Spatial and Spectral Structure of Chromospheric Lines

We are reducing a set of spectra covering the region from 3400 to 4330 Å that show both spatial and spectral structure in chromospheric emission lines from many elements and ions. The spectra were taken with the vacuum tower telescope at the Sacramento Peak Observatory with the spectrograph slit tangent to and touching the limb. Thus some height resolution in the chromosphere is present. Many of the lines show doubly-reversed emission, often asymmetric either for the whole line or for fine structure. The quality of the data is such as to improve our understanding of line blends. The spectral structure can be compared with the well-known structure in the H and K lines of Ca II and in the resonance lines of MgII in order to deduce a model for the lower chromosphere.

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High Resolution Spectroscopy As a Tool for Luminosity Calibration

Highlights of Astronomy ◽

10.1017/s1539299600014647 ◽

2002 ◽

Vol 12 ◽

pp. 676-679

Author(s):

Ruth C. Peterson

Keyword(s):

High Resolution ◽

Reasonable Agreement ◽

Empirical Relationship ◽

Model Atmosphere ◽

Stellar Mass ◽

Physical Basis ◽

Emission Lines ◽

High Resolution Spectroscopy ◽

Chromospheric Emission ◽

Advance Knowledge

AbstractRecent results are reviewed for two methods of luminosity calibration based on high-resolution spectroscopy. The first relies onTeff/loggdeterminations from model-atmosphere analyses based on high-resolution spectra. This method is physically well founded but operationally demanding, and requires advance knowledge of stellar mass. The second, W-B, stems from the empirical relationship between luminosity and the width of chromospheric emission lines first established by Wilson and Bappu. Its physical basis is only partially understood, however, and the calibration depends on stellar metallicity and on the choice of lines.BothTeff/loggand W-B easily distinguish cool dwarfs from cool giants. Generally reasonable agreement is found between distances derived from Hipparcos parallaxes and those inferred from the loggvalues derived for nearby dwarfs with relatively well-known Hipparcos parallaxes, σ(π)/π < 0.2. Constraining Hipparcos parallaxes star-by-star is not possible at present. Improvements are suggested for both approaches.

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Challenges and Techniques for Simulating Line Emission

Galaxies ◽

10.3390/galaxies6040100 ◽

2018 ◽

Vol 6 (4) ◽

pp. 100 ◽

Cited By ~ 8

Author(s):

Karen Olsen ◽

Andrea Pallottini ◽

Aida Wofford ◽

Marios Chatzikos ◽

Mitchell Revalski ◽

...

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Line Emission ◽

Emission Lines ◽

Synthetic Spectra ◽

Recent Advances ◽

The Future ◽

Important Quality ◽

Circumgalactic Medium

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.

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The Measurement of Long-Period Oscillations at Sacramento Peak Observatory and South Pole

Problems of Solar and Stellar Oscillations ◽

10.1007/978-94-009-7088-5_5 ◽

1983 ◽

pp. 43-54

Author(s):

Robin Stebbins ◽

Christopher Wilson

Keyword(s):

South Pole ◽

Sacramento Peak ◽

Long Period ◽

Peak Observatory ◽

Sacramento Peak Observatory

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X-Ray Emission from Flare Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100096019 ◽

1983 ◽

Vol 71 ◽

pp. 125-129

Author(s):

P.C. Agrawal ◽

A.R. Rao ◽

B.V. Sreekantan

Keyword(s):

Emission Lines ◽

Quiescent State ◽

X Ray ◽

Uv Emission ◽

Chromospheric Emission ◽

Flare Stars ◽

Einstein Observatory

Flare stars are a group of mostly dMe stars, which show intense flaring activity in the optical as well as in the radio and X-ray bands. These stars are characterized by the presence of chromospheric emission lines like % and Call H and K which are present even during the quiescent state. The presence of transition regions and coronae have been inferred from the detection of UV emission lines like NV, CIV, SiIV etc. with IUE and X-ray observations made with the Einstein Observatory. We report here X-ray observations of flare stars made with Einstein to measure their coronal X-ray emission during the quiescent state.

