- ID:
- ivo://CDS.VizieR/J/AJ/154/102
- Title:
- LMC blue supergiants spectroscopic observations
- Short Name:
- J/AJ/154/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-quality spectra of 90 blue supergiant stars in the Large Magellanic Cloud are analyzed with respect to effective temperature, gravity, metallicity, reddening, extinction, and extinction law. An average metallicity, based on Fe and Mg abundances, relative to the Sun of [Z]=-0.35+/-0.09 dex is obtained. The reddening distribution peaks at E(B-V)=0.08 mag, but significantly larger values are also encountered. A wide distribution of the ratio of extinction to reddening is found ranging from R_V_=2 to 6. The results are used to investigate the blue supergiant relationship between flux-weighted gravity, g_F_=g/T_eff_^4^, and absolute bolometric magnitude M_bol_. The existence of a tight relationship, the Flux-weighted Gravity-Luminosity Relationship (FGLR), is confirmed. However, in contrast to previous work, the observations reveal that the FGLR is divided into two parts with a different slope. For flux-weighted gravities larger than 1.30 dex, the slope is similar to that found in previous work, but the relationship becomes significantly steeper for smaller values of the flux-weighted gravity. A new calibration of the FGLR for extragalactic distance determinations is provided.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/124/2039
- Title:
- LMC Blue variable stars from MACHO
- Short Name:
- J/AJ/124/2039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric properties of 1280 blue variable stars within the Large Megallanic Cloud. Photometry is derived from the MACHO database. The light curves of the sample exhibit a variety of quasi-periodic and aperiodic outburst behavior. A characteristic feature of the photometric variation is that the objects are reddest when at maximum outburst. A subset of 102 objects were examined spectroscopically. Within this subset, 91% exhibited Balmer emission in at least one epoch, in some cases with spectacular spectral variability. The variability observed in the sample is consistent with the establishment and maintenance of the Be phenomenon.
- ID:
- ivo://CDS.VizieR/J/AcA/58/313
- Title:
- LMC Cepheids in OGLE and MACHO data
- Short Name:
- J/AcA/58/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pulsation period of Cepheids should change as stars evolve through the instability strip. Rates of these changes found by other authors based on the decades-long O−C diagrams show rather good agreement with theoretical predictions. We have checked the variability on the scale of a few years on the data recently published by the Optical Gravitational Lensing Experiment (OGLE) for the Large Magellanic Cloud Cepheids and found period changes for 18% of fundamental mode and 41% of first overtone pulsators. It suggest the overtone pulsations are less stable than the fundamental ones. For stars which had the cross-references in the MACHO catalog we have checked if the period change rates derived from the OGLE and the MACHO data are consistent.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A95
- Title:
- LMC Cepheids radial velocities
- Short Name:
- J/A+A/534/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extragalactic distance scale builds directly on the Cepheid Period-Luminosity (PL) relation as delineated by the sample of Cepheids in the Large Magellanic Cloud (LMC). However, the LMC is a dwarf irregular galaxy, quite different from the massive spiral galaxies used for calibrating the extragalactic distance scale. Recent investigations suggest that not only the zero-point but also the slope of the Milky Way PL relation differ significantly from that of the LMC, casting doubts on the universality of the Cepheid PL relation. We want to make a differential comparison of the PL relations in the two galaxies by delineating the PL relations using the same method, the infrared surface brightness method (IRSB), and the same precepts. The IRSB method is a Baade-Wesselink type method to determine individual distances to Cepheids. We apply a newly revised calibration of the method as described in an accompanying paper (Paper I, Cat. J/A+A/534/A94) to 36 LMC and five SMC Cepheids and delineate new PL relations in the V,I,J, & K bands as well as in the Wesenheit indices in the optical and near-IR. We present 509 new and accurate radial velocity measurements for a sample of 22 LMC Cepheids, enlarging our earlier sample of 14 stars to include 36 LMC Cepheids. The new calibration of the IRSB method is directly tied to the recent HST parallax measurements to ten Milky Way Cepheids, and we find a LMC barycenter distance modulus of 18.45+/-0.04 (random error only) from the 36 individual LMC Cepheid distances. In the J,K bands we find identical slopes for the LMC and Milky Way PL relations and only a weak metallicity effect on the zero points (consistent with a zero effect), metal poor stars being fainter. In the optical we find the Milky Way slopes are slightly shallower than the LMC slopes (but again consistent with no difference in the slopes) and small effects on the zero points. However, the important Wesenheit index in V,(V-I) shows a metallicity effect on the slope and on the zero point which is likely to be significant. We find a significant metallicity effect on the Wvi index gamma(Wvi)=-0.23+/-0.10mag/dex as well as an effect on the slope. The K-band PL relation on the other hand is found to be an excellent extragalactic standard candle being metallicity insensitive in both slope and zero-point and at the same time being reddening insensitive and showing the least internal dispersion.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A29
- Title:
- LMC classical Cepheids Fe and O content
- Short Name:
- J/A+A/658/A29
