scholarly journals Optical Emission Lines from Warm Interstellar Clouds: A Decisive Test of the Decaying Neutrino Theory

1998 ◽  
Vol 505 (1) ◽  
pp. L35-L38 ◽  
Author(s):  
D. W. Sciama
Keyword(s):  
Optical Emission ◽  
Emission Lines ◽  
Interstellar Clouds ◽  
Decisive Test ◽  
Neutrino Theory

scholarly journals Molecular gas around the Wolf-Rayet star WR 18 (WN4)

2003 ◽  
Vol 212 ◽  
pp. 732-733
Author(s):  
Anthony P. Marston
Keyword(s):  
Mass Loss ◽  
Optical Emission ◽  
Emission Lines ◽  
Molecular Gas ◽  
Evolved Stars ◽  
Ring Nebula ◽  
History Of ◽  
Optical Ring ◽  
Ring Nebulae ◽  
Rayet Star

Optically observed ring nebulae and H i cavities around Wolf-Rayet stars have enabled us to obtain information on the history of mass-loss associated with these massive evolved stars. However, such studies have left a number of unanswered questions regarding the amount of mass-loss and the conditions of the stars during a sequence of mass-loss phases. Here we discuss the molecular gas environments of the WR star WR 18, which has an associated optical ring nebula NGC 3199. Our observations show that significant amounts of molecular gas appear close to and associated with the star. Mapping of molecular CO near the star shows that molecular materials appear to substantially avoid areas of optical emission and, instead, form a distorted clumpy shell interior to NGC 3199. Molecular emission lines are broader than lines seen in the interstellar medium and suggest the shell is composed of ejecta. This is further corroborated by the enhanced abundances of molecules containing C, N and O. Implications of the observations for the evolution of WR 18 are discussed.

scholarly journals Filtered CCD images of southern Herbig-Haro objects

1987 ◽  
Vol 122 ◽  
pp. 189-190
Author(s):  
B. Whitmore ◽  
D.H.M. Cameron ◽  
R.F. Warren-Smith
Keyword(s):  
High Velocity ◽  
Optical Emission ◽  
Emission Lines ◽  
Ccd Cameras ◽  
Hh Objects

It is currently believed that Herbig-Haro (HH) objects are a consequence of a high-velocity (up to at least 200 km s−1) outflow of material from a young embedded star. These flows can often be detected by deep observations of optical emission lines using CCD cameras.

scholarly journals Colliding Stellar Winds in O-type Close Binary Systems

1992 ◽  
Vol 135 ◽  
pp. 146-148
Author(s):  
D.R. Gies ◽  
M.S. Wiggs
Keyword(s):  
Binary Systems ◽  
Optical Emission ◽  
Emission Lines ◽  
Optical Observations ◽  
Close Binary ◽  
High Dispersion ◽  
Stellar Winds ◽  
Close Binary Systems ◽  
Circumstellar Gas ◽  
The Individual

In close binary systems of O-type stars, the individual stellar winds will collide between the stars to form shock fronts (Stevens et al. 1992). Binaries with equally luminous stars will have winds of comparable strength, and the shock will occur near the mid-plane between the stars, but in binaries of unequal luminosity, the interaction will occur along a bow shock wrapped around the star with the weaker wind. The presence of the shock region can be detected through excess X-ray emission (Chlebowski & Garmany 1990), and orbital phase-related variations in the UV P Cygni lines (Shore & Brown 1988) and optical emission lines (formed in high density regions of circumstellar gas).We have begun a search for colliding winds through a study of the optical emission lines and UV P Cygni lines in four massive binaries, AO Cas (Gies & Wiggs 1991), Plaskett’s star = HD 47129 (Wiggs & Gies 1992), 29 UW CMa and ι Ori. The optical observations consist of high S/N spectra of the Hα and He I λ6678 region obtained with the University of Texas McDonald Observatory 2.1-m telescope and coudé Reticon system. The UV observations were culled from archival IUE high dispersion spectra of several P Cygni features (N V λ1240, Si IV λ1400, C IV λ1550).

scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

Analysis of the Optical Emission Lines of SN 1987A

1990 ◽  
Vol 99 ◽  
pp. 664 ◽  
Author(s):  
J. A. de Freitas Pacheco
Keyword(s):  
Optical Emission ◽  
Emission Lines ◽  
Sn 1987A

scholarly journals High resolution observations of BD +30 3639 − A young PN

1997 ◽  
Vol 180 ◽  
pp. 99-99
Author(s):  
M. Bryce ◽  
G. Mellema
Keyword(s):  
Hubble Space Telescope ◽  
Optical Emission ◽  
Closed Shell ◽  
Detailed Comparison ◽  
Central Star ◽  
Emission Lines ◽  
Radio Image ◽  
Spatially Resolved ◽  
True Shape ◽  
Spatially Extended

Sub-arcsecond resolution radio and optical images of the young planetary nebula BD +30 3639 look superficially very similar, showing a pronounced box-shaped bright nebular shell. However, a detailed comparison at high spatial resolution reveals several regions where the optical emission is obscured by localised dusty regions. The highest resolution radio image to date of this PN, a 6 cm map obtained by combining MERLIN and VLA observations (Bryce et al, 1996) has been compared to the highest resolution optical Hβ image from the Hubble Space Telescope (obtained by J.P. Harrington and collaborators) to reveal the differences in emission which are probably due in the main to dust obscuration at optical wavelengths (Bryce et al, 1996 & Arnaud, Borkowski & Harrington, 1996). New 6 km s–1 resolution, spatially resolved spectra of optical emission lines, obtained using the Utrecht echelle spectrometer on the 4.2 m William Herschell Telescope, show that this nebula is bright in the low ionisation emission lines of [N II] 6548 + 6584 å and also appears to be more spatially extended than in the fainter, high ionisation [O III] 5007 å emission. The velocity ellipse observed from a long slit oriented north-south was found to be tilted, indicating an inclined, elliptical morphology rather than a simple, radially expanding spherical shell and the gaps in the velocity ellipse observed with an east-west slit suggest that the true shape is probably an open ring-like structure rather than a closed shell. A deep exposure of the [N II] 6584 å emission line appears to show a collimated, accelerating flow in an eastward direction away from the central star and extending well beyond the main bright nebular ring. It was also observed in the Hydrogen and [Nii] 6548 å emission lines. The H2 1–0 S(1) image of BD +30 3639 by Graham et al (1993) also shows a feature to the east of the main nebular ring. This may well be related to faint halo structures detected by Harrington and collaborators from their HST images (private communication).

scholarly journals Fraction of the X-ray selected AGNs with optical emission lines in galaxy groups

2017 ◽  
Vol 362 (4) ◽  
Author(s):  
Feng Li ◽  
Qirong Yuan ◽  
Weihao Bian ◽  
Xi Chen ◽  
Pengfei Yan
Keyword(s):  
Optical Emission ◽  
Emission Lines ◽  
X Ray ◽  
Galaxy Groups

Variations of broad optical emission lines in AGN

1996 ◽  
Vol 10 (3) ◽  
pp. 241-246 ◽  
Author(s):  
N. G. Bochkarev ◽  
A. I. Shapovalova ◽  
L. S. Nazarova
Keyword(s):  
Optical Emission ◽  
Emission Lines
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