Speckle Interferometry at the US Naval Observatory. XIII.
The results of 1424 speckle interferometric observations of doublestars, made with the 26 inch (66 cm) refractor of the US NavalObservatory, are presented. Each speckle interferometric observation ofa system represents a combination of over 2000 short-exposure images.These observations are averaged into 1053 mean relative positions andrange in separation from 0.36″ to 61.92″, with a medianseparation of 10.31″. This is the 13th in a series of paperspresenting measurements obtained with this system and covers the period2006 January 12-December 29. Included in these data are nine oldermeasurements whose positions were previously deemed possibly aberrantbut are no longer classified this way following a confirmingobservation. This paper also includes the first data obtained using anew "secondary" camera, designed and built at USNO.
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New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
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Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
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Derivation of the Galactic rotation curve using space velocities
We present rotation curves of the Galaxy based on the space-velocitiesof 197 OB stars and 144 classical cepheids, respectively, which rangeover a galactocentric distance interval of about 6 to 12kpc. Nosignificant differences between these rotation curves and rotationcurves based solely on radial velocities assuming circular rotation arefound. We derive an angular velocity of the LSR of{OMEGA}_0_=5.5+/-0.4mas/a (OB stars) and {OMEGA}_0_=5.4+/-0.5mas/a(cepheids), which is in agreement with the IAU 1985 value of{OMEGA}_0_=5.5mas/a. If we correct for probable rotations of the FK5system, the corresponding angular velocities are {OMEGA}_0_=6.0mas/a (OBstars) and {OMEGA}_0_=6.2mas/a (cepheids). These values agree betterwith the value of {OMEGA}_0_=6.4mas/a derived from the VLA measurementof the proper motion of SgrA^*^.
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A photometric analysis of the Cepheus OB3 region
Results are presented on Stromgren-Crawford uvby-beta photometry carriedout at Calar Alto (Spain) for 45 stars in the Cepheus OB3 regioncovering an apparent area of 6 deg x 6 deg. The relationship of thesestars with the association is examined. Three of these stars (BD +62 deg2114, BD +62 deg 2152, and BD +62 deg 2156) are identified as members ofthis association, while two more (BD +64 deg 1714 and BD +64 deg 1717)are classified as possible members. It is noted that intrinsic colorsand absolute magnitudes of member stars are consistent with thehypothesis of Blaauw (1964) and Garmany (1973) of the existence of twosubgroups with different evolutionary phases.
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Exciting stars and the distances of the diffuse nebulae
Not Available
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A high-resolution search for small-scale structure in Sharpless H II regions at 4.995 GHz. II - General properties of the entire sample. III - Description of selected sources
A statistical study is presented of the properties of a sample of 75optically visible H II regions from the Sharpless Catalog observed at afrequency of 4.994 GHz by the Westerbork Synthesis Radio Telescope, andthe most interesting small-diameter H II components detected in thesurvey are discussed in detail. The optical and radio properties of theregions are compared, and results are presented of high-andlow-resolution observations. The nebulae are divided into five classesaccording to optical morphology and the presence of obscuration, whichclasses can be interpreted as representing subsequent evolutionarystages of a single H II region. It is also found that the change of theelectron density due to H II region expansion occurs at a higher ratefor H II regions ionized by stars of an earlier spectral type, and thatthe rate of change of the mean electron density for a given type isapproximately hyperbolic. Small-diameter, high-density components arefound preferentially in small, isolated nebulae with high mean electrondensities, while the ratio of the Lyman continuum flux contained in thesmall-diameter component to that contained in the entire H II regioncorrelates with the mean density of the region. Of the 22 objectsdiscussed individually, 12 can be classified as compact H II regionswith an internal source of excitation, and the remaining sources can beattributed to increases in the electron density at ionization frontslocated at the edges of dense molecular clouds. From an analysis ofradio, infrared and molecular line observations of several sources, itis concluded that a single early-type star embedded in the H II regionin the presence of dust can be the energy source of the observedemission.
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Radio Continuum Interferometry of Dark Clouds - Part Two - a Study of the Physical Properties of Local Newly Formed HII Regions
Abstract image available at:http://adsabs.harvard.edu/abs/1980AJ.....85..912G
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Internal motions in H II regions. VI - S 140 and the associated CO cloud
Radial velocities of 283 points obtained by Fabry-Perot interferometryof H(alpha) on S 140 and the contiguous dark CO cloud are discussed. Thevelocities of the dark and emission regions are comparable and yield -22km/s as an average. The bright rim is redshifted with respect to itssurroundings by 2 km/s. UBV photometry discloses a new star cluster ofwhich the brightest member is the source of excitation of S 140. It issuggested that the H(alpha) emission of the dark region is that of S 140scattered by the dust of the dark cloud.
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Spectral types for early-type stars observed by SKYLAB
MK spectral types are presented for 246 early-type stars observed withthe S-019 ultraviolet stellar astronomy experiment on Skylab. K-linetypes are also given where applicable, and various peculiar stars areidentified. The peculiar stars include five silicon stars, a shell star,a helium-rich star, a silicon-strontium star, a chromium-europium star,and two marginal metallic-line stars.
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Carbon recombination line observations of the sharpless 140 region
Carbon recombination-line emission has been detected at two frequenciesfrom a dark cloud contiguous with the small H II region Sharpless 140.The observations show the dark cloud to be of unusually low temperatureand to have a markedly inhomogeneous density distribution, withlocalized region of high density surrounding one or more embedded stars.The carbon is probably ionized by photons from both the exciting star ofS140 and the embedded stars. The dark cloud and S140 apparentlyrepresent two stages of star formation which have occurred over a periodof at least 500,000 years in adjacent regions of the same dark cloud.
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Spectroscopic observations of stars in HII regions.
Not Available
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Photoelectric photometry of early-type stars in a Milky Way field in Cepheus
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....2..251S&db_key=AST
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INHABITED SKY
