We present the TESS-based discoveries of planetary systems orbiting the late G dwarfs TOI-2494 and TOI-5143, each of which harbors a hot giant planet and a smaller interior planet. TOI-2494 hosts a transiting mini-Neptune (P = 2.41 days, RP=2.35-0.15+0.16 R circle plus) and a hot Saturn (P = 8.38 days) with grazing transits, while TOI-5143 hosts a transiting mini-Neptune (P = 2.38 days, RP=2.73-0.17+0.19 R circle plus) and a hot Jupiter (P = 5.21 days) with grazing transits. We measure the masses of TOI-2494 c (80 +/- 19 M circle plus) and TOI-5143 c (208 +/- 14 M circle plus), place upper limits on the masses of the smaller planets, and explore the architectures of the planetary systems. TOI-2494 c and TOI-5143 c join a small but growing number of short-period giant planets known to be flanked by smaller companions. While the absence of close neighbors to most hot Jupiters would be consistent with disruptive dynamical evolution, the presence of nearby small planets in some hot Jupiter systems points to a separate, dynamically quiet formation pathway. In support of this conclusion, we present preliminary evidence that hot giant planets with small nearby companions tend to have low mutual orbital inclinations, consistent with the mutual inclination distribution of the dynamically quiet population of compact systems of multiple super-Earths and mini-Neptunes.

We present four newly validated transiting brown dwarfs identified through TESS photometry and confirmed with high-precision radial velocity measurements obtained from the FEROS and PLATOSpec spectrographs. Notably, three of these companions exhibit orbital periods exceeding 100 days, thereby expanding the sample of long-period transiting brown dwarfs from four to seven systems. The host stars of the long-period brown dwarfs show mild subsolar metallicity. These discoveries highlight the expansion of the metal-poor long-period distribution and help us better understand the brown dwarf desert. In our comparative analysis of eccentricity and metallicity demographics, we utilized catalogs of long-period giant planets, brown dwarfs, and low-mass stellar companions. After accounting for tidal influences, the eccentricity distribution aligns with that of low-mass stellar binaries, presenting a different profile than that observed within the giant planet population. Additionally, the metallicity of the host stars reveals a noteworthy trend: Short-period transiting brown dwarfs are predominantly associated with metal-rich stars, whereas long-period brown dwarfs are more often found around metal-poor stars, thus demonstrating statistical similarities to low-mass stellar hosts. This trend has been previously observed in studies of hot and cold Jupiters and points to a period-coded mixture of channels. A natural explanation is that most brown dwarfs originate from fragmentation at wider separations, with long-period systems retaining this stellar-like imprint, while only those embedded in massive, long-lived metal-rich protoplanetary disks are efficiently delivered and stabilized to short orbits.

Despite decades of research on hot Jupiters, there are still several theories for their formation. Perhaps hot Jupiters form in several ways. Atmospheric and dynamical studies have the capability to constrain the formation scenarios. However, potential targets have to be well characterized before these observations can further constrain the theories. We present the confirmation and characterization of five hot and warm Jupiters discovered by the TESS space mission. Using TESS data combined with ground-based observations, we determine the masses, radii, and other parameters of TOI-2040 b, TOI-2049 b, TOI-2578 b, TOI-4427 b, and TOI-4458 b. Three of the planets have equilibrium temperatures of about 1800 K while two have temperatures of about 1000 K. Particularly interesting for future atmospheric characterizations are TOI-2578 b and TOI-4427 b, because of their low density and large transmission spectroscopy metric. TOI-4458 b is of special interest because it is in the northern PLATO field. It appears that TOI-2040 b has a small, but measurable eccentricity.

The quality of training datasets for deep neural networks is a key factor contributing to the accuracy of resulting models. This effect is amplified in difficult tasks such as object detection. Dealing with errors in datasets is often limited to accepting that some fraction of examples are incorrect, estimating their confidence, and either assigning appropriate weights or ignoring uncertain ones during training. In this work, we propose a different approach. We introduce the Confident Learning for Object Detection (CLOD) algorithm for assessing the quality of each label in object detection datasets, identifying missing, spurious, mislabeled, and mislocated bounding boxes and suggesting corrections. By focusing on finding incorrect examples in the training datasets, we can eliminate them at the root. Suspicious bounding boxes can be reviewed to improve the quality of the dataset, leading to better models without further complicating their already complex architectures. The proposed method is able to point out nearly 80% of artificially disturbed bounding boxes with a false positive rate below 0.1. Cleaning the datasets by applying the most confident automatic suggestions improved mAP scores by 16% to 46%, depending on the dataset, without any modifications to the network architectures. This approach shows promising potential in rectifying state-of-the-art object detection datasets.

