A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
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Revisiting the area of the open cluster Stock 16
Deep CCD UBV(RI)C photometry has been carried out in the areaof the open cluster Stock 16. The different photometric diagramsindicate the presence of three superimposed stellar groups, all composedof early type stars. The first of them, the cluster Stock 16, suffersfrom slightly variable reddening with a mean color excess = 0.51 . The second group, reddened by = 0.84 , includes the Wolf-Rayet star WR 50 (aWC7+OB), and the third one, with a mean < EB-V> = 1.18, also includes another Wolf-Rayet star, WR 51 (a WN4+OB?). Our resultsconfirm the distance and reddening already stated for Stock 16 butinclude new members. Concerning the other two highly reddened groups, weshow that the first one - located at a distance of 3600 pc - is probablyrelated to an anonymous OB association behind Cen OB1 also at 3600 pcalready mentioned in the literature; the other seems to be a distant OBassociation - at more than 9000 pc - which may belong to the Scutum-Cruxspiral arm. In these two groups we find evidence that the absorptionlaw, AV/EB-V = R amounts to 4.0 approximately. Theages of the different star populations in the zone range from 5 ×106 yr to 6.4 × 106 yr for Stock 16, 8× 106 for the second most reddened group and 5 ×106 for the probable association in Scutum-Crux. Adetermination of the IMF slope of Stock 16 was also carried out forstars in the mass range 1.8 < M < 14 Mȯ, givinga normal value x = 1.3.Based on observations collected at the University of Toronto SouthernObservatory (UTSO), Las Campanas, Chile.Table 2 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/471
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The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
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Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
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Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
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Speckle observations of binary systems measured by Hipparcos
From speckle observations made with the PISCO speckle camera at the Picdu Midi Observatory, we present high angular resolution astrometric datafor 43 binary stars already observed by the Hipparcos satellite. Thissample consists of mainly new Hipparcos eclipsing binaries with a visualcompanion closer than one arcsecond, chosen with the aim to study thedynamical implications of a third component on the observationalparameters of the eclipsing system. In addition, we also included aselection of close visual binaries with few speckle data in order toanalyse possible systematic departures between the speckle and thenon-speckle orbits. The reduction method and the results are presentedin detail. For the close visual binaries we confront our observationswith the ephemerides based on the best known orbits. For the wide visualbinaries the confrontation is made directly with the Hipparcos data. Ourobservations are consistent both with previous speckle data and withmost of the Hipparcos measurements. Based on observations made with theTélescope Bernard Lyot at the Pic du Midi Observatory, France andon data obtained by the Hipparcos astrometry satellite. This work hasalso made use of the Simbad database, operated at CDS, Strasbourg,France.
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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
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The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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Newly Discovered Herbig-Haro Objects in the NGC 2068 and NGC 2071 Regions
Taking the advantage of the large field of view at the 60/90 cm Schmidttelescope of Beijing Astronomical Observatory, we were able to carry outa wide-field survey of Herbig-Haro (HH) objects in nearby star-formingregions, including Perseus, Taurus, Orion, and others. In a 58'x58'field centered on NGC 2068 and NGC 2071 (M78), two active regions ofstar formation in the giant molecular cloud complex L1630, we found 17HH objects exhibiting prominent [S II] emission but without continuumemission. Among these, we confirmed all the 11 known HH objects listedin the General Catalogue of Herbig-Haro Objects in this field. Inaddition, we discovered another six new HH objects, including HH 437,438A-C, 440A/B, 442, 443, and 452A/B. These objects exhibit a variety ofmorphological structures, from knot to nebula. The discovery of these HHobjects demonstrates strong activity of young stellar objects in theregion we are studying. The large-scale spatial distribution of HHobjects in the region is discussed by combination of our results andprevious data.
