scholarly journals Optical Polarization and Line Variability in Quasars with Associated Absorption

1997 ◽  
Vol 163 ◽  
pp. 681-682 ◽  
Author(s):  
T. Aldcroft ◽  
J. Bechtold ◽  
P. Smith ◽  
C. Foltz ◽  
G. Schmidt
Keyword(s):  
High Resolution ◽  
Strong Evidence ◽  
Broad Band ◽  
Velocity Profiles ◽  
Absorption Lines ◽  
Optical Polarization ◽  
Physical Origin ◽  
Component Systems

AbstractThe physical origin of associated absorption lines (zabs ≈ zqso) which are observed in radio-loud quasar is generally not well understood. Two observable properties, line variability and quasar optical polarization, can serve to constrain the possibilities. To this end, we have obtained high-resolution spectra (1 Å) and broad-band optical polarizations for over 30 radio-loud quasars with known CIV associated absorption. The quasars are at redshifts between about 1 and 2, and were previously observed spectroscopically at similar resolution between 1985 – 1986 by Foltz et al (1987). The associated CIV absorption systems include a variety of velocity profiles from weak single lines to very complex multi-component systems to the BAL-like profile of PHL 1157+0128. In this poster we show the first strong evidence for line variability in z > 1 radio-loud quasars. We find that in general the variability is less than ~ 30%. The optical polarization of CIV absorbed quasars is consistent with all radio-loud quasars.

scholarly journals Joint Discussion 4 UV astronomy: stars from birth to death

2006 ◽  
Vol 2 (14) ◽  
pp. 169-194
Author(s):  
Ana I. Gómez de Castro ◽  
Martin A. Barstow
Keyword(s):  
High Resolution ◽  
Uv Spectroscopy ◽  
Broad Band ◽  
Mission Planning ◽  
High Resolution Spectroscopy ◽  
Low Resolution ◽  
Short Term ◽  
Uv Astronomy ◽  
Optical Telescope ◽  
The Moment

AbstractThe scientific program is presented as well a the abstracts of the contributions. An extended account is published in “The Ultraviolet Universe: stars from birth to death” (Ed. Gómez de Castro) published by the Editorial Complutense de Madrid (UCM), that can be accessed by electronic format through the website of the Network for UV Astronomy (www.ucm.es/info/nuva).There are five telescopes currently in orbit that have a UV capability of some description. At the moment, only FUSE provides any medium- to high-resolution spectroscopic capability. GALEX, the XMM UV-Optical Telescope (UVOT) and the Swift. UVOT mainly delivers broad-band imaging, but with some low-resolution spectroscopy using grisms. The primary UV spectroscopic capability of HST was lost when the Space Telescope Imaging Spectrograph failed in 2004, but UV imaging is still available with the HST-WFPC2 and HST-ACS instruments.With the expected limited lifetime of sl FUSE, UV spectroscopy will be effectively unavailable in the short-term future. Even if a servicing mission of HST does go ahead, to install COS and repair STIS, the availability of high-resolution spectroscopy well into the next decade will not have been addressed. Therefore, it is important to develop new missions to complement and follow on from the legacy of FUSE and HST, as well as the smaller imaging/low resolution spectroscopy facilities. This contribution presents an outline of the UV projects, some of which are already approved for flight, while others are still at the proposal/study stage of their development.This contribution outlines the main results from Joint Discussion 04 held during the IAU General Assembly in Prague, August 2006, concerning the rationale behind the needs of the astronomical community, in particular the stellar astrophysics community, for new UV instrumentation. Recent results from UV observations were presented and future science goals were laid out. These goals will lay the framework for future mission planning.

High Resolution Spectroscopy of Absorption Lines in the Z = 1.7 BL LAC Object 0215+015

Quasars ◽  
1986 ◽  
pp. 571-572
Author(s):  
J. Chris Blades ◽  
Richard W. Hunstead ◽  
Hugh S. Murdoch ◽  
Max Pettini
Keyword(s):  
High Resolution ◽  
Absorption Lines ◽  
High Resolution Spectroscopy ◽  
Bl Lac

Broad band and high resolution scanning spectrum calibration technology

2020 ◽  
Vol 13 (2) ◽  
pp. 249-257
Author(s):  
迟明波 CHI Ming-bo ◽  
韩欣欣 HAN Xin-xin ◽  
徐 阳 XU Yang ◽  
舒风风 SHU Feng-feng ◽  
吴一辉 WU Yi-hui
Keyword(s):  
High Resolution ◽  
Broad Band ◽  
Spectrum Calibration

scholarly journals Ultraviolet properties of the symbiotic stars

1982 ◽  
Vol 70 ◽  
pp. 103-113
Author(s):  
Mark H. Slovak ◽  
David L. Lambert
Keyword(s):  
High Resolution ◽  
Broad Band ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Interim Report

Prior to the launch of the IDE satellite in early 1978, the only symbiotic star previously detected in the ultraviolet by earlier UV satellites, such as the 0A0-2, TD-1 and ANS experiments, was AG Pegasi = HD 207757 (Gallager et al. 1979). These broad-band observations indicated that the symbiotics as a class may show a significant ultraviolet flux and thus they became natural candidates for a survey with the IUE satellite. The following is an interim report on a survey of the symbiotics, both at low and, for AG Pegasi and CH Cygni, at high resolution.

scholarly journals Are parenchymal AVMs congenital lesions?

