scholarly journals Problems in abundance determination from UV spectra of hot supergiants

2009 ◽  
Vol 5 (S265) ◽  
pp. 211-212
Author(s):  
M. Sarta Deković ◽  
D. Kotnik-Karuza ◽  
T. Jurkić ◽  
D. Dominis Prester
Keyword(s):  
High Resolution ◽  
Massive Stars ◽  
Uv Spectra ◽  
Parallel Model ◽  
Synthetic Spectra ◽  
Abundance Determination

AbstractWe present measurements of equivalent widths of the UV, presumably photospheric lines: C III 1247 Å, N III 1748 Å, N III 1752 Å, N IV 1718 Å and He II 1640 Å in high-resolution IUE spectra of 24 galactic OB supergiants. Equivalent widths measured from the observed spectra have been compared with their counterparts in the Tlusty NLTE synthetic spectra. We discuss possibilities of static plan-parallel model to reproduce observed UV spectra of hot massive stars and possible reasons why observations differ from the model so much.

scholarly journals The UVMag space project: UV and visible spectropolarimetry of massive stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 389-390
Author(s):  
Coralie Neiner ◽  
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Massive Stars ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Medium Size ◽  
Space Project ◽  
First Time ◽  
The Magnetic Field ◽  
Circumstellar Environment

AbstractUVMag is a medium-size space telescope equipped with a high-resolution spectropolarimetrer working in the UV and visible domains. It will be proposed to ESA for a future M mission. It will allow scientists to study all types of stars as well as e.g. exoplanets and the interstellar medium. It will be particularly useful for massive stars, since their spectral energy distribution peaks in the UV. UVMag will allow us to study massive stars and their circumstellar environment (in particular the stellar wind) spectroscopically in great details. Moreover, with UVMag's polarimetric capabilities we will be able, for the first time, to measure the magnetic field of massive stars simultaneously at the stellar surface and in the wind lines, i.e. to completely map their magnetosphere.

scholarly journals Synthetic spectra of young starbursts: exploring the metallicity dependence

1999 ◽  
Vol 193 ◽  
pp. 485-486
Author(s):  
A. de Koter ◽  
S.R. Heap ◽  
D.J. Hillier ◽  
D. I. Hubeny
Keyword(s):  
Uv Spectra ◽  
Initial Mass ◽  
Stellar Winds ◽  
Synthetic Spectra ◽  
First Results

We present first results of fully synthetic UV spectra of young starbursts. With this we mean that the spectra used to model the OB and WN stars result from unified non-LTE model atmospheres, in which stellar winds are accounted for. An important aim of this project is to construct meaningful models for young starbursts at low metallicities. We discuss the presence of He II emission as a function of maximum initial mass and age of the burst.

The Line of Sight of ϵ Canis Majoris: Depletion and Extent of the Local Cloud

1997 ◽  
Vol 166 ◽  
pp. 161-164
Author(s):  
Cécile Gry ◽  
Olivier Dupin
Keyword(s):  
High Resolution ◽  
Column Density ◽  
Uv Spectra ◽  
Line Of Sight ◽  
Gas Density ◽  
Neutral Gas ◽  
Local Cloud

AbstractWith new high resolution UV spectra of ϵ CMa we show that the gas column density in this sight-line is less than 4 1017 cm−2, that the neutral gas density is less than 10−5 cm−3 after the first 3 parsecs, and that the Local Cloud seems to be almost undepleted and to extend to no more than 0.6 pc in this direction.

scholarly journals Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies

2019 ◽  
Vol 488 (3) ◽  
pp. 3492-3506 ◽  
Author(s):  
Peter Senchyna ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot ◽  
Tucker Jones ◽  
...  
Keyword(s):  
Massive Stars ◽  
High Redshift ◽  
Formation Rate ◽  
Uv Spectra ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
High Ionization ◽  
Moderate Resolution ◽  
Low Metallicity ◽  
Nearby Galaxies

Abstract Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 ($\rm W_{C\, {\scriptscriptstyle IV},0}{} \gtrsim 20$ Å) are uniformly stronger than observed locally ($\rm W_{C\, {\scriptscriptstyle IV},0}{} \lesssim 2$ Å), likely due to the relatively high metallicities (Z/Z$\odot$ > 0.1) typically probed by UV surveys of nearby galaxies. We present new HST/COS spectra of six nearby (z < 0.01) extremely metal-poor galaxies (XMPs, Z/Z$\odot$ ≲ 0.1) targeted to address this limitation and provide constraints on the highly uncertain ionizing spectra powered by low-metallicity massive stars. Our data reveal a range of spectral features, including one of the most prominent nebular C iv doublets yet observed in local star-forming systems and strong He ii emission. Using all published UV observations of local XMPs to date, we find that nebular C iv emission is ubiquitous in very high specific star formation rate systems at low metallicity, but still find equivalent widths smaller than those measured in individual lensed systems at z > 6. Our moderate-resolution HST/COS data allow us to conduct an analysis of the stellar winds in a local nebular C iv emitter, which suggests that some of the tension with z > 6 data may be due to existing local samples not yet probing sufficiently high α/Fe abundance ratios. Our results indicate that C iv emission can play a crucial role in the JWST and ELT era by acting as an accessible signpost of very low metallicity (Z/Z$\odot$ < 0.1) massive stars in assembling reionization-era systems.