We present a ground-based transit detection of HIP 41378 f, a long-period ($P = 542$ days), extremely low-density ($0.09 \pm 0.02$ g cm$^{-3}$) giant exoplanet in a dynamically complex system. Using photometry from Tierras, TRAPPIST-North, and multiple LCOGT sites, we constrain the transit center time to $T_{C,6} = 2460438.889 \pm 0.049$ BJD TDB. This marks only the second ground-based detection of HIP 41378 f, currently the longest-period and longest-duration transiting exoplanet observed from the ground. We use this new detection to update the TTV solution for HIP 41378 f and refine the predicted times of its next two transits in November 2025 and April 2027. Incorporating new TESS Sector 88 data, we also rule out the 101-day orbital period alias for HIP 41378 d, and find that the remaining viable solutions are centered on the 278, 371, and 1113-day aliases. The latter two imply dynamical configurations that challenge the canonical view of planet e as the dominant perturber of planet f. Our results suggest that HIP 41378 d may instead play the leading role in shaping the TTV of HIP 41378 f.

Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically-confirmed metal-poor ([Fe/H] = -0.72 +/- 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of 3.4373125 d and a planetary radius of 1.475 +/- 0.029 R_Jup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 +/- 0.14 M_Jup. The planet is therefore inflated, with a low density of 0.159 +0.055/-0.054 g/cm^3. We also characterize the host star, showing that TOI-7169 is ancient (12.3 +/- 0.6 Gyr) and alpha-enhanced ([alpha/Fe] 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.

Dusty disks around planetary and substellar companions in outer reaches of exoplanetary systems can be detected as long-lasting occultations, provided the observer is close to the secondary’s orbital plane. Here we report optical spectroscopy with KOSMOS (Apache Point Observatory), MagE (Magellan), and GHOST (Gemini-S) of ASASSN-24fw (Gaia 07:05:18.97+06:12:19.4), a 4 mag dimming event of a main-sequence star which lasted 8.5 months. We discover multiple low-ionization metal emission lines with velocity dispersion ≲ 10 km s ^−1 blueshifted by 27 km s ^−1 with respect to the star, as well as kinematically complex Na D absorption. If associated with the occulter, these detections suggest that the occulter is gas rich. Further, we detect a blueshifted and broad (∼200 km s ^−1 ) H α line, which likely originates in the inner circumstellar disk. We confirm the previously reported occultations in 1981 and 1937 seen in historic data, yielding a semimajor axis of the occulter’s orbital motion around the star of 14 au. If the occulter is a circumsecondary disk filling 30%–100% of the Hill radius, we estimate the minimum mass of the secondary to be a few Jupiter masses and a disk mass of 1% of the mass of the Moon. Given the age of the star (>2 Gyr), the disk is unlikely to be a survivor of the planet formation stage and may be the result of a planetary collision. If the Na D absorption and/or metal emission lines originate in the disk, the observations presented here are the first discovery of a circumsecondary disk wind or rotation.

We present a homogeneous analysis of rotational variability and spot properties in young stellar objects across multiple star-forming regions observed by the Hunting Outbursting Young Stars (HOYS) project. From over 2000 candidate members, we identify 144 YSOs with robust periodic signals and well-constrained multi-band amplitudes. The sample has a median age of $\sim$1~Myr, effective temperatures of 3500--6500~K (masses $\sim$0.6--2~M$_\odot$), and is dominated by Class~2 objects, one third of which exhibit inner disc dust emission. The rotation period distribution is strongly bimodal, with 55 percent fast rotators ($P<5.5$~d) and 45 percent slow rotators. Fast rotators are predominantly inner disc-less, whereas slow rotators include both disc-bearing and disc-free systems, indicating that disc braking alone cannot explain the observed rotational states. We derive spot properties from multi-band amplitudes and find that, after correcting for observational biases, the intrinsic cold-spot coverage distribution of fast rotators is well described by an exponential function. This implies that small spot coverages are intrinsically much more common than large ones, consistent with stochastic magnetic flux emergence governing spot formation. In contrast, slow rotators show a pronounced deficit of small cold spots. After considering observational biases and alternative physical explanations, we conclude that small spots on slowly rotating YSOs have significantly shorter lifetimes. These results provide new evidence that magnetic surface structure and its evolution depend on stellar rotation, placing new empirical constraints on models of magnetic activity and angular momentum evolution in young stars.

