Light variations of massive stars (alpha Cyg variables). XVI. The LMC supergiants R 85 (LBV) and R 110 (LBV) and the SMC supergiants R 42 and R 45
Multi-colour photometry of four variable supergiants in the LMC and SMC,viz. R 85, R 110, R 42 and R 45, is searched for periods, studied anddiscussed. The suspected LBV R 85 is undoubtedly an active LBV, thoughnot as spectacular as R 110. Their microvariations superimposed on the SDor-activity are analyzed as well as those exhibited by R 42 and R 45.Often, a period search is difficult because of the very complicatedmicro-variability. We suggest that this is caused by an intricatemulti-cyclic behaviour combined with stochastic processes. The length ofthe strongest cyclicity in the power spectrum of R 42 (128 d) is of theorder of the rotation periods of BA-type supergiants. In connection withour findings described in the present paper and the previous ones, wediscuss various competing theoretical models on the instability of alphaCyg variables, including the LBVs. Based on observations obtained at theEuropean Southern Observatory at La Silla, Chile (observing proposals55D-0317, 56D-0249, 57D-0133 and 58D-0118)
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Gas near the center of 30 Doradus as revealed by Hubble Space Telescope images
We present images of a 40 pc region of the 30 Doradus nebula centeredabout 1 arcminute north of the luminous star cluster R136 in the LargeMagellanic Cloud. The region was imaged with the Hubble Space Telescope(HST) Wide Field Camera through H alpha, (S II), and stellar continuumfilters. These data allow us to examine this region of star formationand the breakup of the cloud around R136 on a scale of 0.027 pc perpixel. We also present a complementary ground-based echelle spectrum ofthe H alpha and (N II) emission lines in this region. In the images onesees an extensive filamentary structure surrounding regions that havebeen hollowed out by R136 and other massive stars in the area. The (SII) image shows a sharper, more filamentary appearance than the H alphaimage, and the filaments are offset in (S II) generally away from R136.These characteristics are indicative of ionization fronts that areoutlining the neutral material and dust features. We also find fingersof enhanced (S II) emission located about 90 sec to the northwest ofR136. The (S II) fingers appear to be readiating generally from a commonregion, and we suggest that they are composed of material ablated fromthe high density gas of the ionization fronts and entrained with theflow of the stellar winds from R136. We find that a small knot ofemission resolves into two shells of about 0.5 pc diameter, each ofwhich encircles one or two stars. One of the stars has been identifiedas an early main-sequence O star by Walborn & Blades (1987), and theshell could be a young wind-blown bubble. We also find aparabolic-shaped arc at the head of a long cone that opens up away fromR136. The arc is located near a luminous candidate protostar identifiedby Hyland et al. (1992).
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Variability of luminous blue variables. I. Intermediate-band photometry
An extensive photometric dataset has been compiled for six Luminous BlueVariables (LBVs). The dataset comprises published and unpublishedmeasurements in the Stroemgren, Geneva and Walraven photometric systems.The measurements within each individual system are presented in auniform manner. Combining observations from these three photometricsystems, a V_J_ light curve has been constructed for each LBV.Examination of the light curves reveals variations on widely differentmagnitude and time scales.
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Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
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UBV photometry of galactic foreground and LMC member stars. I - Galactic foreground stars
UBV photometry of 955 galactic foreground stars in the direction to theLarge Magellanic Cloud is presented. The stars have been chosen fromforeground star catalogs and have been measured to complete a new database containing entries of more than 5000 stars in the direction of theLMC. First and second order extinction coefficients at La Silla/Chileare given, which differ from the standard values because of the 1991eruption of the volcano Mt. Pinatubo.
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Photometry of the LMC HII region N159A and of its stellar content. I - Stellar observations and reductions
The paper presents UBV RI photometry, based on CCD frames, of stellarcluster associated with the LMC HII region N159A, as well as of thesurrounding stellar field, with particular attention given to theobservations and to reduction procedures. In the reduction procedures,the DAOPHOT photometry program was adapted to observations of stars inclusters embedded in bright filamentary nebulae. The results presentedinclude the magnitudes for each star, obtained in five wavelength bands,both in the instrumental UBVRI system and after transformation toLandolt's (1983) standard system.
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Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
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Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
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The Galactic foreground reddening of SN 1987 A
Walraven photometric observations of 41 Galactic foreground stars in thedirection of SN 1987 A were used to investigate the interstellarreddening originating to material inside the Galaxy. Two differentmethods, one using the galactic reddenings around SN 1987 A from thedistribution at the sky, and one presenting the reddenings as a functionof the distance, both yield for the galactic reddening of SN 1987 AE(B-V) = 0.08 m + or - 0.01 m, which is larger than the usually assumedvalues. From the relation between the distances of the stars and theirreddening the thickness of the dust layer in the direction of SN 1987 Ais estimated at 110 pc.
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Discovery of an S-Doradus Type Outburst of an Of-Star at La-Silla
Not Available
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Starlight polarization in the Magellanic cloud regions.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24..357S&db_key=AST
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UBV photometry for supergiants of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&A....43..345B&db_key=AST
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Spectroscopic and photometric observations of HDE 269006 in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1975A&A....41..471W
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Radial velocities from objective-prism plates in the direction of the Large Magellanic Cloud. List of 398 stars, LMC members. List of 1434 galactic stars, in the LMC direction
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...13..173F&db_key=AST
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Additional observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&AS....9..447B
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Spectrographic and photometric observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....6..249A&db_key=AST
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Mesures de vitesses radiales dans la direction du Grand Nuage de Magellan
Not Available
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INHABITED SKY
