We report the detection of a new brown dwarf companion to HIP 17453 A, a chemically peculiar A0V star located at a distance of 81 pc. HIP 17453 A was observed with high-resolution adaptive optics imaging using the Near-Infrared Camera 2 on the Keck II telescope as part of the Companions to B and A Stars Snapshot (C-BASS) survey over a ten-year baseline, revealing the presence of a companion with proper motion consistent with the primary. We estimate the age of the HIP 17453 system as 280 ± 125 Myr, and with follow-up intermediate resolution (R 1800) spectroscopic observations with the Gemini Near Infra-Red Spectrograph (GNIRS) on the Gemini-North telescope, we found the spectrum of HIP 17453 B to be consistent with a spectral type of L2 ± 1. Through interpolation of Sonora Diamondback evolutionary models, we calculate an effective temperature of 1953^+84_-78 K and mass of 53^+10_-8 M_Jup for HIP 17453 B, which corresponds to a mass ratio of q = 0.024 ± 0.004 for the HIP 17453 system. With its intermediate mass and young age, HIP 17453 B joins a small set of benchmark brown dwarf companions around early-type stars that are suitable for follow-up atmospheric and evolutionary studies.

On May 24, 2023, the European Space Agency's Trace Gas Orbiter transmitted a simulated extraterrestrial message to Earth, received by telescopes in the United States and Italy. This event was part of the interdisciplinary project A Sign in Space, developed over four years in collaboration with multiple research institutions. The project simulates a scenario where scientists release a potential extraterrestrial signal to the public for decoding and interpretation. Following the data release, an international community on the Discord platform engaged in extensive decoding efforts, generating thousands of interpretations and widespread social media discussion. A Sign in Space reached over a hundred million people globally through media coverage and online channels, demonstrating significant public interest and engagement. The project highlights the importance of public engagement in scientific research and the potential for interdisciplinary collaborations to create meaningful dialogues around complex topics like the search for extraterrestrial life. By fostering a sense of global community and shared exploration, A Sign in Space offers a model for future interdisciplinary projects that seek to inspire and engage diverse audiences. This paper discusses some of the challenges encountered in the global outreach of the project, presenting lessons learnt that could be useful for participatory science around the theme of extraterrestrial communication.

Our purpose is to provide photometric data and tools to compute magnitudes from images obtained by Unistellar telescopes and enhance their usefulness to the broader astronomical community. To do so, we provide relationships transforming Unistellar complementary metal oxide semiconductor sensor Bayer filter bands (blue B-e , green G(e) , and red R-e ) to the Johnson-Cousins photometric system. To enable this calibration, stars with known spectra were observed with Unistellar telescopes by citizen scientists in the Unistellar Network. We obtained the zero-point magnitudes of the telescopes for each band by combining those spectra with the telescope sensor responses. Using the observations of 794 stars with known Johnson-Cousins magnitudes, we established the relations to transform the Unistellar magnitudes. The zero-point magnitudes and their associated errors for the three bands were derived. Polynomial expressions for the relation between the Unistellar colour B-e - R-e and the Johnson-Cousins magnitudes were obtained for stars with Unistellar colour - 0.15 < B-e - R-e < 0.5 . The uncertainties on these transformations increase linearly with the R-e magnitude. These relations were applied to the observation of a type II supernova and an exoplanet transit, with the supernova example showing consistency with other published magnitudes but also demonstrating that narrow-line emission or absorption can bias the transformed magnitudes. Other limitations of the transformations were also identified, largely stemming from significant infrared contributions to all color channels and variability between individual telescope sensors. Nevertheless, the values and color relationships provided here can be used by professional and citizen astronomers alike to compute observed magnitudes and provide measurements in a standard system. This enhances the Unistellar Network's ability to contribute accurate photometry to the astronomical community that can be easily and faithfully combined with measurements from other instruments. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the GPI Exoplanet Survey in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected ∼430 mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semimajor axis of 6 4 − 14 + 32 au and eccentricity 0.23 − 0.16 + 0.24 . Spectral analysis of the GPI H -band spectrum and NIRC2 L′ photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-Radioactive-Convective Equilibrium Model (REM) exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of 104 2 − 132 + 178 K for the planet and translate the derived luminosity of the planet to a mass of 5.6 ± 1.1 M Jup assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultrawide orbit. Future characterization of this object will shed light on the formation of planets around binary star systems.

