transiting planet.
AU Mic is a young (22 Myr) nearby exoplanetary system that exhibits excess TTVs that cannot be accounted for by the two known transiting planets nor stellar activity. We present the statistical ..."validation" of the tentative planet AU Mic d (even though there are examples of "confirmed" planets with ambiguous orbital periods). We add 18 new transits and nine midpoint times in an updated TTV analysis to prior work. We perform the joint modeling of transit light curves using EXOFASTv2 and extract the transit midpoint times. Next, we construct an O-C diagram and use Exo-Striker to model the TTVs. We generate TTV log-likelihood periodograms to explore possible solutions for the period of planet d and then follow those up with detailed TTV and RV MCMC modeling and stability tests. We find several candidate periods for AU Mic d, all of which are near resonances with AU Mic b and c of varying order. Based on our model comparisons, the most-favored orbital period of AU Mic d is 12.73596+/-0.00793 days (T_{C,d}=2458340.55781+/-0.11641 BJD), which puts the three planets near a 4:6:9 mean-motion orbital resonance. The mass for d is 1.053+/-0.511 M_E, making this planet Earth-like in mass. If confirmed, AU Mic d would be the first known Earth-mass planet orbiting a young star and would provide a valuable opportunity in probing a young terrestrial planet's atmosphere. Additional TTV observation of the AU Mic system are needed to further constrain the planetary masses, search for possible transits of AU Mic d, and detect possible additional planets beyond AU Mic c.
We explore the transit timing variations (TTVs) of the young (22 Myr) nearby AU Mic planetary system. For AU Mic b, we introduce three Spitzer (4.5 \(\mu\)m) transits, five TESS transits, 11 LCO ...transits, one PEST transit, one Brierfield transit, and two transit timing measurements from Rossiter-McLaughlin observations; for AU Mic c, we introduce three TESS transits. We present two independent TTV analyses. First, we use EXOFASTv2 to jointly model the Spitzer and ground-based transits and to obtain the midpoint transit times. We then construct an O--C diagram and model the TTVs with Exo-Striker. Second, we reproduce our results with an independent photodynamical analysis. We recover a TTV mass for AU Mic c of 10.8\(^{+2.3}_{-2.2}\) M\(_{E}\). We compare the TTV-derived constraints to a recent radial-velocity (RV) mass determination. We also observe excess TTVs that do not appear to be consistent with the dynamical interactions of b and c alone, and do not appear to be due to spots or flares. Thus, we present a hypothetical non-transiting "middle-d" candidate exoplanet that is consistent with the observed TTVs, the candidate RV signal, and would establish the AU Mic system as a compact resonant multi-planet chain in a 4:6:9 period commensurability. These results demonstrate that the AU Mic planetary system is dynamically interacting producing detectable TTVs, and the implied orbital dynamics may inform the formation mechanisms for this young system. We recommend future RV and TTV observations of AU Mic b and c to further constrain the masses and to confirm the existence of possible additional planet(s).
We present a dedicated transit and radial velocity survey of planets orbiting subgiant stars observed by the TESS Mission. Using $\sim$$16\( nights on Keck/HIRES, we confirm and characterize \)12\( ...new transiting planets -- \)\rm TOI-329\,b\(, \)\rm HD\,39688\,b\( (\)\rm TOI-480\(), \)\rm TOI-603\,b\(, \)\rm TOI-1199\,b\(, \)\rm TOI-1294\,b\(, \)\rm TOI-1439\,b\(, \)\rm TOI-1605\,b\(, \)\rm TOI-1828\,b\(, \)\rm HD\,148193\,b\( (\)\rm TOI-1836\(), \)\rm TOI-1885\,b\(, \)\rm HD\,83342\,b\( (\)\rm TOI-1898\(), \)\rm TOI-2019\,b\( -- and provide updated properties for 9 previously confirmed TESS subgiant systems (\)\rm TOI-197\(, \)\rm TOI-954\(, \)\rm TOI-1181\(, \)\rm TOI-1296\(, \)\rm TOI-1298\(, \)\rm TOI-1601\(, \)\rm TOI-1736\(, \)\rm TOI-1842\(, \)\rm TOI-2145\(). We also report the discovery of an outer, non-transiting planet, \)\rm TOI-1294\,c\( (\)P=160.1\pm2.5\( days, \)M_{\mathrm{p}}=148.3^{+18.2}_{-16.4} \,M_{\oplus}\(), and three additional stars with long-term RV trends. We find that at least \)19\pm8\%\( of subgiants in our sample of \)21\( stars have outer companions, comparable to main-sequence stars. We perform a homogeneous analysis of the stars and planets in the sample, with median uncertainties of \)3\%\(, \)8\%\( and \)15\%\( for planet radii, masses and ages, doubling the number of known planets orbiting subgiant stars with bulk densities measured to better than \)10\%$. We observe a dearth of giant planets around evolved stars with short orbital periods, consistent with tidal dissipation theories that predict the rapid inspiral of planets as their host stars leave the main sequence. We note the possible evidence for two distinct classes of hot Jupiter populations, indicating multiple formation channels to explain the observed distributions around evolved stars. Finally, continued RV monitoring of planets in this sample will provide a more comprehensive understanding of demographics for evolved planetary systems.
