UCAC2 Research Articles

Carte du Ciel andGaia

Context.The Carte du Ciel archive at the University of Helsinki enables us to see the sky as it was about 120 yr ago. The archive consists of single-exposure and triple-exposure plates between epochs 1896.8–1925.8.Aims.Our main aim is to find binary and multiple stars by combining Carte du Ciel andGaiadata.Methods.The plates were digitised with a commercial digital camera. We usedGaiadata to calculate predicted coordinates of stars at the epoch of each plate. These stars were used as reference stars to fit astrometry for each plate, giving fitted coordinates for stars on the Carte du Ciel plates. If the predicted and fitted coordinates differed at a significant level, we classified the star as a non-single star, for which the proper motion values given in theGaiacatalogue can be unreliable.Results.We find that several astrometric quality indicators ofGaiaindicate that the uncertainties ofGaia’ssingle-star model fit are, in general, larger for our non-single-star candidates. The percentage of our non-single-star candidates, which are in the catalogues of known binary stars, is relatively low, ~10% at maximum.Conclusions.The combination of the Carte du Ciel andGaiadata can be used to identify candidates of non-single stars. We propose that the sources with a significant difference between the predicted and fitted coordinates are long-period binaries, although astrophysical and/or instrumental effects as origin for the coordinate difference cannot be excluded for individual cases.

OBSERVATION OF AN OCCULTATION OF THE UCAC4 488-082551 STAR BY ASTEROID (76228) 2000 EH 75 ON 31 MAY 2022

Observations of an occultation of the UCAC4 488-082551 star by asteroid (76228) 2000 EH 75 were carried out on 31 May 2022 at Kryzhanivka observation station of Odesa I. I. Mechnykov National University (the observatory code A85). A set of instruments, which included a Schmidt telescope (the primary mirror diameter D = 271.25 mm; the corrector plate diameter D k = 223.9 mm; the focal length F = 440 mm), a GPS receiver and Videoscan-415-2001 CCD camera, was used to perform observations. The observing conditions were as follows: clear sky, the star’s altitude 49 0 south, the Moon was below the local horizon. The target star from the UCAC4 catalogue (Zacharias et al. 2013) has the following photometric parameters: m B = 14.008; m V = 12.720; m r = 12.284; m i = 11.813. The diameter of the star has not been determined. Asteroid (76228) is a Main Belt asteroid with an orbital period of 4.17178 years. It has an absolute magnitude of 14.93, the visible geometric albedo of 0.123±0.013 and diameter of 5.00±0.23 km (Masiero et al. 2011). The time of occultation predicted using ephemerides was 23:52:44±4 sec. The maximum duration of the occultation was 0.4 sec, provided that the observing site was located at the centre of the occultation track (strip). A drop in the star’s brightness observed during occultation was about 8 m . The occultation event was recorded as a sequence of GIF images with the exposure time of 0.5 sec per frame. The system clock of the computer used for the occultation recording was controlled with a GPS receiver in a fashion similar to that described in the paper by Karbovsky et al. (2017). The data processing yielded an estimate of the occultation duration of 0.46±0.04 sec. The uncertainty of the occultation start time within exposure results in the total estimate of accuracy in timing the maximum phase of occultation 23:52:44.06±0.10 sec. The chord length across the asteroid estimated by timing the occultation is L = 9.2±0.8. This chord length is close to the estimates of the asteroid diameter reported in the paper by Masiero et al. (2011).