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A survey of SiO emission towards interstellar masers. I. SiO line characteristics
We have conducted a survey of SiO emission towards galactic H_2O and OHmasers and ultracompact HII regions using the 15-m SEST and the 20-mOnsala telescope. With the SEST the transitions (v=0,J=2-1) and(v=0,J=3-2) of SiO at 3 and 2 mm were measured simultaneously. WithOnsala only the (v=0,J=2-1) line was accessible. Altogether 369 objectswere observed and SiO was detected towards 137 of them. The detectionrate is highest towards the most intense H_2O masers, which probablyrequire powerful shocks to be excited. The SiO detection rate correlatesalso with the integrated far-infrared flux density and the FIRluminosity of the associated IRAS point source, indicating that theoccurrence of shocks is related to the amount of radiation from thecentral stellar source(s). For flux and luminosity limited samples theSiO detection rate is higher in the inner 7 kpc from the galactic centrethan elsewhere. This suggests that dense cores belonging to the socalled ``molecular ring" provide particularly favourable conditions forthe production of gaseous SiO. The full widths above 2sigma of theSiO(J=2-1) lines, which are likely to be related to the associated shockvelocities, range from 2 to 60 km s(-1) except for the line in Ori KLwhich has a full width of about 100 km s(-1) . The median of our sampleis 19 km s(-1) . The SiO lines are single-peaked and the peak velocitiesare always close to the ambient cloud velocity as determined frompublished CS observations. These line characteristics are compared withthe predictions of kinematical bow-shock models. The SiO line shapescorrespond with the model of \cite[Raga & Cabrit (1993)]{R93} wherethe emission arises from turbulent wakes behind bow-shocks. However, thenumber of symmetric, relatively narrow profiles indicates that at leastin some of the observed sources SiO emission arises also from thequiescent gas component. We suggest that this is due to evaporation ofsilicon compounds from grain mantles and their reprocessing to SiO indense quiescent gas according to the model of \cite[McKay (1995,1996).]{M95} These reactions may be initiated and sustained by ionizingradiation from shocks, in the same way as the enhancement of HCO(+) nearHerbig-Haro objects has been explained in the model of \cite[Wolfire& Koenigl (1993).]{W93} The excitation temperatures of SiO(J=2-1)and (J=3-2) transitions were determined towards three strong sourcesusing measurements in isotopically substituted SiO. In all three sourcesthe transitions are clearly subthermally excited, implying moderatedensities (< 3 10(6) cm(-3) ) in the SiO emission regions. The entireTables~B.1 and B.2 and the spectra of all the detected SiO sources areonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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A Survey of Near-Infrared Emission in Visual Reflection Nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..102..369S&db_key=AST
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Maser search towards young stellar objects
In order to characterize the maser properties of massive young stellarobjects (YSOs), a systematic 1.3-cm wavelength H2O maser search in aflux-limited sample of bright IRAS sources has been made with the 100-mEffelsberg telescope. The sample also included other YSOs thought to bevery young massive stars. Thirty four sources (10 new detections) weredetected in a sample of 88 objects. In the case of the flux-limitedsample, nearly complete information about the molecular outflowproperties is available. It was found that 80 percent of the CO outflowsources examined are associated with H2O masers. It is found that thedetection probability for H2O masers depends on the IRAS color indexR(12/25). This seems to be not a pure color effect, but to be probablyrelated to the luminosity of the sources. Relations between the maserparameters and the outflow and IRAS source properties are analyzed.
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The excitation of 12 micron emission from very small particles
The results of IRAS observations of visual reflection nebulaeilluminated by stars with effective temperatures between 3000 and 33,000K are presented. The ratio of the energy radiated in the IRAS 12-micronsband to the total energy radiated at far-infrared wavelengths (60 and100 microns) is about 0.2, with little or no dependence on thetemperature of the illuminating star for stellar temperatures betweenabout 5000 and 33,000 K. This is interpreted as requiring that visualphotons as well as ultraviolet photons are capable of exciting12-microns emission from very small particles.
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The luminosity of reflection nebulae
Consideration is given to the connection between the dispersion inHubble's relation for reflection nebulae and their morphologicalcharacteristics. Statistical estimates show that the reflection nebulaeconnected with more opaque dust-gas clouds, compared to those near lessopaque clouds, have large values of Delta-B (the measure of deviationsin Hubble's relation) and a high surface brightness. These propertiesare more pronounced in the Herbig Ae/Be stars. Stars in the nebulaeconnected with more opaque dust-gas clouds were found to exhibit excessreddening, with R above 3.1. It is concluded that the dispersion in theHubble relation is mainly due to the optical depth of the nebulae.
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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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Interstellar C2, CH, and CN in translucent molecular clouds
Optical absorption-line techniques have been applied to the study of anumber of translucent molecular clouds in which the total columndensities are large enough that substantial molecular abundances can bemaintained. Results are presented for a survey of absorption lines ofinterstellar C2, CH, and CN. Detections of CN through the A 2Pi-X2Sigma(+) (1,O) and (2,O) bands of the red system are reported andcompared with observations of the violet system for one line of sight.The population distributions in C2 provide diagnostic information ontemperature and density. The measured column densities of the threespecies can be used to test details of the theory of molecule formationin clouds where photoprocesses still play a significant role. The C2 andCH column densities are strongly correlated with each other and probablyalso with the H2 column density. In contrast, the CN column densitiesare found to vary greatly from cloud to cloud. The observations arediscussed with reference to detailed theoretical models.
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1.4 millimeter H2CO observations of NGC 2071
Maps are presented of the central regions of the molecular bipolaroutflows NGC 2071 and L1551 in the J = 3(1, 3)-2(1, 2)-transition ofortho H2CO, which has a rest frequency of 211 GHz. The emission fromL1551 was too weak to be fully mapped. Spectra were obtained of the J =3(1, 2)-2(1, 1) transition of ortho H2CO (225 GHz) at selected positionsin NGC 2071. A large velocity gradient (LVG) model was used to determinethe H2 density and H2CO abundance in NGC 2071, in an effort to find astructure which could collimate the bipolar outflow. The map indicatesthe presence of a small dense cloud which seems to be rotating with itsaxis parallel to the outflow axis; the H2 density inferred from theobservations and the LVG model is not sufficiently high for it tocollimate the outflow by a static pressure confinement mechanism.However, that collimation by this cloud is still possible over the timescale in which it is disrupted by the wind. It is argued evidence for anoverabundance of H2CO in this region has been found.