2014 ◽  
Vol 37 (3) ◽  
pp. E2 ◽  
Author(s):  
Saul F. Morales-Valero ◽  
Carlo Bortolotti ◽  
Carmelo Sturiale ◽  
Giuseppe Lanzino
Keyword(s):  
High Resolution ◽  
Strong Evidence ◽  
Arteriovenous Malformations ◽  
De Novo ◽  
Fetal Mri ◽  
High Resolution Imaging ◽  
Cast Doubt ◽  
Resolution Imaging ◽  
Widespread Availability ◽  
Rare Diagnosis

A long-held dogma in neurosurgery is that parenchymal arteriovenous malformations (AVMs) are congenital. However, there is no strong evidence supporting this theory. An increasing number of documented cases of de novo formation of parenchymal AVMs cast doubt on their congenital nature and suggest that indeed the majority of these lesions may form after birth. Further evidence suggesting the postnatal development of parenchymal AVMs comes from the exceedingly rare diagnosis of these lesions in utero despite the widespread availability of high-resolution imaging modalities such as ultrasound and fetal MRI. The exact mechanism of AVM formation has yet to be elucidated, but most likely involves genetic susceptibility and environmental triggering factors. In this review, the authors report 2 cases of de novo AVM formation and analyze the evidence suggesting that they represent an acquired condition.

Einfluß der Rotation auf die Lebensdauer prädissoziierender Moleküle

1971 ◽  
Vol 26 (3) ◽  
pp. 538-546 ◽  
Author(s):  
F. J. Comes ◽  
G. Schumpe
Keyword(s):  
High Resolution ◽  
Excellent Agreement ◽  
Rotational Motion ◽  
Absorption Lines ◽  
Rare Gases ◽  
Rotational States ◽  
Theoretical Predictions ◽  
Line Widths

Abstract The D 1∏u - X1∑g+system of H2 and D2 shows strong predissociation. High resolution m easurements on the line widths of isolated absorption lines have been carried out, showing the influence of rotation on the predissociation probability of the corresponding rotational states. Their lifetime decreases with increasing rotation of the molecule and with decreasing mass due to the coupling of electronic and rotational motion. Both results are in excellent agreement with theoretical predictions given by Kronig. The shape of the absorption lines broadened by predissociation was found to be typically asymmetric. They are of the Beutler type, well known form the autoionisation of the rare gases.

A Discussion on astronomy in the ultraviolet - The ultraviolet spectrum of B-type supergiants

1975 ◽  
Vol 279 (1289) ◽  
pp. 429-442
Keyword(s):  
High Resolution ◽  
Spectral Type ◽  
Main Sequence ◽  
Ultraviolet Spectrum ◽  
Absorption Lines ◽  
Light Elements ◽  
Main Sequence Stars ◽  
Complete Identification ◽  
Constant Strength

The broad, steep-sided absorption lines in B-type supergiant spectra are stronger than the absorption lines in main-sequence stars. In addition to lines from the second, third and fourth spectra of the light elements and the metals there is a broad, pointed feature at 1720 A which has constant strength in the B-type supergiants regardless of spectral type. The complete identification of this blend is not known. At high resolution the ultraviolet resonance lines of C iv, N v, Si hi and Si iv in the spectra of OB supergiants are shortward displaced by velocities up to 1800 km s-1 indicating the presence of an escaping atmosphere. At type B5 the expanding atmosphere is moving at about 120 km s-1 which means that the material is probably brought to rest before it escapes from the star. Evidence is presented of the presence of a stationary shell around the B5Ia supergiant q Canis Majoris as well as a slowly expanding atmosphere.

scholarly journals Studies of the ISM in the LMC using SN1987A

1991 ◽  
Vol 148 ◽  
pp. 431-431
Author(s):  
Max Pettini
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
Large Scale ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Large Magellanic Cloud ◽  
Absorption Lines ◽  
High Signal ◽  
Hii Region ◽  
Sn 1987A

