scholarly journals Photometry of AM Her Stars – Line and Continuum Emission

1979 ◽  
Vol 53 ◽  
pp. 324-328
Author(s):  
Paula Szkody
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Main Sequence ◽  
Close Binary ◽  
Line Spectrum ◽  
Continuum Emission ◽  
Late Type ◽  
Emission Line Spectrum ◽  
Orbital Periods

The 4 known AM Her stars or polars (AM Her, ANUMa, W Pup, and 2A0311-227) are characterized by large circular polarizations of 10-35%, (Tapia 1977a, b, Krzeminski and Serkowski 1977), an emission line spectrum with strong H and He lines (Crampton and Cowley 1977, Greenstein et al. 1977), complex photometric variations (Szkody 1978, Priedhorsky and Krzeminski 1978, Warner & Nather 1972), long term high and low states and short orbital periods (80-180 min.). Models of these systems envision a close binary containing a magnetic white dwarf primary (B ~ 108G) and late type main sequence secondary transferring material into an accretion funnel over one or both poles of the white dwarf (Stockman et al. 1977, Lamb & Masters 1979, Liebert et al. 1978).

scholarly journals The Ionization of Novae Ejecta

1990 ◽  
Vol 122 ◽  
pp. 215-227
Author(s):  
R.E. Williams
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Line Spectrum ◽  
Ionized Gas ◽  
Grain Formation ◽  
Emission Line Spectrum ◽  
Pass Through

AbstractNovae ejecta pass through four distinct phases of evolution of the emission-line spectrum, caused by different ionization characteristics of the shell. These include a neutral (I), an auroral (II), a coronal (III), and a nebular (IV) phase. Photoionization from the contracting photosphere of the hot white dwarf is the source of the ionization, including the highly ionized coronal phase. Changing emission line ratios in certain novae that develop dust are caused by condensation of grains from the gas, and can be used to determine the composition of the dust. In V1370 Aql, substantial silicate grain formation appears to have taken place, probably within the ionized gas.

scholarly journals Spectral Variations of AG Dra Between 1981 and 1985

1988 ◽  
Vol 103 ◽  
pp. 205-207
Author(s):  
C.C. Huang ◽  
Y.F. Chen ◽  
L. Chen
Keyword(s):  
Emission Line ◽  
Active Phase ◽  
The Other ◽  
Emission Lines ◽  
Continuum Emission ◽  
Late Type ◽  
Stellar Spectrum ◽  
Cool Component ◽  
Strong Emission ◽  
Emission Line Spectrum

After a long quiet phase AG Dra underwent an outstandingly active phase with two outbursts in 1980 Nov. and 1981 Nov.(Viotti et al, 1984). Since then a new quiet phase has followed. In this work we analyse two spectra of AG Dra, of which, one was taken in 1981 by C.C. Huang at the Haute-Provence Observatory using the Marly spectrograph with a dispersion of 80 A/mm at the 1.2 m telescope, the other was obtained by Dr Y.Andrillat in 1985 with the same instrument.Figure 1 shows the spectral variations of AG Dra between 1981 and 1985. The main features of the emission line spectrum are not much different between the two spectra, except that in 1985 there was a new wide weak emission line at 3488 A possibly due to FeII. There were a lot of strong emission lines due to H, HeI, HeII and 0III in both spectra. The spectrum of the late-type component was much more obvious in 1985 than in 1981. In 1985 the lines of CaII K, CaIλ4227 and the G-band of CH were quite strong. In addition we measured a lot of absorption lines due to FeI, SrII and TiII on the 1985 plate. The Balmer continuum emission and the blue contiuum were enhanced in 1981. On the 1981 plate the stellar spectrum in ultraviolet can be traced beyond 3200 A and the blue continuum heavily veiled the spectrum of the cool component. In 1985 they were much weaker.

scholarly journals BI Crucis

1988 ◽  
Vol 103 ◽  
pp. 297-298
Author(s):  
A. Altamore ◽  
C. Rossi ◽  
R. Viotti
Keyword(s):  
Emission Line ◽  
Line Spectrum ◽  
Cool Component ◽  
Iras Source ◽  
Emission Line Spectrum ◽  
Vibration Rotation ◽  
Absorption Features ◽  
Co Emission ◽  
The Continuum

BI Crucis is a 12 mag star whose optical spectrum is characterized by a red continuum and variable emission line spectrum (Allen 1974, Henize and Carlson 1980, Whitelock et al. 1983). In order to investigate its symbiotic character on 18 February 1983 we have obtained at the 1.5m ESO telescope a 59 Å/mm spectrogram of the 5700-6900 Å region. BI Cru displayed a very rich emission line spectrum with very strong Hα. and prominent HeI (5876 and 6678Å) lines. Several FeII lines are also present which appear optically thick (Figure 1). A few absorption features (NaI, 6269-84) of interstellar origin are present. However, we find no trace of TiO bands (or of neutral atoms) in spite of Allen’s (1974) finding, but in agreement with Whitelock et al. (1983). Allen (priv. comm.) remarks that in his spectrum there are slight ‘waves’ in the continuum that looked like TiO absorptions. Thus the symbiotic nature of BI Cru is mostly based on its long term IR variability (T≅280 d, Whitelock et al. 1983). They also found the first overtone vibration rotation band of CO at 2.3 μm in emission. The CO emission band was recently resolved by McGregor et al. (1987). This is the first observation of CO in emission in a symbiotic object. The red continuum is more probably a highly reddened hot continuum. We note that a weak continuum is present in the LWR IUE image taken in March 1981 (Fig.2). This spectrum also shows a few emission lines of Mgll and FeII. BI Cru is also a strong IRAS source. Following the model of Kenyon et al. (1986) for D-type symbiotics, the cool component of BI Cru could be reddened by circumstellar dust. A high resolution ESO CAT/CES red spectrum shows Hα doubled by a central absorption extending from −38 to −290 km/s with respect to the center of the emission line which suggests the presence of intermediate velocity winds like in other symbiotic stars.