HD 143811 AB is the host star to the directly imaged planet HD 143811 AB b, which was recently discovered using data from the Gemini Planet Imager and Keck NIRC2. A member of the Sco-Cen star-forming region with an age of 13 ± 4 Myr, HD 143811 AB is somewhat rare among hosts of directly imaged planets, as it is a close stellar binary, with an ∼18-day period. Accurate values for the orbital and stellar parameters of this binary are needed to understand the formation and evolutionary history of the planet in orbit. We utilize archival high-resolution spectroscopy from FEROS on the MPG/ESO 2.2 m telescope to fit the orbit of the binary, and we combine with unresolved photometry to derive the basic stellar properties of the system. From the orbit, we derive precise values of orbital period of 18.59090 ± 0.00007 days and mass ratio of 0.886 ± 0.003. When combined with stellar evolutionary models, we find masses of both components of M A = 1.3 0 − 0.05 + 0.03 M ⊙ and M B = 1.1 5 − 0.04 + 0.03 M ⊙ . While the current data are consistent with the planet and stellar orbits being coplanar, the 3D orientations of both systems are currently poorly constrained, with additional observations required to more rigorously test for coplanarity.

Context. We report a successful observation of a stellar occultation by asteroid (16583) Oersted, which provides a detailed physical characterization of its shape, spin state, and surface properties. Aims. Our goal is to determine the physical parameters of Oersted by combining multi-chord occultation timing, sparse optical photometry, and thermal infrared observations. Asteroids of this size (similar to 20 km) are rarely modeled in such detail due to observational limitations, making Oersted a valuable case study. Methods. We applied convex light curve inversion to sparse photometric data to derive an initial shape and spin state. We then refined and scaled this model using non-convex shape modeling with the All-Data Asteroid Modelling (ADAM) algorithm, incorporating constraints from the occultation chord profile. Thermophysical modeling based on WISE thermal infrared fluxes was used to determine the asteroid's effective diameter, geometric albedo, and thermal inertia. Results. The non-convex shape model reveals localized surface concavities and provides a size estimate consistent with radiometric measurements. The derived thermal inertia is typical for asteroids of comparable size. Conclusions. This work demonstrates the effectiveness of combining stellar occultations, photometry, and thermal infrared data for asteroid modeling and highlights the valuable contributions of citizen scientists, who played a key role in capturing the occultation and constraining the profile of the asteroid.

We report a successful observation of a stellar occultation by asteroid (16583) Oersted, enabling a detailed physical characterization of its shape, spin state, and surface properties. Our goal is to determine the physical parameters of Oersted by combining multi-chord occultation timing, sparse optical photometry, and thermal infrared observations. Such asteroids (size$\sim$20 km) are rarely modeled in this detail due to observational limitations, making Oersted a valuable case study. We applied convex lightcurve inversion to sparse photometric data to derive an initial shape and spin state. This model was then refined and scaled using non-convex shape modeling with the ADAM algorithm, incorporating constraints from the occultation chord profile. Thermophysical modeling based on WISE thermal infrared fluxes was used to determine the asteroid's effective diameter, geometric albedo, and thermal inertia. The non-convex shape model reveals localized surface concavities and provides a size estimate consistent with radiometric measurements. The derived thermal inertia is typical for asteroids of comparable size. This work demonstrates the effectiveness of combining stellar occultations, photometry, and thermal infrared data for asteroid modeling and highlights the valuable contributions of citizen scientists, who played a key role in capturing the occultation and constraining the asteroid's profile.

Librating around the Lagrange L5, the Jupiter's Trojan (2207) Antenor has been observed in recent years and its rotational light curve suggests it to be a very likely binary asteroid candidate. From stellar occultations, we report results from three events from Europe and North America to estimate the 2D apparent size and shape of Jupiter's Trojan (2207) Antenor. For the best-fitted ellipse in the sky-plane, we determined that Antenor has a 2D apparent equatorial radius of 54.30 +/- 0.99 km at the moment of the occultations, with an apparent oblateness of 0.144 +/- 0.051. We highlight the positive detection from 2021 June 12, which shows an intriguing feature that can be interpreted as a very large topographical feature (of about 11 km) of the body or that can provide further evidence that this object is, in fact, a close or contact binary. We also determine astrometric positions, with uncertainties of a few milliarcseconds (mas) for our preferred solutions.

