Evidence of asymmetries in the Aldebaran photosphere from multiwavelength lunar occultations

We have recorded three lunar occultations of Aldebaran (α Tau) at different telescopes and using various band-passes, from the ultraviolet to the far red. The data have been analysed using both model-dependent and model-independent methods. The derived uniform-disc angular diameter values have been converted to limb-darkened values using model atmosphere relations and are found in broad agreement among themselves and with previous literature values. The limb-darkened diameter is about 20.3 mas on average. However, we have found indications that the photospheric brightness profile of Aldebaran may have not been symmetric, a finding already reported by other authors for this and for similar late-type stars. At the sampling scale of our brightness profile, between 1 and 2 mas, the uniform and limb-darkened disc models may not be a good description for Aldebaran. The asymmetries appear to differ with wavelength and over the 137-d time span of our measurements. Surface spots appear as a likely explanation for the differences between observations and the models

Discovery of a young low-mass brown dwarf transiting a fast-rotating F-type star by the Galactic Plane eXoplanet (GPX) survey

We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of $19.7\pm 1.6$ $M_{\mathrm{Jup}}$ and a radius of $1.47\pm0.10$ $R_{\mathrm{Jup}}$, the first sub-stellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright ($V$ = 12.3 mag) fast-rotating F-type star with a projected rotational velocity $v\sin{ i_*}=40\pm10$ km/s. We use the isochrone placement algorithm to characterize the host star, which has effective temperature $7000\pm200$ K, mass $1.68\pm0.10$ $M_{\mathrm{Sun}}$, radius $1.56\pm0.10$ $R_{\mathrm{Sun}}$ and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1 b has an orbital period of $\sim$1.75 d, and a transit depth of $0.90\pm0.03$ %. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a sub-stellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data is affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of Doppler tomography.Comment: 13 pages, 13 figures, accepted to MNRAS in May 202

KPS-1b: The First Transiting Exoplanet Discovered Using an Amateur Astronomer's Wide-field CCD Data

We report the discovery of the transiting hot Jupiter KPS-1b. This exoplanet orbits a V = 13.0 K1-type main sequence star every 1.7 days, has a mass of 1.090 (+0.086 -0.087) MJup and a radius of 1.03 (+0.13 -0.12) RJup. The discovery was made by the prototype Kourovka Planet Search (KPS) project, which used wide-field CCD data gathered by an amateur astronomer using readily available and relatively affordable equipment. Here we describe the equipment and observing technique used for the discovery of KPS-1b, its characterization with spectroscopic observations by the SOPHIE spectrograph and with high-precision photometry obtained with 1m class telescopes. We also outline the KPS project evolution into the Galactic Plane eXoplanet survey. The discovery of KPS-1b represents a new major step of the contribution of amateur astronomers to the burgeoning field of exoplanetology

Discovery of a Young Low-Mass Brown Dwarf Transiting a Fast-Rotating F-Type Star by the Galactic Plane eXoplanet (GPX) Survey

We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of 19.7 ± 1.6 MJup and a radius of 1.47 ± 0.10 RJup, the first substellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright (V = 12.3 mag) fast-rotating F-type star with a projected rotational velocity v sin i∗ = 40 ± 10 km s−1. We use the isochrone placement algorithm to characterize the host star, which has effective temperature 7000 ± 200 K, mass 1.68 ± 0.10 M☉, radius 1.56 ± 0.10 R☉, and approximate age 0.27-0.15+0.09 Gyr. GPX-1 b has an orbital period of -1.75 d and a transit depth of 0.90 ± 0.03 per cent. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a substellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data are affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of the Doppler tomography. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.The authors would like to thank the anonymous reviewer for their time and attention. The constructive comments we received helped us to improve the quality of the paper. This research has made use of the Exoplanet Orbit Database, the Exoplanet Data Explorer at exoplanets.org, Extrasolar Planets Encyclopaedia at exoplanets.eu, and the NASA Exoplanet Archive, which is operated by the California Institute of Technology under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research was made possible through the use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund and NSF AST-1412587. This research made use of Aladin (Bonnarel et al. 2000). IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. This research made use of ASTROPY,3 a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013; Price-Whelan et al. 2018). We acknowledge the use of TESScut.MAST data from full frame time series images (FFI) collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA?s Science Mission directorate. 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 for the production of the SPOC data products. PB thanks Bruce Gary, the XO survey, and the KELT survey for furthering his education in exoplanet research. AYB would like to thank Catarina Fernandes and Julien de Wit for helpful discussions about the system. Organization of the EXPANSION project (ES), follow-up campaign of the photometry observations, speckle-interferometry observations with 6-m telescope BTA were supported by the Russian Science Foundation grant 19-72-10023. The work of VK was supported by the Ministry of Science and Higher Education of the Russian Federation, topic no. FEUZ-0836-2020-0038. This work was partly supported by the Ministry of Science and High Education of the Russian Federation (project no. FZZE-2020-0024) and Irkutsk State University (project no. 111-14-306). This work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (project nos. FEUZ-2020-0030 and 075-15-2020-780). TRAPPIST-North is a project funded by the University of Liege, in collaboration with Cadi Ayyad University of Marrakech (Morocco). EJ and MG are F.R.S.-FNRS Senior Research Associates. The research leading to these results has received funding from the ARC grant for Concerted Research Actions financed by the Federation Wallonia-Brussels and from the International Balzan Prize Foundation. TRAPPIST is funded by the Belgian National Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) under the grant FRFC 2.5.594.09.F. EP acknowledges the Europlanet 2024 RI project funded by the European Union?s Horizon 2020 Framework Programme (grant agreement no. 871149). AB acknowledge the support from the Program of Development of Lomonosov Moscow State University (Leading Scientific School ’Physics of stars, relativistic objects and galaxies’). OB thanks TÜBİTAK National Observatory for a partial support in using the T100 telescope with the project number 19AT100-1346. ODSD is supported by Portuguese national funds through Fundação para a Ciência e Tecnologia (FCT) in the form of a work contract (DL 57/2016/CP1364/CT0004), institutional funds UIDB/04434/2020 and UIDP/04434/2020, and scientific projects funds PTDC/FIS-AST/28953/2017 and POCI-01-0145-FEDER-028953

Ephemerides of Asteroid Satellites and Estimation of Their Accuracy

International audienc

Research on the HIP 18856 binary system

The results of a study on the binary HIP 18856 and construction of its orbit are presented. New observational data were obtained at the BTA of SAO RAS in 2007-2019. Earlier, Cvetković et al. constructed the orbit for this system. However, it is based on six measurements, which cover a small part of the orbit. The positional parameters of the ESA astrometric satellite Hipparcos published speckle interferometric data (Mason et al., Balega et al., Horch et al.) and new ones were used in this study. Based on the new orbital parameters, the mass sum was calculated and the physical parameters of the components were found. The obtained orbital and fundamental parameters were compared with the data from the study by Cvetković et al.. The comparison shows that the new orbital solution is better than the old one, since it fits new observational data accurately. Also based on a qualitative evaluation performed by Worley & Heintz, the new orbit was classified as "reliable", which means data cover more than half of the orbit with sufficient quantities of residuals of measurements