ASTROMETRIC RESEARCH IN UKRAINE AT THE XIX – BEGINNING OF XX CENTURIES

The paper presents the stages of development of astrometric research at the Ukrainian observatories in the ХIХ – beginning of ХХ century. They are related to the establishment of university astronomical observatories in Kyiv (1845), Odessa (1871), Kharkiv (1888). Mykolaiv Naval observatory was founded in 1821 for navigation needs with assistance of Admiral A.S. Greig. The absolute catalogs compiled at the Pulkovo and Mykolaiv Observatories made a significant contribution to the international work of compilation of a FK3 system. Special attention is paid to the scientific activity of the oldest observatory at the territory of Ukraine – the Astronomical observatory of L’viv University (1771). Researches at this observatory were mainly concerned with the field of geodesy and meteorology. Despite the short first period of scientific activity (near 10 years), it gave impetus to some famous scientists. At the last decades of ХIХ century observatory of the L’viv University renewed their activity in astrometry, solar physics, and astrophysics. Southern departments of Pulkovo observatory in Odessa (1899) and Mykolaiv (1912) played an important role in extension of Pulkovo absolute catalogues to the southern hemisphere. Systematic observations of the Sun conducted at these departments contributed to the more precise determination of the position of vernal equinox. In ХIХ century Ukrainian observatories participated in the international programs, such as AGK (Astronomischer Gesellschaft Katalog), the photographic catalog “Carte du Ciel” (France). Among the actual observational programs were surveys of zodiacal stars (M.P.Ditchenko in Kyiv), near-pole stars (V.I.Fabritius, R.P.Fogel, M.P.Ditchenko in Kyiv, L.O.Struve and K.N.Kuz'menko in Kharkiv, I.O.Djukov, L.F.Cherniev in Odessa). In the frame of observations of Bonner Durchmusterung (BD) and its southern continuation, organized by the German Astronomical Society, observations of the equatorial zone were provided by I.E. Kortazzi at Mykolaiv observatory, B.V.Novopashenny at the Astronomical Observatory of Odessa University in 1930s years. Needs of astrophotography lead to the creation of the “Сatalog of the faint stars” project. In 1932 at the First Astrometric Conference in Leningrad, the Pulkovo astronomers Gerasimovich B.P and Dniprovsky M.I. suggested the idea of using eхtragalactic nebulae as the reference objects for determination of the absolute motion of the stars. Among the tasks to be solved at the project was compilation of a general catalogue (KSZ) and a fundamental catalog of faint stars (FKSZ). It was planned to involve all the meridian instruments of the USSR as well as foreign ones, especially in the southern hemisphere. The idea of orientation of the KSZ coordinates system related to the observations of small planets was suggested by B.V.Numerov. Astronomers of Mykolaiv Astronomical Observatory participated in the international part of this project (AGK3R-catalogue). The Poltava gravimetric observatory was founded by A.Ya.Orlov in 1926 to construct a gravity map of the territory of Ukraine and to establish astrometric research, earth tides, and Latitude Service with zenith-telescopes. The main research fields of the Main Astronomical Observatory of the NAS of Ukraine, founded by A.Ya.Orlov in 1944, were related to the positional and photographic astrometry during the first decade of its work. We defined three “genealogical scientific trees” of astrometric schools. Two of them were formed under the leadership of outstanding personalities of the XX century: Prof. Alexander Ya. Orlov (the founder and first director of the Observatory, 1944–1948, 1950–1951), who moved to Kyiv from Poltava, and Prof. Avenir A.Yakovkin (director of the Observatory in 1952–1959), who moved to Kyiv from Kazan. The third genealogical tree has grown from the Pulkovo astronomical school. Formation of main directions of scientific researches and its transformation are also discussed. Keywords: astrometric research, positional astrometry, photographic astrometry, fundamental astrometry.

