scholarly journals Activity in the circumstellar envelope of the Be/shell star ζ Tau

1994 ◽  
Vol 162 ◽  
pp. 372-373
Author(s):  
Yulian Guo ◽  
Lin Huang ◽  
Jinxin Hao
Keyword(s):  
Radial Velocity ◽  
Orbital Period ◽  
Absorption Lines ◽  
Circumstellar Envelope ◽  
Cyclic Variation ◽  
Spectroscopic Binary ◽  
Velocity Variations ◽  
Shell Star

ζ Tau is a well-known V/R-variable shell star. It is a single-lined spectroscopic binary with an orbital period of 133 days (Harmanec 1984, and Jarad 1987). Delplace (1970) found that the long-term radial velocity variations of the Balmer shell absorption lines are cyclic in 1960–67. Subsequently, similar behaviour has been observed and studied by several authors (Delplace and Chambon 1976, Hubert-Delplace et al 1983, Harmanec 1984, and Guo and Cao 1987). Mon et al (1992) showed that the cyclic variation had terminated and the star seems to have entered a new quiet phase around 1982.

scholarly journals A Spectroscopic and Photometric Study of the Shell Star EW Lac

2000 ◽  
Vol 175 ◽  
pp. 554-557
Author(s):  
Huilai Cao ◽  
Zhongwei Li ◽  
Lin Huang ◽  
Yulian Guo
Keyword(s):  
Active Phase ◽  
Anomalous Behavior ◽  
Absorption Lines ◽  
Photometric Study ◽  
Short Term ◽  
Photometric Observations ◽  
Shell Star

AbstractWe report on combined spectroscopic and photometric observations of EW Lac during its outburst of 1983. At this time the star’s Hα and Hβ lines showed strong doubled-peaked emission profiles which were variable with time. UBV photometry exhibited a long-term and frequent erratic short-term variations. The amplitude of U, B and V variations reached about 0.3 magnitude on October 15, 1983. Both Hβ emission and the structure of the shell absorption lines of the star also displayed anomalous behavior in 1983. It is evident that this star was in a strong active phase at that time.

scholarly journals The Long-term Variation in the RV Tauri Star U Mon

1995 ◽  
Vol 155 ◽  
pp. 409-410 ◽  
Author(s):  
Karen R. Pollard ◽  
P. L. Cottrell
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Radial Velocity ◽  
Tauri Star ◽  
Short Term ◽  
Instability Strip ◽  
Term Variation ◽  
Velocity Variations

The RV Tauri stars are semiregular pulsating variables located in the brightest part of the Cepheid II instability strip. They have a characteristic light curve of alternating deep and shallow minima. A subset of the RV Tauri stars (the RVb subclass) exhibit long-term (500 to 2600 day) light and radial velocity variations. Although it is well established that the short-term variations are due to pulsations, the long-term behaviour is not well understood.BVRI photometry and high-resolution spectra of U Mon (the brightest member of the RVb subclass) were obtained at the Mt John University Observatory (MJUO) between 1990 Aug and 1994 May. The light and colour curves obtained clearly show the long-term variation in U Mon (Fig. 1(a) and (b)). The reddest colours occur slightly later than the long-term minimum in the light curve. The short-term light and colour variations are ‘damped’ at the long-term minimum.

scholarly journals Precise Radial Velocities

1992 ◽  
Vol 135 ◽  
pp. 67-72
Author(s):  
Gordon A.H. Walker
Keyword(s):  
Radial Velocity ◽  
Radial Velocities ◽  
Velocity Variations ◽  
Low Amplitude

AbstractCurrent techniques for the detection of long-term, low-amplitude (<50 m s−1), radial velocity variations are briefly reviewed together with some of their most successful programs. In the era of 8- to 10-m telescopes we must strive for a precision of < 1ms−1.

scholarly journals Precise Radial Velocities of F, G, K Dwarfs

1988 ◽  
Vol 132 ◽  
pp. 79-81
Author(s):  
Bruce Campbell ◽  
Gordon A. H. Walker
Keyword(s):  
Radial Velocities ◽  
Absorption Lines ◽  
Spectroscopic Binaries ◽  
Brown Dwarf ◽  
Dwarf Stars ◽  
Low Level ◽  
The Past ◽  
Velocity Variations

We have monitored changes in the radial velocities of 24 bright F, G and K dwarf stars (known spectroscopic binaries excluded) for the past six years at CFHT by imposing the absorption lines of HF gas in the spectra to act as wavelength fiducials. The average external error in the δ(velocities) which are based on some 16 stellar lines is 13 m/s corresponds to 0.6 micron in the spectrum or 0.04 of a diode spacing per line. Reductions are complete for 16 stars. There is no evidence for brown dwarf companions in the sample. Two previously unknown spectroscopic binaries were found, and seven stars show indications of significant, long-term, low-level velocity variations which could be interpreted as purturbations by companions of a few Jupiter masses with periods greater than 12 years except for γ Cep, which may have a period of 2.7 years, and ε Eri. Observing time has been guaranteed for at least two more years at CFHT.

