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 The NGC 346 massive star census

2020 ◽  
Vol 634 ◽  
pp. A6 ◽  
Author(s):  
P. L. Dufton ◽  
C. J. Evans ◽  
D. J. Lennon ◽  
I. Hunter
Keyword(s):  
Magnetic Field ◽  
Massive Star ◽  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Evolutionary Models ◽  
Qualitative Comparison ◽  
Single Star ◽  
Early Type Stars ◽  
The Magnetic Field

Previous analyses of two large spectroscopic surveys of early-type stars in the Large Magellanic Cloud (LMC) have found an excess of nitrogen enriched B-type targets with a ve sin i ≤ 40 km s−1 compared with the predictions of single star evolutionary models that incorporate rotational mixing. By contrast, the number of such targets with 40 <  ve sin i ≤ 80 km s−1 was consistent with such models. We have undertaken a similar analysis for 61 B-type targets which lie towards the young cluster, NGC 346 in the Small Magellanic Cloud (SMC). These again have projected rotational velocities, ve sin i ≤ 80 km s−1, are not classified as supergiants, and are apparently single. Approximately 65% of these SMC targets could have nitrogen enhancements of less than 0.3 dex, which is consistent with them having experienced only small amounts of mixing due to their low rotational velocities. However, as with the previous LMC surveys, an excess of stars with low projected rotational velocities, ve sin i ≤ 40 km s−1, and significant nitrogen enrichments is found. This is estimated to be approximately 5% of the total population of apparently single B-type stars or 40% of all stars with current rotational velocities of less than 40 km s−1; these percentages are similar to those found previously for the two LMC samples. For all three surveys, the presence of undetected binaries and other uncertainties imply that these percentages might be underestimated and that it is indeed possible for all the single stars with current rotational velocities of less than 40 km s−1 to be nitrogen enriched. Two possible explanations incorporate the effects of the magnetic field, via either a stellar merger followed by magnetic braking or the evolution of a single star with a large magnetic field. Both mechanisms would appear to be compatible with the observed frequency of nitrogen-enriched stars in the Magellanic Clouds. Differences in the properties of the nitrogen-enriched stars compared with the remainder of the sample would be consistent with the former mechanism. For the latter, a qualitative comparison with Galactic evolutionary models that incorporate magnetic fields is encouraging in terms of the amount of nitrogen enrichment and its presence in stars near the zero-age main sequence.

scholarly journals Detection of rotational CO emission from the red-supergiants in the Large Magellanic Cloud

2015 ◽  
Vol 11 (A29B) ◽  
pp. 459-459
Author(s):  
Mikako Matsuura ◽  
B. Sargent ◽  
Bruce Swinyard ◽  
J.A. Yates ◽  
P. Royer ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Evolved Stars ◽  
Solar Metallicity ◽  
Red Supergiants ◽  
Low Metallicity ◽  
Co Emission ◽  
Loss Rates

AbstractIt is yet well understood how mass-loss rates from evolved stars depend on metallicities. With a half of the solar metallicity and the distance of only 50 kpc, the evolved stars of the Large Magellanic Cloud (LMC) are an ideal target for studying mass loss at low metallicity. We have obtained spectra of red-supergiants in the LMC, using the Hershel Space Observatory, detecting CO thermal lines fro J=6–5 up to 15–14 lines. Modelling CO lines with non-LTE Radiative transfer code suggests that CO lines intensities can be well explained with high gas-to-dust ratio, with no obvious reduction in mass-loss rate at the LMC. We conclude that the luminosities of the stars are primary factors on mass-loss rates, rather than the metallicity.

scholarly journals Physical parameters and chemical abundances of Planetary Nebulae in the large Magellanic Cloud

1997 ◽  
Vol 180 ◽  
pp. 471-471 ◽  
Author(s):  
R. E. Carlos Reyes ◽  
J. E. Steiner ◽  
F. Elizalde
Keyword(s):  
Planetary Nebulae ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Physical Parameters ◽  
Chemical Abundances ◽  
The Difference

In the present work we have computed the physical parameters and chemical abundances for 45 planetary nebulae (PN) in the Large Magellanic Cloud (LMC) using the photoionization code CLOUDY, developed by Ferland (1993). CLOUDY is used as a subroutine in the code DIANA, developed by Elizalde & Steiner (1996), which minimises indices that measures the difference between the calculated and real nebula.