scholarly journals Exploring Abundance and Isotope Anomalies in CP Stars with the HST/GHRS: High Resolution UV Spectroscopy of χ Lupi

1993 ◽  
Vol 138 ◽  
pp. 42-59 ◽  
Author(s):  
David S. Leckrone ◽  
Glenn M. Wahlgren ◽  
Sveneric G. Johansson ◽  
Saul J. Adelman
Keyword(s):  
High Resolution ◽  
Uv Spectroscopy ◽  
Uv Spectra ◽  
Heavy Elements

AbstractWe are using the HST/GHRS in a long-term program to obtain UV spectra of unprecedented resolution and precision for bright, ultra-sharp-lined Bp (HgMn) stars and comparable normal stars. To date we have doubled the number of heavy elements for which abundances may be estimated in χ Lupi, and have obtained the first observations of Hg III lines with which to test diffusion scenarios for its extreme Hg isotope anomaly.

scholarly journals Star Formation in Infrared Bright and Infrared Faint Starburst Interacting Galaxies

1990 ◽  
Vol 124 ◽  
pp. 303-308
Author(s):  
Susan A. Lamb ◽  
Howard A. Bushouse ◽  
John W. Towns
Keyword(s):  
Star Formation ◽  
Short Wavelength ◽  
Massive Star ◽  
Massive Stars ◽  
Uv Spectra ◽  
Interacting Galaxies ◽  
Spectral Diagnostics ◽  
Central Regions ◽  
Spectrum Synthesis ◽  
Star Formation Histories

AbstractShort wavelength IUE spectra of Arp 248b and UGC 8315N are combined with optical spectra and interpreted using a combination of spectrum synthesis and spectral diagnostics to place constraints on the massive star populations of the central regions of these galaxies and to deduce information about the star formation histories in the last 108 years. We find that both galaxies have substantial fractions of their optical light coming from massive stars and that Arp 248b may be dominated in the UV by WR stars. The UV spectra are dominated by radiation from evolved massive stars and we place an age on the burst in Arp 248b of a few tens of millions of years.

scholarly journals The Structure of the Envelopes of Symbiotic Novae

1990 ◽  
Vol 122 ◽  
pp. 431-432
Author(s):  
G.B. Baratta ◽  
A. Damineli Neto ◽  
C. Rossi ◽  
R. Viotti
Keyword(s):  
High Resolution ◽  
Uv Spectra ◽  
Emission Lines ◽  
Broad Line ◽  
Line Profiles ◽  
Composite Spectrum ◽  
Multiple Structure ◽  
Broad Emission ◽  
Light History

Symbiotic novae are composite spectrum stars whose light history is characterized by one single major outburst. At high resolution their optical and UV spectra are very rich of emission lines belonging to a wide ionization range. Generally one can identify both narrow and broad line systems. The latter includes emission lines with multiple structure, broad emission wings, WR features, and P Cygnl lines. Frequently the broad line profiles are largely variable with time. They should be associated with the major stellar outburst. An overview of the problem with extensive references can be found in Viotti (1989).

scholarly journals The MiMeS project: overview and current status

2010 ◽  
Vol 6 (S272) ◽  
pp. 118-123 ◽  
Author(s):  
Gregg A. Wade ◽  
Evelyne Alecian ◽  
David A. Bohlender ◽  
Jean-Claude Bouret ◽  
David H. Cohen ◽  
...  
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Data Modeling ◽  
Current Status ◽  
Individual Stars ◽  
Related Theory ◽  
The Status ◽  
Very High

AbstractThe Magnetism in Massive Stars (MiMeS) Project is a consensus collaboration among many of the foremost international researchers of the physics of hot, massive stars, with the basic aim of understanding the origin, evolution and impact of magnetic fields in these objects. At the time of writing, MiMeS Large Programs have acquired over 950 high-resolution polarised spectra of about 150 individual stars with spectral types from B5-O4, discovering new magnetic fields in a dozen hot, massive stars. The quality of this spectral and magnetic matériel is very high, and the Collaboration is keen to connect with colleagues capable of exploiting the data in new or unforeseen ways. In this paper we review the structure of the MiMeS observing programs and report the status of observations, data modeling and development of related theory.

Sign in / Sign up

Export Citation Format

Share Document