scholarly journals Prominence Emission Lines Observed With SUMER and Two Ground-based Telescopes

1998 ◽  
Vol 167 ◽  
pp. 196-200
Author(s):  
C.R. de Boer ◽  
G. Stellmacher ◽  
E. Wiehr
Keyword(s):  
Optical Thickness ◽  
Emission Lines ◽  
Two Dimensional ◽  
Quiescent Prominence ◽  
Euv Emission ◽  
Ionization Temperature ◽  
Balmer Lines ◽  
Higher Temperature ◽  
Line Widths ◽  
Emission Ratios

AbstractTwo sets of H, He, and Ca+ emission lines were observed in a quiescent prominence simultaneously with the VTT and the Gregory telescope on Tenerife. At the same time, SUMER took two scans of low-ionized EUV emission lines.The emission ratios of Ca+–to–Balmer lines from ground vary little in the prominence, indicating a largely constant gas-pressure. In contrast, the ratio of He–to–Balmer from the ground shows the (known) increase toward the prominence borders, indicating higher temperature there. Similarly, the two-dimensional distributions of the ratios S IV/N II and C III/He I show pronounced bright prominence rims.The reduced He 537Å and He 584Å line widths are 2.6 and 3.6 times larger, respectively, than those of He D3 and He 3888Å. Explaining this by the optical thickness yields τ0 = 104 and τ0 = 2 · 105 for the two EUV lines. The total He 584 emission amounts to 13 watt/m2 ster in the main prominence body where the D3 line yields 4 watt/m2 ster; existing models, however, predict a factor 0.18.The widths of simultaneously observed optical lines with different atomic weights yield thermal and non-thermal broadening parameters of Tkin ≈ 8000 K and 2.5 < ξ < 6.5 km/s. The EUV lines, however, show line widths which correspond to much higher temperatures and non-thermal velocities. Assuming for each ion the corresponding ionization temperature, the line widths require non-thermal velocities of 15–40 km/s which is similar to values for the quiet corona.

Spectroscopy of a Solar Prominence with the Narrow-Bandpass Filter

1994 ◽  
Vol 144 ◽  
pp. 343-344
Author(s):  
P. Rudawy
Keyword(s):  
Optical Thickness ◽  
Large Scale ◽  
Bandpass Filter ◽  
Solar Limb ◽  
Physical Parameters ◽  
Two Dimensional ◽  
Line Profiles ◽  
Solar Prominence ◽  
Quiescent Prominence ◽  
Made In

AbstractObservations and analysis of a quiescent prominence above the solar limb are presented. The set of quasi-monochromatic images of the prominence made in a few wavelengths of Hα, Hβand D3lines have been used for reconstruction of the coarse line profiles. Two-dimensional maps of the main physical parameters of the prominence matter-macroscopic and turbulent velocities, electron temperature, density and optical thickness have been constructed. Presented method of low-resolution spectroscopy is useful for investigations of the variety of large-scale solar phenomena.

Electron Densities in Solar Prominences

1994 ◽  
Vol 144 ◽  
pp. 381-383
Author(s):  
J. E. Wiik ◽  
P. Heinzel ◽  
B. Schmieder
Keyword(s):  
Optical Thickness ◽  
Field Of View ◽  
Line Of Sight ◽  
Two Dimensional ◽  
Line Profiles ◽  
Quiescent Prominence ◽  
Electron Densities ◽  
Solar Prominences ◽  
Thickness Variations ◽  
Limiting Values

AbstractObservations of a quiescent prominence made with the MSDP spectrograph at the Pic du Midi Observatory provided Hαline profiles in each pixel of a 2D field of view. Comparing the absolute observed intensities with values derived from NLTE computations, we estimated the range ofelectron densitiesNe≈ 1 – 5 × 1010cm−3,source functionsS/Ic≈ 0.07 – 0.12, andoptical thicknessτ ≈ 0.3 – 8.0 within the observed prominence. Two dimensional maps of the electron densities are presented assuming two limiting values of the geometrical thickness along the line-of-sight. It is shown that if we consider geometrical thickness variations within a factor of about four, the electron density will be determined to within a factor of two, just by measuring the Hαline intensity.

scholarly journals Predicting the broad-lines polarization emitted by supermassive binary black holes

2019 ◽  
Vol 623 ◽  
pp. A56 ◽  
Author(s):  
D. Savić ◽  
F. Marin ◽  
L. Č. Popović
Keyword(s):  
Black Holes ◽  
Emission Lines ◽  
Polarization Angle ◽  
Broad Line ◽  
Line Profiles ◽  
Binary Black Holes ◽  
True Nature ◽  
Line Shapes ◽  
Highly Sensitive ◽  
Balmer Lines