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Classical Cepheids are primary distance indicators and a crucial stepping stone to determining the present-day value of the Hubble constant Ho to the precision and accuracy required to constrain apparent deviations from the LCDM Concordance Cosmological Model. We have measured the iron and oxygen abundances of a statistically significant sample of 89 Cepheids in the LMC, one of the anchors of the local Distance Scale, quadrupling the prior sample and including 68 of the 70 Cepheids used to constrain Ho by the SH0ES program. The goal is to constrain the extent to which the Cepheid luminosity is influenced by their chemical composition, which is an important contributor to the uncertainty on the determination of the Hubble Constant itself and a critical factor in the internal consistency of the distance ladder. We have derived stellar parameters and chemical abundances from a self-consistent spectroscopic analysis based on Equivalent Width of absorption lines. The iron distribution of Cepheids in the LMC can be very accurately described by a single Gaussian with a mean [Fe/H]=-0.409+/-0.003dex and sigma=0.076+/-0.003dex. We estimate a systematic uncertainty on the absolute mean values of 0.1dex. The width of the distribution is fully compatible with the measurement error and supports the low dispersion of 0.069 mag seen in the NIR HST LMC period-luminosity relation. The uniformity of the abundance has the important consequence that the LMC Cepheids alone cannot provide any meaningful constraint on the dependence of the Cepheid Period-Luminosity relation on chemical composition at any wavelength. This revises a prior claim based on a small sample of 22 LMC Cepheids that there was little dependence (or uncertainty) between composition and NIR luminosity, a conclusion which would produce an apparent conflict between anchors of the distance ladder with different mean abundance. The chemical homogeneity of the LMC Cepheid population makes it an ideal environment to calibrate the metallicity dependence between the more metal poor SMC and metal rich Milky Way and NGC 4258.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A33
- Title:
- LMC 162 eccentric eclipsing binaries light curve
- Short Name:
- J/A+A/640/A33
- Date:
- 17 Dec 2021 07:53:18
- Publisher:
- CDS
- Description:
- We present an extensive study of 162 early-type binary systems located in the LMC galaxy that show apsidal motion and have never been studied before. For the ample systems, we performed light curve and apsidal motion modelling for the first time. These systems have a median orbital period of 2.2 days and typical periods of the apsidal motion were derived to be of the order of decades. We identified two record-breaking systems. The first, OGLE LMC-ECL-22613, shows the shortest known apsidal motion period among systems with main sequence components (6.6 years); it contains a third component with an orbital period of 23 years. The second, OGLE LMC-ECL-17226, is an eccentric system with the shortest known orbital period (0.9879 days) and with quite fast apsidal motion period (11 years). Among the studied systems, 36 new triple-star candidates were identified based on the additional period variations. This represents more than 20% of all studied systems, which is in agreement with the statistics of multiples in our Galaxy. However, the fraction should only be considered as a lower limit of these early-type stars in the LMC because of our method of detection, data coverage, and limited precision of individual times of eclipses.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/2616
- Title:
- LMC eccentric ellipsoidal red giant binaries
- Short Name:
- J/MNRAS/421/2616
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Modelling ellipsoidal variables with known distances can lead to exact determination of the masses of both components, even in the absence of eclipses. We present such modelling using light and radial velocity curves of ellipsoidal red giant binaries in the Large Magellanic Cloud (LMC), where they are also known as sequence E stars. Stars were selected as likely eccentric systems on the basis of light curve shape alone. We have confirmed their eccentric nature and obtained system parameters using the Wilson-Devinney code.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A141
- Title:
- LMC emission-line stars. Armagh survey
- Short Name:
- J/A+A/555/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate astrometry is required to reliably cross-match 20th-century photographic catalogues against 21st-century digital surveys. The present work provides modern-area identifications and astrometry for the 801 emission-line objects "of stellar appearance" in the Armagh survey (the largest of its nature to date). Targets have been individually identified in digital images using the Armargh Atlas and, in most cases, unambiguously matched to entries in the UCAC astrometric catalogues.
259. LMC extended catalog
- ID:
- ivo://CDS.VizieR/J/AJ/117/238
- Title:
- LMC extended catalog
- Short Name:
- J/AJ/117/238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of extended objects in the Large Magellanic Cloud was carried out on the ESO/SERC R and J Sky Survey Atlases, checking entries in previous catalogs and searching for new objects. The census provided 6659 objects including star clusters, emission-free associations, and objects related to emission nebulae. Each of these classes contains three subclasses with intermediate properties, which are used to infer total populations. The survey includes cross identifications among catalogs, and we present 3246 new objects. We provide accurate positions, classification, and homogeneous measurements of sizes and position angles, as well as information on cluster pairs and hierarchical relation for superimposed objects. This unification and enlargement of catalogs is important for future searches of fainter and smaller new objects. We discuss the angular and size distributions of the objects of the different classes. The angular distributions show two off-centered systems with different inclinations, suggesting that the LMC disk is warped. The present catalog together with its previous counterpart for the SMC and the inter-Cloud region provide a total population of 7847 extended objects in the Magellanic System. The angular distribution of the ensemble reveals important clues on the interaction between the LMC and SMC.
- ID:
- ivo://CDS.VizieR/J/A+AS/73/37
- Title:
- LMC faint stars BV photometry
- Short Name:
- J/A+AS/73/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric data on the Johnson BV system are given for 947 stars in a field close to the bar of the Large Magellanic Cloud. The data have been determined from electronographs calibrated through photoelectric photometry. The visual magnitudes of the programme stars range from V=14.63 to V=23.13.
