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The qWR star HD 45166 . I. Observations and system parameters
The binary star HD 45166 has been observed since 1922but its orbital period has not yet been found. It is considered apeculiar Wolf-Rayet star, and its assigned classification has varied.For this reason we included the object as a candidate V Sge star andperformed spectroscopy in order to search for its putative orbitalperiod. High-resolution spectroscopic observations show that thespectrum, in emission and in absorption, is quite rich. The emissionlines have great diversity of widths and profiles. The full widths athalf maximum vary from 70 km s-1 for the weakest lines up to370 km s-1 for the most intense ones. The hydrogen and heliumlines are systematically broader than the CNO lines. Assuming thatHD 45166 is a double-line spectroscopic binary, itpresents an orbital period of P = 1.596 ± 0.003 day, with aneccentricity of e = 0.18 ± 0.08. In addition, a search forperiodicity using standard techniques reveals that the emission linespresent at least two other periods, of 5 and 15 h. The secondary starhas a spectral type of B7 V and, therefore, should have a mass of aboutM2 = 4.8 ~Mȯ. Given the radial velocityamplitudes, we determined the mass of the hot (primary) star asM1 = 4.2 ± 0.7~Mȯ and the inclinationangle of the system, i = 0.77° ± 0.09°. As theeccentricity of the orbit is non zero, the Roche lobes increase anddecrease as a function of the orbital phase. At periastron, thesecondary star fills its Roche lobe. The distance to the star has beenre-determined as d = 1.3 ± 0.2 kpc and a color excess ofE(B-V)=0.155~±~0.007 has been derived. This implies an absolute Bmagnitude of -0.6 for the primary star and -0.7 for the B7 star. Wesuggest that the discrete absorption components (DACs) observed in theultraviolet with a periodicity similar to the orbital period may beinduced by periastron events.Based on observations made at the 1.5 m ESO telescope at La Silla, Chile, and at Laboratório Nacional de Astrofísica/CNPq, Brazil.Tables 2-5 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/444/895
| New Perspectives on AX Monocerotis
AX Moncerotis is a 232d, noneclipsing, interacting binary star thatconsists of a K giant, a Be-like giant, and large amounts ofcircumstellar material. The K star is almost certainly a synchronousrotator and is probably in contact with its critical lobe. The Be starwas believed to be a rapid rotator based on extremely wide absorptionlines, but new spectra show that these lines arise from thecircumstellar environment. Hydrogen emission, also circumstellar, ismany times stronger than the continuum. Near-ultraviolet light curvesexhibit a 0.5 mag dip near phase 0.75, but there is no such variabilityat longer wavelengths. Gas flow trajectories from the cusp of the K startoward the Be star provide a simple explanation for the photometric andspectroscopic behavior. We may have found a decreasing orbital period,but more data are necessary to confirm this result. We present severalmodels for AX Mon based on (1) new and archival visible photometry, (2)archival ultraviolet spectroscopy, (3) new and archival visiblespectroscopy, (4) new visible polarimetry, and (5) new radio photometry.Future observations, including optical interferometry, are proposed.
| Far-ultraviolet stellar photometry - A field in Monoceros
FUV photometry of stars in a field in Monoceros in the wavelength rangefrom 1230 to 1600 A has been carried out using data from anelectrographic Schmidt camera carried on a sounding rocket. Ultravioletmagnitudes were extracted for 602 objects in the field. Fifty-eightpercent were tentatively identified with visible stars using the SIMBADdata base while another 25 percent are blends of objects too closetogether to separate with our resolution. Eleven of the UV objectscoincide with parts of the star clusters NGC 2169, NGC 2244, and NGC2264 in which individual stars cannot be resolved. As in previousstudies, the majority of the identified ultraviolet sources areidentified with early-stars. However, there are a significant number forwhich no such identification was possible, and we suggest that many ofthese are nearby white dwarfs.
| An atlas of Hubble Space Telescope photometric, spectrophotometric, and polarimetric calibration objects
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99.1243T&db_key=AST
| 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.
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
| The value of R in Monoceros
Recent photometric and spectroscopic observations are used inconjunction with other data for early-type stars in northern Monocerosin order to investigate the local value of R (the ratio of total toselective extinction). From a variable-extinction analysis, it isconcluded that a ratio of approximately 3.2 is appropriate for thegeneral interstellar extinction in this region and that there is noevidence here for the existence of local anomalies. The two majorassociations Mon OB 1 and Mon OB 2 are clearly delineated and are foundto exhibit properties typical of such young stellar groups. Derivedproperties for a few interesting stars are presented.
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Osservazione e dati astrometrici
| Costellazione: | Unicorno |
| Ascensione retta: | 06h22m22.55s |
| Declinazione: | +08°19'36.5" |
| Magnitudine apparente: | 8.814 |
| Distanza: | 10000000 parsec |
| Moto proprio RA: | -5.9 |
| Moto proprio Dec: | -4.6 |
| B-T magnitude: | 8.736 |
| V-T magnitude: | 8.808 |
Cataloghi e designazioni:
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