THE MEXICAN ASTROGRAPHIC CATALOGUE AND CARTE DU CIEL PROJECT

The participation of Mexican astronomers in international projects dates back to the eighteenth century, when they observed the 1769 transit of Venus. More than a century later, they again participated in attempts to establish a precise value for the astronomical unit through the transits of Venus that occurred in 1874 and 1882. In 1887 Mexican astronomers were invited to join efforts to develop a multinational initiative known as the Carte du Ciel and International Astrographic Project, collaborating with 17 other observatories worldwide. Mexican astronomers obtained support from their Government, and they ordered telescopes from the Irish firm of Sir Howard Grubb and Company. An astrograph was used to photograph stars in Mexico's assigned sky zone (between declinations -10° and -16°) down to a limiting magnitude of 11 for the Astrographic Catalogue, and down to magnitude 14 for the Carte du Ciel. The Astrographic Catalogue photography began in February 1900, and the first of the plates for the Carte du Ciel was exposed in 1905. The Mexican astronomers had to overcome a number of serious difficulties, such as the Mexican Revolution of 1910-1920, which caused several delays and the loss of many personnel from the National Astronomical Observatory of Mexico, and then World War I, 1914-1918, which hindered the arrival of the photographic plates and interrupted communication with the Carte du Ciel Commission in Paris. Women usually were employed as 'computers' to measure the Astrographic Catalogue star positions. Between 1921 and 1962, seven volumes were published listing Mexican Astrographic Catalogue star positions. Mexican astronomers finished taking all of the Carte du Ciel plates, except for the -12° declination zone, but because of financial constraints only 375 plates were printed. Afterwards, from 1941, photography of the -13° zone was repeated in order to obtain stellar positions for proper motion studies. In March 1970 the mounting of the historic 33-cm Grubb astrograph and accompanying 25.4-cm guidescope was used at Miahuatlán, Oaxaca, together with a replacement tube assembly and objective to observe a total solar eclipse. Then from 1976 to 1979 three Astronomy students from the National University of Mexico reconstructed and renovated the original Grubb twin-telescope, which is now at Tonantzintla, near Puebla, and is used mainly for educational purposes.

A revision of the vdB 130 cluster stellar content based on Gaia DR2 data: interstellar extinction toward the Cyg OB1 supershell

ABSTRACT Two star-forming regions are studied: the young embedded open cluster vdB 130 and the protocluster neighbourhood observed in the head and tail of the cometary molecular cloud located in the wall of the expanding supershell surrounding the Cyg OB1 association. The Gaia DR2 catalogue is employed to verify the stellar composition of the vdB 130 cluster whose members were earlier selected using the UCAC4 catalogue. The new sample of vdB 130 members contains 68 stars with close proper motions (within 1 mas yr−1) and close trigonometric parallaxes (ranging from 0.50–0.70 mas). The relative parallax error is shown to increase with distance to objects and depend on their magnitude. At a distance of 1.5–2 kpc it is of about 3–7 per cent and 20–30 per cent for bright and faint stars, respectively. The cluster is not older than ∼10 Myr. New spectroscopic and photometric observations carried out on Russian telescopes are combined with Gaia DR2 to search for optical components in the protocluster region – a new starburst. An analysis of 20 stars in the vicinity of the protocluster revealed no concentration of either proper motions or parallaxes. According to spectroscopic, photometric and trigonometric estimates, the distances to these stars range from 0.4–2.5 kpc, and colour excess is shown to increase with a distance D (kpc) in accordance with the law E(B − V) ≃ 0.6 × D mag.

