TOI-1232 is a G dwarf star with a mass of 1.06(-0.06)(+0.07)M(circle dot) , a radius of 1.07 +/- 0.05 R-circle dot, and a slightly higher metallicity than solar of Fe/H = 0.18 +/- 0.05. The star hosts a transiting warm Jovian-mass planet, TOI-1232 b, with an orbital period of P-b=14.256(-0.001)(+0.001 )days, identified with data from multiple sectors of the TESS space telescope. The TESS light curve of TOI-1232 is complex, as it is contaminated by a background eclipsing binary with a period of 1.37 days. TOI-1232 b was firmly confirmed by ground-based transit follow-up campaigns from the Las Cumbres, Hazelwood, Brierfield, and ASTEP observatories. Additionally, the TESS transits of TOI-1232 b exhibit strong transit-timing variations (TTVs) with a superperiod of 235.5 +/- 0.7 days and a semiamplitude of 27 minutes. Radial velocity (RV) follow-up with the FEROS spectrograph confirms the planetary nature of the transiting candidate, while a self-consistent N-body analysis of RVs and TTVs pinpoints the presence of a second outer Saturn-mass companion, TOI-1232 c with a period of P-c=30.356(-0.012)(+0.010) days. The TOI-1232 warm-giant system is particularly important due to the evidence of two massive planets that reside near the 2:1 commensurability but are not locked in a mean-motion resonance. Thanks to TESS, we have revealed a handful of these rare systems. Hence, TOI-1232 is an important addition to understanding the formation and dynamical evolution of such compact, massive, warm giant planets.

We present the analysis of five long-period TESS Objects of Interest (TOIs), all orbiting Sun-like stars, with orbital periods exceeding one month. Initially identified by the Transiting Exoplanet Survey Satellite (TESS), we extensively monitored these targets with the Antarctic Search for Transiting Exoplanets (ASTEP), supported by other facilities in the TESS Follow-up Observing Program (TFOP) network. These targets occupy a relatively underexplored region of the period-radius parameter space, offering valuable primordial probes for planetary formation and migration as warm planets better maintain their evolutionary fingerprints. To characterise these systems, we leveraged high-resolution speckle imaging to search for nearby stellar companions, and refine stellar parameters using both reconnaissance spectroscopy and spectral energy distribution (SED) fitting. We combined TESS photometry with high-precision ground-based observations from ASTEP, and when available, included additional photometry and radial velocity data. We applied statistical validation to assess the planetary nature of each candidate and used Allesfitter to jointly model the photometric and spectroscopic datasets. We validate the planetary nature of three TOIs, including the two warm Saturns TOI-4507b (8.2 Earth radii, 104d) and TOI-3457b (10.0 Earth radii, 32.6d), as well as the warm sub-Neptune TOI-707b (2.4 Earth radii, 52.8d). The remaining two candidates are most consistent with eclipsing binaries, namely TOI-2404 and TOI-4404. These results help populate the sparse regime of warm planets, which serve as key tracers of planetary evolution, and demonstrate ASTEP's effectiveness as a ground-based follow-up instrument for long-period systems.

We identify two large-radius planets around the F-type star HD 114082 as the longest-period young transiting exoplanets known. From the first transit, detected by NASA's Transiting Exoplanet Survey Satellite (TESS), and a second dip, spotted by the Next-Generation Transit Survey (NGTS), we predicted midtransit times for HD 114082 b (planet b). We pinpoint its orbit (period P-b = 225.5504 +/- 0.0004 days) from a third transit captured with the ESA's CHaracterising ExOplanet Satellite and the upgraded Antarctic Search for Transiting ExoPlanets telescope (ASTEP+), alongside orbit-discriminating observations. Another dimming partly covered by ASTEP+ completes the four-transit series. We support with dynamical evidence the planetary nature of a deeper transit detected with TESS and NGTS, identifying planet c. Additionally, we reexamine the debris disk, fitting its excess emission with two dust components. Fundamental stellar parameters are inferred from stellar evolution models, while a joint modeling of photometric and radial velocity time series yields the planetary parameters, with masses further constrained using an N-body code. For planet b, the semimajor axis a(b) = 0.791 +/- 0.008 au, eccentricity e(b) approximate to 0, inclination i(b) = 89 . degrees 791 +/- 0.014, radius R-b = 1.046 +/- 0.014 R-J, and 95% confidence upper limit on its mass M-95%,M-b = 1.6 M-J. For planet c, a(c) = 0.99 - 0.04 + 0.03 au, e(c) approximate to 0, i(c) = 89 . degrees 701 +/- 0.011, R-c = 1.36 +/- 0.03 R-J, and M-95%,M-c = 2.0 M-J (0.24 M-J if adding transit-timing-variation constraints). They seem to be moderate-to-low-mass giants in nearly resonant, coplanar, circular orbits that formed in situ, or beyond the snow line, and migrated inward, shaping the disk.

