scholarly journals FeII in the UV Spectrum of Luminous Emission Line Stars

1986 ◽  
Vol 116 ◽  
pp. 275-276
Author(s):  
G. Muratorio ◽  
M. Friedjung ◽  
R. Viotti
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
High Velocity ◽  
Previous Analysis ◽  
Magellanic Clouds ◽  
Absorption Lines ◽  
High Dispersion ◽  
Uv Spectrum ◽  
Loss Rates

Following the excessive mass loss rates we derived in a previous analysis of the FeII emission and absorption lines of some luminous Magellanic Clouds stars, assuming the two components formed in the same region (Muratorio et al., 1984), we again analysed the FeII data using the same method (Muratorio, 1985), but taking into account the presence of high velocity winds detected in some stars (R66, R126) by the study of the high dispersion IUE spectra (Stahl et al., 1983; Zickgraf et al., 1985).

scholarly journals High-Dispersion Spectroscopy of the Brightest Emission-Line Stars of the Magellanic Clouds

1986 ◽  
Vol 116 ◽  
pp. 247-248 ◽  
Author(s):  
O. Stahl ◽  
B. Wolf ◽  
M. de Groot ◽  
C. Leitherer
Keyword(s):  
Emission Line ◽  
Wavelength Range ◽  
Spectral Resolution ◽  
Magellanic Clouds ◽  
High Dispersion

We present an atlas of high dispersion spectra of 24 of the brightest peculiar emission-line stars of the Magellanic Clouds.Our spectra cover the wavelength range from 3600 to 4900 Å. They have been obtained from 1970 to 1984 with the coudé spectrograph of the ESO 1.52 m telescope at La Silla, Chile. The spectral resolution is 0.4 Å for most of the spectra and 0.2 Å for the very brightest stars. Up to 11 spectra are available for one star. In addition, we have done UBVRIJHK(LM) photometry at several epochs of all stars of our sample.

scholarly journals Spectroscopic studies of OB stars in the Magellanic Clouds with VLT-UVES

2003 ◽  
Vol 212 ◽  
pp. 176-177
Author(s):  
Christopher J. Evans ◽  
Paul A. Crowther ◽  
Alexander W. Fullerton ◽  
D. John Hillier
Keyword(s):  
Mass Loss ◽  
Model Atmosphere ◽  
Spectroscopic Studies ◽  
Magellanic Clouds ◽  
Ob Stars ◽  
Plane Parallel ◽  
Parallel Models ◽  
Cno Abundances ◽  
Loss Rates

We present results from optical and ultraviolet analysis of nine LMC/SMC supergiants. Temperatures, mass-loss rates and CNO abundances are obtained using the non-LTE, line-blanketed model atmosphere code of Hillier & Miller (1998). In general, the derived temperatures are significantly lower than those determined from unblanketed, plane-parallel models.

scholarly journals Evidence for Mass Loss at Polar Latitudes in ω Ori and 66 Oph

1982 ◽  
Vol 98 ◽  
pp. 401-404
Author(s):  
Geraldine J. Peters
Keyword(s):  
Mass Loss ◽  
High Velocity ◽  
Be Stars ◽  
Loss Rates

IUE observations of the “pole-on” Be stars ω Ori and 66 Oph have revealed the unexpected presence of high velocity (v ≃ −750 km s−1), relatively narrow (Δλ ≃ 1A) absorption components in the resonance lines of C IV, Si III, and Si IV. The C IV features show structure indicative of multiple shells or clouds. Similar high velocity lines were not observed in other pole-on Be stars considered in the program. The nature of these unusual features and the column densities and mass loss rates implied by them are discussed in this paper.

scholarly journals Luminosities and mass-loss rates of carbon stars in the Magellanic Clouds

2007 ◽  
Vol 376 (1) ◽  
pp. 313-337 ◽  
Author(s):  
M. A. T. Groenewegen ◽  
P. R. Wood ◽  
G. C. Sloan ◽  
J. A. D. L. Blommaert ◽  
M.-R. L. Cioni ◽  
...  
Keyword(s):  
Mass Loss ◽  
Magellanic Clouds ◽  
Carbon Stars ◽  
Loss Rates

scholarly journals Evolution of 1–5 Mm⊙ Stars by Mass Loss

1993 ◽  
Vol 155 ◽  
pp. 478-478
Author(s):  
E. Vassiliadis ◽  
P.R. Wood
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Pulsation Period ◽  
Agb Stars ◽  
Loss Formula ◽  
Loss Rates

Stars of mass 1–5 MM⊙ and composition Y=0.25 and Z=0.016 have been evolved from the main-sequence to the white dwarf stage with an empirical mass loss formula based on observations of mass loss rates in AGB stars. This mass loss formula (Wood 1990) causes the mass loss rate to rise exponentially with pulsation period on the AGB until superwind rates are achieved, where these rates correspond to radiation pressure driven mass loss rates. The formula was designed to reproduce the maximum periods observed for optically-visible LPVs and it also reproduces extremely well the maximum AGB luminosities observed in star clusters in the Magellanic Clouds (see Vassiliadis and Wood 1992 for details).

scholarly journals Long Period Variables in the Magellanic Clouds and the Galaxy

1993 ◽  
Vol 139 ◽  
pp. 192-200 ◽  
Author(s):  
S.M.G. Hughes
Keyword(s):  
Mass Loss ◽  
Galactic Disk ◽  
Magellanic Clouds ◽  
Pulsation Mode ◽  
Long Period ◽  
Long Period Variables ◽  
The Galaxy ◽  
Loss Rates

