Refinement of the convex shape model and tumbling spin state of (99942) Apophis using the 2020-2021 apparition data

Context. The close approach of the near-Earth asteroid (99942) Apophis to Earth in 2029 will provide a unique opportunity to examine how the physical properties of the asteroid could be changed due to the Earth's gravitational perturbation. As a result, the Republic of Korea is planning a rendezvous mission to Apophis. Aims. Our aim was to use photometric data from the apparitions in 2020-2021 to refine the shape model and spin state of Apophis. Methods. Using thirty-six 1 to 2-m class ground-based telescopes and the Transiting Exoplanet Survey Satellite, we performed a photometric observation campaign throughout the 2020-2021 apparition. The convex shape model and spin state were refined using the light-curve inversion method. Results. According to our best-fit model, Apophis is rotating in a short axis mode with rotation and precession periods of 264.178 hours and 27.38547 hours, respectively. The angular momentum vector orientation of Apophis was found as (275$^\circ$, -85$^\circ$) in the ecliptic coordinate system. The ratio of the dynamic moments of inertia of this asteroid was fitted to $I_a:I_b:I_c=0.64:0.97:1$, which corresponds to an elongated prolate ellipsoid. These findings regarding the spin state and shape model could be used to not only design the space mission scenario but also investigate the impact of the Earth's tidal force during close encounters.Comment: 14 pages, 5 figures; Accepted for publication on Astronomy & Astrophysic

Young Exoplanet Transit Initiative follow-up observations of the T Tauri star CVSO 30 with transit-like dips

The T Tauri star CVSO 30, also known as PTFO 8-8695, was studied intensively with ground-based telescopes as well as with satellites over the last decade. It showed a variable light curve with additional repeating planetary transit-like dips every ∼10.8 h. However, these dimming events changed in depth and duration since their discovery and from autumn 2018 on, they were not even present or near the predicted observing times. As reason for the detected dips and their changes within the complex light curve, e.g. a disintegrating planet, a circumstellar dust clump, stellar spots, possible multiplicity, and orbiting clouds at a Keplerian co-rotating radius were discussed and are still under debate. In this paper, we present additional optical monitoring of CVSO 30 with the meter class telescopes of the Young Exoplanet Transit Initiative in Asia and Europe over the last 7 yr and characterize CVSO 30 with the new Early Data Release 3 of the European Space Agency-Gaia mission. As a result, we describe the evolution of the dimming events in the optical wavelength range since 2014 and present explanatory approaches for the observed variabilities. We conclude that orbiting clouds of gas at a Keplerian co-rotating radius are the most promising scenario to explain most changes in CVSO 30’s light curve. © 2022 The Author(s).This work is based on observations obtained with telescopes of the University Observatory Jena, operated by the Astrophysical Institute of the Friedrich-Schiller-Universität Jena. We thank B. Baghdasaryan, N. Belko, S. Buder, M. Dadalauri, M. Geymeier, H. Gilbert, A. Gonzalez, F. Hildebrandt, H. Keppler, O. Lux, S. Masda, P. Protte, J. Trautmann, A. Trepanowski, and S. Schlagenhauf, who have been involved in some observations of this project, obtained at the University Observatory Jena. This research was partly based on data obtained at the 1.5 m telescope of the Sierra Nevada Observatory (Spain), which is operated by the Consejo Superior de Investigaciones Científicas (CSIC) through the Instituto de Astrofísica de Andalucía. We thank J.F. Aceituno and V. Casanova for their help with the observations. This publication is partly based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 090.C-0448(A). RB, RN, and MM acknowledge the support of the DFG priority programme SPP 1992 ‘Exploring the Diversity of Extrasolar Planets’ in projects NE 515/58-1 and MU 2695/27-1. We acknowledge financial support from the Spanish Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C52 and AYA2016-79425-C3-3-P, and the Centre of Excellence ‘Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). We thank R. Errmann for developing and providing the photometry routine ‘AUTOMAT.PY’ and also C. Broeg for his program ‘PHOTOMETRY’. This publication makes use of data products of the SIMBAD and VizieR data bases, operated at CDS, Strasbourg, France. We also thank the Gaia Data Processing and Analysis Consortium of the ESA for processing and providing the data of the Gaia mission. We thank the MAST portal for providing the TESS photometric results and the MESA Isochrones & Stellar Tracks website for the bolometric correction tables.Peer reviewe