We report photometric observations of Comet 103P/Hartley 2 during its 2023 apparition. Our campaign, conducted from August through 2023 December, combined data from a global network of citizen astronomers coordinated by Unistellar and the Association Fran & ccedil;aise d'Astronomie. Photometry was derived using an automated pipeline for eVscope observations in partnership with the SETI Institute and aperture photometry via AstroLab Stellar. We find that the comet's peak reduced brightness, measured at Gmin=10.24 +/- 0.47 , continues a long-term fading trend since 1991. The decline in activity follows a per-apparition minimum magnitude increase of Delta Gmin=0.59 +/- 0.11 mag, corresponding to a similar to 42% reduction in brightness each return. This trend implies that the comet's active fraction has declined by approximately an order of magnitude since 1991 and may indicate that Hartley 2 is no longer hyperactive by definition. The fading is consistent with progressive volatile depletion rather than orbital effects. These results offer insight into the evolutionary processes shaping Jupiter-family comets.

NASA's Transiting Exoplanet Survey Satellite (TESS) has identified over 7,000 candidate exoplanets via the transit method, with gas giants among the most readily detected due to their large radii. Even so, long intervals between TESS observations for much of the sky lead to candidates for which only a single transit is detected in one TESS sector, leaving those candidate exoplanets with unconstrained orbital periods. Here, we confirm the planetary nature of TIC 393818343 b, originally identified via a single TESS transit, using radial velocity data and ground-based photometric observations from citizen scientists with the Unistellar Network and Exoplanet Watch. We determine a period of $P$ = 16.24921 $\substack{+0.00010 \\ -0.00011}$ days, a mass $M_{P}$ = 4.34 $\pm$ 0.15 $M_{J}$, and semi-major axis $a$ = 0.1291 $\substack{+0.0021 \\ -0.0022}$ au, placing TIC 393818343 b in the "warm Jupiter" population of exoplanets. With an eccentricity $e$ = 0.6058 $\pm$ 0.0023, TIC 393818343 b is the most eccentric warm Jupiter to be discovered by TESS orbiting less than 0.15 au from its host star and therefore an excellent candidate for follow-up, as it may inform our future understanding of how hot and warm Jupiter populations are linked.

Abstract:This study investigates the physical properties of asteroids using optical data obtained by the Unistellar network of citizen astronomers. Leveraging the extensive observations provided by hundreds of users, we aim to characterize the size, shape, and rotation properties of a diverse sample of asteroids. Our analysis encompasses data collected over multiple observing campaigns conducted between 2021 and 2024, focusing on both near-Earth and main belt asteroids. By combining photometric light curves and stellar occultations, we derive comprehensive physical models for these celestial bodies. Our findings contribute to a deeper understanding of the asteroid population and provide valuable insights into their formation and evolution.Introduction:Asteroids represent remnants of the early solar system and offer valuable insights into its formation and evolution. Studying their physical properties, such as size, shape, and rotation, is crucial for understanding their composition and origins. The Unistellar network of citizen astronomers comprised of over 10,000 telescopes provides a unique opportunity to collect large-scale optical data for a wide range of asteroids, enabling comprehensive studies of their physical characteristics.Data and Methods:We utilized optical data collected by the Unistellar network between 2021 and 2024, focusing on observations of both near-Earth and main belt asteroids. Photometric light curves and stellar occultations were used to derive the sizes, shapes, and rotation properties of the asteroids. We analyzed data from multiple observing campaigns that targeted specific asteroids of scientific interest. We utilized the convex inversion method developed by Mikko Kaasalainen.Results:Our analysis resulted in rotation state properties and detailed 3D models for tens of asteroids. We obtained accurate measurements of size, shape, and rotation period for numerous celestial bodies, shedding light on their individual characteristics and variability within the asteroid population. Additionally, we identified intriguing phenomena, such as concavities and asymmetric light curves, providing insights into the dynamical processes shaping these objects.Conclusions:The optical data obtained by the Unistellar network of citizen astronomers offers valuable insights into the physical properties of asteroids. By leveraging these observations, we have advanced our understanding of the asteroid population, contributing to ongoing efforts to explore the solar system's early history. Our study highlights the importance of citizen science initiatives in expanding our knowledge of celestial objects and their origins.Figure 1. The Unistellar European network comprises citizen astronomers. As of May 2023, approximately 10,000 eVscopes are distributed globally, with over 3,000 of them located in EuropeFigure 2. The plot showcases light curve observations of asteroid (216) Kleopatra revealing variations in brightness over its rotation.Figure 3. The plot showcases light curve observations of near-Earth asteroid (1627) Ivar revealing variations in brightness over its rotation.