COMPARISSON OF THE RESULTS OF PROCESSING OF CCD OBSERVATIONS OF SELECTED OPEN CLUSTERS

Observations of open clusters at the Re- search Institute “Mykolaiv Astronomical Observatory” (RI MAO) were performed using the KT-50 telescope (D=500mm, F=3000mm) in 2011 – 2018. As the light re- ceiver, a CCD camera Apogee Alta U9000 (3K x 3K, FOV 42.6' x 42.6') in short drift scan mode was used. In short drift scan mode each observation consisted of several CCD frames with partial overlap in right ascension. All observa- tions were performed using R light filter. The exposure time was 20 seconds for all frames. All previous astromet- ric processing was carried out by the Astrometrica program and UCAC4 reference catalog. Using this data we received two catalogs of positions of 4.2 million stars (J2013.6) and 3.3 million starts (J2017.3) in the vicinity of open clusters with accuracy (0.03-0.07). Unfortunately, current version of Astrometrica program have problem with data reduction with Gaia reference catalog in areas with big star density, like vicinity of open clusters near the plane of the Galaxy. At this article, we compared our old results with the new one for several open clusters which carried out with the author's set of programs with primary processing in the MIDAS environment. As reference stars the Tycho2, UCAC4 and Gaia DR2 catalogs were used. The reduction of 548 frames was performed using a polynomial of the third degree. The results obtained by author programs with reference catalogs UCAC4 and Gaia, showed good con- vergence. Several catalogs of positions of stars up to 17.5 m was obtained. The accuracy of the catalogs is σ RA =0.027 and σ Dec =0.033 for Gaia reference catalog and σ RA =0.032 and σ Dec =0.036 for UCAC4 reference catalog. At the same time, the accuracy of intraframe processing with the Gaia reference catalog turned out to be near 2 times better than the analogous one with the UCAC4 catalog. The compari- son showed the possibility of receiving more good results with Gaia reference catalog.

PROBABILITIES OF PHYSICAL LINK BETWEEN THE COMPONENTS OF THE SELECTED MULTIPLE SYSTEMS FROM WDS CATALOG

Astrometric CCD observations of visual components of double and multiple stars were performed using the RI MAO Axial Meridian Circle (AMC) with new Apogee Alta AI-F8300 CCD camera mounted at the telescope in 2018. Observations were carried out automatically in drift- scan mode using a standard R filter. Objects for observational program were selected from the Washington Double Star Catalog (WDS). During the 23 nights, 983 observations of 579 double and multiple systems from the WDS catalog were obtained. Astrometric reductions of the observations showed high accuracy, with an average error of one position about 0.1 in right ascension and declination for stars up to 16 mag , which were observed more than 3 times. The purpose of our study was to measure the parameters of the mutual configuration of pairs from the original images and to draw some conclusions about the physical connection of the components in the selected systems. The measurement array that will be sent to the WDS database includes values of positional angle, angular separation, stellar magnitude difference, and epoch of the observation. A detailed analysis of the pairs of stars in the selected 5 systems to clarify their composition and the nature of the link between them was made. Positional data from the Hipparcos, Tycho2, UCAC4, Gaia DR2, and Pan-STARRS (PS1) catalogs were used as sources of additional information about the investigated stars. The search for possible invisible stars in the selected systems was performed using the statistical Wielen method, based on the analysis of the differences of instantaneous and long-term averaged proper motions of the stars. The proper motions of the space Gaia DR2 catalog were considered to be instantaneous, the long-term averaged proper motions were used from Tycho-2 and UCAC4 catalogs. Obtained values of the statistical parameter in some cases indicate a high probability of existence of invisible close components in the studied systems. Detailed comments of the results for each of the selected systems are provided.

ON THE FON ASTROPLATE PROJECT ACCOMPLISHMENT

The plan of the photographic survey of the northern sky (FON) was proposed in 1976 in Golosiiv ob- servatory (now MAO NAS of Ukraine) by I. Kolchinsky and A. Onegina. The final project of the Compiled FONAC catalog (FON Astrographic Catalog) is based on the digital data of photographic plates exposed at four observatories. They are MAO NAS of Ukraine (Kyiv, Ukraine), Kitab astronomical observatory (Tashkent, Uzbekistan), Hissar astronomical observatory (Dushanbe, Tajikistan), and Bal- done observatory (Latvia)). The total amount of plates is 5700. The result is expected to be the catalog of positions and B-magnitudes of stars covered the declination area from -20 to 90 degrees. The estimated mean epoch of the catalog is ~1987. The limiting B-magnitude is ~17.5 m . The reference system for positions is Tycho-2. B-magnitudes are being obtained in the system of photoelectric standards. The resulted data of photometric reduction are corrected for the photometric color equation in B magnitudes. The com- plement for the photometric content of the catalog is U and V magnitudes of stars being obtained from the processing of 5400 plates from the glass collection of 1.2 m Schmidt telescope in Baldone. Photometric data of bright stars with V < 8.5 m U, B,V magnitudes cannot be obtained from pho- tographic material, so those objects will gain photometric data from photoelectric catalogs. The catalog will be com- plemented with proper motions from GAIA.