Mixed-morphology supernova remnants: the case of SNR 0520–69.4 in the Large Magellanic Cloud

2020 ◽  
Vol 499 (3) ◽  
pp. 4213-4222
Author(s):  
I Ramírez-Ballinas ◽  
J Reyes-Iturbide ◽  
P Ambrocio-Cruz ◽  
R Gabbasov ◽  
M Rosado
Keyword(s):  
Supernova Remnants ◽  
Plasma Temperature ◽  
Optical Emission ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Physical Parameters ◽  
X Ray ◽  
Hot Plasma ◽  
Observatory Data ◽  
Fabry Perot

ABSTRACT We present observations in X-ray and optical emission of the supernova remnant (SNR) 0520–69.4 in the Large Magellanic Cloud. Using XMM–Newton observatory data, we produced images of the diffuse X-ray emission and spectra to obtain the X-ray parameters, such as luminosity and temperature, of hot plasma in the SNR. Diffuse X-ray emission with filled-centre morphology goes beyond the Hα region, suggesting that the hot gas escapes through the pores of the Hα shell. We fitted a model that has a plasma temperature of 1.1 × 107 K for an X-ray thermal luminosity of 3.3 × 1035 erg s−1. However, from Hα and [O iii] Fabry–Perot observations obtained with the Marseille Hα Survey of the Magellanic Clouds and the Milky Way at La Silla, European Southern Observatory, we are able to obtain physical parameters such as the velocity of the shock induced in the cloudlets emitting at optical wavelengths and the electron density of this gas. With the parameters described above, we test the model proposed by White & Long (1991, ApJ, 373, 543) for explaining the mixed-morphology observed.

scholarly journals A detailed non-LTE analysis of LB-1: Revised parameters and surface abundances

2020 ◽  
Vol 634 ◽  
pp. L7 ◽  
Author(s):  
S. Simón-Díaz ◽  
J. Maíz Apellániz ◽  
D. J. Lennon ◽  
J. I. González Hernández ◽  
C. Allende Prieto ◽  
...  
Keyword(s):  
Goodness Of Fit ◽  
Rotational Velocity ◽  
Stellar Atmosphere ◽  
Type Star ◽  
Evolutionary Status ◽  
Single Star ◽  
High Resolution Data ◽  
Star Evolution ◽  
Solar Metallicity ◽  
Massive Star Evolution

Context. It has recently been proposed that LB-1 is a binary system at 4 kpc consisting of a B-type star of 8 M⊙ and a massive stellar black hole (BH) of 70 M⊙. This finding challenges our current theories of massive star evolution and formation of BHs at solar metallicity. Aims. Our objective is to derive the effective temperature, surface gravity, and chemical composition of the B-type component in order to determine its nature and evolutionary status and, indirectly, to constrain the mass of the BH. Methods. We use the non-LTE stellar atmosphere code FASTWIND to analyze new and archival high-resolution data. Results. We determine (Teff, log g) values of (14 000 ± 500 K, 3.50 ± 0.15 dex) that, combined with the Gaia parallax, imply a spectroscopic mass, from log g, of 3.2+2.1−1.9 M⊙ and an evolutionary mass, assuming single star evolution, of 5.2+0.3−0.6 M⊙. We determine an upper limit of 8 km s−1 for the projected rotational velocity and derive the surface abundances; we find the star to have a silicon abundance below solar, and to be significantly enhanced in nitrogen and iron and depleted in carbon and magnesium. Complementary evidence derived from a photometric extinction analysis and Gaia yields similar results for Teff and log g and a consistent distance around 2 kpc. Conclusions. We propose that the B-type star is a slightly evolved main sequence star of 3–5 M⊙ with surface abundances reminiscent of diffusion in late B/A chemically peculiar stars with low rotational velocities. There is also evidence for CN-processed material in its atmosphere. These conclusions rely critically on the distance inferred from the Gaia parallax. The goodness of fit of the Gaia astrometry also favors a high-inclination orbit. If the orbit is edge-on and the B-type star has a mass of 3–5 M⊙, the mass of the dark companion would be 4–5 M⊙, which would be easier to explain with our current stellar evolutionary models.

scholarly journals Spectroscopy of Overluminous Cepheids in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 223-224
Author(s):  
Horace A. Smith ◽  
Leo Connolly
Keyword(s):  
Globular Cluster ◽  
Large Magellanic Cloud ◽  
Variable Stars ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Small Magellanic Cloud ◽  
Single Star ◽  
Rr Lyrae ◽  
Short Period ◽  
The Galaxy

The Small Magellanic Cloud is known to contain types of short period Cepheid variable stars not yet discovered in either the Large Magellanic Cloud or, with the exception of a single star, in the Galaxy. These variables can be divided into two categories: anomalous Cepheids and Wesselink-Shuttleworth (WS) stars. The former, which have also been found in dwarf spheroidal systems and in the globular cluster NGC 5466, have periods of 0.4–3 days, but average 0.7–1.0 mag. brighter than RR Lyrae and BL Her stars of equal period. The stars we call WS stars have periods less than about 1.1 day and, at MV = −1 to −2, are brighter than anomalous Cepheids of equal period.

