The Exciting Star of the Berkeley 59/Cepheus OB4 Complex and Other Chance Variable Star Discoveries
A study is presented regarding the nature of several variable starssampled during a campaign of photometric monitoring from the Abbey RidgeObservatory: three eclipsing binaries, two semiregulars, a luminous Bestar, and a star of uncertain classification. For one of the eclipsingsystems, BD+66°1673, spectroscopic observations reveal it to be anO5 V((f))n star and the probable ionizing star of the Berkeley 59/CepOB4 complex. An analysis of spectroscopic observations and BV photometryfor Berkeley 59 members in conjunction with published observations implya cluster age of ~2 Myr, a distance of d = 883 ±43 pc, and areddening of EB-V = 1.38 ±0.02. Two of theeclipsing systems are Algol-type, but one appears to be a cataclysmicvariable associated with an X-ray source. ALS 10588, a B3 IVn starassociated with the Cepheid SV Vul, is of uncertain classification,although consideration is given to it being a slowly pulsating B star.The environmental context of the variables is examined usingspectroscopic parallax, 2MASS photometry, and proper motion data, thelatter to evaluate the membership of the variable B2 Iabe star HDE229059 in Berkeley 87, an open cluster that could offer a uniqueopportunity to constrain empirically the evolutionary lineage of youngmassive stars. Also presented are our null results for observations of asample of northern stars listed as Cepheid candidates in the NewCatalogue of Suspected Variable Stars (NSV, in Samus et al. 2004).
|
Stellar contents and star formation in the young star cluster Be 59
We present UBV Ic CCD photometry of the young open cluster Be59 with the aim to study the star formation scenario in the cluster. Theradial extent of the cluster is found to be ~10 arcmin (2.9 pc). Theinterstellar extinction in the cluster region varies between E(B - V) ~=1.4 to 1.8 mag. The ratio of total-to-selective extinction in thecluster region is estimated as 3.7 +/- 0.3. The distance of the clusteris found to be 1.00 +/- 0.05 kpc. Using near-infrared (NIR) colours andslitless spectroscopy, we have identified young stellar objects (YSOs)in the open cluster Be 59 region. The ages of these YSOs range between<1 and ~2 Myr, whereas the mean age of the massive stars in thecluster region is found to be ~2 Myr. There is evidence forsecond-generation star formation outside the boundary of the cluster,which may be triggered by massive stars in the cluster. The slope of theinitial mass function, ?, in the mass range 2.5
|
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.
|
Interstellar absorption lines toward Cep OB4
An analysis of optical echelle spectra towards nine stars in the Cep OB4association is presented. Interstellar absorption lines which arise inthe (1, 0) and (2, 0) bands of the CN A 2Π - X2Σ+ red system towards BD+66o1661, BD+66o 1674, and BD+66o 1675 are used toinfer accurate CN column densities N(CN). A comparison with earliermeasurements in the CN violet system allows to infer a CN Doppler bparameter of b(CN) = 1.2{-}2.4 km s-1. Molecular carbonabsorption lines which arise in the (1, 0), (2, 0) and (3, 0) bands ofthe C2 A1Πu -X1Σg+ Phillips system is used toinfer gaskinetic temperatures of 35±10 K and densities of n = 700± 200 cm-3 towards BD+66o 1661 andBD+66o 1675, and a temperature of 60±10 K and adensity of 800 ± 400 cm-3 towards BD+66o1674. The R(1) line of the (0, 0) band of the CH A2Δ -X2Π system is detected towards 6 stars. A tightcorrelation exists between N(C2) and N(CH). N(CN) increaseswith N(CH) and with N(C2). Interstellar CH+ ismarginally detected towards four stars. Inferred CH+ columndensities are significantly lower than towards other lines of sight withsimilar reddening. The velocity structure towards Cep OB4 and thechemical abundances suggest that CN, C2, CH, andCH+ are formed in quiescent material. A previous suggestionthat the molecules form in a photon-dominated region close to the starsis not supported by the observations.Based on observations collected at the Centro Astronómico HispanoAlemán (CAHA) at Calar Alto, operated jointly by the Max-PlanckInstitut für Astronomie and the Instituto de Astrofisica deAndalucia (CSIC).
