scholarly journals Resolving the dusty torus and the mystery surrounding LMC red supergiant WOH G64

2008 ◽  
Vol 4 (S256) ◽  
pp. 454-458
Author(s):  
Keiichi Ohnaka ◽  
Thomas Driebe ◽  
Karl-Heinz Hofmann ◽  
Gerd Weigelt ◽  
Markus Wittkowski
Keyword(s):  
Radiative Transfer ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Large Telescope ◽  
Previous Estimate ◽  
Long Baseline ◽  
Very Large Telescope ◽  
Radiative Transfer Modeling ◽  
Stellar Source ◽  
Dusty Torus

AbstractWe present mid-IR long-baseline interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud with MIDI at the ESO's Very Large Telescope Interferometer (VLTI). Our MIDI observations of WOH G64 are the first VLTI observations to spatially resolve an individual stellar source in an extragalactic system. Our 2-D radiative transfer modeling reveals the presence of a geometrically and optically thick torus seen nearly pole-on. This model brings WOH G64 in much better agreement with the current evolutionary tracks for a 25 M⊙ star — about a half of the previous estimate of 40 M⊙ — and solves the serious discrepancy between theory and observation which existed for this object.

scholarly journals Very Large Telescope Spectra of Carbon Stars in the Large Magellanic Cloud and Their Metallicity Dependence

2002 ◽  
Vol 580 (2) ◽  
pp. L133-L136 ◽  
Author(s):  
M. Matsuura ◽  
Albert A. Zijlstra ◽  
J. Th. van Loon ◽  
I. Yamamura ◽  
A. J. Markwick ◽  
...  
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Large Telescope ◽  
Carbon Stars ◽  
Very Large Telescope

scholarly journals Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud

2006 ◽  
Vol 447 (3) ◽  
pp. 971-989 ◽  
Author(s):  
J. Th. van Loon ◽  
J. R. Marshall ◽  
M. Cohen ◽  
M. Matsuura ◽  
P. R. Wood ◽  
...  
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Red Giants ◽  
Large Telescope ◽  
Very Large Telescope

scholarly journals Long Baseline Interferometric Observations of Circumstellar Dust Shells at 11 Microns

1994 ◽  
Vol 158 ◽  
pp. 383-386
Author(s):  
W.C. Danchi ◽  
L. Greenhill ◽  
M. Bester ◽  
C.G. Degiacomi ◽  
C.H. Townes ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Radiative Transfer ◽  
Circumstellar Dust ◽  
Dust Formation ◽  
Late Type ◽  
Dust Shells ◽  
Long Baseline ◽  
Higher Temperature ◽  
Single Baseline ◽  
Radiative Transfer Modeling

The spatial distribution of dust around a sample of well-known late-type stars has been studied with the Infrared Spatial Interferometer (ISI) located at Mt. Wilson. Currently operating with a single baseline as a heterodyne interferometer at 11.15 μm, the ISI has obtained visibility curves of these stars. Radiative transfer modeling of the visibility curves has yielded estimates of the inner radii of the dust shells, the optical depth at 11 μm, and the temperature of the dust at the inner radii. For stars in which the dust is resolved, estimates of the stellar diameter and temperature can also be made. Broadly speaking two classes of stars have been found. One class has inner radii of their dust shells very close to the photospheres of the stars themselves (3–5 stellar radii) and at a higher temperature (~ 1200 K) than previously measured. This class includes VY CMa, NML Tau, IRC +10216, and o Ceti. For the latter two the visibility curves change with the luminosity phase of the star and new dust appears to form at still smaller radii during minimum luminosity. The second class of stars has dust shells with substantially larger inner radii and very little dust close to the stars, and includes α Ori, α Sco, α Her, R Leo, and χ Cyg. This indicates sporadic production of dust and no dust formation within the last several decades.

The MAGIC project – II. Discovery of two new Galactic lithium-rich Cepheids

2019 ◽  
Vol 488 (3) ◽  
pp. 3211-3221
Author(s):  
V Kovtyukh ◽  
B Lemasle ◽  
A Kniazev ◽  
L Berdnikov ◽  
G Bono ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Mixed Mode ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Large Telescope ◽  
Instability Strip ◽  
Red Giant ◽  
First Time

Abstract We report the discovery of two new lithium-rich Cepheids in the Milky Way (A(Li) ≈ 2.9 dex) among the targets of the MAGIC spectroscopic survey with the Southern African Large Telescope spectrographs. The 6707 Å Li feature is usually not detectable in the atmosphere of Cepheids. Only three Cepheids (two in the Milky Way and one in the Large Magellanic Cloud) had been reported so far with high lithium abundances. We examine the possibility that the Li-rich Cepheids are evolving towards the red giant branch, crossing the instability strip for the first time, as well as other possible scenarios. The two stars are mixed-mode Cepheids pulsating simultaneously in the first and in the second overtone modes. We briefly discuss the possible connection between their unusual chemical composition and their pulsational properties.

scholarly journals Magellanic Diffuse Interstellar Bands and Carbon Chemistry

2005 ◽  
Vol 13 ◽  
pp. 864-866
Author(s):  
P. Ehrenfreund ◽  
N. Cox ◽  
J. Cami ◽  
B.H. Foing ◽  
L. Kaper ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Echelle Spectrograph ◽  
Diffuse Interstellar Bands ◽  
Very Large Telescope ◽  
External Galaxies ◽  
Low Metallicity ◽  
Carbon Molecules

