Revised Stellar Temperatures for Magellanic Cloud O Supergiants fromFar Ultraviolet Spectroscopic Explorerand Very Large Telescope UV‐Visual Echelle Spectrograph Spectroscopy

2002 ◽  
Vol 579 (2) ◽  
pp. 774-799 ◽  
Author(s):  
P. A. Crowther ◽  
D. J. Hillier ◽  
C. J. Evans ◽  
A. W. Fullerton ◽  
O. De Marco ◽  
...  
Keyword(s):  
Magellanic Cloud ◽  
Large Telescope ◽  
Echelle Spectrograph ◽  
Very Large Telescope ◽  
Stellar Temperatures

scholarly journals Physical conditions and chemical abundances in PN M 2-36. Results from deep echelle observations

2021 ◽  
Author(s):  
José N Espíritu ◽  
Antonio Peimbert
Keyword(s):  
Chemical Structure ◽  
Ultra Violet ◽  
Emission Lines ◽  
High Spectral Resolution ◽  
Large Telescope ◽  
Echelle Spectrograph ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Very Large Telescope ◽  
Physical And Chemical

Abstract We present a spectrum of the planetary nebula M 2-36 obtained using the Ultra Violet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT). 446 emission lines are detected. We perform an analysis of the chemical composition using multiple electron temperature (Te) and density (ne) diagnostics. Te and ne are computed using a variety of methods, including collisionally excited line (CEL) ratios, O++ optical recombination lines (ORLs), and measuring the intensity of the Balmer jump. Besides the classical CEL abundances, we also present robust ionic abundances from ORLs of heavy elements. From CELs and ORLs of O++, we obtain a new value for the Abundance Discrepancy Factor (ADF) of this nebula, being ADF(O++) = 6.76 ± 0.50. From all the different line ratios that we study, we find that the object cannot be chemically homogeneous; moreover, we find that two-phased photoionization models are unable to simultaneously reproduce critical ${\rm O\, \small {II}}$ and [${\rm O\, \small {III}}$] line ratios. However, we find a three-phased model able to adequately reproduce such ratios. While we consider this to be a toy model, it is able to reproduce the observed temperature and density line diagnostics. Our analysis shows that it is important to study high ADF PNe with high spectral resolution, since its physical and chemical structure may be more complicated than previously thought.

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 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 The possible disappearance of a massive star in the low-metallicity galaxy PHL 293B

2020 ◽  
Vol 496 (2) ◽  
pp. 1902-1908 ◽  
Author(s):  
Andrew P Allan ◽  
Jose H Groh ◽  
Andrea Mehner ◽  
Nathan Smith ◽  
Ioana Boian ◽  
...  
Keyword(s):  
Massive Star ◽  
Hubble Space Telescope ◽  
Mass Loss Rate ◽  
Spectroscopic Observation ◽  
Echelle Spectrograph ◽  
Massive Black Hole ◽  
Very Large Telescope ◽  
Low Metallicity ◽  
Stellar Temperatures ◽  
Stellar Properties

ABSTRACT We investigate a suspected very massive star in one of the most metal-poor dwarf galaxies, PHL 293B. Excitingly, we find the sudden disappearance of the stellar signatures from our 2019 spectra, in particular the broad H lines with P Cygni profiles that have been associated with a massive luminous blue variable (LBV) star. Such features are absent from our spectra obtained in 2019 with the Echelle Spectrograph for Rocky Exoplanet- and Stable Spectroscopic Observation and X-shooter instruments of the European Southern Observatory’s Very Large Telescope. We compute radiative transfer models using cmfgen, which fit the observed spectrum of the LBV and are consistent with ground-based and archival Hubble Space Telescope photometry. Our models show that during 2001–2011, the LBV had a luminosity L* = 2.5–3.5 × 106 L⊙, a mass-loss rate $\dot{M} = 0.005{-}0.020 ~{\rm M}_{\odot }$ yr−1, a wind velocity of 1000 km s−1, and effective and stellar temperatures of Teff = 6000–6800 and T* = 9500–15 000 K. These stellar properties indicate an eruptive state. We consider two main hypotheses for the absence of the broad emission components from the spectra obtained since 2011. One possibility is that we are seeing the end of an LBV eruption of a surviving star, with a mild drop in luminosity, a shift to hotter effective temperatures, and some dust obscuration. Alternatively, the LBV could have collapsed to a massive black hole without the production of a bright supernova.

scholarly journals Exoplanet atmospheres at high spectral resolution: A CRIRES survey of hot-Jupiters

2010 ◽  
Vol 6 (S276) ◽  
pp. 208-211
Author(s):  
Ignas Snellen ◽  
Remco de Kok ◽  
Ernst de Mooij ◽  
Matteo Brogi ◽  
Bas Nefs ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
Mass Composition ◽  
Large Telescope ◽  
Test Bed ◽  
Echelle Spectrograph ◽  
Hot Jupiters ◽  
Transiting Planets ◽  
Very Large Telescope

AbstractRecently, we presented the detection of carbon monoxide in the transmission spectrum of extrasolar planet HD209458b, using CRIRES, the Cryogenic high-resolution Infrared Echelle Spectrograph at ESO's Very Large Telescope (VLT). The high spectral resolution observations (R=100,000) provide a wealth of information on the planet's orbit, mass, composition, and even on its atmospheric dynamics. The new observational strategy and data analysis techniques open up a whole world of opportunities. We therefore started an ESO large program using CRIRES to explore these, targeting both transiting and non-transiting planets in carbon monoxide, water vapour, and methane. Observations of the latter molecule will also serve as a test-bed for METIS, the proposed mid-infrared imager and spectrograph for the European Extremely Large Telescope.

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 First detection of the O III 495.8911 and 500.6843 nm lines in the Earth's upper atmosphere

2011 ◽  
Vol 29 (12) ◽  
pp. 2235-2238 ◽  
Author(s):  
O. Witasse ◽  
T. Slanger ◽  
R. Thissen
Keyword(s):  
Atomic Oxygen ◽  
The State ◽  
Upper Atmosphere ◽  
Emission Lines ◽  
Large Telescope ◽  
Echelle Spectrograph ◽  
Very Large Telescope ◽  
Doubly Charged

Abstract. We report the first detection of two emission lines of the atomic oxygen doubly-charged ion at 495.8911 and 500.6843 nm in the terrestrial upper atmosphere. They correspond to the transitions 1D2-3P1 and 1D2-3P2 of the O++ ion, respectively. The measurements were performed on 30 October 2003 during the "Halloween" storms, with the Ultraviolet and Visual Echelle Spectrograph (UVES) mounted on the Very Large Telescope (VLT) in Chile. The intensities of these emissions are ~70 mRayleigh, and ~260 mRayleigh, respectively. These emissions constitute a new diagnostic of the state of the ionosphere.

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 Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph and FORS2 spectroscopy of the GRB 081008 afterglow★

2011 ◽  
Vol 418 (1) ◽  
pp. 680-690 ◽  
Author(s):  
V. D’Elia ◽  
S. Campana ◽  
S. Covino ◽  
P. D’Avanzo ◽  
S. Piranomonte ◽  
...  
Keyword(s):  
Large Telescope ◽  
Echelle Spectrograph ◽  
Very Large Telescope
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