- ID:
- ivo://CDS.VizieR/J/ApJ/789/139
- Title:
- Three O-type binaries photometry in LMC
- Short Name:
- J/ApJ/789/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper in a series devoted to the study of massive binary systems in the Large Magellanic Cloud (LMC). We mainly aim to provide accurate data that constrains the mass-luminosity relation for the most massive stars but also to address the long lasting problem known as the "mass discrepancy." We present here our results for three binaries (LMC 169782, LMC 171520, and [P93] 921) harboring the earliest O-type components-ranging from O4 V to O6.5 V-among our sample of 17 systems. Our photometry provided accurate periods for the studied systems, allowing the spectroscopic observations to be performed at selected phases where the radial velocity separation between binary components is larger. Following the procedure outlined in our first paper of this series, after solving the radial velocity curves for orbital parameters, we used tomographic reconstruction to obtain the individual spectra of each star, from which we determined effective temperatures via a model atmosphere fitting with FASTWIND. This information, combined with the light-curve analysis that was performed with GENSYN, enabled the determination of absolute masses, radii, and bolometric luminosities that are compared with those predicted by modern stellar evolutionary models finding that they agree within the uncertainties. Nevertheless, the comparison seems to confirm the small differences found in the first paper of this series in the sense that the evolutionary masses are slightly larger than the Keplerian ones, with differences averaging ~10%, or alternatively, the stellar evolutionary models predict luminosities that are somewhat lower than observed. Still, the overall agreement between the current evolutionary models and the empirically determined stellar parameters is remarkable.
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- ID:
- ivo://CDS.VizieR/J/A+A/658/A36
- Title:
- Transition disks around evolved stars
- Short Name:
- J/A+A/658/A36
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Post-AGB binaries are surrounded by massive disks of gas and dust that are similar to protoplanetary disks surrounding young stars. We assembled a catalog of all known Galactic post-AGB binaries with disks. We explore correlations between the different observables with the aim to learn more about potential disk-binary interactions. We compiled spectral energy distributions of 85 Galactic post-AGB binary systems. We built-up a color-color diagram to differentiate between the different disk morphologies traced by the characteristics of the infrared excess. We categorised different disk types and looked for correlations with other observational characteristics of these systems. 8 to 12% of our targets are surrounded by transition disks, i.e. disks having no or low near-infrared excesses. We find a strong link between these transition disks and the depletion of refractory elements seen on the surface of the post-AGB star. We interpret this correlation as evidence for the presence of a mechanism that stimulates the dust and gas separation within the disk and which also produces the transition disk structure. We propose that such a mechanism can be a giant planet carving a hole in the disk which traps the dust in the outer disk parts. We propose two disk evolutionary scenarios, depending on the presence of such a giant planet in the disk. We advocate that giant planets can successfully explain the correlation between the transition disks and the depletion of refractory materials observed in post-AGB binaries. If the planetary scenario is confirmed, disks around post-AGB binaries could be a unique laboratory to test planet-disk interactions and their influence on the late evolution of binary stars. Whether the planets are first or second generation also remains to be studied. We argue that these disks are the perfect place to study planet formation scenarios in an unprecedented parameter space.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A49
- Title:
- UBV and spectroscopic variations of V2368 Oph
- Short Name:
- J/A+A/531/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The A-type star HR 6412 = V2368 Oph was used by several investigators as a photometric comparison star for the known eclipsing binary U Oph but was found to be variable by three independent groups, including us. By analysing series of new spectral and photometric observations and a critical compilation of available radial velocities, we were able to find the correct period of light and radial-velocity variations and demonstrate that the object is an eclipsing and double-lined spectroscopic binary moving in a highly eccentric orbit. We derived a linear ephemeris Tmin.I=HJD(2454294.67+/-0.01)+(38.32712+/-0.00004)d*E and estimated preliminary basic physical properties of the binary.