The gravity database for Belgium

AbstractData and metadata products based on intensive terrestrial gravity measurements covering the Belgian territory have been established compliant to the new ISO19115‐1 profile for gravity‐related data. A short historical introduction on gravity measurements on the Belgian territory is presented, starting with the first gravity measurement in 1892. This paper focuses on gravity data acquired after 1971, which marks the adoption of IGSN71 as a reference for the world network by the International Association of Geodesy (IAG). Next to a complete dataset containing all Belgian gravity data, the available gravity data were reduced to the corresponding measurement campaign, enabling determination of specific metadata (e.g. used gravimeter, tide system parameters, time of acquisition, etc.). New gravity and spirit levelling measurements were executed by the Royal Observatory Belgium and the National Geographic Institute (Federal Mapping Agency) to validate the g‐value at the historical reference base station ‘Carte du Ciel’ in Brussels. Taking into account the instrumental errors and the varying ground water content, the retrieved data are validated and approved for use in further research.

The first President of the IAU, Benjamin Baillaud

AbstractBenjamin Baillaud was appointed president of the First Executive Committee of the International Astronomical Union which met in Brussels during the Constitutive Assembly of the International Research Council (IRC) on July 28th, 1919. He served in this position until 1922, at the time of the First General Assembly of the IAU which took place in Rome, May 2–10. At that time, Baillaud was director of the Paris Observatory. He had previously been director of the Toulouse Observatory for a period of 30 years and Dean of the School of Sciences of the University of Toulouse. He specialized in celestial mechanics and he was a strong supporter of the “Carte du Ciel” project; he was elected chairman of the permanent international committee of the Carte du Ciel in 1909. He also was the founding president of the Bureau International de l’Heure (BIH) and he was directly involved in the coordination of the ephemerides at an international level. In this paper, we present some of his activities, particularly those concerning international programmes, for which he received international recognition and which eventually led to his election in 1919 to the position of first president of the IAU. We also briefly recount the very first meetings and years of the IAU.

“Carte du Ciel” Catalogs and Their Importance for Modern Astrometry

Astronomical catalogs created as a result of the “Carte du Ciel” project are considered, including the work of K.V. Kuimov in this area, its methodological importance, and perspectives in the GAIA era. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

The Carte du Ciel and the Latin American Observatories

Abstract2017 marked the 130th anniversary of the start of the Carte du Ciel project, an ambitious proposal by the Paris Observatory to map the entire sky using photographiy, which required the joint work of numerous observatories in the world. For this endeavour, an impressive organization was designed that included congresses, commissions and publications, which lasted through many years. The Carte du Ciel finally became one of the immediate antecedents of the International Astronomical Union, which in 2019 celebrates its first century. In Latin America, the observatories of Santiago de Chile, La Plata and Rio de Janeiro, the Argentine National Observatory and the Tacubaya Observatory, in Mexico, were involved in the project. In this presentation, we present part of the history of the failures and successes of one of the most important collaborative astronomical projects on the planet.

Astronomy in Mexico during the first years of the IAU

AbstractIn 1918 the only Mexican institution dedicated professionally to astronomical work was the National Astronomical Observatory, which had begun operations in 1878. In that year of the 20th century, Mexico was immersed in the armed movement known as the Mexican Revolution, which strongly affected the social and economic structure of the country. The Mexican astronomers saw their group drastically reduced and their infrastructure limited; however, they made great efforts to continue their participation in the international project of the Carte du Ciel, since they were part of the 18 observatories that originally participated in it. Despite the limitations they suffered, they soon joined the group of seven nations that in 1919 formed the IAU, and two members of that observatory actively participated in the first general assembly held in Rome in May 1922.

