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Zdanavicius J.,Vilnius University | Vrba F.J.,Us Naval Observatory Flagstaff Station | Zdanavicius K.,Vilnius University | Straizys V.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group
Baltic Astronomy | Year: 2011

We present the results of eight-color CCD photometry of 674 stars in the direction of the open cluster Tombaugh 5 in Camelopardalis. The stars are observed in the Vilnius system supplemented by the broad-band I filter; the field is of 22' diameter, the limiting magnitude is V = 17.7 mag. The catalog contains the coordinates, V magnitudes, seven color indices, two-dimensional spectral types determined from photometric parameters, interstellar extinctions and distances. The color-magnitude diagram plotted for 480 individually dereddened stars is used to identify cluster members and to determine the distance (1.74 kpc) and age (200-250 Myr) of the cluster. The faintest cluster stars classified are of spectral class G0. The cluster contains two blue stragglers of spectral classes B2-B4, both of them seem to be visual binaries. The extinction A V for the cluster stars is non-uniform, being spread between 2 and 3 mag, with a mean value of 2.42 mag. The extinction vs. distance dependence can be modeled by the Parenago exponential curve with two dust concentrations in the Camelopardalis dark clouds at about 150 pc and the Cam OB1 association clouds at 0.9-1.0 kpc.

Zdanavicius J.,Vilnius University | Bartasiute S.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Vrba F.J.,Us Naval Observatory Flagstaff Station | Zdanavicius K.,Vilnius University
Baltic Astronomy | Year: 2010

CCD photometry in the eight-color Vilnius + I system for 7250 stars down to I = 19.6 mag has been obtained in the 20′ x 26′ field of the open cluster IC 361 in Camelopardalis. The catalog of 1420 stars down to V ∼ 18.5 mag is presented. It contains the coordinates, V magnitudes and seven color indices, quantitative photometric spectral types, absolute magnitudes and distances. The interstellar extinction is found to be non-uniform across the field, with the values of AV in the range 1.9 to 2.4 mag. The distribution of distance moduli of individual stars shows that the cluster is located as far as, or just beyond, the Perseus spiral arm.

Straizys V.,Vilnius University | Vrba F.J.,Us Naval Observatory Flagstaff Station | Boyle R.P.,Vatican Observatory Research Group | Milasius K.,Vilnius University | And 6 more authors.
Astronomical Journal | Year: 2015

The interstellar extinction is investigated in a 1.5 deg2 area in the direction of the open cluster M29 (NGC 6913) in Cygnus, centered at R.A. = 20h 24m, decl. = +38° 30′. The study is based on photometric classification of 1110 stars in spectral and luminosity classes down to V = 19 mag using photometry in the Vilnius seven-color system published in Paper I (Milašius et al. 2013). Additionally, in the same area the extinction is investigated using 1147 red clump giants (RCGs), identified by combining selected two-color diagrams of the 2MASS and Spitzer surveys. The investigated area is divided into three parts with different obscuration and in these directions the extinction versus distance plots up to 5 kpc are presented. In the whole area a steep rise of the extinction is observed at a distance of ∼800 pc; it should be related to dust clouds in the Great Cygnus Rift obscuring the stars behind it by AV = 4.0-4.7 mag. RCGs exhibit much larger extinction values, up to = 1.2-1.3 mag in the more transparent areas and 1.45 mag in the northeastern part of the area and above it, where the dust cloud TGU H466 is located. These values of correspond to AV = 10-12 mag. We do not exclude the possibility that the largest values of the extinction belong not to RCGs but to some contaminating intrinsically red AGB stars penetrated through the applied RCG selection constraints. The extinction in the TGU H466 cloud probably originates in two cloud systems - the Great Cygnus Rift at 800 pc and the Cygnus X complex of dust and molecular clouds at 1.3-1.5 kpc. © 2015. The American Astronomical Society. All rights reserved..

