- ID:
- ivo://CDS.VizieR/J/MNRAS/234/583
- Title:
- Abundances in Magellanic Cloud planetary nebulae
- Short Name:
- J/MNRAS/234/583
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical spectroscopic data for 71 Planetary Nebulae (PN) in the Large and Small Magellanic Clouds have been analysed. The line fluxes have been used to determine nebular temperatures, densities, and the abundances of He, N, O, Ne and Ar, relative to H. In our sample there are 12 nebulae with N/O>=0.5, resembling Peimbert's Type I PN; six low-excitation objects [1<=I(5007)/I(H{beat})<=4], and four very-low excitation (VLE) nebulae [I(H{beta})>I(5007)], similar to the Galactic VLE class. Mean abundances have been calculated for the nebulae not in these special groups. After correction for collisional excitation contributions to the nebular He I lines, PN in the SMC and LMC yield mass fractions of Y=0.249+/-0.025 and Y=0.258+/-0.012, respectively.
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- ID:
- ivo://CDS.VizieR/J/A+A/345/430
- Title:
- Abundances of 6 cool supergiants in NGC 330
- Short Name:
- J/A+A/345/430
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 330 is the brightest SMC young cluster and contains many bright supergiants. This cluster has aroused special interest, since the earlier abundance determinations indicated an abundance lower by a factor 5 than in the SMC field young population. In this Paper we analyse high resolution spectra of 6 cool supergiants in NGC 330, and compare in an homogeneous way, the metallicity and abundance ratios of various elements in NGC 330 and in the field of the SMC. The following Table is the Apendix to this Paper, giving the line list used in the analysis, together with the measured equivalent width and the derived abundance for each of the 6 stars.
- ID:
- ivo://CDS.VizieR/J/A+A/560/A44
- Title:
- Abundances of LMC bar and disk stars
- Short Name:
- J/A+A/560/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper compares the chemical evolution of the Large Magellanic Cloud (LMC) to that of the Milky Way (MW) and investigates the relation between the bar and the inner disc of the LMC in the context of the formation of the bar. We obtained high-resolution and mid signal-to-noise ratio spectra with FLAMES/GIRAFFE at ESO/VLT (Proposals 072.B-0293(B) and 078.B-0323(A), P.I. Vanessa Hill) and performed a detailed chemical analysis of 106 and 58 LMC field red giant stars (mostly older than 1Gyr), located in the bar and the disc of the LMC respectively. To validate our stellar parameter determinations and abundance measurement procedures, we performed thorough tests using the well-known mildly metal-poor Milky-Way thick disc giant Arcturus (HD 124897, alpha Boo). We measured elemental abundances for O, Mg, Si, Ca, Ti (alpha-elements), Na (light odd element), Sc, V, Cr, Co, Ni, Cu (iron-peak elements), Y, Zr, Ba, La and Eu (s- and r-elements). We used the automated tool DAOSPEC to measure the equivalent width (EW) and their associated error, and we used the grid of OSMARCS model atmospheres together with the spectrum synthesis code turbospectrum to convert the EW into abundances. Since our stars are giants, atmosphere models and radiative transfer were both in spherical geometry. We built the atmosphere model for a given set of stellar parameters by interpolation onto the OSMARCS grid with the interpolation routine written by T. Masseron.
- ID:
- ivo://CDS.VizieR/J/A+A/480/379
- Title:
- Abundances of 59 red giants in LMC
- Short Name:
- J/A+A/480/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used FLAMES (the Fibre Large Array Multi Element Spectrograph) at the VLT-UT2 telescope to obtain spectra of a large sample of red giant stars from the inner disk of the LMC, ~2kpc from the center of the galaxy. We investigate the chemical abundances of key elements to understand the star formation and evolution of the LMC disk: heavy and light [s-process/Fe] and [alpha/Fe] give constraints on the time scales of formation of the stellar population. Cu, Na, Sc, and the iron-peak elements are also studied aiming to better understand the build up of the elements of this population and the origin of these elements. We aim to provide a more complete picture of the LMC's evolution by compiling a large sample of field star abundances. LTE abundances were derived using line spectrum synthesis or equivalent width analysis. We used OSMARCS model atmospheres and an updated line list.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A106
- Title:
- Abundance study of LMC post-AGB stars
- Short Name:
- J/A+A/554/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photospheric abundances of evolved solar-type stars of different metallicities serve as probes into stellar evolution theory. Stellar photospheres of post-asymptotic giant branch (post-AGB) stars bear witness to the internal chemical enrichment processes, integrated over their entire stellar evolution. Here we study post-AGB stars in the Large Magellanic Cloud (LMC). With their known distances, these rare objects are ideal tracers of AGB nucleosynthesis and dredge-up phenomena.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A56
- Title:
- Abundance study of two LMC post-AGB stars
- Short Name:
- J/A+A/583/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is part of a larger project in which we systematically study the chemical abundances of extra-galactic post-asymptotic giant branch (post-AGB) stars. The aim of our programme is to derive chemical abundances of stars covering a large range in luminosity and metallicity with the ultimate goal of testing, constraining, and improving our knowledge of the poorly understood AGB phase, especially the third dredge-up mixing processes and associated s-process nucleosynthesis. Post-AGB photospheres are dominated by atomic lines and indicate the effects of internal chemical enrichment processes over the entire stellar lifetime. In this paper, we study two carefully selected post-AGB stars: J051213.81-693537.1 and J051848.86-700246.9 in the Large Magellanic Cloud (LMC). Both objects show signs of s-process enhancement. The combination of favourable atmospheric parameters for detailed abundance studies and their known distances (and hence luminosities and initial masses) make these objects ideal probes of the AGB third dredge-up and s-process nucleosynthesis in that they provide observational constraints for theoretical AGB models.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/358
