scholarly journals The VLT-FLAMES Tarantula Survey

2019 ◽  
Vol 624 ◽  
pp. A128 ◽  
Author(s):  
N. Britavskiy ◽  
D. J. Lennon ◽  
L. R. Patrick ◽  
C. J. Evans ◽  
A. Herrero ◽  
...  
Keyword(s):  
Near Infrared ◽  
Interstellar Extinction ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Physical Parameters ◽  
Single Star ◽  
Near Ir ◽  
Large Spread ◽  
Red Supergiants ◽  
Young Star Clusters

Aims. We estimate physical parameters for the late-type massive stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud (LMC). Methods. The observational sample comprises 20 candidate red supergiants (RSGs) which are the reddest ((B − V) > 1 mag) and brightest (V < 16 mag) objects in the VFTS. We use optical and near-infrared (near-IR) photometry to estimate their temperatures and luminosities, and introduce the luminosity–age diagram to estimate their ages. Results. We derive physical parameters for our targets, including temperatures from a new calibration of (J − Ks)0 colour for luminous cool stars in the LMC, luminosities from their J-band magnitudes (thence radii), and ages from comparisons with current evolutionary models. We show that interstellar extinction is a significant factor for our targets, highlighting the need to take it into account in the analysis of the physical parameters of RSGs. We find that some of the candidate RSGs could be massive AGB stars. The apparent ages of the RSGs in the Hodge 301 and SL 639 clusters show a significant spread (12–24 Myr). We also apply our approach to the RSG population of the relatively nearby NGC 2100 cluster, finding a similarly large spread. Conclusions. We argue that the effects of mass transfer in binaries may lead to more massive and luminous RSGs (which we call “red stragglers”) than expected from single-star evolution, and that the true cluster ages correspond to the upper limit of the estimated RSG ages. In this way, the RSGs can serve as a new and potentially reliable age tracer in young star clusters. The corresponding analysis yields ages of 24−3+5 Myr for Hodge 301, 22−5+6 Myr for SL 639, and 23−2+4 Myr for NGC 2100.

scholarly journals Testing Evolutionary Models with Red Supergiant and Wolf–Rayet Populations

2021 ◽  
Vol 922 (2) ◽  
pp. 177
Author(s):  
Philip Massey ◽  
Kathryn F. Neugent ◽  
Trevor Z. Dorn-Wallenstein ◽  
J. J. Eldridge ◽  
E. R. Stanway ◽  
...  
Keyword(s):  
Near Infrared ◽  
Relative Number ◽  
Interference Filter ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Evolutionary Models ◽  
Image Subtraction ◽  
Single Star ◽  
Red Supergiants ◽  
Effective Temperatures

Abstract Despite the many successes that modern massive star evolutionary theory has enjoyed, reproducing the apparent trend in the relative number of red supergiants (RSGs) and Wolf–Rayet (WR) stars has remained elusive. Previous estimates show the RSG/WR ratio decreasing strongly with increasing metallicity. However, the evolutionary models have always predicted a relatively flat distribution for the RSG/WR ratio. In this paper we reexamine this issue, drawing on recent surveys for RSGs and WRs in the Magellanic Clouds, M31, and M33. The RSG surveys have used Gaia astrometry to eliminate foreground contamination and have separated RSGs from asymptotic giant branch stars using near-infrared colors. The surveys for WRs have utilized interference-filter imaging, photometry, and image subtraction techniques to identify candidates, which have then been confirmed spectroscopically. After carefully matching the observational criteria to the models, we now find good agreement in both the single-star Geneva and binary BPASS models with the new observations. The agreement is better when we shift the RSG effective temperatures derived from J − Ks photometry downwards by 200 K in order to agree with the Levesque TiO effective temperature scale. In an appendix we also present a source list of RSGs for the SMC which includes effective temperatures and luminosities derived from near-infrared 2MASS photometry, in the same manner as used for the other galaxies.

scholarly journals The Physical Parameters of Four WC-type Wolf–Rayet Stars in the Large Magellanic Cloud: Evidence of Evolution*

