Observations of the profiles of solar UV emission lines and their analysis in terms of the heating and production of the corona

1972 ◽  
Vol 13 (4-6) ◽  
pp. 639-641 ◽  
Author(s):  
B. C. Boland ◽  
S. F. T. Engstrom ◽  
B. B. Jones ◽  
R. W. P. McWhirter ◽  
P. C. Thonemann ◽  
...  
Keyword(s):  
Emission Lines ◽  
Uv Emission ◽  
Solar Uv

scholarly journals X-Ray Emission from Flare Stars

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.

The influence of shock-waves on UV-emission-lines

Solar Physics ◽  
1975 ◽  
Vol 45 (1) ◽  
pp. 93-103 ◽  
Author(s):  
Lutz R. Elzner
Keyword(s):  
Shock Waves ◽  
Emission Lines ◽  
Uv Emission

scholarly journals Obscured AGN at 1.5 < z < 3.0 from the zCOSMOS-deep Survey

2019 ◽  
Vol 626 ◽  
pp. A9 ◽  
Author(s):  
M. Mignoli ◽  
A. Feltre ◽  
A. Bongiorno ◽  
F. Calura ◽  
R. Gilli ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Metal Content ◽  
High Redshift ◽  
Strong Relationship ◽  
Emission Lines ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Uv Emission

Context. The physics and demographics of high-redshift obscured active galactic nuclei (AGN) is still scarcely investigated. New samples of such objects, selected with different techniques, can provide useful insights into their physical properties. Aims. With the goal to determine the properties of the gas in the emitting region of type 2 AGN, in particular, the gas metal content, we exploit predictions from photoionization models, including new parameterizations for the distance of gas distribution from the central source and internal microturbulence in the emitting clouds, to interpret rest-frame UV spectral data. Methods. We selected a sample of 90 obscured (type 2) AGN with 1.45 ≤ z ≤ 3.05 from the zCOSMOS-deep galaxy sample by 5σ detection of the high-ionization C IV λ1549 narrow emission line. This feature in a galaxy spectrum is often associated with nuclear activity, and the selection effectiveness has also been confirmed by diagnostic diagrams based on utraviolet (UV) emission-line ratios. We applied the same selection technique and collected a sample of 102 unobscured (type 1) AGN. Taking advantage of the large amount of multiband data available in the COSMOS field, we investigated the properties of the C IV-selected type 2 AGN, focusing on their host galaxies, X-ray emission, and UV emission lines. Finally, we investigated the physical properties of the ionized gas in the narrow-line region (NLR) of this type 2 AGN sample by combining the analysis of strong UV emission lines with predictions from photoionization models. Results. We find that in order to successfully reproduce the relative intensity of UV emission lines of the selected high-z type 2 AGN, two new ingredients in the photoionization models are fundamental: small inner radii of the NLR (≈90 pc for LAGN = 1045 erg s−1), and the internal dissipative microturbulence of the gas-emitting clouds (with vmicr ≈ 100 km s−1). With these modified models, we compute the gas-phase metallicity of the NLR, and our measurements indicate a statistically significant evolution of the metal content with redshift. Finally, we do not observe a strong relationship between the NLR gas metallicity and the stellar mass of the host galaxy in our C IV-selected type 2 AGN sample.

scholarly journals Metallicity evolution of AGNs from UV emission lines based on a new index

2014 ◽  
Vol 443 (2) ◽  
pp. 1291-1300 ◽  
Author(s):  
Oli L. Dors ◽  
Mónica V. Cardaci ◽  
Guillermo F. Hägele ◽  
Ângela C. Krabbe
Keyword(s):  
Emission Lines ◽  
Uv Emission

scholarly journals SN 1006 at optical and UV wavelengths

2006 ◽  
Vol 2 (14) ◽  
pp. 306-306
Author(s):  
Knox S. Long
Keyword(s):  
Optical Properties ◽  
Galactic Plane ◽  
Shock Velocity ◽  
Emission Lines ◽  
Type Ia Supernovae ◽  
Interstellar Gas ◽  
Broad Absorption ◽  
Uv Emission ◽  
Type Ia ◽  
Ia Supernovae

