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The luminous B[e] binary AS 381
We present the results of optical and near-IR spectroscopic andbroadband multicolour photometric observations of the emission-line starAS 381. Its properties were found to be similar to those of Be starswith warm dust, a group of galactic objects recently defined by Sheikinaet al. (\cite{smc}). The spectrum of AS 381 indicates the presence ofboth a hot (early B-type) and a cool (K-type) star in the system. A highinterstellar reddening (AV ~ 7 mag) suggests that it islocated at a distance of ge 3 kpc, and the companions have luminositytypes II or higher. The emission-line profiles indicate that the systemis surrounded by a flattened circumstellar envelope, which is viewedclose to pole-on. The hot companion is found to be ~ 2 mag brighter inthe V-band and more massive ( ~ 20 Msun) than the cool one (~ 7 Msun). The strong line emission and position of thecompanions in the Hertzsprung-Russell diagram indicate that the systemis experiencing mass exchange. We suggest that AS 381 is the first B[e]supergiant binary discovered in the Milky Way.
| Coordinated observations of Cyg X-1 (V1357 Cyg) from 1994 1998 in the commonwealth of independent states
We present observations of Cyg X-1 obtained during the coordinatedinternational campaign “Optical Monitoring of Unique AstrophysicalObjects,” carried out in observatories of CIS countries (Georgia,Kazakhstan, Russia, Uzbekistan, and Ukraine) in 1994 1998. The data arepresented as a single set, taking into account systematic differencesbetween individual data sets. In total, 2258 UBVR observations wereobtained during 407 nights. The observations were carried outsimultaneously with X-ray observations at 2 10 keV (ASM/RXTE) and 20 100keV (BATSE/CGRO), and also with radio observations (in 1997). Ouroptical data partially overlap the soft X-ray outburst in 1996 (JD2450200-320) and subsequent hard state, which displayed various types ofincreases and decreases of the X-ray flux. The 1996 outburst was notaccompanied by any optical brightening. However, an orbital light curvecorresponding to a tidally distorted star was superimposed on individualflares and brightness dips. For example, in two independent sets ofobservations, an intense optical flare with amplitude above thequiescent level was detected on JD 2450988, preceding the X-ray flare onJD 2451000-51040. In this time interval, the system displayed chaoticintrinsic variability on a timescale of a day, and flares and brightnessdips with amplitude lasting up to several days. The variability powerspectra display a predominant secondary period at 147d±2d, whichis half the 294d “precessional” period previously found atboth X-ray and optical wavelengths. We show that the 147d perioddominates in X-ray data (ASM/RXTE) in the quiescent state, or aftersubtraction of the 1996 outburst radiation from the X-ray light curve.This period is also close to the period of 142d±7d derived fromrecent radio data. Cross-correlation analysis confirms a significantcorrelation between the long-term optical and 2 10 keV X-ray variations(without the soft X-ray outburst), with the X-ray variations lagging by12±2 days.
| Variability of Cyg X-1 (V1357 Cyg) in 1995-1996 during the Hard and Soft X-ray Spectral States
We report photoelectric UBVR observations of Cyg X-1 with the 1-mTien-Shan and 48-cm Mount Maidanak reflectors from October 1995 throughNovember 1996. The orbital light curve is represented by the model of atidally deformed star. Various types of flare and fading are observed.The optical and X-ray (ASM/RXTE 2-10 keV) variabilities are compared. A90-day soft X-ray outburst occurred in the summer of 1996, but nosimilar event was detected at optical wavelengths. Nevertheless, aninterrelation was found between the variabilities in these bands,suggesting that they are affected by the same processes. A correlationbetween changes in the mean X-ray and optical fluxes was found after the90-day X-ray outburst and the mean optical orbital light curve weresubtracted. A Fourier analysis reveals common features in Fourierspectra of the X-ray and optical data. An orbital X-ray variability witha 5.6-percent amplitude is confirmed. Optical flares with a 0.04-magamplitude and a duration of several days, which coincided with localX-ray minima, were detected. The optical brightness of Cyg X-1 declinedby 0.04-mag in about a week early in November 1996. A possible physicalinterpretation of the flares and the orbital X-ray variability in termsof accretion instability is offered. The characteristic time it takesfor matter to pass through the accretion structure is estimated directlyfrom observations; it was approximately a week in 1996.
| a Study of the Microvariable Star V1674 Cygni
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| Unusual Fading of V1357 Cygni (Cyg X-1) in Early November, 1996
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| UvbyHbeta_ photometry of main sequence A type stars.
We present Stroemgren uvby and Hbeta_ photometry for a set of575 northern main sequence A type stars, most of them belonging to theHipparcos Input Catalogue, with V from 5mag to 10mag and with knownradial velocities. These observations enlarge the catalogue we began tocompile some years ago to more than 1500 stars. Our catalogue includeskinematic and astrophysical data for each star. Our future goal is toperform an accurate analysis of the kinematical behaviour of these starsin the solar neighbourhood.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Mesures de vitesses radiales. VII. Accompagnement AU sol DU programme d'observation DU satellite Hipparcos. Radial velocities. VII. Ground based measurements for Hipparcos.
We publish 734 radial velocities of stars distributed in 28 fields of4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot etal. 1990 and 1992), using the Fehrenbach objective prism method.
| 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.
| Positions moyennes et mouvements propres de 355 etoiles DU GC de la zone de declinaison +33 +36.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...26..219M&db_key=AST
| Stellar Spectra and Colors in an Irregular Region in Cygnus.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1953ApJ...118...77A&db_key=AST
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Observation and Astrometry data
| Constellation: | Schwan |
| Right ascension: | 19h58m51.64s |
| Declination: | +35°29'51.9" |
| Apparent magnitude: | 6.997 |
| Distance: | 263.158 parsecs |
| Proper motion RA: | 26.4 |
| Proper motion Dec: | 9.6 |
| B-T magnitude: | 7.025 |
| V-T magnitude: | 7 |
Catalogs and designations:
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