Beyond orbital periods of 10 days, there is a dearth of known transiting gas giants. On longer orbits, planets are less affected by their host star, and become ideal probes of planet formation, migration and evolution. We report the discovery of a long period Neptune and two Saturns, each initially identified as single transits in the TESS photometry, and solved through additional transits from ground-based follow-up photometric observations by NGTS and ASTEP. High-resolution radial velocity mass measurements using CORALIE and HARPS confirm their planetary nature. From joint modelling of the photometric and spectroscopic data, we determine an orbital period of $43.12655_{-0.00017}^{+0.00012}~$days, radius of 3.65 ± 0.22 R⊕, and mass of $19.1_{-4.5}^{+4.9}~\mathrm{M_{\rm{\oplus }}}$ for NGTS-34 b, making it one of the longest period well-characterized transiting Neptunes. Orbiting a late F-type star, bright in the K-band (Kmag ≃ 7.9), it is amenable for cool atmosphere studies using JWST or Ariel. TOI-4940 b is a small Saturn on a $25.867811_{-0.000056}^{+0.000058}~$day orbit with a radius of 6.61 ± 0.37 R⊕ and an upper mass limit <89 M⊕. NGTS-35 b(=TOI-6669 b) is a larger Saturn on a 25.241192 ± 0.000022 day, moderately eccentric orbit ($e = 0.192_{-0.033}^{+0.037}$), with a radius of 10.90 ± 0.65 R⊕ and a mass of $152_{-19}^{+22}~\mathrm{M_{\rm{\oplus }}}$. With an assumed albedo A = 0.3, each of these planets has an equilibrium temperature below 700K, with NGTS-35 b especially cold at 450 K. These three giants add to the small but growing population of long period planets that can further our understanding of planet formation mechanisms.

On 27 December 2024, near-Earth object (NEO) 2024 YR_4 was discovered by the ATLAS survey and identified as a virtual impactor. A few weeks later, it eventually reached level 3 on the Torino Scale and was the first and only asteroid to be ever classified at that level. Here we report an intensive observational campaign combining time-series photometry in the visible, broadband visible and near-infrared colors, and low-resolution visible reflectance spectroscopy to assess its physical properties. Fourier analysis of the lightcurves yields a synodic rotation period of P = 19.46341 ± 0.00008 min, placing 2024 YR_4 among the fast rotators, even if such rotation is common for objects of similar H magnitude. Its visible and near-infrared colors and spectra are most consistent with an Sq or K taxonomic classification, though some ambiguity remains. Finally, its phase curve exhibits a notably shallow slope (G = 0.51 ± 0.11), from which we derive an absolute magnitude of H_R = 23.82±0.09 mag. After color correction and taking into account other models for the phase function, we report an absolute magnitude of H_V = 24.14±0.25 mag. These characterizations, rotation period, taxonomy, and surface properties, would have been crucial for risk assessment and mitigation planning had the initially high impact probability scenario been confirmed, underscoring the importance for planetary defense of a rapid, coordinated international response.