We report the discovery of two planets, a hot Jupiter and a nearby outer sub-Neptune, orbiting the star TOI-4468. This system is unique among the current exoplanet census in that it features a close outer companion to a hot Jupiter without an accompanying inner companion. By jointly fitting radial velocity measurements taken with the NEID spectrograph and transit photometry from TESS and several ground-based observatories, we constrain the orbital periods, masses, and radii of these two planets. We confirm the planetary nature of the hot Jupiter TOI-4468 b (R = 1.01 R_J, m = 0.54 M_J, P = 2.77 days). We also validate the outer planet TOI-4468 c (R = 0.28 R_J, P = 7.01 days) statistically, incorporating constraints from ground-based observations. We also identify, but cannot confirm, an additional radial velocity signal which may be due to an outer giant in this system with an orbital period of 624 days. From the observed geometry of this system, we argue that it must never have encountered an early secular resonance that is thought to excite the mutual inclination of other hot Jupiter/outer companion systems. We discuss the possibility of an undetected inner companion, as well as potential implications for hot Jupiter formation.

The overwhelming majority of CVs have orbital periods shorter than 10 hr. However, a few have much longer periods, and their formation and existence pose challenges for the CV evolution models. These extremely long-period CVs must host nuclearly evolved donor stars, as otherwise, the companion of the white dwarf would be too small to fill its Roche lobe. This makes them natural laboratories for testing binary evolution models and accretion processes with subgiant donors. To shed light on the formation and evolution of accreting compact objects with subgiant companions, we investigated two extremely long-period CVs in detail, namely V479 And and V1082 Sgr. We searched for reasonable formation pathways to explain their refined stellar and binary parameters. We used a broad set of new observations, including ultraviolet and infrared spectroscopy, results of circular polarimetry, and improved Gaia distance estimates to determine fundamental parameters to be confronted with numerical simulations. Furthermore, we utilized the MESA code to conduct numerical simulations, employing state-of-the-art prescriptions, such as the CARB model for strong magnetic braking. Both systems have unusual chemical compositions and very low masses for their assigned spectral classes. This most likely indicates that they underwent thermal timescale mass transfer. We found models for both that can reasonably reproduce their properties. We conclude that the donor stars in both V479 And and V1082 Sgr are filling their Roche lobes. Our findings suggest that orbital angular momentum loss is stronger due to magnetic braking in CVs with subgiant donors compared to those with unevolved donors. In addition, our findings suggest that extremely long-period CVs could significantly contribute to the population of double white dwarf binaries in close orbits.

We present the discovery of 30 transiting giant planets that were initially detected using data from NASA's Transiting Exoplanet Survey Satellite mission. These new planets orbit relatively bright (G <= 12.5) FGK host stars with orbital periods between 1.6 and 8.2 days, and have radii between 0.9 and 1.7 Jupiter radii. We performed follow-up ground-based photometry, high angular resolution imaging, high-resolution spectroscopy, and radial velocity monitoring for each of these objects to confirm that they are planets and determine their masses and other system parameters. The planets' masses span more than an order of magnitude (0.17 M-J < M-p < 3.3 M-J). For two planets, TOI-3593 b and TOI-4961 b, we measured significant nonzero eccentricities of 0.11(-0.03)(+0.05) and 0.18(-0.05)(+0.04 ), respectively, while for the other planets, the data typically provide a 1 sigma upper bound of 0.15 on the eccentricity. These discoveries represent a major step toward assembling a complete, magnitude-limited sample of transiting hot Jupiters around FGK stars.

Solar flares, originating from sudden energy releases in the Sun’s atmosphere, pose significant risks to spaceborne and terrestrial technological systems, including satellite operations, communications networks, and power grids. Accurate solar flare forecasting is therefore essential for mitigating these impacts and advancing space weather prediction capabilities. In this study, we present a comprehensive deep-learning-based approach utilizing multi-channel observations from the Solar Dynamics Observatory (SDO), a spaceborne remote sensing platform dedicated to solar monitoring. Our analysis focuses on classifying solar flares under three scenarios: C vs. 0, M vs. C, and M vs. 0, leveraging ten distinct image channels spanning photospheric magnetograms and extreme ultraviolet (EUV) wavelengths. We trained and evaluated three modern convolutional neural network architectures—ResNet50, GoogLeNet, and DenseNet121—using the True Skill Score (TSS) and Gini coefficient to assess performance. The results highlight the superior predictive power of magnetogram data, with additional contributions from EUV channels such as 94 and 211 Å. This work underscores the utility of combining multi-spectral solar observations with state-of-the-art deep learning architectures to capture subtle pre-flare signatures and improve flare prediction accuracy. Furthermore, the methodology and open dataset provide a reproducible benchmark for advancing solar flare forecasting, supporting the broader remote sensing and space weather research communities.