Characterizing the bulk compositions of transiting exoplanets within the M dwarf radius valley offers a unique means to establish whether the radius valley emerges from an atmospheric mass loss ...process or is imprinted by planet formation itself. We present the confirmation of such a planet orbiting an early M dwarf (\(T_{\rm mag} = 11.0294 \pm 0.0074, M_s = 0.513 \pm 0.012\ M_\odot, R_s = 0.515 \pm 0.015\ R_\odot, T_{\rm eff} =3690\pm 50 K\)): TOI-1695 b (\(P = 3.13\) days, \(R_p = 1.90^{+0.16}_{-0.14}\ R_\oplus\)). TOI-1695 b's radius and orbital period situate the planet between model predictions from thermally-driven mass loss versus gas depleted formation, offering an important test case for radius valley emergence models around early M dwarfs. We confirm the planetary nature of TOI-1695 b based on five sectors of TESS data and a suite of follow-up observations including 49 precise radial velocity measurements taken with the HARPS-N spectrograph. We measure a planetary mass of \(6.36 \pm 1.00\ M_\oplus\), which reveals that TOI-1695 b is inconsistent with a purely terrestrial composition of iron and magnesium silicate, and instead is likely a water-rich planet. Our finding that TOI-1695 b is not terrestrial is inconsistent with the planetary system being sculpted by thermally driven mass loss. We present a statistical analysis of seven well-characterized planets within the M dwarf radius valley demonstrating that a thermally-driven mass loss scenario is unlikely to explain this population.
NASA's Transiting Exoplanet Survey Satellite (TESS) is an all-sky survey mission designed to find transiting exoplanets orbiting nearby bright stars. It has identified more than 329 transiting ...exoplanets, and almost 6,000 candidates remain unvalidated. In this manuscript, we discuss the findings from the ongoing VaTEST (Validation of Transiting Exoplanets using Statistical Tools) project, which aims to validate new exoplanets for further characterization. We validated 11 new exoplanets by examining the light curves of 24 candidates using the LATTE and TESS-Plot tools and computing the False Positive Probabilities using the statistical validation tool TRICERATOPS. These include planets suitable for atmospheric characterization using transmission spectroscopy (TOI-2194b), emission spectroscopy (TOI-3082b and TOI-5704b) and for both transmission and emission spectroscopy (TOI-672b, TOI- 1694b, and TOI-2443b); One super-Earth (TOI-2194b) orbiting a bright (V = 8.42 mag), metal-poor (Fe/H = -0.3720 \(\pm\) 0.1) star; one short-period Neptune-like planet (TOI-5704) in the Hot Neptune Desert. In total, we validated 1 super-Earth, 7 sub-Neptunes, 1 Neptune-like, and 2 sub-Saturn or super-Neptune-like exoplanets. Additionally, we identify five likely planet candidates (TOI-323, TOI- 1180, TOI-2200, TOI-2408 and TOI-3913) which can be further studied to establish their planetary nature.
We present the TESS discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright ...(\(V_J\)=12.5, \(K_s\)=8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70\(\pm\)0.04 \(R_\oplus\) and 0.98\(\pm\)0.06 \(R_\oplus\) in 0.86-day and 3.69-day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. HARPS RV monitoring yields 97.7 percentile mass upper limits of 0.35 \(M_\oplus\) and 1.4 \(M_\oplus\) for planets b and c, respectively. The astrometric companion detected by the CTIO/SMARTS 0.9m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the JWST and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9\(\pm\)0.1 \(R_\oplus\) in a 4.97-day orbit is also identified in multi-Cycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung-Russell diagram. This gap is tied to the transition from partially- to fully-convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars.