- Title:
- Ae/Be stars of Magellanic Bridge in JHKs
- Short Name:
- J/ApJ/658/358
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have found Herbig Ae/Be star candidates in the western region of the Magellanic Bridge. Using the near-infrared camera SIRIUS and the 1.4m telescope IRSF, we surveyed ~3.0{deg}x1.3{deg} (24{deg}<~RA<~36{deg}, -75.0{deg}<~DE<~-73.7{deg}) in the J, H, and Ks bands. On the basis of colors and magnitudes, about 200 Herbig Ae/Be star candidates are selected. Considering the contaminations by miscellaneous sources, such as foreground stars and early-type dwarfs in the Magellanic Bridge, we estimate that about 80 (#40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one concentration of the candidates at the young star cluster NGC 796, strongly suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic Bridge. This is the first detection of PMS star candidates in the Magellanic Bridge, and if they are genuine PMS stars, this could be direct evidence of recent star formation. However, the estimate of the number of Herbig Ae/Be stars depends on the fraction of classical Be stars, and thus a more precise determination of the Be star fraction or observations to differentiate between the Herbig Ae/Be stars and classical Be stars are required.
- ID:
- ivo://CDS.VizieR/J/A+AS/145/11
- Title:
- AGAPEROS: variable stars in the LMC Bar
- Short Name:
- J/A+AS/145/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 91-92 EROS-1 data set has been used to select Long Timescale and Long Period Variables (LT&LPV). We choose to perform a selection of variable objects as comprehensive as possible, independent of periodicity and of their position on the colour magnitude diagram, and produce a catalogue of 632 variable objects. Table 2 provides the parameters of the variable objects detected in this paper. They are sorted in order of increasing right ascension. The columns contains the name of the variable including the RA,DEC (J2000.0) coordinates, the number of the chip and (x,y) position, the blending flags (PhiC/Phi0)_B_, (PhiC/Phi0)_R_ in both colours, the B_EROS_ and R_EROS_ magnitude, the number of star N_star_B, N_star_R found in the superpixel, the magnitude B_EROS_DAO and R_EROS_DAO estimated with DAOPHOT, and when available the cross-identifications with previous catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A16
- Title:
- Age and metallicity relation in MC clusters
- Short Name:
- J/A+A/554/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study small open star clusters, using Stroemgren photometry to investigate a possible dependence between age and metallicity in the Magellanic Clouds (MCs). Our goals are to trace evidence of an age metallicity relation (AMR) and correlate it with the mutual interactions of the two MCs and to correlate the AMR with the spatial distribution of the clusters. In the Large Magellanic Cloud (LMC), the majority of the selected clusters are young (up to 1Gyr), and we search for an AMR at this epoch, which has not been much studied. We report results for 15 LMC and 8 Small Magellanic Cloud (SMC) clusters, scattered all over the area of these galaxies, to cover a wide spatial distribution and metallicity range. The selected LMC clusters were observed with the 1.54m Danish Telescope in Chile, using the Danish Faint Object Spectrograph and Camera (DFOSC) with a single 2kx2k CCD. The SMC clusters were observed with the ESO 3.6m Telescope, also in Chile, using the ESO Faint Object Spectrograph and Camera (EFOSC). The obtained frames were analysed with the conventional DAOPHOT and IRAF software. We used Stroemgren filters in order to achieve reliable metallicities from photometry. Isochrone fitting was used to determine the ages and metallicities. The AMR for the LMC displays a metallicity gradient, with higher metallicities for the younger ages. The AMR for LMC-SMC star clusters shows a possible jump in metallicity and a considerable increase at about 6x10^8^yr. It is possible that this is connected to the latest LMC-SMC interaction. The AMR for the LMC also displays a metallicity gradient with distance from the centre. The metallicities in SMC are lower, as expected for a metal-poor host galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/784
- Title:
- Age estimates of SMC clusters
- Short Name:
- J/MNRAS/478/784
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Small Magellanic Cloud (SMC) has recently been found to harbour an increase of more than 200 per cent in its known cluster population. Here, we provide solid evidence that this unprecedented number of clusters could be greatly overestimated. On the one hand, the fully automatic procedure used to identify such an enormous cluster candidate sample did not recover ~50 per cent, on average, of the known relatively bright clusters located in the SMC main body. On the other hand, the number of new cluster candidates per time unit as a function of time is noticeably different from the intrinsic SMC cluster frequency (CF), which should not be the case if these new detections were genuine physical systems. We found additionally that the SMC CF varies spatially, in such a way that it resembles an outside-in process coupled with the effects of a relatively recent interaction with the Large Magellanic Cloud. By assuming that clusters and field stars share the same formation history, we showed for the first time that the cluster dissolution rate also depends on position in the galaxy. The cluster dissolution becomes higher as the concentration of galaxy mass increases or if external tidal forces are present.