Griffin R.E.,Dominion | Griffin R.E.,Herzberg Institute for Astrophysics | Gray R.O.,Appalachian State University | Corbally C.J.,Vatican Observatory Research Group
Astronomy and Astrophysics | Year: 2012

The existence of the λ Boo type as a class of chemically-peculiar stars in its own right has taxed numerous researchers, and has challenged spectroscopists to produce a model which is plausible, comprehensive and predictive. Stars which are recognized as members of the λ Boo class have late-B to early-F spectral types, and exhibit (often substantially) low abundances of Fe-peak elements although elements such as C, N, O and S may have more nearly solar abundances. Since less than 2% of objects within the relevant spectral-type domain appear to be λ Boo stars their existence has demanded rather special conditions, and has triggered opinion that this group may not in fact exist but that each case can be explained as an unrecognized binary. In this paper we examine those claims by monitoring 10 stars, listed in the literature as possible λ Boo stars but said to be "likely candidates" for composite-spectrum binaries, by employing high-dispersion spectroscopy in an intermittent observing programme designed to reveal the sort of line-profile changes that should be detectable if each object were really a pair of similar stars in an SB2 system. We also monitor two other stars: HR 7903, said to be a binary (but is more like an Ap star), and λ Boo itself. The sample includes 1 possible, 1 marginal and 4 definite λ Boo classifications. In addition, we derive the physical properties of the 12 stars by photometric and spectroscopic synthesis, and measure their radial velocities. Three of the sample show small line-profile variations, but not of the sort that can be attributed to the presence of a companion star; they are the suspected Ap star HR 7903, HR 6878 (which exhibits spectrum peculiarities very similar to those of HR 7903 but has not previously been classified as Bp or Ap), and λ Aql, whose rapid spectrum variations resemble those observed in spotted or CP stars. None of the stars shows any evidence to suggest that it could be a composite-spectrum binary. © 2012 ESO.

Straizys V.,Vilnius University | Maskoliunas M.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Prada Moroni P.G.,University of Pisa | And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

The dust cloud TGU H645 P2 and embedded in it the young open cluster NGC 7129 are investigated using the results of medium-band photometry of 159 stars in the Vilnius sevencolour system down to V = 18.8 mag. The photometric data were used to classify about 50 per cent of the measured stars in spectral and luminosity classes. The extinction AV versus distance diagram for the 20 arcmin × 20 arcmin area is plotted for 155 stars with two-dimensional classification from the present and the previous catalogues. The extinction values are found in the range between 0.6 and 3.4 mag. However, some red giants, located in the direction of the dense parts of the cloud, exhibit the infrared extinction equivalent up to AV = 13 mag. The distance to the cloud (and the cluster) is found to be 1.15 kpc (the true distance modulus 10.30 mag). For determining the age of NGC 7129, a luminosity versus temperature diagram for six cluster members of spectral classes B3-A1 was compared with the Pisa pre-main-sequence evolution tracks and the Palla birthlines. The cluster can be as old as about 3Myr, but star formation continues till now as witnessed by the presence in the cloud of many younger pre-main-sequence objects identified with photometry from 2MASS, Spitzer and WISE infrared surveys. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Gray R.O.,Appalachian State University | Corbally C.J.,Vatican Observatory Research Group
Astronomical Journal | Year: 2014

This paper describes an expert computer program (MKCLASS) designed to classify stellar spectra on the MK Spectral Classification system in a way similar to humans - by direct comparison with the MK classification standards. Like an expert human classifier, the program first comes up with a rough spectral type, and then refines that spectral type by direct comparison with MK standards drawn from a standards library. A number of spectral peculiarities, including barium stars, Ap and Am stars, λ Bootis stars, carbon-rich giants, etc., can be detected and classified by the program. The program also evaluates the quality of the delivered spectral type. The program currently is capable of classifying spectra in the violet-green region in either the rectified or flux-calibrated format, although the accuracy of the flux calibration is not important. We report on tests of MKCLASS on spectra classified by human classifiers; those tests suggest that over the entire HR diagram, MKCLASS will classify in the temperature dimension with a precision of 0.6 spectral subclass, and in the luminosity dimension with a precision of about one half of a luminosity class. These results compare well with human classifiers. © 2014. The American Astronomical Society. All rights reserved..