We report the discovery and confirmation of the Transiting Exoplanet Survey Satellite (TESS) single-transit, warm and dense sub-Saturn, TIC 139270665 b. This planet is unusually dense for its size: with a bulk density of 2.13 g cm-3 (0.645R J , 0.463M J ), it is the densest warm sub-Saturn of the TESS family. It orbits a metal-rich G2 star. We also found evidence of a second planet, TIC 139270665 c, with a longer period of 1010-220+780 days and minimum mass MPsini of 4.89-0.37+0.66 M J . First clues of TIC 139270665 b's existence were found by citizen scientists inspecting TESS photometric data from sector 47 in 2022 January. Radial velocity measurements from the Automated Planet Finder combined with TESS photometry and spectral energy distributions via EXOFASTv2 system modeling suggested a 23.624-0.031+0.030 day orbital period for TIC 139270665 b and also showed evidence for the second planet. Based on this estimated period, we mobilized the Unistellar citizen science network for photometric follow-up, capitalizing on their global distribution to capture a second transit of TIC 139270665 b. This citizen science effort also served as a test bed for an education initiative that integrates young students into modern astrophysics data collection. The Unistellar photometry did not definitively detect a second transit, but did enable us to further constrain the planet's period. As a transiting, warm, and dense sub-Saturn, TIC 139270665 b represents an interesting laboratory for further study to enhance our models of planetary formation and evolution.

The Fiber Imager foR a Single Telescope (FIRST) is a visible spectro-interferometer (600-760 nm, R~400) installed on the Subaru telescope's extreme adaptive optics platform (SCExAO). It provides high-precision spatial coherence measurements with high angular resolution (~8 mas at 656 nm, ~1% coherence accuracy) by combining light from sub-apertures of the telescope pupil. We present two upgrades of the instrument towards H𝛼 detection of protoplanets. We report on the integration of a new 4000-resolution spectrograph and on the sensitivity of the instrument. We also present the characterisation of a high performance visible photonic integrated circuit prototype used for the interferometric combination of 5 sub-apertures.

In situ elemental imaging of planetary surface regolith at a spatial resolution of 100s to 1000s of microns can provide evidence of the provenance of rocks or sediments and their habitability, and can identify post-depositional diagenetic alteration affecting preservation. We use high-resolution elemental maps and XRF spectra from MapX, a flight prototype in situ X-ray imaging instrument, to demonstrate this technology in rock types relevant to astrobiology. Examples are given for various petrologies and depositional/diagenetic environments, including ultramafic/mafic rocks, serpentinites, hydrothermal carbonates, evaporites, stromatolitic cherts and diagenetic concretions.

Context. In about 2000, the south pole of Triton experienced an extreme summer solstice that occurs every similar to 650 years, when the subsolar latitude reached about 50 degrees S. Bracketing this epoch, a few occultations probed the Triton atmosphere in 1989, 1995, 1997, 2008, and 2017. A recent ground-based stellar occultation observed on 6 October 2022 provides a new measurement of the atmospheric pressure on Triton. This is presented here. Aims. The goal is to constrain the volatile transport models (VTMs) of the Triton atmosphere. The atmosphere is basically in vapor pressure equilibrium with the nitrogen ice at its surface. Methods. Fits to the occultation light curves yield the atmospheric pressure of Triton at the reference radius 1400 km, from which the surface pressure is deduced. Results. The fits provide a pressure p(1400) = 1.211 +/- 0.039 mu bar at radius 1400 km (47 km altitude), from which a surface pressure of p(surf) = 14.54 +/- 0.47 mu bar is deduced (1 sigma error bars). To within the error bars, this is identical to the pressure derived from the previous occultation of 5 October 2017, p(14)00 = 1.18 +/- 0.03 mu bar and p(surf) = 14.1 +/- 0.4 mu bar, respectively. Based on recent models of the volatile cycles of Triton, the overall evolution of the surface pressure over the last 30 years is consistent with N-2 condensation taking place in the northern hemisphere. However, models typically predict a steady decrease in the surface pressure for the period 2005-2060, which is not confirmed by this observation. Complex surface-atmosphere interactions, such as ice albedo runaway and formation of local N-2 frosts in the equatorial regions of Triton, could explain the relatively constant pressure between 2017 and 2022.

