Measurements of balmer line radiation from self-sustained townsend discharges in hydrogen

1965 ◽  
Vol 12 (2) ◽  
pp. 91-100
Author(s):  
Kaare J. Nygaard
Keyword(s):  
Balmer Line ◽  
Line Radiation

scholarly journals Quiescent chromospheric response to the (E)UV/optical flare radiation field on dMe stars

1990 ◽  
Vol 137 ◽  
pp. 313-316
Author(s):  
E. R. Houdebine ◽  
C. J. Butler
Keyword(s):  
Radiation Field ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Balmer Line ◽  
Line Radiation ◽  
Balmer Lines ◽  
Ceti Type ◽  
Optical Continuum ◽  
Flare Plasma ◽  
Optical Flare

We examine the response of the quiescent chromosphere to the large (E)UV and optical continuum and spectral line radiation field arising from a flare. We show that during a UV Ceti type flare, which displays a large U-band enhancement, a major part of the Balmer line flux may arise from the “quiescent chromosphere”, rather than the heated flare plasma itself. This leads us to distinguish two main phases in the Balmer lines, as first proposed by Houdebine et al. (1989): an early, mainly impulsive, phase, driven by radiative pumping of the quiescent chromosphere, which is mainly correlated with continuum variations, and a later one, related to the thermal flare phase, which arises from the cooling of the flare plasma itself. The effect of the radiative pumping is much larger for stellar (dMe) than for solar flares, due to substantial differences in the flare, relative to the quiescent, level and the quiescent chromospheric density and temperature.

scholarly journals An updated Type II supernova Hubble diagram

2018 ◽  
Vol 611 ◽  
pp. A25 ◽  
Author(s):  
E. E. E. Gall ◽  
R. Kotak ◽  
B. Leibundgut ◽  
S. Taubenberger ◽  
W. Hillebrandt ◽  
...  
Keyword(s):  
Spectral Lines ◽  
Balmer Line ◽  
Type Ii ◽  
Dependent Relation ◽  
Measuring Techniques ◽  
Distance Indicators ◽  
Larger Sample ◽  
Current Record ◽  
Initial Results ◽  
The Continuum

We present photometry and spectroscopy of nine Type II-P/L supernovae (SNe) with redshifts in the 0.045 ≲ z ≲ 0.335 range, with a view to re-examining their utility as distance indicators. Specifically, we apply the expanding photosphere method (EPM) and the standardized candle method (SCM) to each target, and find that both methods yield distances that are in reasonable agreement with each other. The current record-holder for the highest-redshift spectroscopically confirmed supernova (SN) II-P is PS1-13bni (z = 0.335−0.012+0.009), and illustrates the promise of Type II SNe as cosmological tools. We updated existing EPM and SCM Hubble diagrams by adding our sample to those previously published. Within the context of Type II SN distance measuring techniques, we investigated two related questions. First, we explored the possibility of utilising spectral lines other than the traditionally used Fe iiλ5169 to infer the photospheric velocity of SN ejecta. Using local well-observed objects, we derive an epoch-dependent relation between the strong Balmer line and Fe iiλ5169 velocities that is applicable 30 to 40 days post-explosion. Motivated in part by the continuum of key observables such as rise time and decline rates exhibited from II-P to II-L SNe, we assessed the possibility of using Hubble-flow Type II-L SNe as distance indicators. These yield similar distances as the Type II-P SNe. Although these initial results are encouraging, a significantly larger sample of SNe II-L would be required to draw definitive conclusions.

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