Gray R.O.,Appalachian State University | McGahee C.E.,Appalachian State University | Griffin R.E.M.,Herzberg Institute for Astrophysics | Corbally C.J.,Vatican Observatory Research Group
Astronomical Journal | Year: 2011

Barium II (Ba) stars are chemically peculiar F-, G-, and K-type objects that show enhanced abundances of s-process elements. Since s-process nucleosynthesis is unlikely to take place in stars prior to the advanced asymptotic giant branch (AGB) stage, the prevailing hypothesis is that each present Bastar was contaminated by an AGB companion which is now a white dwarf (WD). Unless the initial mass ratio of such a binary was fairly close to unity, the receiving star is thus at least as likely to be a dwarf as a giant. So although most known Bastars appear to be giants, the hypothesis requires that Badwarfs be comparably plentiful and moreover that they should all have WD companions. However, despite dedicated searches with the IUE satellite, no WD companions have been directly detected to date among the classical Badwarfs, even though some 90% of those stars are spectroscopic binaries, so the contamination hypothesis is therefore presently in some jeopardy. In this paper, we analyze recent deep, near-UV and far-UV Galaxy Evolution Explorer (GALEX) exposures of four of the brightest of the class (HD 2454, 15360, 26367, and 221531), together with archived GALEX data for two newly recognized Badwarfs: HD 34654 and HD 114520 (which also prove to be spectroscopic binaries). The GALEX observations of the Badwarfs as a group show a significant far-UV excess compared to a control sample of normal F-type dwarfs. We suggest that this ensemble far-UV excess constitutes the first direct evidence that Badwarfs have WD companions. © 2011. The American Astronomical Society. All rights reserved.

Cernis K.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Laugalys V.,Vilnius University | Wlodarczyk I.,Chorzow Astronomical Observatory
Baltic Astronomy | Year: 2012

A project for astrometric and photometric observations of asteroids at Mt. Graham Observatory with the VATT telescope is described. One of the most important results is a discovery of the Centaur 2012 DS85. Astrometrie and photometric data on the asteroid are presented. The orbit of the asteroid was computed from 67 observations. Combined with its apparent brightness, the orbit gives an absolute magnitude of 9.43. Using a typical albedo value of 0.08 for Centaurs and TNOs (Moullet et al. 2011), we get a diameter of 2012 DS85 at about 61 km.

Wlodarczyk I.,Chorzow Astronomical Observatory MPC 553 | Cernis K.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Laugalys V.,Vilnius University
Monthly Notices of the Royal Astronomical Society | Year: 2014

The near-Earth asteroid belt is continuously replenished with material originally moving in Amor-class orbits. Here, the orbit of the dynamically interesting Amor-class asteroid 2012 XH16 is analysed. This asteroid was discovered with the Vatican Advanced Technology Telescope (VATT) at the Mt Graham International Observatory as part of an ongoing asteroid survey focused on astrometry and photometry. The orbit of the asteroid was computed using 66 observations (57 obtained with VATT and 9 from the Lunar and Planetary Laboratory-Spacewatch II project) to give a = 1.63 au, e = 0.36, i = 3°. 76. The absolute magnitude of the asteroid is 22.3 which translates into a diameter in the range 104-231 m, assuming the average albedos of S-type and C-type asteroids, respectively. We have used the current orbit to study the future dynamical evolution of the asteroid under the perturbations of the planets and the Moon, relativistic effects, and the Yarkovsky force. Asteroid 2012 XH16 is locked close to the strong 1:2 mean motion resonance with the Earth. The object shows stable evolution and could survive in near-resonance for a relatively long period of time despite experiencing frequent close encounters with Mars. Moreover, results of our computations show that the asteroid 2012 XH16 can survive in the Amor region at most for about 200-400 Myr. The evolution is highly chaotic with a characteristic Lyapunov time of 245 yr. Jupiter is the main perturber but the effects of Saturn, Mars and the Earth-Moon system are also important. In particular, secular resonances with Saturn are significant. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Kazlauskas A.,Vilnius University | Sperauskas J.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group
New Astronomy | Year: 2013

We present Strömvil photometry and radial-velocity measurements of the brightest (V<12 mag) stars in the region of the suspected open cluster Dol-Dzim 5. The long-term radial-velocity monitoring has revealed that one of the stars, BD + 38°2777, is a spectroscopic binary star. Its orbit, with a period of P=541 days, is calculated from 16 Coravel-type radial-velocity measurements. The analysis of the available astrometric, photometric and spectroscopic data has shown that reality of Dol-Dzim 5 seems unlikely. © 2012 Elsevier B.V. All rights reserved.

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