- ID:
- ivo://CDS.VizieR/J/A+A/584/A5
- Title:
- Massive LMC stars AAOmega spectroscopy
- Short Name:
- J/A+A/584/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectral classifications from optical spectroscopy of 263 massive stars in the north-eastern region of the Large Magellanic Cloud. The observed two-degree field includes the massive 30 Doradus star-forming region, the environs of SN1987A, and a number of star-forming complexes to the south of 30 Dor. These are the first classifications for the majority (203) of the stars and include eleven double-lined spectroscopic binaries. The sample also includes the first examples of early OC-type spectra (AAOmega 30 Dor 248 and 280), distinguished by the weakness of their nitrogen spectra and by CIV {lambda}4658 emission. We propose that these stars have relatively unprocessed CNO abundances compared to morphologically normal O-type stars, indicative of an earlier evolutionary phase. From analysis of observations obtained on two consecutive nights, we present radial-velocity estimates for 233 stars, finding one apparent single-lined binary and nine (>3{sigma}) outliers compared to the systemic velocity; the latter objects could be runaway stars or large-amplitude binary systems and further spectroscopy is required to investigate their nature.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/834/122
- Title:
- Massive star formation in the LMC. I. N159 & N160
- Short Name:
- J/ApJ/834/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present images and spectral energy distributions (SEDs) of massive young stellar objects (YSOs) in three star-forming H II regions of the Large Magellanic Cloud: N159A, N159 Papillon, and N160. We use photometry from SOFIA/FORCAST at 25.3-37.1{mu}m to constrain model fits to the SEDs and determine luminosities, ages, and dust content of the embedded YSOs and their local environments. By placing these sources on mid-infrared color-magnitude and color-color diagrams, we analyze their dust properties and consider their evolutionary status. Since each object in the FORCAST images has an obvious bright near-infrared counterpart in Spitzer Space Telescope images, we do not find any evidence for new, very cool, previously undiscovered Class 0 YSOs. Additionally, based on its mid-infrared colors and model parameters, N159A is younger than N160 and the Papillon. The nature of the first extragalactic protostars in N159, P1, and P2, is also discussed.
- ID:
- ivo://CDS.VizieR/J/other/Sci/359.69
- Title:
- Massive stars in 30 Dor
- Short Name:
- J/other/Sci/359.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large star-formation events in the distant universe. We determined the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic observations of 247 stars more massive than 15 solar masses (M_{sun}_). The main episode of massive star formation began about 8 million years (My) ago, and the star-formation rate seems to have declined in the last 1My. The IMF is densely sampled up to 200 Embedded Image and contains 32+/-12% more stars above 30M_{sun}_ than predicted by a standard Salpeter IMF. In the mass range of 15 to 200M_{sun}_, the IMF power-law exponent is 190^+0.37^_-0.26_, shallower than the Salpeter value of 2.35.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A50
- Title:
- Massive stars in NGC 346
- Short Name:
- J/A+A/626/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopy for 247 stars towards the young cluster NGC 346 in the Small Magellanic Cloud has been combined with that for 116 targets from the VLT-FLAMES Survey of Massive Stars. Spectral classification yields a sample of 47 O-type and 287 B-type spectra, while radial-velocity variations and/or spectral multiplicity have been used to identify 45 candidate single-lined (SB1) systems, 17 double-lined (SB2) systems, and one triple-lined (SB3) system. Atmospheric parameters (T_eff_ and log g) and projected rotational velocities (v_e_sini) have been estimated usingTLUSTY model atmospheres; independent estimates of v_e_sini were also obtained using a Fourier Transform method. Luminosities have been inferred from stellar apparent magnitudes and used in conjunction with the T_eff_ and v_e_sini estimates to constrain stellar masses and ages using theBONNSAI package. We find that targets towards the inner region of NGC 346 have higher median masses and projected rotational velocities, together with smaller median ages than the rest of the sample. There appears to be a population of very young targets with ages of less than 2Myr, which have presumably all formed within the cluster. The more massive targets are found to have lower projected rotational velocities consistent with previous studies. No significant evidence is found for differences with metallicity in the stellar rotational velocities of early-type stars, although the targets in the Small Magellanic Cloud may rotate faster than those in young Galactic clusters. The rotational velocity distribution for single non-supergiant B-type stars is inferred and implies that a significant number have low rotational velocity (~=10% with v_e_<40km/s), together with a peak in the probability distribution at v_e_~=300km/s. Larger projected rotational velocity estimates have been found for our Be-type sample and imply that most have rotational velocities between 200-450km/s.