We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density <0.2 g cm(-3) on a 10(5) days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M-circle plus at 95% confidence. The radial velocities also exhibit the Rossiter-McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity lambda=-15(-44)(+50 degrees )(divided by lambda divided by < 80 degrees at 3 sigma). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest "superpuff" planets yet discovered.

Studying planetary interactions in exoplanet systems informs theories of planet formation and evolution, providing essential context for understanding our own solar system. We combine spectroscopy, transit photometry, transit timing variations, and astrometry to characterize the TOI-201 system. The cotransiting system consists of a super-Earth, warm Jupiter, and massive companion at 5.8-, 53-, and 2900-day orbital periods, respectively. We perform dynamical simulations to study the past and future of the system. von-Zeipel-Kozai-Lidov oscillations emerge as the most plausible scenario to explain the outer companion's high orbital eccentricity, with planet-planet scattering a possible but less likely contender. Because of nonzero mutual inclinations between the planets, the system is visibly evolving on very short timescales, with the current cotransiting configuration ending in 200 years.

Context. Long-period transiting planets are essential edge-cases for understanding exoplanet formation and evolution. Their detection is challenging due to the infrequent nature of their transits, making every observation of these objects very valuable. Aims. Our goal is to confirm and further characterise the long-period planetary candidate TOI-4409 b (initially identified by TESS) through additional observations using the Antarctica-based ASTEP telescope, supplemented with CHAT, OMES, LCOGT, and PEST light-curve data and radial-velocity (RV) measurements collected with the HARPS, FEROS, and PFS instruments. Methods. We jointly analysed the photometric data from eight TESS, four ASTEP, one CHAT, two OMES, four LCOGT, and one PEST light curve(s), and RV data from the HARPS, FEROS, and PFS instruments, covering observations from 2018 to 2024. Results. TOI-4409 b is a bona fide puffy warm super-Neptune exoplanet with a planet radius of 7.44 ± 0.19 R⊕ and a mass of 0.047 ± 0.017 MJ (3σ upper limit <0.095 MJ) orbiting a low-mass main-sequence star (effective temperature of 4928 ± 48 K and a stellar radius of 0.720 ± 0.018 R⊙) with a period of 92.49179 ± 0.00010 days. The integration of various observational methods and consistent transit signals across multiple instruments confirms the planetary nature of TOI-4409 b. The combined transit, imaging, chromaticity, and RV evidence supports the confirmation of the planet. Conclusions. With a radius of 7.44 ± 0.19 R⊕ and a low bulk density of 0.20 ± 0.07 g cm−3, TOI-4409 b occupies a sparsely populated region of parameter space among warm, puffy super-Neptunes on long-period orbits. The detection of candidate transit timing variations with an ~10-minute semi-amplitude hints at the presence of an additional body in the system. The favourable host-star brightness and extended transit duration (~7 hours) make TOI-4409 b a promising target for atmospheric characterisation with JWST and Ariel.

We present new post-perihelion polarimetric observations of the third discovered interstellar object, 3I/ATLAS (C/2025 N1; hereafter 3I), obtained using FORS2 at the Very Large Telescope, ALFOSC at the Nordic Optical Telescope, and FoReRo2 at the 2 m Ritchey-Chrétien-Coudé telescope. The observations span phase angles 1-30^∘, providing the most extensive polarimetric phase angle coverage obtained for an interstellar object to date. The post-perihelion measurements reveal that the unusual polarimetric properties of 3I persist across perihelion and match recent independent post-perihelion observations, indicating no significant evolution in the polarimetric properties. The increased phase angle coverage allowed us to further constrain the minimum polarisation to -2.9% at phase angle 5.5^∘. Multi-band BVRI observations reveal a wavelength dependence of polarisation, with the negative polarisation branch becoming deeper and shifted toward smaller phase angles at longer wavelengths. The polarimetric colour is predominantly red and increases with phase angle, consistent with behaviour observed in other comets. Imaging and polarimetric maps show a substantially more extended coma after perihelion, while the polarisation distribution itself remains smooth and spatially homogeneous. Numerical modelling suggests that the unusually deep polarisation phase curve originates from moderately porous dust aggregates consisting of weakly absorbing sub-micron monomers, resulting in much brighter dust than that in typical solar system comets.