scholarly journals Eclipsing Binaries in the Magellanic Clouds

2005 ◽  
Vol 13 ◽  
pp. 451-451
Author(s):  
Andrzej Udalski
Keyword(s):  
Gravitational Lensing ◽  
Direct Determination ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Eclipsing Binaries ◽  
Physical Parameters ◽  
Second Phase ◽  
Internet Archive ◽  
Pulsating Stars ◽  
Eclipsing Stars

We present results of a search for eclipsing binaries in the Magellanic Cloud fields covering central parts of these galaxies. The data were collected during the second phase of the Optical Gravitational Lensing Experiment survey (OGLE-II) in 1997-2000. In total, about 1500 and 3000 eclipsing stars were found in the Small and Large Magellanic Cloud, respectively (Udalski et al. 1998, Wyrzykowski et al. 2003). The photometric data of all objects are available to the astronomical community from the OGLE Internet archive (http://sirius.astrouw.edu.pl/~ogle/). OGLE-II data contain a full variety of classical eclipsing objects of all types: Algol EA-type, β-Lyr EB-type and W UMA EW-type stars. Large samples of stars allow to study in detail statistical properties of eclipsing objects. OGLE data also contain many very unusual eclipsing stars. Examples include eclipsing variable B-type stars (Mennickent et al. 2003), many spotted stars or eclipsing stars with a Cepheid as a component (Udalski et al. 1999). Recently three objects from the LMC revealing simultaneously RR Lyr and eclipsing binary type variability were discovered (Soszyński et al 2003). If the follow-up observations confirm that both components are physically bound and not optical blends these stars will provide a unique opportunity of direct determination of physical parameters of RR Lyr pulsating stars.

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 Stellar population of the superbubble N 206 in the LMC

2017 ◽  
Vol 609 ◽  
pp. A7 ◽  
Author(s):  
Varsha Ramachandran ◽  
R. Hainich ◽  
W.-R. Hamann ◽  
L. M. Oskinova ◽  
T. Shenar ◽  
...  
Keyword(s):  
Energy Input ◽  
Large Scale ◽  
Massive Stars ◽  
Mechanical Energy ◽  
Mass Loss Rate ◽  
Large Magellanic Cloud ◽  
High Mass ◽  
Clear Correlation ◽  
Physical Parameters ◽  
X Ray

Context. Massive stars severely influence their environment by their strong ionizing radiation and by the momentum and kinetic energy input provided by their stellar winds and supernovae. Quantitative analyses of massive stars are required to understand how their feedback creates and shapes large scale structures of the interstellar medium. The giant H ii region N 206 in the Large Magellanic Cloud contains an OB association that powers a superbubble filled with hot X-ray emitting gas, serving as an ideal laboratory in this context. Aims. We aim to estimate stellar and wind parameters of all OB stars in N 206 by means of quantitative spectroscopic analyses. In this first paper, we focus on the nine Of-type stars located in this region. We determine their ionizing flux and wind mechanical energy. The analysis of nitrogen abundances in our sample probes rotational mixing. Methods. We obtained optical spectra with the multi-object spectrograph FLAMES at the ESO-VLT. When possible, the optical spectroscopy was complemented by UV spectra from the HST, IUE, and FUSE archives. Detailed spectral classifications are presented for our sample Of-type stars. For the quantitative spectroscopic analysis we used the Potsdam Wolf-Rayet model atmosphere code. We determined the physical parameters and nitrogen abundances of our sample stars by fitting synthetic spectra to the observations. Results. The stellar and wind parameters of nine Of-type stars, which are largely derived from spectral analysis are used to construct wind momentum − luminosity relationship. We find that our sample follows a relation close to the theoretical prediction, assuming clumped winds. The most massive star in the N 206 association is an Of supergiant that has a very high mass-loss rate. Two objects in our sample reveal composite spectra, showing that the Of primaries have companions of late O subtype. All stars in our sample have an evolutionary age of less than 4 million yr, with the O2-type star being the youngest. All these stars show a systematic discrepancy between evolutionary and spectroscopic masses. All stars in our sample are nitrogen enriched. Nitrogen enrichment shows a clear correlation with increasing projected rotational velocities. Conclusions. The mechanical energy input from the Of stars alone is comparable to the energy stored in the N 206 superbubble as measured from the observed X-ray and Hα emission.

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