Context. Some Type-1 active galactic nuclei (AGN) show extremely asymmetric Balmer lines with the broad peak redshifted or blueshifted by thousands of km s−1. These AGN may be good candidates for supermassive binary black holes (SMBBHs). The complex line shapes can be due to the complex kinematics of the two broad line regions (BLRs). Therefore other methods should be applied to confirm the SMBBHs. One of them is spectropolarimetry. Aims. We rely on numerical modeling of the polarimetry of binary black holes systems, since polarimetry is highly sensitive to geometry, in order to find the specific influence of supermassive binary black hole (SMBBH) geometry and dynamics on polarized parameters across the broad line profiles. We apply our method to SMBBHs in which both components are assumed to be AGN with distances at the subparsec scale. Methods. We used a Monte Carlo radiative transfer code that simulates the geometry, dynamics, and emission pattern of a binary system where two black holes are getting increasingly close. Each gravitational well is accompanied by its own BLR and the whole system is surrounded by an accretion flow from the distant torus. We examined the emission line deformation and predicted the associated polarization that could be observed. Results. We modeled scattering-induced broad line polarization for various BLR geometries with complex kinematics. We find that the presence of SMBBHs can produce complex polarization angle profiles φ and strongly affect the polarized and unpolarized line profiles. Depending on the phase of the SMBBH, the resulting double-peaked emission lines either show red or blue peak dominance, or both the peaks can have the same intensity. In some cases, the whole line profile appears as a single Gaussian line, hiding the true nature of the source. Conclusions. Our results suggest that future observation with the high resolution spectropolarimetry of optical broad emission lines could play an important role in detecting subparsec SMBBHs.

scholarly journals Spectrophotometry of Supernovae

1974 ◽  
Vol 3 ◽  
pp. 533-544
Author(s):  
R. P. Kirshner
Keyword(s):  
Emission Lines ◽  
Absorption Lines ◽  
Spectral Energy ◽  
Line Profiles ◽  
Energy Distributions ◽  
Maximum Light ◽  
Balmer Lines ◽  
B Lines ◽  
Infrared Triplet ◽  
The Continuum

AbstractAbsolute spectral energy distributions for supernovae of both types I and II have been obtained. These observations demonstrate three facets of supernova spectra. First, both SN I’s and SN II’s have a continuum that varies slowly and uniformly with time, and which carries the bulk of the radiated flux at early epochs. Second, some lines in both SN I’s and SN II’s have P Cygni profiles: broad emissions flanked on their violet edges by broad absorptions. Third, some lines are common to SN I’s and SN II’s and persist throughout the evolution of the spectrum. The continuum temperatures for both SN I’s and SN II’s are about 10000 K at the earliest times of observation and drop in one month’s time to about 6000 K for SN II’s and about 7000 K for SN I’s. After several months, the continuum may cease to carry the bulk of the flux, which might be in emission lines, but continues to exist, as shown by the presence of absorption lines. The P Cygni line profiles indicate expansion velocities of 15000 km s-1 in SN II’s and 20000 km s-11 in the SN I 1972e in NGC 5253. Line identifications for SN II’s include Hα, Hβ, H and K of Ca II, the Ca II infrared triplet at λ8600, the Na I D-lines, the Mg I b-lines at λ5174, and perhaps Fe II. The [O I] lines λλ6300, 6363 and [Ca II] lines λλ7291, 7323 appear after eight months. For SN I’s, the lines identified are H and K of Ca II, the infrared Ca II lines, the Na I D-lines, and the Mg I b-lines. There is some evidence that Balmer lines are present two weeks after maximum. The strong and puzzling λ4600 features drifts with time from λ4600 near maximum light to λ4750 after 400 days.

Thermally boosted upconversion and downshifting luminescence in Sc2(MoO4)3:Yb/Er with two-dimensional negative thermal expansion

2021 ◽  
Author(s):  
Jinsheng Liao ◽  
Minghua Wang ◽  
Fulin Lin ◽  
Zhuo Han ◽  
Datao Tu ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Near Infrared ◽  
Negative Thermal Expansion ◽  
Thermal Quenching ◽  
Relative Sensitivity ◽  
Strong Temperature Dependence ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Higher Temperature

Abstract Lanthanide (Ln3+)-doped phosphors generally suffer from thermal quenching, in which their photoluminescence (PL) intensities decrease at the higher temperature. Herein, we report a class of unique two-dimensional negative-thermal-expansion phosphor of Sc2(MoO4)3:Yb/Er. By virtue of the reduced distances between sensitizers and emitters as well as confined energy migration with increasing the temperature, a 45-fold enhancement of green upconversion (UC) luminescence and a 450-fold enhancement of near-infrared downshifting (DS) luminescence of Er3+ are achieved from 25 to 500 ˚C. The thermally boosted UC and DS luminescence mechanism is systematically investigated through in situ temperature-dependent Raman spectroscopy, synchrotron X-ray diffraction and PL dynamics. Moreover, the luminescence lifetime of 4I11/2 of Er3+ in Sc2(MoO4)3:Yb/Er displays a strong temperature dependence, enabling ratiometric thermometry with the highest relative sensitivity of 13.4%/K at 298 K. These findings may gain a vital insight into the design of negative-thermal-expansion Ln3+-doped phosphors for versatile applications.

scholarly journals Interacting Binaries as Be Stars

1987 ◽  
Vol 92 ◽  
pp. 451-455
Author(s):  
Mirek J. Plavec
Keyword(s):  
Spectral Type ◽  
Binary Stars ◽  
Emission Lines ◽  
Close Binary ◽  
High Electron ◽  
Be Stars ◽  
Close Binary Stars ◽  
High Ionization ◽  
Mass Outflow ◽  
Balmer Lines