Gas giant planets with periods 20 < P < 300 d orbiting Sun-like stars are a relatively uncommon outcome of planetary formation, and key questions about the nature and formation of this subpopulation remain unanswered. Theoretical models for the location of their formation ( in situ or ex situ ) and for their subsequent migration predict different outcomes in terms of planet masses and eccentricities, indicating that observations have a key role to play in disentangling their histories. In this work, we present the discovery and confirmation of a pair of long-period Jupiter-sized planets transiting an F7 star: TOI-791 b is a 0.993 +/- 0.033 R-Jup planet on a 139.29931(-0.00012)(+0.00011) d orbit, and TOI-791 c, a 1.155 +/- 0.040 R-Jup planet on a 232.01570(-0.00071 )(+0.00067)d orbit. The two planets are within 0.07 per cent of a second-order 5:3 period commensurability leading to transit timing variations (TTVs) of up to 50 min. We confirm their planetary nature using ground-based photometry, including multiple full detections of the > 11 h transits of both TOI-791 b and c from Antarctica with ASTEP, making these the longest-duration transits ever observed in their entirety from the ground. Our detailed analysis of the TTV signal allows us to measure dynamical masses for both planets, which yield densities of rho(b) = 0.038 +/- 0.008 g cm(-3) and rho(c) = 0.047 +/- 0.006 g cm(-3), indicating that TOI-791 b and c are two of the lowest density giant planets ever detected. While these measurements are robust, further follow-up is needed to fully characterize the TTV signal and the architecture of the system.

Context. We present the analysis of five long-period TESS Objects of Interest (TOIs), all orbiting Sun-like stars, with orbital periods exceeding one month. Initially identified by the Transiting Exoplanet Survey Satellite (TESS), we extensively monitored these targets with the Antarctic Search for Transiting Exoplanets (ASTEP), supported by other facilities in the TESS Follow-up Observing Program (TFOP) network. Aims. These targets occupy a relatively underexplored region of the period-radius parameter space, offering valuable primordial probes for planetary formation and migration as warm planets better maintain their evolutionary fingerprints. Methods. To characterise these systems, we leveraged high-resolution speckle imaging to search for nearby stellar companions, and refine stellar parameters using both reconnaissance spectroscopy and spectral energy distribution (SED) fitting. We combined TESS photometry with high-precision ground-based observations from ASTEP, and when available, included additional photometry and radial velocity data. We applied statistical validation to assess the planetary nature of each candidate and used allesfitter to jointly model the photometric and spectroscopic datasets. Results. We validate the planetary nature of three TOIs, including the two warm Saturns TOI-4507 b (8.2 R⊕, 104 d) and TOI-3457 b (10.0 R⊕, 32.6 d), as well as the warm sub-Neptune TOI-707 b (2.4 R⊕, 52.8 d). The remaining two candidates are most consistent with eclipsing binaries, namely TOI-2404 and TOI-4404. Conclusions. These results help populate the sparse regime of warm planets, which serve as key tracers of planetary evolution, and demonstrate ASTEP’s effectiveness as a ground-based follow-up instrument for long-period systems.

We present the first polarimetric observations of the third discovered interstellar object (ISO), 3I/ATLAS (C/2025 N1, or 3I), obtained preperihelion with FORS2 at the Very Large Telescope, ALFOSC at the Nordic Optical Telescope, and FoReRo2 at the 2 m Ritchey-Chr & eacute;tien-Coud & eacute; telescope, over a phase angle range of 7 .degrees 7-22 .degrees 4. This marks the second-ever polarimetric study of an ISO, the first distinguishing 2I/Borisov from most solar system comets by its higher positive polarization. Our polarimetric measurements as a function of phase angle reveal that 3I is characterized by a deep and narrow negative polarization branch, reaching a minimum value of -2.7% at phase angle 7 degrees, and an inversion angle of 17 degrees-a combination unprecedented among asteroids and comets, including 2I/Borisov. At very small phase angles, the extrapolated slope of the polarization phase curve is consistent with that of certain small trans-Neptunian objects and Centaur Pholus, consistent with independent spectroscopic evidence for a red, possibly water-ice-bearing object. Imaging confirms a diffuse coma present from our earliest observations, though no strong polarimetric features are spatially resolved. These findings may demonstrate that 3I represents a distinct type of comet, expanding the diversity of known interstellar bodies.