|
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.
|
Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|
UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
|
A CO study of Sharpless 171 - Evidence for interaction between the H II region and its neighboring molecular cloud
Observations of the S171 region were made using the J = 1-0 lines of(C-12)O, (C-13)O, and (C-18)O emission. The large-scale molecular gasdistribution in S171 and its neighborhood has been mapped. Two densemolecular clumps have been revealed near the young star cluster Be 59 inthe central region of S171. The mass of these clumps is estimated intotal to be 600 solar masses. A comparison with radio continuumobservations shows that the dense gas is contacting with the continuumsource. Spectra of (C-13)O and (C-18)O exhibit highly asymmetric shapes,indicating that the dense clumps are suffering dynamic disturbance dueto the H II region. The disturbed gas component of one of the clumpsshows good correspondence with the luminous ridge of the continuumemission. The interpretation is made that ionization fronts generated bythe nearby star cluster drive shocks into the molecular clumps. Theevolutionary effects of the molecular clumps under the ionization fieldof massive stars in the region are discussed.
|
The initial mass function for massive stars
A machine readable catalog of over 750 galactic O stars with publishedphotometry, spectral types, and luminosity classes has been compiled.The catalog is probably complete to a distance of about 2.5 kpc. Fromthis volume-limited data, the initial mass function (IMF) for stars moremassive than 20 solar masses has been derived. This IMF differs fromthat of Miller and Scalo (1979) and of Lequeux (1979), in havingproportionately more O type stars and not as steep a fall-off in numberof stars with increasing mass. Dividing the sample into stars inside andoutside the solar circle, a substantial difference in the IMF of themost massive stars is found. There are proportionally more toward thegalactic center. This gradient in the IMF may be related to the observedspace density of Wolf-Rayet stars, which are descendants of O typestars.
|
21-cm observations of the CEP IV star-formation region
The Cep IV star-formation region has been mapped at 21 cm. The resultingH I distribution indicates that the available gas forms a broken ringcoincident with the optical nebulosity. Comparison of this feature withother kinematic data for both stars and gas suggests that sequentialstar formation is an ongoing process in this region.
|
2.8 and 6 CM wavelength observations of NGC 7822
Abstract image available at:http://adsabs.harvard.edu/abs/1977A&A....61..285A
|
Isolated Stroemgren spheres as a source of galactic H alpha emission
The isolated H alpha emission features reported by Reynolds et al. areidentified with Stroemgren spheres surrounding observed O stars; theroot mean square electron densities and Stroemgren radii are calculatedfrom the observed emission measure and stellar type. The density has anaverage value of 2 per cu cm but increases to 3.3 per cu cm for starswithin 200 pc of the galactic plane. An analysis of the Catalogue ofGalactic O Stars shows that enhanced H alpha emission is observed aroundall known O stars. The diffuse component of H alpha emission is what onewould expect from the line-of-sight overlapping of isolated Stroemgrenspheres surrounding B stars and appears to correlate with features onextinction maps, as derived. There is no compelling reason to suggestany large-scale intercloud ionization from H alpha data alone.
|
A catalogue of galactic O stars. The ionization of the low density interstellar medium by runaway stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..211C&db_key=AST
|
A new general O type stars catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...12..277G&db_key=AST
|
Individual reddening laws from O type stars. I. Computation method, first results.
Not Available
|
A Comparison of Radio Observations of NGC 7822 (Wi) with the OB Stars in the Coph IV Association
Abstract image available at:http://adsabs.harvard.edu/abs/1970A&A.....4..309C
|
A Study of the Cepheus IV Association
Abstract image available at:http://adsabs.harvard.edu/abs/1968ApJS...16..275M
|
The Cepheus IV Association.
Abstract image available at:http://adsabs.harvard.edu/abs/1965ApJ...141..660W
|
A New O - B Association with an Unusual Reddening Effect.
Abstract image available at:http://adsabs.harvard.edu/abs/1959ApJ...130..482B
|