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/3765
- Title:
- Mass-loss rates in LMC and SMC O stars
- Short Name:
- J/MNRAS/470/3765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a combination of BVJHK and Spitzer [3.6], [5.8] and [8.0] photometry to determine infrared (IR) excesses for a sample of 58 Large Magellanic Cloud and 46 Small Magellanic Cloud O stars. This sample is ideal for determining IR excesses because the very small line-of-sight reddening minimizes uncertainties due to extinction corrections. We use the core-halo model developed by Lamers & Waters to translate the excesses into mass-loss rates and demonstrate that the results of this simple model agree with the more sophisticated CMFGEN models to within a factor of 2. Taken at face value, the derived mass-loss rates are larger than those predicted by Vink et al. (2001A&A...369..574V), and the magnitude of the disagreement increases with decreasing luminosity. However, the IR excesses need not imply large mass-loss rates. Instead, we argue that they probably indicate that the outer atmospheres of O stars contain complex structures and that their winds are launched with much smaller velocity gradients than normally assumed. If this is the case, it could affect the theoretical and observational interpretations of the 'weak wind' problem, where classical mass-loss indicators suggest that the mass-loss rates of lower luminosity O stars are far less than expected.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/71
- Title:
- Mass-loss return from LMC evolved stars. VI.
- Short Name:
- J/ApJ/753/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ~30000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry.
- ID:
- ivo://CDS.VizieR/IV/33
- Title:
- Master Catalogue towards the Magellanic Clouds (MC2)
- Short Name:
- IV/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Master Catalogue of stars towards the Magellanic Clouds (MC2) is a multi-wavelength reference catalogue. The current paper presents the first results of the MC2 project. We started with a massive cross-identification of the two recently released near-infrared surveys: the DENIS Catalogue towards the Magellanic Clouds (DCMC) with more than 1.3 million sources identified in at least two of the three DENIS filters (I J Ks) and the 2nd Incremental Release of the 2MASS point source catalogue (J H Ks) covering the same region of the sky. Both point source catalogues provide an unprecedented wealth of data on the stellar populations of the Magellanic Clouds (MCs). The cross-matching procedure has been extended to optical wavelength ranges, including the UCAC1 (USNO) and GSC2.2 catalogues. New cross-matching procedures for very large catalogues have been developed and important results on the astrometric and photometric accuracy of the cross-identified catalogues were derived. The cross-matching of large surveys is an essential tool to improve our understanding of their specific contents. This study has been partly supported by the ASTROVIRTEL project that aims at improving access to astronomical archives as virtual telescopes. This work has been supported by ASTROVIRTEL, a project funded by the European Commission under FP5 Contract No. HPRI-CT-1999-00081.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/2702
- Title:
- MC Cepheids, RR Lyrae stars and binaries
- Short Name:
- J/MNRAS/437/2702
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA near-infrared Y, J, Ks survey of the Magellanic System (VMC) survey is obtaining multi-epoch photometry in the Ks band of the Magellanic System down to a limiting magnitude of Ks~19.3 for individual epoch data. The observations are spaced in time such as to provide optimal sampling of the light curves for RR Lyrae stars and for Cepheids with periods up to 20-30d. We present examples of the Ks-band light curves of Classical Cepheids and RR Lyrae stars we are obtaining from the VMC data and outline the strategy we put in place to measure distances and infer the System three-dimensional geometry from the variable stars. For this purpose, the near-infrared Period-Luminosity, Period-Wesenheit and Period-Luminosity-Colour relations of the system RR Lyrae stars and Cepheids are used. We extensively exploit the catalogues of the Magellanic Clouds' variable stars provided by the EROS-2 and OGLE III/IV microlensing surveys. By combining these surveys, we present the currently widest-area view of the Large Magellanic Cloud as captured by the galaxy Cepheids, RR Lyrae stars and binaries. This reveals the full extent of the main structures (bar/s - spiral arms) that have only been vaguely guessed before. Our work strengthens the case for a detailed study of the Large Magellanic Cloud three-dimensional geometry.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A137
- Title:
- MC cool supergiants spectra
- Short Name:
- J/A+A/618/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This atlas composed by more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and Calcium Triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are Carbon or S~Stars and the remaining 12% are foreground stars of lesser luminosities).
- ID:
- ivo://CDS.VizieR/J/ApJS/91/583
- Title:
- MC massive stars IMF. I.
- Short Name:
- J/ApJS/91/583
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV CCD photometry has been obtained for 14 OB associations in the Magellanic Clouds using the University of Toronto's 0.6m telescope and the Carnegie Institution of Washington's 1.0m reflector, both on Las Campanas, Chile. The data are presented and used to construct color-magnitude diagrams for the purposes of investigating the massive-star content of the associations.