We present Cryoscope, a new 50 deg 2 field-of-view, 1.2 m aperture, K dark survey telescope to be located at Dome C, Antarctica. Cryoscope has an innovative optical–thermal design wherein the entire telescope is cryogenically cooled. Cryoscope also explores new detector technology to cost-effectively tile the full focal plane. Leveraging the dark Antarctic sky and minimizing telescope thermal emission, Cryoscope achieves unprecedented deep, wide, fast, and red observations, matching and exceeding volumetric survey speeds from the Ultraviolet Explorer, Vera Rubin Observatory, Nancy Grace Roman Space Telescope, SPHEREx, and NEO Surveyor. By providing coverage beyond wavelengths of 2 μ m, we aim to create the most comprehensive dynamic movie of the most obscured reaches of the Universe. Cryoscope will be a dedicated discovery engine for electromagnetic emission from coalescing compact binaries, Earth-like exoplanets orbiting cold stars, and multiple facets of time-domain, stellar, and solar system science. In this paper, we describe the scientific drivers and technical innovations for this new discovery engine operating in the K dark passband, why we choose to deploy it in Antarctica, and the status of a fifth-scale prototype designed as a Pathfinder to retire technological risks prior to full-scale implementation. We plan to deploy the Cryoscope Pathfinder to Dome C in 2026 December and the full-scale telescope by 2030.

We present relative astrometric measurements of visual double stars, made in 2017-2018 with the speckle camera PISCO at the 1-m Epsilon telescope of the C2PU facility (Observatoire de la C & ocirc;te d'Azur, Calern site). Our observing list contains orbital couples as well as double stars whose motion is still uncertain. From our observations of 1400 multiple stars, we obtained 1376 new measurements with angular separations in the range 0 ''.1$$ {0}<^>{{\prime\prime} }.1 $$-8 ''.5$$ {8}<^>{{\prime\prime} }.5 $$, and an average accuracy of 0 ''.008$$ {0}<^>{{\prime\prime} }.008 $$. The mean error on the position angles is 0 degrees.50. Most of the position angles were determined without the usual 180 degrees ambiguity with the application of the direct vector auto-correlation technique and/or by inspection of the long integration files. We present new and revised orbits for A1913 AB, A1710, COU1394, BU1185, A122, A570, HU577, COU812, HU332, A2095 AB, and A884, partly derived from our PISCO observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types.

On 2020 April 29, the near-Earth object (52768) 1998 OR2 experienced a close approach to Earth at a distance of 16.4 lunar distances (LD). 1998 OR2 is a potentially hazardous asteroid of absolute magnitude H = 16.04 that can currently come as close to Earth as 3.4 LD. We report here observations of this object in polarimetry, photometry, and radar. Our observations show that the physical characteristics of 1998 OR2 are similar to those of both M- and S-type asteroids. Arecibo's radar observations provide a high radar albedo of sigma OC= 0.29 +/- 0.08, suggesting that metals are present in 1998 OR2 near-surface. We find a circular polarization ratio of mu c = 0.291 +/- 0.012, and the delay-Doppler images show that the surface of 1998 OR2 is a top-shape asteroid with large-scale structures such as large craters and concavities. The polarimetric observations display a consistent variation of the polarimetric response as a function of the rotational phase, suggesting that the surface of 1998 OR2 is heterogeneous. Color observations suggest an X-complex taxonomy in the Bus-DeMeo classification. Combining optical polarization, radar, and two epochs from the NEOWISE satellite observations, we derived an equivalent diameter of D = 1.80 +/- 0.1 km and a visual albedo p v = 0.21 +/- 0.02. Photometric and radar data provide a sidereal rotation period of P = 4.10872 +/- 0.00001 hr, a pole orientation of (332.degrees 3 +/- 5 degrees, 20.degrees 7 +/- 5 degrees), and a shape model with dimensions of (2.08-0.10+0.10,1.93-0.10+0.10,1.60-0.05+0.05) km.