Long-term radial velocity variations in some Be stars

1982 ◽  
Vol 83 (1-2) ◽  
pp. 381-390 ◽  
Author(s):  
Elio Antonello ◽  
Massimo Fracassini ◽  
Laura Enrica Pasinetti ◽  
Livio Pastori
Keyword(s):  
Radial Velocity ◽  
Be Stars ◽  
Velocity Variations

Radial Velocity Variations of the Be Shell Star V923 AQL /HD 183556/ in the Past Sixty Years

Algols ◽  
1989 ◽  
pp. 377-377
Author(s):  
P. Koubský ◽  
A. F. Gulliver ◽  
P. Harmanec ◽  
D. Ballereau ◽  
J. Chauville ◽  
...  
Keyword(s):  
Radial Velocity ◽  
The Past ◽  
Velocity Variations ◽  
Shell Star

scholarly journals Two new double-lined spectroscopic binary white dwarfs

2020 ◽  
Vol 493 (2) ◽  
pp. 2805-2816 ◽  
Author(s):  
Mukremin Kilic ◽  
A Bédard ◽  
P Bergeron ◽  
Alekzander Kosakowski
Keyword(s):  
Radial Velocity ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Mass Ratio ◽  
Orbital Parameters ◽  
Long Period ◽  
Spectroscopic Binary ◽  
Velocity Variations ◽  
Period System

ABSTRACT We present radial velocity observations of four binary white dwarf candidates identified through their overluminosity. We identify two new double-lined spectroscopic binary systems, WD 0311–649 and WD 1606+422, and constrain their orbital parameters. WD 0311–649 is a 17.7 h period system with a mass ratio of 1.44 ± 0.06 and WD 1606+422 is a 20.1 h period system with a mass ratio of 1.33 ± 0.03. An additional object, WD 1447–190, is a 43 h period single-lined white dwarf binary, whereas WD 1418–088 does not show any significant velocity variations over time-scales ranging from minutes to decades. We present an overview of the 14 overluminous white dwarfs that were identified by Bédard et al., and find the fraction of double- and single-lined systems to be both 31 per cent. However, an additional 31 per cent of these overluminous white dwarfs do not show any significant radial velocity variations. We demonstrate that these must be in long-period binaries that may be resolved by Gaia astrometry. We also discuss the overabundance of single low-mass white dwarfs identified in the SPY survey, and suggest that some of those systems are also likely long-period binary systems of more massive white dwarfs.

Radial Velocity and Profile Variations of the Ultraviolet Circumstellar Lines in ζ Tauri

1984 ◽  
Vol 80 ◽  
pp. 139-144
Author(s):  
D. N. Dawanas ◽  
R. Hirata
Keyword(s):  
Radial Velocity ◽  
Resonance Line ◽  
Neutral Atoms ◽  
The Core ◽  
Velocity Variations ◽  
Shell Star

AbstractThe radial velocity and profile variations of UV lines of the shell star ζ Tau have been examined in the IUE spectra obtained in 1978-1982. The neutral atoms, and once or twice-ionized ions (except C II, Al III, Si III resonance lines) follow the same velocity variations as in the visual spectra, while the Si IV and C IV resonance lines show a constant negative velocity (~ -50 km s− at the core). The Al III, C II resonance lines and probably Fe III (mult. No. 34) are formed in both regions, i.e., in lowly-ionized and highly-ionized regions and the Si III resonance line is formed in a highly-ionized region.

scholarly journals Voyager Observations of Zeta Tau

1987 ◽  
Vol 92 ◽  
pp. 274-277
Author(s):  
T. E. Carone ◽  
R. S. Polidan
Keyword(s):  
Spectral Type ◽  
Orbital Period ◽  
Shell Star ◽  
Long Term Variations

Zeta Tau (HD 37202) is a well known Be/shell star of spectral type B1 IVe and vsin(i) = 220 km/sec (Slettebak 1982). Its visual and UV variability have been studied extensively (Heap 1975; Hubert-Delplace and van der Hucht 1978; Hubert-Delplace et al. 1983; Dawanas and Hirata 1984; Harmanec 1984). Zeta Tau has also been found to be a binary with an orbital period of 132.97 days (Harmanec 1984). Irregular light variations have been observed (Hoffleit 1982) and long term variations not associated with the 132.97 day period have also been seen (Hubert-Delplace et al. 1983).

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