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eta Car: the optical features at the 2003.5 low-excitation event
UBV and BVR photometry of eta Car during the 2003.5 low-excitationevent - the considered periastron passage of a binary - is presented.The light and colour curves show a number of features, which were alsoseen at previous periastron passages: a light maximum of long durationwith a superimposed flare-like event which is temporarily interrupted byan eclipse-like dip, and a steep decline in the U-B color index. The Rbrightness reached a minimum at the time of mid X-ray totality, probablyimplying that the Hα emission line reached a minimum. The sourceof the optical flare-like event is probably not the same as the onecausing the the X-ray radiation. It is tempting to consider the epoch ofthe R minimum and the mid- X ray totality - which roughly coincides withthe UBV minimum - as the central moment of the 2003.5 low-excitationevent.
| A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| On the recent brightening of eta Carinae
We report and discuss the steady brightening of etaCarinae, and conclude that this brightening is not aneruption, but an expected LBV S-Doradus phase which, typically, displaysintense brightening coupled to strong reddening when the star movesredwards in the H-R diagram. The brightness gradient amounts to -0.15my(-1) over the last two years. Based on observations obtained at theEuropean Southern Observatory at La Silla, Chile (Applications 60D-0148and 62H-0110)
| MSC - a catalogue of physical multiple stars
The MSC catalogue contains data on 612 physical multiple stars ofmultiplicity 3 to 7 which are hierarchical with few exceptions. Orbitalperiods, angular separations and mass ratios are estimated for eachsub-system. Orbital elements are given when available. The catalogue canbe accessed through CDS (Strasbourg). Half of the systems are within 100pc from the Sun. The comparison of the periods of close and widesub-systems reveals that there is no preferred period ratio and allpossible combinations of periods are found. The distribution of thelogarithms of short periods is bimodal, probably due to observationalselection. In 82\% of triple stars the close sub-system is related tothe primary of a wide pair. However, the analysis of mass ratiodistribution gives some support to the idea that component masses areindependently selected from the Salpeter mass function. Orbits of wideand close sub-systems are not always coplanar, although thecorresponding orbital angular momentum vectors do show a weak tendencyof alignment. Some observational programs based on the MSC aresuggested. Tables 2 and 3 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
| A pulsating star inside η Carinae. I. Light variations, 1992-1994.
We present and analyze two seasons of intense photometric monitoring inthe Stroemgren uvbyHβ system of η Carinae (October 1992-August1994). The luminous blue variable (LBV) in the core did not show much SDor activity, i.e. it was in a relatively quiescent stage. Thissituation was very favourable for studying its optical micro variations.It appears that the central LBV pulsates (presumably in a non-radialmode) like other massive evolved stars, the α Cyg variables. Thequasi-period is 58.56d. The linear ephemeris is: JD_max_ = 2448875.0+58.56 E. Support was found for the existence of the presumedperiodicity of 52.4d of the so-called "dimples", shallow dips in thelight curve which only last for a few days. The cause may be the eclipseof a small companion or of a hot spot in an accretion disk. The Hβindex became bluer by ~0.07mag during the last 11/2 years and shows anoscillation in anti-phase with the 58.56d pulsation, suggesting that theHII region(s) responsible for the hydrogen line emission has arelatively high luminosity. This is another reason to suppose that asecond luminous source, perhaps a luminous disk (with a hot spot), maybe present in the η Car system.
| Ubvy-Beta Photometry of 100 Stars in the Region of Eta-Carinae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.269..857S&db_key=AST
| 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.
| 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
| 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.
| Close binaries observed polarimetrically
Not Available
| A photometric survey of the bright southern Be stars
Repeated UBV photometric measurements were made of the 86 bright Bestars south of declination -20 deg, and a network of comparison starswas set up. From a statistical study of the differential photometry itwas found that short- or intermediate-term variability seems to beoccurring in about half of the Be stars, and to be more evident in thestars of earlier spectral type. It was also possible to identify 11individual short- or intermediate-term variables. Four of these (all ofearly B spectral type) appear to exhibit significant variability on atime-scale of a day or less. More intensive observations of one of thesestars, 28 Omega CMA, indicate short-term variations consistent with thepublished spectroscopic period of 1.37 day.
| Instrumental effects and the Stroemgren photometric system
The extent to which the use of different photometers can affect resultson stellar color indices was investigated by simultaneously observing asample of widely different stars with several uvby photometric systemsavailable at the ESO, La Silla, Chile. In one instance, the ESO 50-cmtelescope and the four-channel photometer at the Danish 50-cm telescopewere used simultaneously. The reductions were performed separately oneach data set, using a linear color transformation procedure. Theresults agree with theoretical investigations which showed thatsubstantial errors can arise from the nonconformity of passbands. It isemphasized that it is necessary to use separate color transformationsfor various stellar types and classes and for different interstellarreddenings.
| The A0 stars
A photometric grid, standardized on MK spectral standards, has been usedto compare spectral types and luminosity classes obtainedphotometrically with those in two extensive spectral surveys coveringthe entire sky. Major discrepancies include the spectroscopicclassification of B9.5, which may indicate an otherwise unrecognizedspectral peculiarity, a different A0/A1 spectral type boundary in thetwo samples involved, the well-known misclassification of weak heliumstars, and an appreciable percentage of stars which are called dwarfsspectroscopically but are of higher photometric luminosity. The spacemotion vectors of these stars for which radial velocities are available,and excluding the minimum of 25 percent that are spectroscopic binarieswithout orbital elements, show structure in their distribution in the(U, V)-plane, with members of the Local Association and the Hyades andSirius superclusters forming obvious concentrations. The members of theLocal Association in the samples are mainly old (more than 200 millionyears) mode A stars, although a few much younger stars are included. Themembers of the Hyades and Sirius superclusters contain many bluestragglers, including several peculiar stars of the Hg, Mn, and Sivarieties.
| Polarization measurements of 313 nearby stars
The linear polarization of 313 low galactic latitude stars has beenmeasured. With few exceptions all program stars have a spectral typelater than B9 and are within 600 parsec of the sun. 181 stars aresituated at the southern sky and 132 at the northern sky.
| Bright southern stars of astrophysical interest
The paper lists a number of bright peculiar stars in the SouthernHemisphere discovered on 20-A/mm spectrograms. Recent information isalso given for a few known peculiar objects. The lists include: oneLambda Boo star, 4 Hg and other Bp stars, 7 Am stars, 17 shell oremission-line stars, and 37 double-lined spectroscopic binaries, amongwhich are two triple-lined, four composite, eight variable or eclipsing,and three peculiar shell and/or emission-line systems.
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Osservazione e dati astrometrici
| Costellazione: | Carena |
| Ascensione retta: | 10h46m16.80s |
| Declinazione: | -60°36'12.0" |
| Magnitudine apparente: | 6.25 |
| Distanza: | 111.982 parsec |
| Moto proprio RA: | -42.3 |
| Moto proprio Dec: | 7.9 |
| B-T magnitude: | 6.313 |
| V-T magnitude: | 6.272 |
Cataloghi e designazioni:
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INHABITED SKY