This article introduces an innovative meteor detection system that integrates high-speed photodiode detectors with traditional camera-based systems. The system employs four photodiodes to record changes in sky brightness at 100 Hz, enabling meteor detection and the observation of their dynamics. This technology serves as a valuable complement to existing imaging techniques, offering a cost-effective solution for measuring meteor ablation at frequencies beyond the capabilities of camera-based systems. We showcase findings from the Perseid meteor shower, demonstrating the potential of our system. Moreover, our system addresses the current limitations in meteor radiometry, where many existing instruments either remain in developmental stages or have not been validated with a substantial number of confirmed meteor events. Our approach successfully addresses these limitations, demonstrating effectiveness across multiple meteor events simultaneously recorded on video.

Heliophysics phenomena on the Sun, such as radio bursts, can strongly affect satellites and ground-based electronic systems. Therefore, an insight into the actual image of the Sun with good spatial and temporal resolution is crucial. In this paper, we explore the possibility of using fully convolutional networks (FCNs) to improve the images acquired from remotely operated small solar telescopes whose resolution is limited by the size of the lens aperture and by atmospheric turbulence. For this purpose, we use chromosphere data from the 50 mm small H $$\alpha$$ Telescope of the Silesian University of Technology acquired over many months under various atmospheric conditions. We compare the obtained results with the results of raw data processing by a state-of-the-art deterministic algorithm, multi-frame blind deconvolution (MFBD). In our research, we investigate the impact of the amount of data and the complexity of FCNs on the quality of the results and their processing time. We show that the use of FCNs is a very attractive alternative to MFBD because they are more energy efficient and allow for the obtaining of comparable results in orders of magnitude shorter time.

Context. The overwhelming majority of cataclysmic variables (CVs) have orbital periods shorter than 10 h. However, a few have much longer orbital periods, and their formation and existence pose certain challenges for the CV evolution models. These extremely long-period CVs must host nuclearly evolved donor stars (i.e., subgiants), as the companion of the white dwarf would otherwise be too small to fill its Roche lobe. This makes the extremely long-period CVs natural laboratories for testing binary evolution models and accretion processes with subgiant donors, with applications extending beyond white dwarf binaries. Despite the importance of compact objects accreting from subgiant donors, the process by which they form and evolve remains unclear. Aims. To shed light on the formation and evolution of accreting compact objects with subgiant companions, we investigated two extremely long-period CVs in detail, namely V479 And (P-orb similar or equal to 14 h) and V1082 Sgr (P-orb similar or equal to 21 h). We searched for reasonable formation pathways to explain their refined stellar and binary parameters. Methods. We used a broad set of new observations, including ultraviolet and infrared spectroscopy, results of circular polarimetry, and improved Gaia DR3 distance estimates, to determine the fundamental parameters (e.g., effective temperatures, masses, and radii of the donor stars) that would be confronted with numerical simulations. Furthermore, we utilized the MESA code to conduct numerical simulations, employing state-of-the-art prescriptions, such as the Convection And Rotation Boosted (CARB) model for strong magnetic braking. Results. The two systems have an unusual chemical composition and very low masses for their assigned spectral classes. This most likely indicates that they underwent thermal timescale mass transfer. We found models for the two extremely long-period CVs that can reasonably reproduce their properties. CV evolution needs to be convergent (i.e., toward shorter orbital periods), which is only possible if the magnetic braking is sufficiently strong. Conclusions. We conclude that the donor stars in both V479 And and V1082 Sgr are filling their Roche lobes, ruling out previous models in which they are underfilling their Roche lobes. Our findings suggest that orbital angular momentum loss is stronger due to magnetic braking in CVs with subgiant donors compared to those with unevolved donors. In addition, our findings suggest that extremely long-period CVs could significantly contribute to the population of double white dwarf binaries in close orbits (orbital periods less than or similar to 1 d).

Deep neural networks (DNNs) are widely considered essential for developing perception systems in autonomous applications. These models are often vulnerable to small perturbations in input data, even if the changes appear negligible to a human observer. This vulnerability introduces an additional risk of failure in safety-critical systems during normal operation. Unfortunately, there is currently no quantitative risk analysis addressing such image defects. In contrast, this work examines the risk that one-pixel defects may occur naturally within image data, and evaluates how frequently such seemingly minor defects can lead to incorrect decisions by neural networks. Extensive experiments reveal that the number of impactful image defects may be relatively high, depending on both the DNN architecture and the dataset used. These findings establish that image defects require significant attention and it might not be sufficient to argue for an acceptable level of safety based solely on the low probability of occurrence these defects.