The DOSSA (Decentralization of Space Situational Awareness) project, led by SpaceAble in collaboration with Unistellar and the Laboratoire d'Astrophysique de Marseille, aims to enhance space surveillance through a collaborative effort involving amateur astronomers, researchers, and industrial networks, leveraging advanced technology and data collection to improve space situational awareness in an era of escalating satellite numbers. This project aims to create a comprehensive sky map of objects transiting around Earth. It benefits from a large dataset collected by the Unistellar telescope network, a global network comprised primarily of robotically controllable evScopes 1 and 2 telescopes, each featuring a 11.4 centimeter aperture diameter. We develop dedicated deep learning algorithms to account for the relatively compact diameters of the telescopes and to extend detection thresholds. Firstly, we use traditional convolutional neural networks (CNNs) based classifiers to detect images including a satellite streak, and secondly, we use UNet to identify pixels affected by such streaks. Both neural networks are trained on realistic simulations generated using our optical Fourier simulation software, by combining observed sky backgrounds and synthetic satellite streaks spanning a wide range of orbital parameters. With this strategy, we reach excellent performance on the segmentation of images in test set, with a recall of 79.6% pixels belonging to the satellites masks, at a false positive rate of 0.001%. For 90% of streak pixels recovered by the neural networks, we obtain a precision of 96.3% on the predicted satellite masks. This exceeds the performance of non-ML algorithms and paves the way to measuring accurate satellite positions over broader magnitudes ranges and down to lower S/N, in order to increase the precision on their orbital parameters.

Context . The rotation state of small asteroids is affected in the long term by perturbing torques of gravitational and radiative origin (the YORP effect). The former can be detected by a change in the spin-axis orientation in the inertial space; the latter manifests itself by a quadratic increase in the rotation phase. Aims . Direct observational evidence of the YORP effect is the primary goal of our work. This includes both the YORP detection for new objects and an improvement in the accuracy of previously known detections. Methods . We carried out photometric observations of five near-Earth asteroids: (1862) Apollo, (2100) Ra-Shalom, (85989) 1999 JD6, (138852) 2000 WN10, and (161989) Cacus. Then we applied the light-curve inversion method to all available data to determine the spin state and a convex shape model for each of the five studied asteroids. The YORP effect was modeled as a linear change of the rotation frequency υ ≡ d ω /d t . In the case of (2100) Ra-Shalom, the analysis required that the spin-axis precession due to the solar gravitational torque also be included. Results . We obtained two new detections of the YORP effect: (i) υ = (2.9 ± 2.0) × 10 −9 rad d −2 for (2100) Ra-Shalom, and (ii) υ = (5.5 ± 0.7) × 10 −8 rad d −2 for (138852) 2000 WN10. The analysis of Ra-Shalom also reveals a precession of the spin axis with a precession constant α ~ 3000″ yr −1 . This is the first such detection from Earth-bound photometric data. For the other two asteroids, we improved the accuracy of the previously reported YORP detection: (i) υ = (4.94 ± 0.09) × 10 −8 rad d −2 for (1862) Apollo, and (ii) υ = (1.86 ± 0.09) × 10 −8 rad d −2 for (161989) Cacus. With this value, Apollo has the most precisely determined YORP effect so far. Despite the recent report of a detected YORP effect for (85989) 1999 JD6, we show that the model without YORP cannot be rejected statistically. Therefore, the detection of the YORP effect for this asteroid requires future observations. In several of our targets, the currently available observations do not provide enough constraints on the shape model (even at large scales) to compute the theoretical YORP effect with sufficient precision. Nevertheless, the interpretation of the detected signal as the YORP effect is fairly plausible. The spin-axis precession constant of Ra-Shalom determined from observations matches the theoretically expected value. Conclusions . The total number of asteroids with a YORP detection has increased to 12. In all cases, the rotation frequency increases in time. The analysis of a rich photometric data set of irregularly shaped asteroids may require inclusion of spin-axis precession in future studies.