Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574

While following up L dwarf candidates selected photometrically from the Two Micron All Sky Survey, we uncovered an unusual object designated 2MASS J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium oxide but abnormally weak absorptions by titanium oxide, potassium, and sodium. Morphologically such spectroscopic characteristics fall intermediate between old, field early-L dwarfs (log(g)~5) and very late M giants (log(g)~0), leading us to favor low gravity as the explanation for the unique spectral signatures of this L dwarf. Such a low gravity can be explained only if this L dwarf is much lower in mass than a typical old field L dwarf of similar temperature and is still contracting to its final radius. These conditions imply a very young age. Further evidence of youth is found in the near-infrared spectrum, including a triangular-shaped H-band continuum reminiscent of young brown dwarf candidates discovered in the Orion Nebula Cluster. Using the above information along with comparisons to brown dwarf atmospheric and interior models, our current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of 6-25 M_Jupiter. The location of 2MASS 0141-4633 on the sky coupled with a distance estimate of ~35 pc and the above age estimate suggests that this object may be a brown dwarf member of either the 30-Myr-old Tucana/Horologium Association or the ~12-Myr-old beta Pic Moving Group.Comment: Accepted for publication in the 10 March 2006 issue (volume 639) of the Astrophysical Journa

Pulsations and Long-Term Light Variability of Three Candidates to Protoplanetary Nebulae

We present new photometric data and analysis of the long-duration UBV photoelectric observations for three candidates to protoplanetary objects - F-supergiants with IR-excesses located at large galactic latitudes, IRAS 18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All three stars have revealed quasiperiodic low-amplitude variabilities caused by pulsations observed against the long-term trends of brightnesses. For IRAS 18095+2704=V887 Her we have found a pulsation period of 109 days and a linear trend of brightness under the constant colours if being averaged over the year timescale. The light curve of IRAS 19386+0155=V1648 Aql over 2000-2008 can be approximated by a wave with a main period of 102 days which is modulated by close frequency, with a period of 98 days, that results in brightness oscillations with a variable amplitude. V1648 Aql has also shown synchronous reddening together with a persistent rise of brightness in the V-band. IRAS 19500-1709=V5112 Sgr experiences irregular pulsations with the periods of 39 and 47 days. The long-term component of the variability of V5112 Sgr may be related to the binary character of this star.Comment: 11 pages, 6 figures, accepted for publication in Pis'ma Astron. Z

GU Boo: A New 0.6 Msun Detached Eclipsing Binary

We have found a new low-mass, double-lined, detached eclipsing binary, GU Boo, among a sample of new variables from the ROTSE-I database. The binary has an orbital period of 0.488728 +/- 0.000002 days, and estimated apparent magnitudes Vrotse = 13.7 and I = 11.8. Our analysis of the light and radial velocity curves of the system yields individual masses and radii of M1= 0.610 +/- 0.007 Msun, M2 = 0.599 +/- 0.006 Msun, R1= 0.623 +/- 0.016 Rsun, R2= 0.620 +/- 0.020 Rsun. The stars in GU Boo are therefore very similar to the components of the eclipsing binary YY Gem. For this study we have adopted a mean effective temperature for the binary of Teff = 3870 +/- 130 K. Based on its space velocities we suggest that GU Boo is a main sequence binary, possibly with an age of several Gyr. The metallicity of the binary is not well constrained at this point but we speculate that it should not be very different from solar. We have compared the physical parameters of GU Boo with current low-mass stellar models, where we accounted for uncertainties in age and metallicity by considering a wide range of values for those parameters. Our comparisons reveal that all the models underestimate the radii of the components of GU Boo by at least 10-15%. This result is in agreement with the recent studies of YY Gem and CU Cnc.Comment: 41 pages, 10 figures, 11 tables; accepted by Ap

Мониторинг производственного использования коров в условиях дойных стад с высокопродуктивным маточным поголовьем

