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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..

Zdanavicius J.,Vilnius University | Vrba F.J.,U.S. 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.

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.

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.

Zdanavicius J.,Vilnius University | Bartasiute S.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Vrba F.J.,U.S. 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.

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