AbstractWith the Ultraviolet Visual Echelle Spectrograph mounted at the Very Large Telescope, we have observed at unprecedented spectral resolution the absorption spectrum toward reddened stars in the Magellanic Clouds over the wavelength range of 3500-10500 Å. This range covers the strong transitions associated with neutral and charged large carbon molecules of varying sizes and structures. We report the first detection of diffuse interstellar bands (DIBs) at 5780 and 5797 Å in the Small Magellanic Cloud and the variation of those DIBs toward several targets in the Large Magellanic Cloud. The variation of DIBs in the Magellanic Clouds compared with Galactic targets may be governed by a combination of the different chemical processes prevailing in low-metallicity regions and the local environmental conditions. The analysis of high-resolution absorption spectra allows us to reveal the global effects in the chemistry and recycling of cosmic dust in the Magellanic Clouds which are relevant for the chemical pathways forming large organic molecules in external galaxies.

scholarly journals Interferometric Observations of η Carinae - the VLTI Takes Its First Glimpse at the Central Source

2002 ◽  
Vol 187 ◽  
pp. 99-105 ◽  
Author(s):  
P. Kervella ◽  
M. Schöller ◽  
R. van Boekel ◽  
E. di Folco ◽  
S. Correia ◽  
...  
Keyword(s):  
Data Analysis ◽  
Large Telescope ◽  
Central Source ◽  
Long Baseline ◽  
Interferometric Measurement ◽  
Very Large Telescope ◽  
The Future ◽  
Luminous Blue Variable

AbstractWe describe the first long-baseline interferometric measurement ever made of the luminous blue variable η Carinae. η Car was observed with the Very Large Telescope Interferometer (VLTI) with the 8.2 m Unit Telescopes as well as with the 40 cm test siderostats on three different baselines. We will detail the measurements and data analysis and discuss briefly the implications of the derived visibility on the morphology of the central source. Furthermore we will discuss the future possibilities of interferometric observations and will show that η Car is one of the prime candidates for imaging with the VLTI.

scholarly journals Water alteration on (42355) Typhon?

2009 ◽  
Vol 5 (S263) ◽  
pp. 197-200
Author(s):  
Alvaro Alvarez-Candal ◽  
Maria Antonietta Barucci
Keyword(s):  
Radiative Transfer ◽  
Spectral Range ◽  
Surface Composition ◽  
Parent Body ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Large Telescope ◽  
Aqueous Alteration ◽  
Very Large Telescope ◽  
Visible Spectra

AbstractThe visible spectra of (42355) Typhon showed evidence for aqueously altered materials. Therefore we seek to understand if such an event is possible.We use data from the ESO/Very Large Telescope together with the Hapke Hapke radiative transfer model to interpret the surface composition of (42355) Typhon over the whole spectral range (~0.5 − 2.4 μm).Our results points that (42355) Typhon could be a fragment from a larger parent body that suffered aqueous alteration.

scholarly journals Spatially resolved dusty torus toward the red supergiant WOH G64 in the Large Magellanic Cloud

2008 ◽  
Vol 484 (2) ◽  
pp. 371-379 ◽  
Author(s):  
K. Ohnaka ◽  
T. Driebe ◽  
K.-H. Hofmann ◽  
G. Weigelt ◽  
M. Wittkowski
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Spatially Resolved ◽  
Dusty Torus

scholarly journals VLT/X-shooter spectroscopy of massive young stellar objects in the 30 Doradus region of the Large Magellanic Cloud

2020 ◽  
Vol 636 ◽  
pp. A54 ◽  
Author(s):  
M. L. van Gelder ◽  
L. Kaper ◽  
J. Japelj ◽  
M. C. Ramírez-Tannus ◽  
L. E. Ellerbroek ◽  
...  
Keyword(s):  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Young Stellar Objects ◽  
Clear Correlation ◽  
Infrared Excess ◽  
Stellar Objects ◽  
Very Large Telescope ◽  
Circumstellar Extinction ◽  
30 Doradus

The process of massive star (M ≥ 8 M⊙) formation is still poorly understood. Observations of massive young stellar objects (MYSOs) are challenging due to their rarity, short formation timescale, large distances, and high circumstellar extinction. Here, we present the results of a spectroscopic analysis of a population of MYSOs in the Large Magellanic Cloud. We took advantage of the spectral resolution and wavelength coverage of X-shooter (300−2500 nm), which is mounted on the European Southern Observatory Very Large Telescope, to detect characteristic spectral features in a dozen MYSO candidates near 30 Doradus, the largest starburst region in the Local Group hosting the most massive stars known. The X-shooter spectra are strongly contaminated by nebular emission. We used a scaling method to subtract the nebular contamination from our objects. We detect Hα, β, [O I] 630.0 nm, Ca II, infrared triplet [Fe II] 1643.5 nm, fluorescent Fe II 1687.8 nm, H2 2121.8 nm, Brγ, and CO bandhead emission in the spectra of multiple candidates. This leads to the spectroscopic confirmation of ten candidates as bona fide MYSOs. We compared our observations with photometric observations from the literature and find all MYSOs to have a strong near-infrared excess. We computed lower limits to the brightness and luminosity of the MYSO candidates, confirming the near-infrared excess and the massive nature of the objects. No clear correlation is seen between the Brγ luminosity and metallicity. Combining our sample with other LMC samples results in a combined detection rate of disk features, such as fluorescent Fe II and CO bandheads, which is consistent with the Galactic rate (40%). Most of our MYSOs show outflow features.

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