 Over the past decades, in many countries with developed dairy cattle breeding milk yield per cow per lactation has significantly increased, and period of cow productive use has been significantly reduced. The average duration of cow use in many countries is 2.5–2.8 lactations, and this is not enough for sustainable implementation of genetic potential of animals, which is revealed only at the 5–6th lactations. There is an increase in milk productivity and improvement of exterior type of black-and-white breed of cows in the Republic of Belarus, which is due to the use of Holstein cattle with outstanding milk productivity potential and a well-defined milk exterior type, however, as in other countries, there is a decrease in cow use period. The paper presents the results of monitoring of production use of cows in dairy herd conditions with highly productive breeding livestock. 5670 Holsteinized cows of Belarusian black-and-white breed were evaluated in two herds. The main causes of cows culling are determined, effect of genetic (blood level of Holstein breed, level of fathers and mothers performance) and paratypic (age of the 1st calving, level of heifers milking, inter-calving period, service period, results of the first insemination) factors for the life-long milk performance and cow use period. Correlation and heritability of indicators of productive longevity of cows is determined. A system of arrangement and breeding measures to improve longevity of highly productive livestock has been developed. Implementation of the developed system will allow to improve the integrated indices of breeding value of bulls and dairy cows and increase profitability of milk production by increasing the period of use of dairy herd maternal livestock.  Acknowledgments. The work was carried out as part of the state research and technical program “Agropromcomplex – sustainable development” for 2011–2015 sub-task 3.3.1 on topic “Develop system of breeding work with maternal livestock of Holsteinized dairy herds of different productivity levels”.  За последние десятилетия во многих странах с развитым молочным скотоводством значительно увеличился удой на корову за лактацию, при этом существенно сократился срок продуктивного использования коров. Средняя продолжительность использования коров во многих странах составляет 2,5–2,8 лактации, этого недостаточно для полной реализации генетического потенциала животных, который раскрывается только на 5–6-й лактации. В Республике Беларусь отмечается рост молочной продуктивности и улучшение типа телосложения коров черно-пестрой породы, что обусловлено использованием скота голштинской породы с выдающимся потенциалом молочной продуктивности и хорошо выраженным молочным типом телосложения, однако при этом, как и в других странах, отмечается снижение продолжительности использования коров. В статье приведены результаты мониторинга производственного использования коров в условиях дойных стад с высокопродуктивным маточным поголовьем. В двух стадах оценено 5670 голштинизированных коров белорусской черно-пестрой породы. Установлены основные причины выбытия коров из стад, влияние генетических (кровности по голштинской породе, уровень продуктивности отцов и матерей) и паратипических (возраст 1-го отела, уровень раздоя первотелок, межотельный период, сервис-период, результаты первого осеменения) факторов на пожизненную молочную продуктивность и продолжительность использования коров. Установлена взаимосвязь и наследуемость показателей продуктивного долголетия коров. Разработана система организационно-селекционных мероприятий по повышению долголетия высокопродуктивного скота. Внедрение разработанной системы позволит усовершенствовать комплексные индексы племенной ценности быков и коров молочных пород и добиться повышения рентабельности производства молока за счет увеличения продолжительности использования маточного поголовья в дойных стадах.Благодарности. Работа выполнена в рамках государственной научно-технической программы «Агропромкомплекс – устойчивое развитие» на 2011–2015 годы подзадания 3.3.1 по теме «Разработать систему племенной работы с маточным поголовьем голштинизированных дойных стад разного уровня продуктивности».

A Radial Velocity Survey of the Cygnus OB2 Association

We conducted a radial velocity survey of the Cygnus OB2 Association over a 6 year (1999 - 2005) time interval to search for massive close binaries. During this time we obtained 1139 spectra on 146 OB stars to measure mean systemic radial velocities and radial velocity variations. We spectroscopically identify 73 new OB stars for the first time, the majority of which are likely to be Association members. Spectroscopic evidence is also presented for a B3Iae classification and temperature class variation (B3 - B8) on the order of 1 year for Cygnus OB2 No. 12. Calculations of the intial mass function with the current spectroscopic sample yield Gamma = -2.2 +/- 0.1. Of the 120 stars with the most reliable data, 36 are probable and 9 are possible single-lined spectroscopic binaries. We also identify 3 new and 8 candidate double-lined spectroscopic binaries. These data imply a lower limit on the massive binary fraction of 30% - 42%. The calculated velocity dispersion for Cygnus OB2 is 2.44 +/- km/s, which is typical of open clusters. No runaway OB stars were found.Comment: 56 pages, 23 figures, 5 tables, accepted for publication in the Astrophysical Journa

ТЕХНОЛОГИЯ ИСПОЛЬЗОВАНИЯ ВЫСОКОПРОДУКТИВНЫХ ПЛЕМЕННЫХ ЖИВОТНЫХ В МОЛОЧНОМ СКОТОВОДСТВЕ

The article deals with new stages of the technology of breeding of high yield cows in milking herds. The yield of cows of different functions is characterized. The distribution of cows of a definite group in accordance with the age of the highest yield is described. The influence of selection and the qualities of mothers on the yield of daughters is presented.Приведены основные этапы технологии племенной работы с высокопродуктивными племенными животными в дойных стадах. Дана характеристика продуктивности коров разного функционального назначения, распределения коров селекционной группы по возрасту достижения наивысшего удоя. Показано влияние качества матерей на продуктивность дочерей, а также роль внутрилинейного подбора на их продуктивность

Optical Multicolor Photometry of Spectrophotometric Standard Stars

Photoelectric data on the Johnson-Kron-Cousins UBVRI broadband photometric system are provided for a set of stars which have been used as spectrophotometric standard stars at the Hubble Space Telescope.Comment: 76 pages, 48 figures - published version available here: http://www.journals.uchicago.edu/AJ/journal/issues/v133n3/205588/205588.html . Also see ERRATUM at: http://www.journals.uchicago.edu/AJ/journal/issues/v133n5/205838/205838.htm

On the nature of the EXor accretion events: an unfrequent manifestation of a common phenomenology ?