We present the eccentricity distribution of warm sub-Saturns (4-8 Re, 8-200 day periods) as derived from an analysis of transit light curves from NASA's Transiting Exoplanet Survey Satellite (TESS) mission. We use the "photoeccentric" effect to constrain the eccentricities of 76 planets, comprising 60 and 16 from single- and multi-transiting systems, respectively. We employ Hierarchical Bayesian Modelling to infer the eccentricity distribution of the population, testing both a Beta and Mixture Beta distribution. We identify a few highly eccentric (e 0.7-0.8) warm sub-Saturns with eccentricities that appear too high to be explained by disk migration or planet-planet scattering alone, suggesting high-eccentricity migration may play a role in their formation. The majority of the population have a mean eccentricity of e = 0.103+0.047-0.045, consistent with both planet-disk and planet-planet interactions. Notably, we find that the highly eccentric sub-Saturns occur in single-transiting systems. This study presents the first evidence at the population level that the eccentricities of sub-Saturns may be sculpted by dynamical processes.

The eight-planet Kepler-90 system exhibits the greatest multiplicity of planets found to date. All eight planets are transiting and were discovered in photometry from the NASA Kepler primary mission. The two outermost planets, g ( P _g = 211 days) and h ( P _h = 332 days), exhibit significant transit-timing variations (TTVs), but were only observed six and three times, respectively, by Kepler. These TTVs allow for the determination of planetary masses through dynamical modeling of the pair’s gravitational interactions, but the paucity of transits allows a broad range of solutions for the masses and orbital ephemerides. To determine accurate masses and orbital parameters for planets g and h, we combined 34 radial velocities (RVs) of Kepler-90, collected over a decade, with the Kepler transit data. We jointly modeled the transit times of the outer two planets and the RV time series, then used our two-planet model to predict their future times of transit. These predictions led us to recover a transit of Kepler-90 g with ground-based observatories in 2024 May. We then combined the 2024 transit and several previously unpublished transit times of planets g and h with the Kepler photometry and RV data to update the masses and linear ephemerides of the planets, finding masses for g and h of 15.0 ± 1.3 M _⊕ and 203 ± 16 M _⊕, respectively, from a Markov Chain Monte Carlo analysis. These results enable further insights into the architecturally rich Kepler-90 system and pave the way for atmospheric characterization with space-based facilities.

Dusty disks around planetary and substellar companions in outer reaches of exo-planetary systems can be detected as long-lasting occultations, provided the observer is close to the secondary's orbital plane. Here we report optical spectroscopy with KOSMOS (APO), MagE (Magellan) and GHOST (Gemini-S) of ASASSN-24fw (Gaia 07:05:18.97+06:12:19.4), a 4-magnitude dimming event of a main-sequence star which lasted 8.5 months. We discover multiple low-ionization metal emission lines with velocity dispersion ≲ 10 km/s blue-shifted by 27 km/s with respect to the star, as well as kinematically complex Na D absorption. If associated with the occulter, these detections suggest that the occulter is gas-rich. Further, we detect blue-shifted and broad (∼ 200 km/s) Hα line, which likely originates in the inner circumstellar disk. We confirm the previously reported occultations in 1981 and 1937 seen in historic data, yielding a semi-major axis of the occulter's orbital motion around the star of 14 AU. If the occulter is a circumsecondary disk filling 30-100

T CrB is a symbiotic recurrent nova that last erupted in 1946. Given its recurrence timescale of approximately 80 years, the next outburst is eagerly anticipated by the astronomical community. In this work, we analyse the optical light curves of T CrB, comparing recent photometric evolution with historical data to evaluate potential predictive indicators of nova eruptions. Although the "super-active" phases preceding both the 1946 and anticipated eruptions are strikingly similar, the subsequent photometric behaviour differs. We find that the decline in brightness observed in 2023, interpreted by some as a "pre-eruption dip", deviates from the deep minimum recorded prior to the 1946 event and does not reliably predict the eruption timing. Recent photometric and spectroscopic observations indicate that the system is returning to a high-accretion state. Given this, an eruption may be imminent, even without distinct precursors. While the next eruption of T CrB will be a major scientific event, its expected peak brightness of V ∼ 2 mag highlights the importance of setting realistic public expectations for what will be a visually modest, yet astrophysically very significant, celestial event.