- ID:
- ivo://CDS.VizieR/J/ApJ/856/170
- Title:
- Tracers of stellar mass-loss. II.
- Short Name:
- J/ApJ/856/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present integrated colors and surface brightness fluctuation magnitudes in the mid-infrared (IR), derived from stellar population synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14Gyr, and comprise metallicities between Z=0.0001 and Z=0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of "extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5{mu}m and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate-age populations, between 100Myr and 2-3Gyr.
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- ID:
- ivo://CDS.VizieR/J/AcA/58/293
- Title:
- Type-II and anomalous Cepheids in LMC
- Short Name:
- J/AcA/58/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the second part of the OGLE-III Catalog of Variable Stars (OIII-CVS) we present 197 type II Cepheids and 83 anomalous Cepheids in the Large Magellanic Cloud (LMC). The sample of type II Cepheids consists of 64 BL Her stars, 96 W Vir stars and 37 RV Tau stars. Anomalous Cepheids are divided into 62 fundamental-mode and 21 first-overtone pulsators. These are the largest samples of such types of variable stars detected anywhere outside the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A70
- Title:
- Type II and anomalous Cepheids luminosities
- Short Name:
- J/A+A/603/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Type II and anomalous Cepheids (ACs) are useful distance indicators when there are too few classical Cepheids or when RR Lyrae stars are too faint. Type II and ACs follow a period-luminosity relation as well, but they are less well-studied classes of objects. In this paper we study the sample of 335 Type II and ACs in the Small and Large Magellanic Clouds detected in OGLE-III data. The spectral energy distributions (SEDs) are constructed from photometric data available in the literature and fitted with a dust radiative transfer model, thereby leading to a determination of luminosity and effective temperature. In addition, a subsample of targets is investigated for possible binarity by looking for the light-time travel effect (LITE). Hertzsprung-Russell diagrams (HRD) are constructed and compared to evolutionary tracks and theoretical instability strips (ISs). In agreement with previous suggestions, the BL Her subclass can be explained by the evolution of ~0.5-0.6M_{sun}_ stars evolving off the zero-age horizontal branch and the ACs can be explained by the evolution of ~1.1-2.3M_{sun}_ stars. The evolution of the W Vir subclass is not clear. These objects are at higher luminosities than ACs and evolutionary tracks of ~2.5-4M_{sun}_ stars cross this region in the HRD, but the periods of the W Vir are longer than those of the short period classical Cepheids at these luminosities, which indicates the former have lower masses. A low-mass star experiencing a thermal pulse when the envelope mass is small can make a blue loop into the IS region of the W Vir stars. But the timescale is extremely short, so this is also no explanation for the W Vir as a class. A relation to binarity might be at the origin of the W Vir stars, which has already been explicitly suggested for the peculiar W Vir stars. For ~60% of the RV Tau and ~10% of the W Vir objects an infrared excess is detected from the SED fitting. A recent result is confirmed that stars exist with luminosities below that predicted from single-star evolution, which show a clear infrared excess, and the shape of the excess suggests a connection to binary evolution. The investigation of the LITE effect revealed 20 systems that appear to show periodic variations and may be new binaries, although this study requires follow-up. About 40 stars show significant period changes.
- ID:
- ivo://CDS.VizieR/J/A+AS/30/261
- Title:
- UBV and Radial Velocities of SMC Supergiants
- Short Name:
- J/A+AS/30/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From observations at the European Southern Observatory, spectrographic and photometric data are presented for 91 supergiant stars belonging to the Small Magellanic Cloud and its Wing. The data include MK classes for 52 stars, radial velocity data for 51 stars and UBV photometry for 90 stars. In V the limiting magnitude for the spectrographic observations is 13.7 and for the photometric observations 13.9. Whenever possible, radial velocities for interstellar CaII and [OII] have been measured and listed. In Remarks to the Catalogue notes are given for the individual stars concerning the obtained data and comparisons with results of previous investigations.