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CCD surface photometry of bright reflection nebulae
Surface brightness measurements in the B, V, R, and I photometric bandsare presented for 14 reflection nebulae. The analysis of nebula-starcolor differences leads to the conclusion that excess emission in the Iband beyond that expected from scattering is a common phenomenon amongreflection nebulae illuminated by B stars. An ultraviolet-poweredfluorescence mechanism is suggested. Both the absolute and the relativeV surface brightnesses of the nebulae in the sample are analyzed. Thedata can be explained, if the nebulae arise in moderately denseinterstellar clouds with illuminating stars embedded at an optical depthlevel of order unity and with dust of high albedo and with a stronglyforward-directed phase function. It is concluded that bright reflectionnebulae must arise under almost optimal scattering conditions, whichapparently are found when newly formed low-mass star clusters are stillembedded in the material from which they originated.
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Ultraviolet-pumped infrared fluorescent molecular hydrogen emission in reflection nebulae
Strong molecular hydrogen emission at 2.41 microns has been observed inthree out of six reflection nebulae surveyed. A spectrum of one nebula,Parsamyan 18, shows several H2 lines whose intensity ratios have valuesagreeing with those predicted if the excitation is due to UV-pumpedfluoresence and disagreeing with those predicted for shock and X-rayexcitations.
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Eclipsing binaries in open clusters. I - Preliminary study
A preliminary list of suspected eclipsing binaries in open clusters ispresented. The period, the mass ratio, the correlation between the massratio and cluster age, and the periodicity diagram are investigated.
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Polarization of stars in R-associations - Observational data
Polarimetric data are assembled for 95 stars that are illuminatingreflection nebulae. Most of these belong to 18 standard R-associations.The observed dependence of the percentage polarization P on wavelengthand color excess E(B-V) suggest that the unpolarized light ofR-association members may become polarized as it traverses an ensembleof dust grains aligned by a magnetic field which in some cases (Tau R2,Ori R1/R2, Sco R1, Cep R2) is intrinsic to the association. In certainR-associations the grain size is variable and the stochastic magneticfield component fluctuates on a scale of 10-30 pc.
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On delta Scuti Stars in Open Clusters
Not Available
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Energetic activity in a star-forming molecular cloud core - A disk constrained bipolar outflow in NGC 2071
The discovery of an extended, high-velocity molecular outflow associatedwith the IR sources in NGC 2071 is reported. High-velocity CO emissionfrom this star-forming molecular cloud core can be traced over a region4 arcmin in diameter and detected over a velocity range of 70 km/sec.The flow is bipolar; the blueshifted CO emission is displaced to thenortheast, while the redshifted emission is displaced to the southwest.Observations in the 98 GHz transition of CS reveal a ridge of dense gasoriented orthogonal to the high-velocity flow axis. A systematicvelocity gradient seen in the CS line core suggests that the ridge is adense, rotating disk centered on the IR source. The disk may beresponsible for collimating a spherically symmetric wind originatingnear the IR source into the bipolar flow observed in the high-velocityCO line wings. The high-velocity CO line wings are modeled as beamdiluted emission from clumps or filaments with C-12O optical depthsclose to unity and a small filling factor. The clumps may be eitherobjects ejected from the vicinity of the central infrared source orshocked gas at the front where a higher velocity but invisible flowencounters ambient cloud material.
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Molecular line observations of the I ORI OB association including NGC 2068, NGC 2071 and the HH-24 region
Molecular line observations of the giant molecular cloud associated withthe northern Orion complex of the I Ori OB association are presented. Anarea of 1.5 sq deg including the reflection nebulae NGC 2068 and NGC2071, the Herbig-Haro complex M-78 HH and parts of the extended dustclouds L 1627 and L 1630 was surveyed in the CO and (C-13)O J = 1-0lines at millimeter wavelengths. At least 12 molecular clouds areobserved within the extended cloud, with CO intensity well correlatedwith regions of optical absorption. Intense molecular clouds are alsoobserved close to NGC 2068 and NGC 2071, while the region surroundingthe Herbig-Haro complex appears as a 5-K temperature enhancement. Avelocity gradient of approximately 0.43 km/sec per pc is observed acrossthe cloud complex, indicating rotation about an axis lying along theminor axis of the northern Orion complex and at an angle ofapproximately 75 deg to the gradient plane.
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Infrared surveys of dark-cloud complexes. I. The LYNDS 1630 dark cloud.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..308S&db_key=AST
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M 78 : an active region of star formation in the dark cloud LYNDS 1630.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJ...196..489S&db_key=AST
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Infrared and optical observations of Herbig-Haro objects. .
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJ...191..111S&db_key=AST
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Stars in reflection nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..233R&db_key=AST
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A study of reflection nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..990V&db_key=AST
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INHABITED SKY