Spectroscopic classification and Gaia DR2 parallaxes of new nearby white dwarfs among selected blue proper motion stars

Aims. With our low-resolution spectroscopic observing programme for selected blue proper motion stars, we tried to find new white dwarfs (WDs) in the solar neighbourhood. Methods. We used the Lépine &amp; Shara Proper Motion (LSPM) catalogue with a lower proper motion limit of 150 mas yr−1 and the Second US Naval Observatory CCD Astrograph Catalog (UCAC2) for proper motions down to about 90 mas yr−1. The LSPM and UCAC2 photometry was combined with Two Micron All Sky Survey (2MASS) near-infrared (NIR) photometry. Targets selected according to their blue optical-to-NIR and NIR colours were observed mainly at Calar Alto. The spectra were classified by comparison with a large number of already known comparison objects, including WDs, simultaneously observed within our programme. Gaia DR2 parallaxes and colours were used to confirm or reject spectroscopic WD candidates and to derive improved effective temperatures. Results. We found ten new WDs at distances between 24.4 pc and 79.8 pc, including six hot DA WDs: GD 221 (DA2.0), HD 166435 B (DA2.2), GD 277 (DA2.2), 2MASS J19293865+1117523 (DA2.4), 2MASS J05280449+4105253 (DA3.6), and 2MASS J05005185-0930549 (DA4.2). The latter is rather bright (G ≍ 12.6) and with its Gaia DR2 parallax of ≍14 mas it appears overluminous by about 3 mag compared to the WD sequence in the Gaia DR2 colour-magnitude diagram. It may be the closest extremely low mass (ELM) WD to the Sun. We further classified 2MASS J07035743+2534184 as DB4.1. With its distance of 25.6 pc it is the second nearest known representative of its class. With GD 28 (DA6.1), LP 740-47 (DA7.5), and LSPM J1919+4527 (DC10.3) three additional cool WDs were found. Gaia DR2 parallaxes show that four of our candidates, but also two previously supposed WDs (WD 1004+665 and LSPM J1445+2527) are in fact distant Galactic halo stars with high tangential velocities. Among our rejected WD candidates, we identified a bright (G = 13.4 mag) G-type carbon dwarf, LSPM J0937+2803, at a distance of 272 pc.

Refining the origins of the gamma-ray binary 1FGL J1018.6–5856

Context. Gamma-ray binaries are systems composed of a massive star and a compact object that exhibit emission from radio to very high energy gamma rays. They are ideal laboratories to study particle acceleration and a variety of physical processes that vary as a function of the orbital phase. Aims. We aim to study the radio emission of the gamma-ray binary 1FGL J1018.6–5856 to constrain the emitting region and determine the peculiar motion of the system within the Galaxy to clarify its origin. Methods. We analyzed an observation of 1FGL J1018.6–5856 with the Australian Long Baseline Array (LBA) at 8.4 GHz to obtain an accurate astrometry of the system and study its emission on milliarcsecond scales. We combined these data with the optical Gaia DR2 and UCAC4 catalogs to consolidate the astrometry information therein. Results. The gamma-ray binary 1FGL J1018.6–5856 shows compact radio emission (&lt; 3 mas or ≲20 au at ∼6.4 kpc distance), implying a brightness temperature of ≳5.6 × 106 K, and confirming its nonthermal origin. We report consistent results between the proper motion reported by Gaia DR2 and the positions obtained from the Gaia DR2, UCAC4, and LBA data (spanning 20 yr in total). We also determined the distance to 1FGL J1018.6–5856 to be 6.4−0.7+1.7. Together with the radial velocity of the source we computed its three-dimensional (3D) proper and peculiar motion within the Galaxy. We obtained a peculiar motion of 1FGL J1018.6–5856 on its regional standard of rest (RSR) frame of |u| = 45−9+30, with the system moving away from the Galactic plane. In the simplest scenario of a symmetric stellar core collapse we estimate a mass loss of 4 ≲ ΔM ≲ 9 M⊙ during the creation of the compact object. Conclusions. 1FGL J1018.6–5856 exhibits compact radio emission similar to that detected in other gamma-ray binaries. We provide the first accurate peculiar motion estimations of the system and place it within the Galaxy. The obtained motion and distance excludes the physical relation of the binary source with the supernova remnant (SNR) G284.3−1.8.