Resurrection and redescription of Varestrongylus alces (Nematoda; Protostrongylidae), a lungworm of the Eurasian moose (Alces alces), with report on associated pathology

Varestrongylus alces, a lungworm in Eurasian moose from Europe has been considered a junior synonym of Varestrongylus capreoli, in European roe deer, due to a poorly detailed morphological description and the absence of a type-series. Methods Specimens used in the redescription were collected from lesions in the lungs of Eurasian moose, from Vestby, Norway. Specimens were described based on comparative morphology and integrated approaches. Molecular identification was based on PCR, cloning and sequencing of the ITS-2 region of the nuclear ribosomal DNA. Phylogenetic analysis compared V. alces ITS-2 sequences to these of other Varestrongylus species and other protostrongylids. Results Varestrongylus alces is resurrected for protostrongylid nematodes of Eurasian moose from Europe. Varestrongylus alces causes firm nodular lesions that are clearly differentiated from the adjacent lung tissue. Histologically, lesions are restricted to the parenchyma with adult, egg and larval parasites surrounded by multinucleated giant cells, macrophages, eosinophilic granulocytes, lymphocytes. The species is valid and distinct from others referred to Varestrongylus, and should be separated from V. capreoli. Morphologically, V. alces can be distinguished from other species by characters in the males that include a distally bifurcated gubernaculum, arched denticulate crura, spicules that are equal in length and relatively short, and a dorsal ray that is elongate and bifurcated. Females have a well-developed provagina, and are very similar to those of V. capreoli. Morphometrics of first-stage larvae largely overlap with those of other Varestrongylus. Sequences of the ITS-2 region strongly support mutual independence of V. alces, V. cf. capreoli, and the yet undescribed species of Varestrongylus from North American ungulates. These three taxa form a well-supported crown-clade as the putative sister of V. alpenae. The association of V. alces and Alces or its ancestors is discussed in light of host and parasite phylogeny and host historical biogeography. Varestrongylus alces is a valid species, and should be considered distinct from V. capreoli. Phylogenetic relationships among Varestrongylus spp. from Eurasia and North America are complex and consistent with faunal assembly involving recurrent events of geographic expansion, host switching and subsequent speciation. Cervidae, Cryptic species, Historical biogeography, ITS-2, Metastrongyloidea, Parasite biodiversity, Varestrongylinae, Varestrongylus capreoli, Verminous pneumoniapublishedVersio

A Multi-Epoch, Multiwavelength Study of the Classical FUor V1515 Cyg Approaching Quiescence

Historically, FU Orionis-type stars are low-mass, pre-main-sequence stars. The members of this class experience powerful accretion outbursts and remain in an enhanced accretion state for decades or centuries. V1515 Cyg, a classical FUor, started brightening in the 1940s and reached its peak brightness in the late 1970s. Following a sudden decrease in brightness, it stayed in a minimum state for a few months, then started brightening for several years. We present the results of our ground-based photometric monitoring complemented with optical/near-infrared spectroscopic monitoring. Our light curves show a long-term fading with strong variability on weekly and monthly timescales. The optical spectra show P Cygni profiles and broad blueshifted absorption lines, common properties of FUors. However, V1515 Cyg lacks the P Cygni profile in the Ca II 8498 Å line, a part of the Ca infrared triplet, formed by an outflowing wind, suggesting that the absorbing gas in the wind is optically thin. The newly obtained near-infrared spectrum shows the strengthening of the CO bandhead and the FeH molecular band, indicating that the disk has become cooler since the last spectroscopic observation in 2015. The current luminosity of the accretion disk dropped from the peak value of 138 L ⊙ to about 45 L ⊙, suggesting that the long-term fading is also partly caused by the dropping of the accretion rate

Refinement of the convex shape model and tumbling spin state of (99942) Apophis using the 2020-2021 apparition data

