Ultraviolet spectral morphology of the O stars - The remarkable luminosity dependence of the SI IV stellar wind effect

Walborn, N. R.; Panek, R. J.

doi:10.1086/184262

Cited by 50 publications

(33 citation statements)

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“…We measured the terminal velocity of the C iii] P-Cygni profile (shown in Figure 4) to be about 1700 km s −1 , consistent with a T eff = 20-40 kK (Kudritzki & Puls 2000). In contrast with these features, Walborn & Panek (1984) show that O stars of The expected contribution from IRS 1 is shown below, accounting for at least a third of the flux in the trough of the P-Cygni profile. These data have been binned to 20 pixels (0.2 Å).…”

Section: Discussionsupporting

confidence: 56%

Cosmic Origins Spectrograph Observations of NGC 2024: An Indirect View Into the Heart of the Flame

Burgh

France

Snow

2012

ApJ

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As part of a program to study translucent interstellar clouds, NGC 2024 IRS 1 was observed by the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope. IRS 1 is a heavily reddened B0.5 V star (E(B − V ) = 1.69, R V = 4.5, and A V = 7.61) lying outside the core of the NGC 2024 cluster and not considered to be the ionizing source of the nebula. At wavelengths below about 1300 Å, the observed spectrum deviates from that expected of a reddened B star, showing an increase in flux to shorter wavelengths and the presence of P-Cygni profiles in both the C iii] λ1176 and N v λ1240 lines. Because of the presence of these lines, the absence of any P-Cygni signature in the Si iv λ1394/1403 lines, and the measurement of extended emission on the detector focal plane, we believe this portion of the spectrum to be scattered light from an O6 to B0 supergiant. The COS entrance aperture is 2.5 arcsec in diameter and can let in substantial scattered light from the nebula. NGC 2024 IRS 2b is an O8 star and believed to be the ionizing source of the nebula. It is currently identified as a main-sequence star, but should it be a supergiant the presence of such an evolved star implies an age for the cluster of the order of 3 Myr, in conflict with age determinations based on infrared spectroscopy, and may have implications for the energetics and density structure of the nebula.

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Section: Discussionsupporting

confidence: 56%

Cosmic Origins Spectrograph Observations of NGC 2024: An Indirect View Into the Heart of the Flame

Burgh

France

Snow

2012

ApJ

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“…The O-star classification is supported by the strength of the Fe v lines in the ultraviolet (specially the ratio Fe v λ1431/ C iii λ1427 > 1; Walborn et al 1985) and the strong He ii λ4200Å and N iii λ4515Å in the blue (Walborn & Fitzpatrick 1990), none of which would be expected at the temperature of an early B-type star. The luminosity classification is supported by the shallow and broad photospheric lines in the ultraviolet and fundamentally the lack of wind troughs in the Si iv λλ1394, 1403Å resonance lines, which show a very strong luminosity dependence (Walborn & Panek 1984b). The photospheric lines are those characteristic of a late-O/early-B main-sequence star, with Fe v lines dominating the spectrum shortwards of λ1500Å.…”

Section: The Optical/uv Spectrummentioning

confidence: 91%

On the nature of the hard X-ray source 4U 2206+54

Negueruela

Reig

2001

A&A

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Abstract. The recent discovery of a ∼9.5d period in the X-ray lightcurve of the massive X-ray binary 4U 2206+54 has opened the possibility that it is a Be/X-ray binary with an unusually close orbit, which, together with its low intrinsic luminosity, suggests that the system is actually a Be + WD binary, in which a white dwarf accretes material from the dense circumstellar disc surrounding a classical Be star. In this paper we present new X-ray observations and for the first time high-resolution optical spectroscopy of the source. We show that both the X-ray behaviour and the characteristics of the optical counterpart, BD +53 • 2790, are more consistent with a neutron star accreting from the wind of an early-type star. The X-ray lightcurve shows irregular flaring and no indications of pulsations, while the very high hydrogen column density supports accretion from a dense wind. BD +53 • 2790 is shown not to be a classical Be star, as believed until now, but rather a very peculiar late O-type active star, exhibiting emission components in the He ii lines, complex spectral variability and strong wind resonance lines in the ultraviolet. Though many of the characteristics of the spectrum resemble those of the He-rich stars, the absence of He i variability makes a connection unlikely. The spectrum is compatible with a composite of two stars of similar spectral type, though circumstantial evidence points to a single very peculiar active early-type star. This adds weight to the growing evidence that the traditional subdivisions of supergiant and Be/X-ray binaries fail to cover the whole phenomenology of massive X-ray binaries.

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“…There are numerous weak features that are not marked, as well as several features blueward of Ly that become visible only by averaging over many sight lines through the IGM. [See the electronic edition of the Journal for a color version of this figure. ] wind feature is strong in main-sequence, giant, and supergiant O stars (Walborn & Panek 1984). Consequently, the interstellar rather than the wind component seems to dominate the Si iv doublet in the LBG composite spectrum, while the C iv feature exhibits both the blueshifted broad absorption and redshifted emission associated with stellar winds, in addition to a strong, narrower, interstellar absorption component.…”

Section: Stellar Featuresmentioning

confidence: 94%

Rest‐Frame Ultraviolet Spectra of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \De

Shapley

Steidel

Pettini

et al. 2003

ApJ

1,272

148

999

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We present the results of a systematic study of the rest-frame UV spectroscopic properties of Lyman break galaxies (LBGs). The database of almost 1000 LBG spectra proves useful for constructing high signalto-noise composite spectra. The composite spectrum of the entire sample reveals a wealth of features attributable to hot stars, H ii regions, dust, and outflowing neutral and ionized gas. By grouping the database according to galaxy parameters such as Ly equivalent width, UV spectral slope, and interstellar kinematics, we isolate some of the major trends in LBG spectra that are least compromised by selection effects. We find that LBGs with stronger Ly emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Ly and the interstellar absorption lines, and lower star formation rates. There is a decoupling between the dependence of low-and high-ionization outflow features on other spectral properties. Additionally, galaxies with rest-frame W Ly ! 20 Å in emission have weaker than average high-ionization lines and nebular emission lines that are significantly stronger than in the sample as a whole. Most of the above trends can be explained in terms of the properties of the large-scale outflows seen in LBGs. According to this scenario, the appearance of LBG spectra is determined by a combination of the covering fraction of outflowing neutral gas, which contains dust and the range of velocities over which this gas is absorbing. In contrast, the strengths of collisionally excited nebular emission lines should not be affected by the nature of the outflow, and variations in these lines may indicate differences in the temperatures and metallicities in H ii regions of galaxies with very strong Ly emission. Higher sensitivity and spectral resolution observations are still required for a full understanding of the covering fraction and velocity dispersion of the outflowing neutral gas in LBGs and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z $ 3.

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Ultraviolet spectral morphology of the O stars - The remarkable luminosity dependence of the SI IV stellar wind effect

Cited by 50 publications

References 0 publications

Cosmic Origins Spectrograph Observations of NGC 2024: An Indirect View Into the Heart of the Flame

Cosmic Origins Spectrograph Observations of NGC 2024: An Indirect View Into the Heart of the Flame

On the nature of the hard X-ray source 4U 2206+54

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