Digitization and astrometric calibration of Carte du Ciel photographic plates with Gaia DR1

Context. Carte du Ciel was a global international project at the end of the nineteenth and beginning of the twentieth century to map the sky to about magnitude 14 on photographic plates. The full project was never observationally completed and a large fraction of the observations made remain unanalyzed. Aims. We want to study whether the astrometric and photometric accuracies obtained for the Carte du Ciel plates digitized with a commercial digital camera are high enough for scientific exploitation of the plates. Methods. We use a digital camera Canon EOS 5Ds, with a 100 mm macrolens for digitizing. We analyze six single-exposure plates and four triple-exposure plates from the Helsinki zone of Carte du Ciel (+39∘ ≤ δ ≤ +47∘). Each plate is digitized using four images, with a significant central area being covered twice for quality control purposes. The astrometric calibration of the digitized images is done with the data from the Tycho-Gaia Astrometric Solution (Gaia TGAS) of the first Gaia data release (Gaia DR1), Tycho-2, Hot Stuff for One Year (HSOY), USNO CCD Astrograph Catalog (UCAC5), and PMA catalogs. Results. The best astrometric accuracy is obtained with the UCAC5 reference stars. The astrometric accuracy for single-exposure plates is σ(α cos(δ)) = 0.16″ and σ(δ)=0.15″, expressed as a Gaussian deviation of the astrometric residuals. For triple-exposure plates the astrometric accuracy is σ(α cos(δ)) = 0.12″ and σ(δ)=0.13″. The 1 − σ uncertainty of photometric calibration is about 0.28 mag and 0.24 mag for single- and triple-exposure plates, respectively. We detect the photographic adjacency (Kostinsky) effect in the triple-exposure plates. Conclusions. We show that accuracies at least of the level of scanning machines can be achieved with a digital camera, without any corrections for possible distortions caused by our instrumental setup. This method can be used to rapidly and inexpensively digitize and calibrate old photographic plates enabling their scientific exploitation.

Characterising open clusters in the solar neighbourhood with the Tycho-Gaia Astrometric Solution

Context. The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G ~ 12 mag. Aims. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or the fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4) proper motions, and TGAS parallaxes. Methods. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/Markov Chain Monte Carlo technique to fit stellar isochrones to the observed 2MASS JHKS magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. Results. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2 kpc, and cluster parameters from isochrone fitting for 26 of them located within a distance of 1 kpc from the Sun. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.

Update of membership and mean proper motion of open clusters from UCAC5 catalogue

We present mean proper motions and membership probabilities of individual stars for optically visible open clusters, which have been determined using data from the UCAC5 catalog. This follows our previous studies with the UCAC2 and UCAC4 catalogs, but now using improved proper motions in the GAIA reference frame. In the present study results were obtained for a sample of 1108 open clusters. For five clusters, this is the first determination of mean proper motion, and for the whole sample, we present results with a much larger number of identified astrometric member stars than on previous studies. It is the last update of our Open cluster Catalog based on proper motion data only. Future updates will count on astrometric, photometric and spectroscopic GAIA data as input for analyses.

