- ID:
- ivo://CDS.VizieR/J/A+AS/125/75
- Title:
- UBV photometry of Be stars
- Short Name:
- J/A+AS/125/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A summary of results of the systematic UBV photoelectric monitoring of bright northern Be stars carried out at the Hvar Observatory between 1972 and 1990 is presented. Altogether, 76 Be stars of all luminosity classes were observed and 13848 UBV measurements secured. Simultaneously, 9648 UBV measurements of 48 check stars (most of them of early spectral types) were obtained. A careful transformation of all observations into the standard Johnson system allowed detection and monitoring of even very mild long-term light and colour variations of these objects. Almost all early-type Be stars in the sample turned out to be variable. For several stars phase-locked light variations related to their binary nature were established. Sudden brightenings, on a time scale of a few days, were detected for o Cas and QR Vul.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/350/566
- Title:
- UBV photometry of OT Gem
- Short Name:
- J/A+A/350/566
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of photometric observations of the Be star OT Gem (HD 58050, HR 2817, 2000 position: 07 24 27.64 +15 31 02.0) is presented. A positive correlation between the light and colour variations and the emission strength was found.
- ID:
- ivo://CDS.VizieR/J/A+A/324/965
- Title:
- UBV photometry of V360 Lac
- Short Name:
- J/A+A/324/965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of an extensive collection of photometric and spectroscopic observations of the little studied bright Be star V360 Lac lead to the following main conclusions: (1) V360 Lac is a binary system consisting of a B3e primary and a F9IV secondary which probably fills the Roche lobe and losses mass towards the primary. Radial-velocity curves of both components were obtained. (2) The light variations arise from superposition of variations on at least three time scales: phase-locked orbital brightness and colour changes with two minima; sinusoidal variation with a 322.24^d^ period and low-amplitude rapid changes with a possible period of 1.6738^d^. (3) A tentative solution of the B and V light curves which assumes the semi-detached configuration and presence of a disk around the primary, combined with the orbital solution, leads to preliminary basic physical elements of the system which are consistent with the radiative properties of the binary components.
- ID:
- ivo://CDS.VizieR/J/AZh/79/309
- Title:
- UBVR and spectroscopic observations of CI Cam
- Short Name:
- J/AZh/79/309
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric (UBVR) observations in 1998-2001 and medium-resolution spectroscopy obtained in the SAO in the same period for the B[e]/X-ray transient CI Cam display cyclic variations with a period of 1100 days.
- ID:
- ivo://CDS.VizieR/J/A+A/335/973
- Title:
- 84 UMa ubvy photometry
- Short Name:
- J/A+A/335/973
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new longitudinal magnetic field and Stroemgren photometric measurements of the Bp star 84 UMa. From these data we determine a new rotational period P_rot_=1.38576+/-0.00080d, which is inconsistent with previously published values. The magnetic measurements indicate the presence of a weak, dominantly dipolar magnetic field in the photosphere of 84 UMa. We employ a new value of the rotational axis inclination in conjunction with the magnetic data in order to constrain the magnetic field geometry. We derive the following dipole oblique rotator parameters: i=59^+17^_-9_{deg}, {beta}=48^+17^_-29_{deg}, and B_d_=1620^+1270^_-30_G. A precise value of the radius (which we calculate in conjunction with the inclination using the Hipparcos parallax) allows us to locate 84 UMa on the radius-effective temperature plane. Using theoretical evolutionary tracks (Schaller et al., 1992, Cat. <J/A+AS/96/269>), we obtain values for the mass, age and surface gravity. These results place 84 UMa quite close to the ZAMS, a result inconsistent with the suggestion by Hubrig & Mathys (1994AN....315..343H) that the magnetic Ap stars may be near the end of their main sequence life.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/66
- Title:
- uvby{beta} photometry of NGC 663
- Short Name:
- J/MNRAS/358/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD uvby{beta} photometry for stars in the central area of the young open cluster NGC 663. We find that the reddening is highly variable, with values ranging from E(b-y)=0.639+/-0.032 in the central part to E(b-y)=0.555+/-0.038 in the south-east. The distance modulus is found to be 11.6+/-0.1mag. (2.1kpc), and the age logt=7.25+/-0.1 years (25+7/-5Myr).