AbstractOptical and UV emission from SN 1006 is observed on the periphery of the SNR, particularly in the NW, and arises as material from interstellar gas is ionized behind the shock front. The shapes of the emission lines have been used to infer a shock velocity of about 2900 km s−1 and to show that the electron and ion temperatures are close to that expected from standard shock theory. The combination of the shock velocity and the proper motion of the filaments in the NE accurately locates SN1006 at a distance of 2.2 kpc, some 550 pc above the Galactic plane. At UV wavelengths, ejecta from SN 1006 have also been observed as broad absorption lines from Si, Ca and Fe in spectra of the Schweitzer-Middleditch star and two quasars. The observations appear to limit the mass of Fe in SN 1006 to less than 0.16 M⊙, much less than expected from models of Type Ia supernovae. In this brief review of the UV and optical properties of SN 1006, I will summarize how these observations yield a fairly consistent description of SN 1006, and suggest what further observations might be undertaken to extend our understanding of SN 1006 in its second millennium.

scholarly journals UV Absorption and Emission Lines from Highly Ionized Gas in the Galactic Halo

1991 ◽  
Vol 144 ◽  
pp. 131-141
Author(s):  
Blair D. Savage
Keyword(s):  
Absorption Line ◽  
Flow Rate ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Uv Absorption ◽  
Emission Lines ◽  
Line Profiles ◽  
Ionized Gas ◽  
Absorption And Emission ◽  
Uv Emission

Highly ionized gas in the galactic halo has been detected through UV absorption and emission lines. In absorption the species studied include Si IV, C IV and N V. The UV emission studies have recorded C IV and O III]. Absorption measurements toward galactic stars reveal that the |z| distribution of the gas is roughly exponential with a scale height of approximately 3 kpc and has column densities perpendicular to the galactic plane of N ~ 2×1013, 1×1014 and 3×1013 atoms cm−2, for Si IV, C IV and NV, respectively. Similar absorption line profiles for these species suggests a common process for their origin. The presence of N V absorption implies the existence of some gas with a temperature near T ~ 2×105 K. The highly ionized absorbing gas toward distant stars in direction b < −50° has simple and relatively narrow line profiles (FWHM ~ 45 to 70 km−1) and small average LSR velocities while the gas in the direction b > 50° reveals a complex pattern of motions with substantial inflow and outflow velocities. Galactic rotation has an appreciable effect on the absorption line profiles to very distant stars located in the low halo. C IV emission has been seen at greater than a 3σ level of significance in 4 of 8 directions. The emission brightens toward the galactic poles and has a polar intensity I(C IV) ~ 5000 photons cm−2s−1ster−1. If the emitting and absorbing gas coincide in space the measurements imply ne ~ 0.01 cm−3 and P/k ~ 2000 cm−3 K for gas with T ~ 105 K. This phase of the gas fills only a small volume of the space (f ~ 0.03) and accounts for only a small fraction of the total column density of gas perpendicular to the galactic plane [~3×1018 atoms cm −2 vs 3.5×1020 atoms cm −2 for H I and 1×1020 atoms cm −2 for H+]. However, the gas provides a large EUV/UV emission line flux (~1×10−5erg. cm−2 s−1) which corresponds to a H I ionizing flux of ~2×105 ionizations cm−2 s−1. Gas with T near 2×105 K cools very rapidly. Its origin may be associated with the cooling gas of a galactic fountain flow or with thermal condensations in cosmic ray driven fountains. In the nonequilbrium cooling of a Galactic fountain, a flow rate of 4 MO/ year to each side of the Galaxy is required to produce the amount of N V absorption found in the halo while a flow rate 5x larger is required to produce the observed level of C IV emission.

scholarly journals The Structure of the BLR in 3C 390.3

2009 ◽  
Vol 5 (S267) ◽  
pp. 126-126
Author(s):  
L. S. Nazarova ◽  
N. G. Bochkarev ◽  
C. M. Gaskell
Keyword(s):  
Emission Lines ◽  
Uv Emission

AbstractVelocity-dependent flux ratios of the broad Lyα, Civ, Hβ, and Hα lines are used to investigate conditions in the archetypical displaced BLR peak emitter 3C 390.3. Our results suggest that gas producing the the UV emission lines has a lower density than the higher-velocity gas producing broad disk-like profile and is less flattened.

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