scholarly journals The magnetic field and emission-line spectrum of the remarkable white dwarf GD 356

1997 ◽  
Vol 289 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Lilia Ferrario ◽  
D. T. Wickramasinghe ◽  
J. Liebert ◽  
Gary D. Schmidt ◽  
John H. Bieging
Keyword(s):  
Magnetic Field ◽  
Emission Line ◽  
White Dwarf ◽  
Line Spectrum ◽  
Emission Line Spectrum ◽  
The Magnetic Field

scholarly journals The unusual emission line spectrum of I Zw 1

2004 ◽  
Vol 2004 (IAUS222) ◽  
pp. 271-274
Author(s):  
Monique Joly ◽  
M.-P. Véron-Cetty ◽  
P. Véron
Keyword(s):  
Emission Line ◽  
Line Spectrum ◽  
Emission Line Spectrum

scholarly journals The May 1985 Superoutburst of OY Carinae: II. Phase-Resolved IUE Spectroscopy and Exosat Observations

1987 ◽  
Vol 93 ◽  
pp. 371-376 ◽  
Author(s):  
B.J.M. Hassall ◽  
T. Naylor ◽  
G.T. Bath ◽  
P.A. Charles ◽  
G. Sonneborn ◽  
...  
Keyword(s):  
Emission Line ◽  
Line Spectrum ◽  
X Ray ◽  
Dwarf Nova ◽  
Uv Emission ◽  
Emission Line Spectrum ◽  
Coronal Region

AbstractWe present ultraviolet and X-ray observations of the eclipsing SU UMa dwarf nova OY Car early in the decline from a superoutburst. From the UV emission line spectrum and lack of X-ray eclipse, we deduce the presence of an extended coronal region.

scholarly journals Classical Novae – Before and After Outburst

1988 ◽  
Vol 108 ◽  
pp. 226-231
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Orbital Parameters ◽  
Classical Novae ◽  
Classical Nova ◽  
Before And After ◽  
Low Mass ◽  
Orbital Periods ◽  
Thermonuclear Runaway ◽  
Nova Outburst

Classical nova (CN) and dwarf nova (DN) systems have the same binary components (a low-mass main sequence star and a white dwarf) and the same orbital periods. An important question that therefore arises is: are these systems really different ? (and if so, what is the fundamental difference ?) or, are these the same systems, metamorphosing from one class to the other ?The first thing to note in this respect is that the white dwarfs in DN systems are believed to accrete continuously (both at quiescence and during eruptions). At the same time, both analytic (e.g. Fujimoto 1982) and numerical calculations show, that when sufficient mass accumulates on the white dwarf, a thermonuclear runaway (TNR) is obtained and a nova outburst ensues (see e.g. reviews by Gallagher and Starrfield 1978, Truran 1982). It is thus only natural, to ask the question, is the fact that we have not seen a DN undergo a CN outburst (in about 50 years of almost complete coverage) consistent with observations of DN systems ? In an attempt to answer this question, we have calculated the probability for a nova outburst not to occur (in 50 years) in 86 DN systems (for which at least some of the orbital parameters are known).

scholarly journals Models for the Emission-Line Spectra of the Low-Excitation Herbig-Haro Objects

1987 ◽  
Vol 115 ◽  
pp. 346-347
Author(s):  
Michael A. Dopita ◽  
Saul Caganoff ◽  
Richard D. Schwartz ◽  
Martin Cohen
Keyword(s):  
Emission Line ◽  
Theoretical Description ◽  
Line Spectrum ◽  
High Excitation ◽  
Two Photon ◽  
Shock Models ◽  
Uv Excess ◽  
Hh Objects ◽  
Emission Line Spectrum

The class of Low-Excitation Herbig-Haro Objects are characterised by [SII] and [OI] lines which are comparable in strength to H-Alpha, by [NI] lines that are comparable to H-Beta, relatively weak [NII] and [OII] lines, little or no [OIII] emission and a very strong blue-UV “excess”. This blue and UV continuum in low-excitation HH Objects was noted as a problem by Brugel, Böhm and Mannery (1981), Ortalani and D'Odorico (1980) and Böhm, Böhm-Vitense and Brugel (1981). The first suggestion that it results from collisionally enhanced Hydrogen two-photon (2q) continuum was by Dopita (1981). The subsequent observations of Dopita, Binette and Schwartz (1982) proved that this was indeed the case. However, although very close correlations between this enhancement and the emission-line spectrum were found, a fair theoretical description could only be obtained for very youthful shock models with ages of order 30 years. However, there seems to be no reason why low excitation HH shocks should be much younger than the high excitation shocks.

Calculation of the ionization and emission line spectrum of the T Tau nebula

Astrophysics ◽  
1979 ◽  
Vol 15 (2) ◽  
pp. 188-194
Author(s):  
V. V. Golovatyi ◽  
I. V. Shpychka ◽  
O. S. Yatsyk
Keyword(s):  
Emission Line ◽  
Line Spectrum ◽  
Emission Line Spectrum ◽  
T Tau
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