We present the results of a comparison between classical and newly identified EXor based on literature data and aimed at recognizing possible differences or similarities of both categories. Optical and near-IR two-color diagrams, modalities of fluctuations, and derived values of the mass accretion rates are indicative of strong similarities between the two samples. We demonstrate how the difference between the outburst and the quiescence spectral energy distribution of all the EXor can be well fitted with a single blackbody, as if an additional thermal component appears during the outbursting phase. Temperatures of this additional component span between 1000 and 4500 K, while the radii of the emitting regions (assumed to be a uniform disk) span between 0.01 and 0.1 AU, sizes typical of the inner portions of the circumstellar disk. Spots persisting up to 50% of the outburst duration, not exceeding the 10% of the stellar surface, and with temperatures compatible with the EXor mass accretion rates, are able to account for both the appearance of the additional thermal component and the dust sublimation in the inner structures of the disk. We also compare the EXor events with the most significant color and magnitude fluctuations of active T Tauri stars finding that (i} burst accretion phenomena should also be important for this latter class; (ii} EXor events could be more frequent then those accidentally discovered. Remarkable is the case of the source V2493 Cyg, a T Tauri star recently identified as a strong outbursting object: new optical and near-IR photometric and spectroscopic data are presented trying to clarify its EXor or FUor nature.Comment: Accepted for publication in Ap

Spectroscopic abundance analysis of dwarfs in young open cluster IC 4665

We report a detailed spectroscopic abundance analysis for a sample of 18 F-K dwarfs of the young open cluster IC 4665. Stellar parameters and element abundances of Li, O, Mg, Si, Ca, Ti, Cr, Fe and Ni have been derived using the spectroscopic synthesis tool SME (Spectroscopy Made Easy). Within the measurement uncertainties the iron abundance is uniform with a standard deviation of 0.04 dex. No correlation is found between the iron abundance and the mass of the stellar convective zone, and between the Li abundance and the Fe abundance. In other words, our results do not reveal any signature of accretion and therefore do not support the scenario that stars with planets (SWPs) acquire their on the average higher metallicity compared to field stars via accretion of metal-rich planetary material. Instead the higher metallicity of SWPs may simply reflect the fact that planet formation is more efficient in high metallicity environs. However, since that many details of the planet system formation processes remain poorly understood, further studies are needed for a final settlement of the problem of the high metallicity of SWPs. The standard deviation of [Fe/H] deduced from our observations, taken as an upper limit on the metallicity dispersion amongst the IC 4665 member stars, has been used to constrain proto-planetary disk evolution, terrestrial and giant planets formation and evolution processes. Our results do not support the possibility that the migration of gas giants and the circularization of terrestrial planets' orbits are regulated by their interaction with a residual population of planetesimals and dust particles.Comment: 18 pages, 6 figures, accepted for publication in Ap

A RAVE investigation on Galactic open clusters I. Radial velocities and metallicities

Context. Galactic open clusters (OCs) mainly belong to the young stellar population in the Milky Way disk, but are there groups and complexes of OCs that possibly define an additional level in hierarchical star formation? Current compilations are too incomplete to address this question, especially regarding radial velocities (RVs) and metallicities ([M/H]). Aims. Here we provide and discuss newly obtained RV and [M/H] data, which will enable us to reinvestigate potential groupings of open clusters and associations. Methods. We extracted additional RVs and [M/H] from the RAdial Velocity Experiment (RAVE) via a cross-match with the Catalogue of Stars in Open Cluster Areas (CSOCA). For the identified OCs in RAVE we derived (RV) over bar and ([M/H]) over bar from a cleaned working sample and compared the results with previous findings. Results. Although our RAVE sample does not show the same accuracy as the entire survey, we were able to derive reliable (RV) over bar for 110 Galactic open clusters. For 37 OCs we publish (RV) over bar for the first time. Moreover, we determined ([M/H]) over bar for 81 open clusters, extending the number of OCs with ([M/H]) over bar by 69