Context. The close approach of the near-Earth asteroid (99942) Apophis to Earth in 2029 will provide a unique opportunity to examine how the physical properties of the asteroid could be changed due to the Eartha's gravitational perturbation. As a result, the Republic of Korea is planning a rendezvous mission to Apophis. Aims. Our aim was to use photometric data from the apparitions in 2020 2021 to refine the shape model and spin state of Apophis. Methods. Using thirty-six 1-to 2-meter-class ground-based telescopes and the Transiting Exoplanet Survey Satellite, we carried out a photometric observation campaign throughout the 2020 2021 apparition. The convex shape model and spin state were refined using the light-curve inversion method. Results. According to our best-fit model, Apophis is rotating in a short-axis mode with rotation and precession periods of 264.178 h and 27.38547 h, respectively. The angular momentum vector orientation of Apophis was found to be (275, 85) in the ecliptic coordinate system. The ratio of the dynamic moments of inertia of this asteroid was fitted to Iaa:a Iba:a Ica =a 0.64a:a 0.97a:a 1, which corresponds to an elongated prolate ellipsoid. These findings regarding the spin state and shape model can be used to both design the space mission scenario and investigate the impact of the Eartha's tidal force during close encounters

Apophis planetary defense campaign

We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 December–2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. These community-led global exercises were carried out with the support of NASA's Planetary Defense Coordination Office and the International Asteroid Warning Network. The Apophis campaign is the third in our series of planetary defense exercises. The goal of this campaign was to recover, track, and characterize Apophis as a potential impactor to exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication. Based on the campaign results, we present lessons learned about our ability to observe and model a potential impactor. Data products derived from astrometric observations were available for inclusion in our risk assessment model almost immediately, allowing real-time updates to the impact probability calculation and possible impact locations. An early NEOWISE diameter measurement provided a significant improvement in the uncertainty on the range of hypothetical impact outcomes. The availability of different characterization methods such as photometry, spectroscopy, and radar provided robustness to our ability to assess the potential impact risk

Scaling slowly rotating asteroids with stellar occultations

Context. As evidenced by recent survey results, the majority of asteroids are slow rotators (spin periods longer than 12 h), but lack spin and shape models because of selection bias. This bias is skewing our overall understanding of the spins, shapes, and sizes of asteroids, as well as of their other properties. Also, diameter determinations for large (>60 km) and medium-sized asteroids (between 30 and 60 km) often vary by over 30% for multiple reasons. Aims. Our long-term project is focused on a few tens of slow rotators with periods of up to 60 h. We aim to obtain their full light curves and reconstruct their spins and shapes. We also precisely scale the models, typically with an accuracy of a few percent. Methods. We used wide sets of dense light curves for spin and shape reconstructions via light-curve inversion. Precisely scaling them with thermal data was not possible here because of poor infrared datasets: large bodies tend to saturate in WISE mission detectors. Therefore, we recently also launched a special campaign among stellar occultation observers, both in order to scale these models and to verify the shape solutions, often allowing us to break the mirror pole ambiguity. Results. The presented scheme resulted in shape models for 16 slow rotators, most of them for the first time. Fitting them to chords from stellar occultation timings resolved previous inconsistencies in size determinations. For around half of the targets, this fitting also allowed us to identify a clearly preferred pole solution from the pair of two mirror pole solutions, thus removing the ambiguity inherent to light-curve inversion. We also address the influence of the uncertainty of the shape models on the derived diameters. Conclusions. Overall, our project has already provided reliable models for around 50 slow rotators. Such well-determined and scaled asteroid shapes will, for example, constitute a solid basis for precise density determinations when coupled with mass information. Spin and shape models in general continue to fill the gaps caused by various biases