AbstractSemidetached close binary stars of the Algol type often have primary components of spectral type A0 or earlier and display emission at Hα (sometimes also at higher Balmer lines). They are therefore Be stars. Many binaries of this type are not eclipsing and must look like “ordinary” Be stars. We have discovered high-ionization emission lines of N V, C IV, Si IV, Fe III, etc. in the ultraviolet spectra of totally eclipsing Algols. They probably originate in circumstellar turbulent regions at fairly high electron temperatures, of the order of 100 000 K. They are not detectable in most non-eclipsing systems, but may be there and may play an important role in the dynamics of accretion and mass outflow from the systems.

scholarly journals The Nature of Balmer Line Variability in Chemically Peculiar Stars

1986 ◽  
Vol 90 ◽  
pp. 179-180 ◽  
Author(s):  
B. Musielok
Keyword(s):  
Wavelength Region ◽  
Model Atmosphere ◽  
Balmer Line ◽  
Peculiar Stars ◽  
Metal Abundance ◽  
Balmer Lines ◽  
Higher Temperature ◽  
Chemically Peculiar Stars ◽  
Photoelectric Measurements ◽  
Ap Stars

Photoelectric measurements of the β-index were made for six Ap-stars (56 Ari, 41 Tau, φ Dra, HD 188041, HD 215441, HD 221568) and one He-rich star (HD 184927). For all these stars the minimum of β occurs at a phase of maximum light at a wavelength longward of the null-wavelength region. Such coincidence can be explained by the blanketing mechanism proposed by Kodaira (1973) for the explanation of the Hγ line variations in HD 221568. According to Kurucz (1979), for stars hotter than 9000K an increase of metal abundance in the atmosphere causes an increase of the visible flux and an simultanous decrease of equivalent widths of Balmer lines. The same changes of the visible flux and equivalent widths of Balmer lines can be obtained using a model atmosphere with a suitable higher temperature. Using the Kurucz (1979) model atmospheres, temperature differences were calculated, which are necessary to obtain the observed decrease of the (β-index and the increase of the flux in a given photometric band.

scholarly journals Composite Models: A Tool for Interpreting the Emission-Line Spectra of Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 316-317
Author(s):  
S.M. Viegas-Aldrovandi ◽  
M. Contini
Keyword(s):  
Energy Source ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Additional Energy ◽  
Physical Conditions ◽  
Dilute Gas ◽  
Composite Models ◽  
Line Widths ◽  
Narrow Emission

In the last decade, emission-lines from a large number of active galactic nuclei (AGN) have been observed. Most of the models built to explain the observed narrow emission-lines are based on photoionization. Although these photoionization models account for the observed general features, many points remain unexplained and several authors suggest an additional energy source (Ferland and Mushotzky 1984, Ferland and Osterbrock 1986, Stasinska 1984, Viegas-Aldrovandi and Gruenwald 1988). Another possible explanation is suggested by the emitting cloud motions, which account for the observed line widths. If the clouds are moving throughout a dilute gas (n0 ≃ 300 cm−3), a shock can develop. Then, the physical conditions in the cloud are determined by the coupled effect of photoionization and shock hydrodynamics.

scholarly journals Statistical Features of the Quiet Sun in EUV

2001 ◽  
Vol 203 ◽  
pp. 416-418
Author(s):  
A. Pauluhn ◽  
S. K. Solanki ◽  
I. Rüedi ◽  
E. Landi ◽  
U. Schühle
Keyword(s):  
Lognormal Distribution ◽  
Distribution Functions ◽  
Spectral Lines ◽  
Emission Lines ◽  
Statistical Features ◽  
Frequency Distributions ◽  
Quiet Sun ◽  
Euv Emission ◽  
The Past ◽  
Radiance Distribution

Frequency distributions of the intensities of EUV emission lines in the quiet Sun have in the past usually been modelled using two Gaussians. Here we test this and other distribution functions against observed distributions with exceptional statistics. The data were obtained in a number of spectral lines observed with CDS and SUMER. We show that the frequency distribution of the radiance is best modelled by a lognormal distribution. The fact that the radiance distribution of the quiet Sun including the network and the intranetwork is better reproduced by a single lognormal distribution function than by two Gaussians suggests that the same heating processes are acting in both types of features.

scholarly journals Detection of an Extended Optical Halo around IC 418

1989 ◽  
Vol 131 ◽  
pp. 197-197
Author(s):  
D. J. Monk ◽  
M. J. Barlow ◽  
R.E.S. Clegg
Keyword(s):  
Wavelength Region ◽  
Central Star ◽  
Emission Lines ◽  
Two Dimensional ◽  
Angular Radius

Two-dimensional long slit AAT IPCS spectra of IC 418 (in the 3400–4400 A wavelength region) show faint extensions in the [O II] 3726, 3729 A and Hγ emission lines out to at least 60 arcsec south and 50 arcsec north of the central star, compared to the angular radius of only 6 arcsec for the bright nebula.

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