2022 ◽  
Vol 924 (2) ◽  
pp. 44
Author(s):  
Erin Aadland ◽  
Philip Massey ◽  
D. John Hillier ◽  
Nidia Morrell
Keyword(s):  
Spectral Synthesis ◽  
Mass Loss Rate ◽  
Large Magellanic Cloud ◽  
Stellar Atmosphere ◽  
Magellanic Cloud ◽  
Physical Parameters ◽  
Evolutionary Models ◽  
Single Star ◽  
Oxygen Abundance ◽  
Solar Metallicity

Abstract We present a spectral analysis of four Large Magellanic Cloud (LMC) WC-type Wolf–Rayet (WR) stars (BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary questions surrounding massive stars. The first is: are WO-type WR stars more oxygen enriched than WC-type stars, indicating further chemical evolution, or are the strong high-excitation oxygen lines in WO-type stars an indication of higher temperatures. This study will act as a baseline for answering the question of where WO-type stars fall in WR evolution. Each star’s spectrum, extending from 1100 to 25000 Å, was modeled using cmfgen to determine the star’s physical properties such as luminosity, mass-loss rate, and chemical abundances. The oxygen abundance is a key evolutionary diagnostic, and with higher resolution data and an improved stellar atmosphere code, we found the oxygen abundance to be up to a factor of 5 lower than that of previous studies. The second evolutionary question revolves around the formation of WR stars: do they evolve by themselves or is a close companion star necessary for their formation? Using our derived physical parameters, we compared our results to the Geneva single-star evolutionary models and the Binary Population and Spectral Synthesis (BPASS) binary evolutionary models. We found that both the Geneva solar-metallicity models and BPASS LMC-metallicity models are in agreement with the four WC-type stars, while the Geneva LMC-metallicity models are not. Therefore, these four WC4 stars could have been formed either via binary or single-star evolution.

scholarly journals Extinction and dust/gas ratio in the H i ridge region of the LMC based on the IRSF/SIRIUS near-infrared survey

2019 ◽  
Vol 71 (5) ◽  
Author(s):  
Takuya Furuta ◽  
Hidehiro Kaneda ◽  
Takuma Kokusho ◽  
Daisuke Ishihara ◽  
Yasushi Nakajima ◽  
...  
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Dust Extinction ◽  
Near Ir ◽  
Hydrogen Column Density ◽  
Color Excess ◽  
Gas Ratio ◽  
Infrared Survey

ABSTRACT We present a dust extinction AV map of the Large Magellanic Cloud (LMC) in the H i ridge region using the InfraRed Survey Facility (IRSF) near-infrared (IR) data, and compare the AV map with the total hydrogen column density N(H) maps derived from the CO and H i observations. In the LMC H i ridge region, the two-velocity H i components (plus an intermediate velocity component) are identified, and the young massive star cluster is possibly formed by collision between them. In addition, one of the components is suggested to be an inflow gas from the Small Magellanic Cloud (SMC) which is expected to have even lower metallicity gas (Fukui et al. 2017, PASJ, 69, L5). To evaluate dust/gas ratios in the H i ridge region in detail, we derive the AV map from the near-IR color excess of the IRSF data updated with the latest calibration, and fit the resultant AV map with a combination of the N(H) maps of the different velocity components to decompose it successfully into the three components. As a result, we find difference by a factor of 2 in AV/N(H) between the components. In additon, the CO-to-H2 conversion factor also indicates difference between the components, implying a difference in the metallicity. Our results are likely to support the scenario that the gas in the LMC H i ridge region is contaminated with an inflow gas from the SMC with a geometry consistent with the on-going collision between the two-velocity components.