Apophis Planetary Defense Campaign

We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 December–2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. These community-led global exercises were carried out with the support of NASA’s Planetary Defense Coordination Office and the International Asteroid Warning Network. The Apophis campaign is the third in our series of planetary defense exercises. The goal of this campaign was to recover, track, and characterize Apophis as a potential impactor to exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication. Based on the campaign results, we present lessons learned about our ability to observe and model a potential impactor. Data products derived from astrometric observations were available for inclusion in our risk assessment model almost immediately, allowing real-time updates to the impact probability calculation and possible impact locations. An early NEOWISE diameter measurement provided a significant improvement in the uncertainty on the range of hypothetical impact outcomes. The availability of different characterization methods such as photometry, spectroscopy, and radar provided robustness to our ability to assess the potential impact risk. © 2022. The Author(s). Published by the American Astronomical Society.Brinson Foundation of ChicagoMoscow CenterNASA’s Planetary Defense Coordination Office, (80NSSC18K0284, 80NSSC18K1575, NN12AR55G)NEOOPlanetary Data SystemNational Aeronautics and Space Administration, NASA, (80NSSC18K0971)University of Maryland, UMDHorizon 2020 Framework Programme, H2020, (870403)Planetary Science Division, PSDNational Research Foundation, NRFMinistry of Education and Science of the Russian Federation, Minobrnauka, (075-15-2019-1623)National Research Foundation of Korea, NRFMinistry of Science and Higher Education of the Russian Federation, (80NSSC18K0849, FEUZ-2020-0030)Overall, the campaign successfully demonstrated the capability of the planetary defense community to respond in real time to a potentially impacting object and obtain data sufficient to characterize its orbit, brightness, size, spectrum, rotation period, and hazard to Earth. Timely reporting of astrometry and preliminary physical property analyses, with appropriate error bars, significantly improved our knowledge of the potential impact consequences. Human factors, such as the end-of-year holiday season, had a distinct impact on rapidly constraining the rotation period of Apophis and demonstrate the importance of building a broad coalition for planetary defense spanning continents and cultures. Future planetary defense campaigns should focus on targets with less-favorable apparitions that might better simulate a future discovery of a hazardous object. Acknowledgments The Apophis campaign was conducted as part of the International Asteroid Warning Network (IAWN). IAWN is supported by the Planetary Data System (PDS) Small Bodies Node (SBN) at the University of Maryland College Park. The work at the Jet Propulsion Laboratory, California Institute of Technology, was performed under a contract with the National Aeronautics and Space Administration (NASA). This material is based in part on work supported by NASA under the Science Mission Directorate Research and Analysis Programs. This publication makes use of data products from NEOWISE, which is a joint project of the University of Arizona and the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of NASA. Pan-STARRS is supported by the National Aeronautics and Space Administration under Grant No. 80NSSC18K0971 issued through the SSO Near Earth Object Observations Program. Part of this work was supported by the Russian Ministry of Science and Higher Education via the State Assignment Project FEUZ-2020-0030. Part of the observations performed with the Zeiss-1000 telescope of the Terskol Observatory Shared Research Centre of the Institute of Astronomy of the Russian Academy of Sciences. We are extremely grateful to the IRTF and GTC Observatories’ night and day staff for their overwhelming support and assistance that made the observations possible. D.P. & M.M. are thankful to Richard Binzel and Francesca DeMeo for sharing their experience and wisdom while planning and conducting the measurements. D.P. is grateful to the Israeli Space Agency. M.M. was supported by the National Aeronautics and Space Administration under grant No. 80NSSC18K0849 issued through the Planetary Astronomy Program. J.d.L., J.L., and M.P. acknowledge financial support from the NEOROCKS project, which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870403. This work was funded by NASA’s Planetary Defense Coordination Office. Supercomputing resources supporting this work were provided by the NASA High End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. ATLAS is primarily funded to search for NEAs through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575byproducts of the NEA search include images and catalogs from the survey area. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen’s University Belfast, the Space Telescope Science Institute, and the South African Astronomical Observatory. This work is partially supported by the South African National Research Foundation (NRF). Spacewatch is supported by NASA/NEOO grants and the Brinson Foundation of Chicago, IL. We thank TUBITAK National Observatory for partial support in using the T100 telescope with project number 20CT100-1743. This work was supported by the Moscow Center of Fundamental and Applied Mathematics, Agreement with the Ministry of Science and Higher Education of the Russian Federation, No. 075-15-2019-1623. This work made extensive use of Python, specifically the NumPy (Harris et al. 2020), Astropy (Astropy Collaboration et al. 2013, 2018), Matplotlib (Hunter 2007), and SciPy (Virtanen et al. 2020b) packages