- ID:
- ivo://CDS.VizieR/J/A+A/329/579
- Title:
- uvby photometry of theta CrB
- Short Name:
- J/A+A/329/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present differential uvby photometry of {theta} CrB obtained in 1994 and 1995, complemented by Balmer line spectroscopy. This star has been constant during this period, showing no short term periodic variability with an amplitude greater than 0.005mag., nor long term variations greater than 0.01mag. The lack of variability is associated with an inactive phase of the Be star, in which no emission features are present in the spectra. The only remarkable event observed was a fading episode on JD 2449779, with an amplitude of about 0.02 magnitudes in all bandpasses and duration of 0.2-0.3 days.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A108
- Title:
- Variability survey of brightest stars
- Short Name:
- J/A+A/598/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar evolution theory of massive stars remains uncalibrated with high-precision photometric observational data mainly due to small number of luminous stars monitored from space. Automated all-sky surveys have revealed numerous variable stars but most luminous stars are often overexposed. Targeted campaigns can improve the time base of photometric data for those objects. The aim of this investigation is to study the variability of luminous stars at different time-scales in young open clusters and OB associations. We monitored 22 open clusters and associations from 2011 to 2013 using a 0.25-m telescope. Variable stars were detected by comparing the overall light-curve scatter with measurement uncertainties. Variability was analysed by the light curve feature extraction tool FATS. Periods of pulsating stars were determined using the discrete Fourier transform code SigSpec. We then classified the variable stars based on their pulsation periods and available spectral information. We obtained light curves for more than 20000 sources of which 354 were found to be variable. Amongst them we find 80 eclipsing binaries, 31 {alpha} Cyg, 13 {beta} Cep, 62 Be, 16 slowly pulsating B, 7 Cepheid, 1 {gamma} Doradus, 3 Wolf-Rayet and 63 late-type variable stars. Up to 55% of these stars are potential new discoveries as they are not present in the Variable Star Index (VSX) database. We find the cluster membership fraction for variable stars to be 13% with an upper limit of 35%.
- ID:
- ivo://CDS.VizieR/J/AJ/156/174
- Title:
- Visual photometry for the Be star {mu} Centauri
- Short Name:
- J/AJ/156/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the aim of contributing to the understanding of the disk formation process in Be stars, we pursued a one-year spectroscopic observing campaign of the Be star {mu} Centauri in the L-band, using VLT/ISAAC. We present the nine near-IR spectra we obtained in an epoch of relative photometric quiescence prior to an outburst of {Delta}V=0.4 magnitude. Visual estimates during the epoch of our L-band spectroscopy are also presented for the first time, together with the unpublished complete visual light curve between the years 1998 and 2014. We observe significant and monotonic changes in emission line strength of Bracket-{alpha} and Pfund-{gamma} lines relative to Humphreys lines, and also in the continuum slope. We interpret these observed changes in terms of important changes to the column density of the line emitting regions, moving from an optically thin to an optically thick stage just prior to a major outburst. For each observing date, we provide estimates for the column density and relative extension of the line emitting region. If the changes observed toward the end of our observing campaign were related to mass-loss changes from the central star, they would correspond to an increase in a factor of two in the mass of the disk in the innermost region. If related to the visual outburst observed one month later, the variability observed in our spectra would be the first detection of the early disk formation process in the L-band.
- ID:
- ivo://CDS.VizieR/J/A+A/564/L7
- Title:
- VLT-FLAMES Tarantula Survey: VFTS 822
- Short Name:
- J/A+A/564/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of the B[e] star VFTS 822 in the 30 Doradus star-forming region of the Large Magellanic Cloud, classified by optical spectroscopy from the VLT-FLAMES Tarantula Survey and complementary infrared photometry. VFTS 822 is a relatively low-luminosity (logL=4.04+/-0.25L_{sun}_) B8[e] star. In this Letter, we evaluate the evolutionary status of VFTS 822 and discuss its candidacy as a Herbig B[e] star. If the object is indeed in the pre-main sequence phase, it would present an exciting opportunity to spectroscopically measure mass accretion rates at low metallicity, to probe the effect of metallicity on accretion rates.