AbstractNew results (∼last two years) on mainly observational properties of Long Period Variables (LPVs) in the Magellanic Clouds and the Galaxy are reviewed. These properties include the effects of metallicity variations on their mass loss rates, the use of AGB LPVs to map the stellar distributions of the Galactic disk and bulge, and using detailed observations of nearby Miras to investigate their structure and to obtain new parallax distances, with implications for the pulsation mode of Miras.

scholarly journals Wolf-Rayet stars in I Zw 18

1999 ◽  
Vol 193 ◽  
pp. 606-607
Author(s):  
Francoid Legrand ◽  
Daniel Kunth ◽  
Jean-René Roy ◽  
J. Miguel Mas-Hesse ◽  
Jeremy R. Walsh
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
High Mass ◽  
Starburst Galaxy ◽  
Individual Stars ◽  
Binary Channel ◽  
High Mass Loss ◽  
Low Metallicity ◽  
Loss Rates ◽  
Integrated Luminosity

Wolf-Rayet stars have been detected in the NW region of the metal–poor starburst galaxy I Zw 18. The integrated luminosity and FWHM of the bumps at 4650 Å and 5808 Å are consistent with the presence of a few individual stars of WC4 or WC5 type. The unexpected presence of WC stars in such a low-metallicity galaxy could, however, be explained by high mass loss rates, or alternatively favor a binary channel for WR formation. WC stars could also account for the strong and narrow He II 4686Å emission line which peaks co-spatially with the WR bump emission (see Schaerer 1996).

scholarly journals Swift UVOT near-UV transit observations of WASP-121 b

2019 ◽  
Vol 623 ◽  
pp. A57 ◽  
Author(s):  
M. Salz ◽  
P. C. Schneider ◽  
L. Fossati ◽  
S. Czesla ◽  
K. France ◽  
...  
Keyword(s):  
Mass Loss ◽  
Spectral Range ◽  
Relative Accuracy ◽  
Uv Absorption ◽  
Absorption Lines ◽  
Optical Telescope ◽  
Hot Jupiters ◽  
Excess Absorption ◽  
Loss Rates ◽  
Gas Planets

Close-in gas planets are subject to continuous photoevaporation that can erode their volatile envelopes. Today, ongoing mass loss has been confirmed in a few individual systems via transit observations in the ultraviolet spectral range. We demonstrate that the Ultraviolet/Optical Telescope (UVOT) onboard the Neil Gehrels Swift Observatory enables photometry to a relative accuracy of about 0.5% and present the first near-UV (200–270 nm, NUV) transit observations of WASP-121 b, a hot Jupiter with one of the highest predicted mass-loss rates. The data cover the orbital phases 0.85–1.15 with three visits. We measure a broadband NUV transit depth of 2.10 ± 0.29%. While still consistent with the optical value of 1.55%, the NUV data indicate excess absorption of 0.55% at a 1.9σ level. Such excess absorption is known from the WASP-12 system, and both of these hot Jupiters are expected to undergo mass loss at extremely high rates. With a Cloudy simulation, we show that absorption lines of Fe II in a dense extended atmosphere can cause broadband near-UV absorption at the 0.5% level. Given the numerous lines of low-ionization metals, the NUV range is a promising tracer of photoevaporation in the hottest gas planets.

scholarly journals Mass Loss from Carbon Stars: Circumstellar C2 Swan Band

2003 ◽  
Vol 209 ◽  
pp. 69-70
Author(s):  
Rie Kimata ◽  
Hideyuki Izumiura
Keyword(s):  
Mass Loss ◽  
Absorption Lines ◽  
High Dispersion ◽  
Circumstellar Envelope ◽  
Carbon Stars ◽  
Echelle Spectrograph ◽  
Innermost Part ◽  
Band Absorption ◽  
Swan Band

We have searched 44 optical carbon stars for circumstellar C2 Swan (0,0) band absorption lines using the high dispersion echelle spectrograph for the 188 cm reflector at Okayama Astrophysical Observatory. We have detected the circumsteller C2 lines definitely in 18 stars, possibly in 6 stars, and not detected in 20 stars. We discuss the observed properties of the circumstellar C2 lines. We infer the C2 line-forming region is located at the innermost part of the circumstellar envelope.

scholarly journals Cool Star Winds – Recent Observations and Theoretical Implications

1983 ◽  
Vol 6 ◽  
pp. 549-563 ◽  
Author(s):  
L. Hartmann
Keyword(s):  
Mass Loss ◽  
Absorption Lines ◽  
Late Type ◽  
Cool Star ◽  
Circumstellar Shells ◽  
Loss Rates ◽  
Loss Mechanisms

Much of our knowledge of winds from late-type stars comes from the detection of ejected material, called circumstellar shells, as observed in absorption lines of low-excitation species such as Mg II, Ca II, Na I, and K I (cf. Reimers 1977). Observations of CS shells are difficult to translate into quantitative mass loss rates, a limitation which has not helped to test various mass loss mechanisms. The data clearly demonstrate one very important fact: shell velocities are very low. In fact, they are so much lower than surface escape velocitiesthat it was not clear that material is actually being lost until Deutsch (1956) detected the existence of the CS absorption shells ejected from α Her and α Sco in the spectra of distant companion stars. Today it is possible to demonstrate the expansion of shells out to several thousand stellar radii in K I scattering (Honeycutt et al. 1980).

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