Mature super-Earths and sub-Neptunes are predicted to be \(\simeq\)Jovian radius when younger than 10 Myr. Thus, we expect to find 5-15\(R_\oplus\) planets around young stars even if their older ...counterparts harbor none. We report the discovery and validation of TOI 1227 b, a \(0.85\pm0.05R_J\) (9.5\(R_\oplus\)) planet transiting a very low-mass star (\(0.170\pm0.015M_\odot\)) every 27.4 days. TOI~1227's kinematics and strong lithium absorption confirm it is a member of a previously discovered sub-group in the Lower Centaurus Crux OB association, which we designate the Musca group. We derive an age of 11\(\pm\)2 Myr for Musca, based on lithium, rotation, and the color-magnitude diagram of Musca members. The TESS data and ground-based follow-up show a deep (2.5\%) transit. We use multiwavelength transit observations and radial velocities from the IGRINS spectrograph to validate the signal as planetary in nature, and we obtain an upper limit on the planet mass of \(\simeq0.5 M_J\). Because such large planets are exceptionally rare around mature low-mass stars, we suggest that TOI 1227 b is still contracting and will eventually turn into one of the more common \(<5R_\oplus\) planets.
We report the discovery of ten short-period giant planets (TOI-2193A b, TOI-2207 b, TOI-2236 b, TOI-2421 b, TOI-2567 b, TOI-2570 b, TOI-3331 b, TOI-3540A b, TOI-3693 b, TOI-4137 b). All of the ...planets were identified as planet candidates based on periodic flux dips observed by NASA's Transiting Exoplanet Survey Satellite (TESS). The signals were confirmed to be from transiting planets using ground-based time-series photometry, high angular resolution imaging, and high-resolution spectroscopy coordinated with the TESS Follow-up Observing Program. The ten newly discovered planets orbit relatively bright F and G stars (\(G < 12.5\),~\(T_\mathrm{eff}\) between 4800 and 6200 K). The planets' orbital periods range from 2 to 10~days, and their masses range from 0.2 to 2.2 Jupiter masses. TOI-2421 b is notable for being a Saturn-mass planet and TOI-2567 b for being a ``sub-Saturn'', with masses of \(0.322\pm 0.073\) and \(0.195\pm 0.030\) Jupiter masses, respectively. In most cases, we have little information about the orbital eccentricities. Two exceptions are TOI-2207 b, which has an 8-day period and a detectably eccentric orbit (\(e = 0.17\pm0.05\)), and TOI-3693 b, a 9-day planet for which we can set an upper limit of \(e < 0.052\). The ten planets described here are the first new planets resulting from an effort to use TESS data to unify and expand on the work of previous ground-based transit surveys in order to create a large and statistically useful sample of hot Jupiters.
The Differential Absorption Hard X-ray (DAHX) spectrometer has been developed to diagnose photon energies above 80 keV and provides a time-resolved measurement of the x-ray spectrum from the plasma ...driven by Z. The DAHX spectrometer is a revitalization of the Hard X-Ray Spectrometer (HXRS) fielded on Z prior to refurbishment 1 . DAHX consists of an array of seven collimated silicon PIN diodes with varying filters in a 2 to 4 inch thick tungsten cylinder that shields the diodes from the surrounding radiation environment. Analyzed data from DAHX will be presented for several wire array experiments. Development of DAHX is driven by the need to extend the present diagnostic suite on Z to energies above 25 keV to investigate the origin, intensity, and spectrum of warm and hard x-rays within the emitting plasma. Filtered PCDs 2 and TLDs were also fielded. The PCDs are capable of measuring time resolved output up to a few tens of keV while TLDs are capable of measuring time integrated yield up to hundreds of MeV. These measurements pair well with the time resolved hard x-ray information that DAHX provides. To aid analysis of the silicon PIN diode signals, the diode performance was studied using the short pulse Z-Petawatt laser. Data and analysis from this study will be presented along with wire array measurements from TLDs, PCDs, and DAHX. The analysis of the DAHX data will be discussed, both in isolation and in conjunction with the additional diagnostics. The design of an updated version of DAHX with 15 diodes tailored to the current Z machine radiation environment will also be presented.
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