New nearby white dwarfs from Gaia DR1 TGAS and UCAC5/URAT

Aims. Using an accurate Tycho-Gaia Astrometric Solution (TGAS) 25 pc sample that is nearly complete for GK stars and selecting common proper motion (CPM) candidates from the 5th United States Naval Observatory CCD Astrograph Catalog (UCAC5), we search for new white dwarf (WD) companions around nearby stars with relatively small proper motions. Methods. To investigate known CPM systems in TGAS and to select CPM candidates in TGAS+UCAC5, we took into account the expected effect of orbital motion on the proper motion and proper motion catalogue errors. Colour-magnitude diagrams (CMDs) MJ ∕J − Ks and MG ∕G − J were used to verify CPM candidates from UCAC5. Assuming their common distance with a given TGAS star, we searched for candidates that occupied similar regions in the CMDs as the few known nearby WDs (four in TGAS) and WD companions (three in TGAS+UCAC5). The CPM candidates with colours and absolute magnitudes corresponding neither to the main sequence nor to the WD sequence were considered as doubtful or subdwarf candidates. Results. With a minimum proper motion of 60 mas yr−1, we selected three WD companion candidates; two of which are also confirmed by their significant parallaxes measured in URAT data, whereas the third may also be a chance alignment of a distant halo star with a nearby TGAS star that has an angular separation of about 465 arcsec. One additional nearby WD candidate was found from its URAT parallax and GJKs photometry. With HD 166435 B orbiting a well-known G1 star at ≈24.6 pc with a projected physical separation of ≈700 AU, we discovered one of the hottest WDs, classified by us as DA2.0 ± 0.2, in the solar neighbourhood. We also found TYC 3980-1081-1 B, a strong cool WD companion candidate around a recently identified new solar neighbour with a TGAS parallax corresponding to a distance of ≈8.3 pc and our photometric classification as ≈M2 dwarf. This raises the question of whether previous assumptions on the completeness of the WD sample to a distance of 13 pc were correct.

The VMC survey

We use deep multi-epoch point-spread function (PSF) photometry taken with the Visible and Infrared Survey Telescope for Astronomy (VISTA) to measure and analyze the proper motions of stars within the Galactic globular cluster 47 Tucanae (47 Tuc, NGC 104). The observations are part of the ongoing near-infrared VISTA survey of the Magellanic Cloud system (VMC). The data analyzed in this study correspond to one VMC tile, which covers a total sky area of 1.77 deg2. Absolute proper motions with respect to ~9070 background galaxies are calculated from a linear regression model applied to the positions of stars in 11 epochs in the Ks filter. The data extend over a total time baseline of about 17 months. We found an overall median proper motion of the stars within 47 Tuc of (μαcos(δ), μδ) = (+5.89 ± 0.02 (statistical) ± 0.13 (systematic), −2.14 ± 0.02 (statistical) ± 0.08 (systematic)) mas yr−1, based on the measurements of ~35 000 individual sources between 5′ and 42′ from the cluster center. We compared our result to the proper motions from the newest US Naval Observatory CCD Astrograph Catalog (UCAC5), which includes data from the Gaia data release 1. Selecting cluster members ( ~2700 stars), we found a median proper motion of (μαcos(δ), μδ) = (+5.30 ± 0.03 (statistical) ± 0.70 (systematic), −2.70 ± 0.03 (statistical) ± 0.70 (systematic)) mas yr−1. Comparing the results with measurements in the literature, we found that the values derived from the VMC data are consistent with the UCAC5 result, and are close to measurements obtained using the Hubble Space Telescope. We combined our proper motion results with radial velocity measurements from the literature and reconstructed the orbit of 47 Tuc, finding that the cluster is on an orbit with a low ellipticity and is confined within the inner ~7.5 kpc of the Galaxy. We show that the use of an increased time baseline in combination with PSF-determined stellar centroids in crowded regions significantly improves the accuracy of the method. In future works, we will apply the methods described here to more VMC tiles to study in detail the kinematics of the Magellanic Clouds.