- ID:
- ivo://CDS.VizieR/J/ApJ/811/131
- Title:
- UBV light curves of DQ Tau and UZ Tau E
- Short Name:
- J/ApJ/811/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The transfer of matter between a circumbinary disk and a young binary system remains poorly understood, obscuring the interpretation of accretion indicators. To explore the behavior of these indicators in multiple systems, we have performed the first systematic time-domain study of young binaries in the ultraviolet. We obtained far- and near-ultraviolet HST/COS spectra of the young spectroscopic binaries DQ Tau and UZ Tau E. Here we focus on the continuum from 2800 to 3200{AA} and on the CIV doublet ({lambda}{lambda}1548.19,1550.77{AA}) as accretion diagnostics. Each system was observed over three or four consecutive binary orbits, at phases ~0, 0.2, 0.5, and 0.7. Those observations are complemented by ground-based U-band measurements. Contrary to model predictions, we do not detect any clear correlation between accretion luminosity and phase. Further, we do not detect any correlation between CIV flux and phase. For both stars the appearance of the CIV line is similar to that of single Classical T Tauri Stars (CTTSs), despite the lack of stable long-lived circumstellar disks. However, unlike the case in single CTTSs, the narrow and broad components of the CIV lines are uncorrelated, and we argue that the narrow component is powered by processes other than accretion, such as flares in the stellar magnetospheres and/or enhanced activity in the upper atmosphere. We find that both stars contribute equally to the narrow component CIV flux in DQ Tau, but the primary dominates the narrow component CIV emission in UZ Tau E. The CIV broad component flux is correlated with other accretion indicators, suggesting an accretion origin. However, the line is blueshifted, which is inconsistent with its origin in an infall flow close to the star. It is possible that the complicated geometry of the region, as well as turbulence in the shock region, are responsible for the blueshifted line profiles.
- ID:
- ivo://CDS.VizieR/J/A+A/464/263
- Title:
- UBV photometry of HD 143418
- Short Name:
- J/A+A/464/263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After a serendipitious discovery that HD 143418 is a light variable, we analyzed numerous UBV observations and Hipparcos H_p_ magnitudes transformed to Johnson V to find out whether the object is a very unusual spectroscopic binary. Initial reductions of new photometry were carried out with the HEC22 program, while the new spectra were reduced in the IRAF and SPEFO programs. Orbital elements were derived with the FOTEL program, the KOREL disentangling was applied, and period searches were carried out using phase dispersion minimalization technique and the program PERIOD04. Final modeling of radial-velocity and light variations was carried out in PHOEBE.
- ID:
- ivo://CDS.VizieR/J/A+A/416/669
- Title:
- UBV photometry of HD 6226
- Short Name:
- J/A+A/416/669
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric and spectroscopic monitoring of the B star resulted in the finding that this object is a new bright Be star with a clear positive correlation between the brightness and emission-line strength. The emission-line episodes are relatively short and seem to repeat frequently which makes this star an ideal target for studying the causes of the Be phenomenon.
- ID:
- ivo://CDS.VizieR/J/PASP/121/1070
- Title:
- UBV photometry of 2006-2008 outburst of AG Dra
- Short Name:
- J/PASP/121/1070
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe photometric and spectroscopic observations of the major outburst that AG Dra underwent between 2006 and 2008. The outburst peaked at U=8.4, B=9.0, V=8.7 around 2006 September 6, making it the brightest U-band event since the 1994 outburst. It was of the cold type, according to the classification of AG Dra outbursts introduced by Gonzalez-Riestra et al. (2006JAVSO..35..172G ). A second, fainter maximum (this time of the hot type) followed 400 days after the primary one, peaking at U=9.1, B=9.7, V=9.0 on 2007 October 7. The outburst phase ended about 600 days after the primary maximum. High resolution spectra obtained during early decline from primary maximum showed emission lines of Mg II, Si II, Ti II, and Fe II in addition to the usual lines of H, He I, and He II.
- ID:
- ivo://CDS.VizieR/J/A+A/387/580
- Title:
- UBV photometry of V832 Cyg
- Short Name:
- J/A+A/387/580
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of numerous homogenized UBV photoelectric observations and red spectra of the Be star from several observatories is presented.
- 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/MNRAS/394/872
- Title:
- UBVRI differential photometry of DM UMa
- Short Name:
- J/MNRAS/394/872
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present extensive UBVRI photometry of the active RS CVn binary DM UMa obtained at two different observatories over 1988-2008.