- ID:
- ivo://CDS.VizieR/J/A+A/400/917
- Title:
- UBVI photometry in NGC 458
- Short Name:
- J/A+A/400/917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new photometry of the Small Magellanic Cloud star cluster NGC 458 in UBVI filters. We determine the reddening E(B-V)=0.04+/-0.02. By comparison with the isochrones by Bertelli et al. (1994, Cat. <J/A+AS/106/275>) we derive an age of ~140Myr. Three candidate blue straggler stars are proposed. The evolved "blue loop'' stars of NGC 458 have masses between 4 and 5M_{sun}_ and are hotter than model predictions.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1275
- Title:
- UBV photometry in 5 fields of the LMC
- Short Name:
- J/AJ/116/1275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBV photometry of four fields within Shapley Constellation III and one field on the edge of the shell. Our fields cover roughly 20% of the region, mostly in the southern half. Determinations are made of ages of the fields, the star formation densities, and the initial mass function (IMF) slopes.
- ID:
- ivo://CDS.VizieR/J/ApJ/452/210
- Title:
- UBV photometry in LH 47/48
- Short Name:
- J/ApJ/452/210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the stellar population of an OB association, LH 47/48, which is associated with a superbubble H II region, DEM 152 in the N44 nebular complex of the Large Magellanic Cloud. With CCD photometry and spectroscopy of the massive stars, we find no evidence that an unusual stellar population gave rise to the shell morphology of the gas. The slope of the initial mass function, {Gamma}=1.3+/-0.2, is consistent with that of other OB associations in the LMC, and there is no significant difference in the initial mass function internal or external to the supershell. The inferred stellar ionizing flux is consistent with the observed nebular H alpha flux. We do find evidence for triggered star formation: the H-R diagram suggests an age of >10Myr for the population interior to the bubble with more recent, <5Myr, star formation on the exterior. Using the detailed data on the stellar population, we compare a numerical form of the Weaver et al. (1977ApJ...218..377W) evolutionary model for wind-driven bubbles with the observed shell kinematics. We find a substantial discrepancy: the observed shell radius is too small and/or expansion velocity too large to be explained with this version of the model. We discuss possible explanations for the inconsistency.
- ID:
- ivo://CDS.VizieR/J/AJ/73/772
- Title:
- UBV photometry in two LMC associations
- Short Name:
- J/AJ/73/772
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric UBV observations were made in two associations in the Large Magellanic Cloud, in the magnitude range 10.6 to 16.2. The observations were made at the Cerro Tololo Inter-American Observatory with the 36-inch telescope in the nights of 1-5 December 1967. The positions were computed by B. Skiff (Lowell Obs.) in 2009.
- ID:
- ivo://CDS.VizieR/J/AJ/118/1684
- Title:
- UBV photometry of 4 LMC compact OB groups
- Short Name:
- J/AJ/118/1684
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blue-violet spectrograms of individual components in four compact OB groups of the Large Magellanic Cloud, obtained with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS), are presented and discussed. Two of the massive multiple systems are in the 30 Doradus periphery, while the other two represent the core and the peripheral, triggered associations in the giant shell H II region Henize N11. Uncontaminated spectrograms of three Wolf-Rayet and two very early Of components have been obtained for the first time; they can be observed only as composites with their close companions from the ground. Many of the companions have also been observed separately with the HST FOS, and several are of special interest in their own right. These observations provide information on the initial masses and ages of the peculiar objects, and on the evolutionary relationships among different spectral categories within the presumably coeval systems.
- ID:
- ivo://CDS.VizieR/J/A+AS/99/591
- Title:
- UBV photometry of LMC foreground stars
- Short Name:
- J/A+AS/99/591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV photometry of 955 galactic foreground stars in the direction to the Large Magellanic Cloud is presented. The stars have been chosen from foreground star catalogues and have been measured to complete a new data base containing entries of more than 5000 stars in the direction of the LMC. First and second order extinction coefficients at La Silla/Chile are given, which differ from the standard values because of the 1991 eruption of the volcano Mt. Pinatubo.