The structure of young star clusters in the Large Magellanic Cloud

1987 ◽  
Vol 323 ◽  
pp. 54 ◽  
Author(s):  
Rebecca A. W. Elson ◽  
S. Michael Fall ◽  
Kenneth C. Freeman
Keyword(s):  
Star Clusters ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Magellanic Cloud ◽  
Young Star Clusters

The internal velocity dispersions of three young star clusters in the Large Magellanic Cloud

1989 ◽  
Vol 347 ◽  
pp. 201 ◽  
Author(s):  
Robert H. Lupton ◽  
S. Michael Fall ◽  
Kenneth C. Freeman ◽  
Rebecca A. W. Elson
Keyword(s):  
Star Clusters ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Magellanic Cloud ◽  
Velocity Dispersions ◽  
Internal Velocity ◽  
Young Star Clusters

Core expansion in young star clusters in the Large Magellanic Cloud

1989 ◽  
Vol 347 ◽  
pp. L69 ◽  
Author(s):  
Rebecca A. W. Elson ◽  
Kenneth C. Freeman ◽  
Tod R. Lauer
Keyword(s):  
Star Clusters ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Magellanic Cloud ◽  
Young Star Clusters

scholarly journals Binary black holes in the pair instability mass gap

2020 ◽  
Vol 497 (1) ◽  
pp. 1043-1049 ◽  
Author(s):  
Ugo N Di Carlo ◽  
Michela Mapelli ◽  
Yann Bouffanais ◽  
Nicola Giacobbo ◽  
Filippo Santoliquido ◽  
...  
Keyword(s):  
Black Holes ◽  
Formation Rate ◽  
Star Clusters ◽  
Design Sensitivity ◽  
Young Star ◽  
Binary Black Holes ◽  
Single Star ◽  
Mass Gap ◽  
Young Star Clusters ◽  
Stellar Mergers

ABSTRACT Pair instability (PI) and pulsational PI prevent the formation of black holes (BHs) with mass ≳60 M⊙ from single star evolution. Here, we investigate the possibility that BHs with mass in the PI gap form via stellar mergers and multiple stellar mergers, facilitated by dynamical encounters in young star clusters. We analyse 104 simulations, run with the direct N-body code nbody6++gpu coupled with the population synthesis code mobse. We find that up to ∼6 per cent of all simulated BHs have mass in the PI gap, depending on progenitor’s metallicity. This formation channel is strongly suppressed in metal-rich (Z = 0.02) star clusters because of stellar winds. BHs with mass in the PI gap are initially single BHs but can efficiently acquire companions through dynamical exchanges. We find that ∼21 per cent, 10 per cent, and 0.5 per cent of all binary BHs have at least one component in the PI mass gap at metallicity Z = 0.0002, 0.002, and 0.02, respectively. Based on the evolution of the cosmic star formation rate and metallicity, and under the assumption that all stars form in young star clusters, we predict that ∼5 per cent of all binary BH mergers detectable by advanced LIGO and Virgo at their design sensitivity have at least one component in the PI mass gap.

scholarly journals Multiple populations of Hβ emission line stars in the Large Magellanic Cloud cluster NGC 1971

2020 ◽  
Vol 644 ◽  
pp. A98
Author(s):  
Andrés E. Piatti
Keyword(s):  
Emission Line ◽  
Star Clusters ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Magellanic Cloud ◽  
Observational Result ◽  
Be Stars ◽  
Membership Probability ◽  
Element Abundances ◽  
Young Star Clusters

We revisited the young Large Magellanic Cloud star cluster NGC 1971 with the aim of providing additional clues to our understanding of its observed extended main-sequence turnoff (eMSTO), a feature commonly seen in young star clusters that has recently been argued to be caused by a real age spread similar to the cluster age (∼160 Myr). We combined accurate Washington and Strömgren photometry of stars with high membership probability to explore the nature of this eMSTO. From different ad hoc defined pseudo-colors, we found that bluer and redder stars distributed throughout the eMSTO do not show any inhomogeneities of light- and heavy-element abundances. These blue and red stars are split into two clearly different groups only when the Washington M magnitudes are employed, which delimites the number of spectral features that cause the appearance of the eMSTO. We speculate that Be stars populate the eMSTO of NGC 1971 because (i) Hβ contributes to the M passband, (ii) Hβ emissions are common features of Be stars, and (iii) the Washington M and T1 magnitudes are tightly correlated; the latter measuring the observed contribution of Hα emission line in Be stars, which is in turn correlated with Hβ emissions. This is the first observational result to our knowledge that indicates that Hβ emissions are the origin of eMSTOs observed in young star clusters. Our results certainly open new possibilities of studying eMSTO from photometric systems with passbands centered at features commonly seen in Be stars.

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