The exceptional brightness of SN1987A provided a wealth of opportunities for probing not only the interstellar medium in our Galaxy and in the Large Magellanic Cloud (LMC), but also any intergalactic matter between the two. Spectroscopic work has been directed both towards searches for very weak absorption lines, which require data of exceptionally high signal-to-noise ratio, and towards recording spectra of known features at unprecedentedly high resolution. Both approaches have yielded exciting and unexpected results. The first detection of [FeX] absorption has revealed the presence of million-degree gas in the interstellar medium of the LMC, possibly resulting from the explosions of previous supernovae in the 30-Doradus HII region. The ultra-high-resolution observations have been successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds along the line of sight to the supernova. This implies that the clouds are at temperatures of, at most, 170 K and have internal turbulent velocities of not more than 0.2 km s−1; large-scale motions thus appear to be mainly subsonic in these clouds. Radio observations of HI emission at 21-cm with the Parkes telescope have been combined with measurements of a variety of ultraviolet absorption lines, obtained with the International Ultraviolet Explorer satellite, to give the most detailed picture yet of the chemical composition of the gas between the Galaxy and the LMC. Finally, photographic monitoring of the light echo of SN 1987A over the last two years has provided a three-dimensional view of the interstellar environment in which SN 1987A exploded, complementing vividly the information deduced from the spectroscopic results.

scholarly journals Analysis of absorption lines in the high-resolution spectra of five hot post-AGB candidates

2020 ◽  
Vol 494 (2) ◽  
pp. 2117-2130
Author(s):  
A Herrero ◽  
M Parthasarathy ◽  
S Simón-Díaz ◽  
S Hubrig ◽  
G Sarkar ◽  
...  
Keyword(s):  
High Resolution ◽  
Rotational Velocity ◽  
Asymptotic Giant Branch ◽  
Absorption Lines ◽  
Binary Interaction ◽  
Strength Parameter ◽  
Galactic Latitude ◽  
History Of ◽  
Similar Temperature ◽  
Absolute Magnitudes

ABSTRACT From an analysis of absorption lines in the high-resolution spectra, we have derived the radial velocities, stellar parameters (Teff, log g, wind-strength parameter log Q, and projected rotational velocity), and abundances (C, N, O, and Si) of IRAS 17460-3114, IRAS 18131-3008, IRAS 19336-0400, LSE 45, and LSE 163. Abundances are found to be solar, except for a low Si abundance in IRAS 19336-0400 and a mild CNO pattern in LSE 163, which rotates at an unusual large rotational velocity for its spectral classification. Combining the stellar parameters information with the Gaia DR2 data, we are able to derive absolute magnitudes, radii, and luminosities and clarify the possible post-asymptotic giant branch (AGB) nature of the objects. IRAS 17460-3114 and IRAS 18131-3008 are found to be massive OB stars, whereas IRAS 19336-0400 is found to be a post-AGB star, already showing nebular lines in the spectrum. However, we could not confirm the nature of LSE 45 and LSE 163 as post-AGB stars, although their parameters are much more inconsistent with those of massive stars. In both cases, we find a discrepancy between the spectroscopic mass and that derived from the predictions of post-AGB evolutionary tracks. In addition, LSE 45 lacks nebular lines, which are present in IRAS 19336-0400 at a similar temperature. In the case of LSE 163, the rotational velocity (259 ± 15 $\rm km\, s^{-1}$) would be extremely large for a star evolving to central stars of planetary nebulae. The combination of this rotational velocity, the high Galactic latitude, slightly large radial velocity, and mild CNO enhancement suggests a history of binary interaction.

scholarly journals The Chemical Evolution of the Universe

2001 ◽  
Vol 204 ◽  
pp. 323-331
Author(s):  
Antoinette Songaila ◽  
Lennox L. Cowie
Keyword(s):  
High Resolution ◽  
Chemical Evolution ◽  
Metal Contamination ◽  
Metal Distribution ◽  
Absorption Lines ◽  
Low Density ◽  
Intergalactic Gas ◽  
Quasar Absorption Lines ◽  
Future Work ◽  
The Universe

We still know relatively little about the local metal density outside of galaxies and clusters, but at high redshifts (z ~ 3) the advent of highly efficient high-resolution spectrographs on the new 8–10m telescopes has revolutionized the study of quasar absorption lines. This allows us to track the bulk of the baryons in the Universe, which are in highly observable form at this redshift, and to determine the metal density of the gas that contains most of the baryonic material. One of the more surprising results that has emerged is how uniformly the intergalactic gas at redshifts 2–4 is pervaded by metals, and we discuss current limits on such metal contamination of the low density gas. These measurements will be useful in understanding and calibrating feedback processes in early generations of small galaxies. Future work will track the metal distribution at higher redshift using bright z = 5 SDSS quasars.

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