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Analysis of Extended Energy-Loss Fine Structure of Nanometerscale Clusters

Microscopy and Microanalysis ◽

10.1017/s143192760001686x ◽

1999 ◽

Vol 5 (S2) ◽

pp. 708-709

Author(s):

Y. Ito ◽

H. Jain ◽

D.B. Williams

Keyword(s):

Fine Structure ◽

Energy Loss ◽

Atomic Clusters ◽

Nanometer Scale ◽

X Ray ◽

Small Clusters ◽

Electron Energy Loss ◽

X Ray Absorption ◽

Ionization Edge

Small atomic clusters are of great importance for applications such as catalysts whose activity depends on the surface of the cluster. Attempts to determine the atomic short-range order and size of clusters have been made by analyzing the extended X-ray absorption fine structure (EXAFS). However, the analysis was made on an average of many small clusters. Analysis of extended energy-loss fine structure (EXELFS) in an electron energy-loss spectrum (EELS) has developed to the point where in some cases, the quality of the results is comparable to its X-ray analogue, EXAFS. No other technique provides nanometer-scale spatial resolution of the analyzed area for determining the atomic structure. Most EXELFS analysis has been performed on the K-ionization edge of lighter elements. For heavier elements, a more complex ionization edge such as the L-edge has to be used, due to the inefficiency of collecting high quality EEL spectra at higher energy-losses (Z > 18).

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The Impact of Dust/Gas Ratios on Chromospheric Activity in Red Giant and Supergiant Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318005872 ◽

2018 ◽

Vol 14 (S343) ◽

pp. 365-367

Author(s):

Kenneth G. Carpenter ◽

Gioia Rau

Keyword(s):

Surface Fluxes ◽

Emission Lines ◽

Chromospheric Activity ◽

Cool Stars ◽

Chromospheric Emission ◽

Activity Temperature ◽

Wind Characteristics ◽

Red Giant ◽

The Impact ◽

Reduced Activity

AbstractStencel et al. (1986) analyzed IUE spectra of a modest set of cool stars and found that they continue to produce chromospheres even in the presence of high dust levels in their outer atmospheres. This reversed the previous results of Jennings (1973) and Jennings & Dyck (1972). We describe an on-going extension of these studies to a sample of stars representing a broader range in dust/gas ratios, using archival IUE and archival and new HST data on both RGB and AGB stars. Surface fluxes in emission lines will be analyzed to assess the chromospheric activity and obscuration by dust in each star, as those fluxes will follow a different pattern for reduced activity (temperature/density dependent) vs. dust obscuration (wavelength dependent). Wind characteristics will be measured by modeling of wind-reversed chromospheric emission lines.

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Sacramento Peak Observatory

Solar Physics ◽

10.1007/bf00150005 ◽

1981 ◽

Vol 69 (2) ◽

pp. 411-418 ◽

Cited By ~ 8

Author(s):

Lawrence E. Cram

Keyword(s):

Sacramento Peak ◽

Peak Observatory ◽

Sacramento Peak Observatory

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Voltage Spectral Structure as a Parameter of System Technical Diagnostics of Ship Diesel Engine-Synchronous Generators

Electrical Control and Communication Engineering ◽

10.1515/ecce-2015-0005 ◽

2015 ◽

Vol 8 (1) ◽

pp. 37-42 ◽

Cited By ~ 1

Author(s):

Aleksandrs Gasparjans ◽

Aleksandrs Terebkovs ◽

Anastasia Zhiravetska

Keyword(s):

Diesel Engine ◽

Spectral Power ◽

Angular Acceleration ◽

Piston Compressor ◽

Technical Condition ◽

Electric Machine ◽

Technical Diagnostics ◽

Spectral Structure ◽

Diagnostic Parameters

Abstract A method of technical diagnostics of ship diesel engine – generator installation – is proposed. Spectral-power diagnostic parameters of the synchronous generator voltage and currents are used. The electric machine in this case is the multipurpose sensor of diagnostic parameters. A judgment on the quality of the operational processes in diesel engine cylinders and its technical condition is possible on the basis of these parameters. This method is applicable to piston compressor installations with electric drive. On the basis of such parameters as rotating torque, angular speed and angular acceleration it is possible to estimate the quality of the operating process in the cylinders of a diesel engine, the condition of its cylinder-piston group and the crank gear mechanism. The investigation was realized on the basis of a diesel-generator with linear load. The generator operation was considered for the case of constant RL load. Together with the above mentioned, the condition of bearings of synchronous machines, uniformity of the air gap, windings of the electric machine were estimated during the experiments as well. The frequency spectrum of the stator current of the generator was researched and analyzed. In this case the synchronous machine is becoming a rather exact multipurpose diagnostic sensor. The signal of non-uniformity in the operation process of diesel engine cylinders and its technical condition is the increasing of the amplitudes of typical frequencies.

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