Dome-C in the Antarctic Plateau is a privileged site for Astronomy, with one of the lowest concentrations of water vapor in the world, providing a pristine atmospheric window for IR observations. Together with the long winter nights, this allows for extended continuous observational campaigns. At the Concordia Station, ASTEP has taken advantage of the weather and long nights to observe long-period transiting exoplanets for over a decade. With the Cryoscope Pathfinder we now plan to take advantage of the dark IR window between 2.35 and 2.55𝜇m. The unique design of Cryoscope Pathfinder is optimized for a very wide field of view and very thermal background. It is a cryogenic 0.26 m telescope designed for observations in K-dark with a field of view of 16 deg^2. This is the first step for a much more ambitious project, the full scale 1-meter class Cryoscope telescope, with a field of view of 50 deg^2. The initial science drivers are the study of exoplanets and of the infrared transient sky, where it will play a major role in the localization of gravitational wave sources. Furthermore, many other science topics will be enabled by Cryoscope and through synergies with other surveys.

We present the spectroscopic confirmation and precise mass measurement of the warm giant planet TOI-199 b. This planet was first identified in TESS photometry and confirmed using ground-based photometry from ASTEP in Antarctica including a full 6.5 hr long transit, PEST, Hazelwood, and LCO; space photometry from NEOSSat; and radial velocities (RVs) from FEROS, HARPS, CORALIE, and CHIRON. Orbiting a late G-type star, TOI-199 b has a 104.854 − 0.002 + 0.001 day period, a mass of 0.17 ± 0.02 M J , and a radius of 0.810 ± 0.005 R J . It is the first warm exo-Saturn with a precisely determined mass and radius. The TESS and ASTEP transits show strong transit timing variations (TTVs), pointing to the existence of a second planet in the system. The joint analysis of the RVs and TTVs provides a unique solution for the nontransiting companion TOI-199 c, which has a period of 273.69 − 0.22 + 0.26 days and an estimated mass of 0.28 − 0.01 + 0.02 M J . This period places it within the conservative habitable zone.

The impact of the Double Asteroid Redirection Test spacecraft into Dimorphos, moon of the asteroid Didymos, changed Dimorphos’s orbit substantially, largely from the ejection of material. We present results from 12 Earth-based facilities involved in a world-wide campaign to monitor the brightness and morphology of the ejecta in the first 35 days after impact. After an initial brightening of ∼1.4 mag, we find consistent dimming rates of 0.11–0.12 mag day ^−1 in the first week, and 0.08–0.09 mag day ^−1 over the entire study period. The system returned to its pre-impact brightness 24.3–25.3 days after impact though the primary ejecta tail remained. The dimming paused briefly eight days after impact, near in time to the appearance of the second tail. This was likely due to a secondary release of material after re-impact of a boulder released in the initial impact, though movement of the primary ejecta through the aperture likely played a role.

We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite TESS as TOI-588 b. HIP 33609 b is a large (R$_{b}$ = 1.580$_{-0.070}^{+0.074}$ R$_{J}$) brown dwarf on a highly eccentric (e = 0.560$_{-0.031}^{+0.029}$) orbit with a 39-day period. The host star is a bright (V = 7.3 mag), T$_{eff}$ = 10,400$_{-660}^{+800}$ K star with a mass of M$_{*}$ = 2.383$_{-0.095}^{+0.10}$ M$_{\odot}$ and radius of R$_{*}$ = 1.863$_{-0.082}^{+0.087}$ R$_{\odot}$, making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M$_{b}$ = 68.0$_{-7.1}^{+7.4}$ M$_{J}$ as well as the host star's rotation rate ($vsini_{*} = 55.6 \pm 1.8$ km/s). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 $\pm$ 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.