scholarly journals Rapid variability of Hα emission line in Be stars

1994 ◽  
Vol 162 ◽  
pp. 254-256
Author(s):  
B. G. Anandarao ◽  
A. Chakraborty ◽  
R. Swaminathan ◽  
B. Lokanadham
Keyword(s):  
Emission Line ◽  
Emission Lines ◽  
Be Stars ◽  
Rapid Variability ◽  
Fabry Perot ◽  
Dark Counts ◽  
Hα Emission

We have initiated an observational campaign on some bright Be stars in order to investigate the rapid variability in emission lines using a Fabry-Perot spectrometer(λ/δλ = 104; FSR = 21.3Å) at the Nasmyth focus of the 1.22 m JRO telescope at Hyderabad, India. The PMT dark counts were 1 – 2sec-1. Here we report our first observations on four stars.

scholarly journals Simultaneous Spectroscopy and Polarimetry of Be Stars

1987 ◽  
Vol 92 ◽  
pp. 84-86
Author(s):  
D. R. Gies ◽  
David McDavid
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Absorption Line ◽  
Line Profile ◽  
Circumstellar Envelope ◽  
Be Stars ◽  
Line Profiles ◽  
Initial Attempt ◽  
Rapid Variability ◽  
Hα Emission

Evidence is now accumulating that many Be stars display photospheric line profile variations on timescales of days or less that are probably caused by nonradial pulsations (Baade 1984; Penrod 1986). In some circumstances these pulsations can promote mass loss into the circumstellar envelope, and consequently the conditions in the inner part of the envelope may vary on similar timescales. Changes in the envelope could produce variations in the polarization and emission line profiles, and observers have reported rapid variability in both. We describe here an initial attempt to search for simultaneous variations in continuum polarization, Hα emission, and the He I λ6678 photospheric absorption line in order to investigate correlated changes on short timescales.

scholarly journals Variability of Some Be Stars on High-Resolution, High S/N Spectra

1988 ◽  
Vol 132 ◽  
pp. 131-134
Author(s):  
A. M. Hubert ◽  
H. Hubert ◽  
B. Dagostinoz ◽  
M. Floquet
Keyword(s):  
Emission Line ◽  
Time Scale ◽  
Signal To Noise Ratio ◽  
Complex Structure ◽  
Ccd Camera ◽  
Brightness Distribution ◽  
Short Time Scale ◽  
Be Stars ◽  
Rapid Variability ◽  
Hα Emission

Rapid variability in Be stars could be understood by non radial pulsations or by rotation of an inhomogeous surface brightness distribution…The structure and the variability of the Hα and of the HeI λ6678 lines have been investigated with an optical fiber spectrograph and a CCD camera. The signal to noise ratio, measured in the continuum, is between 300 and 500.Weak changes in the Hα emission line profile of γ Cas have been detected on time-scale of hours and days. This line has an asymmetric profile exhibiting only one blue-shifted maximum while the HeI λ6678 has a double-peak emission, superimposed to the photospheric contribution, with a violet to red peak ratio V/R >1.The Hα emission line of φ Per exhibits a complex structure with significant changes in its core, from night to night and on a short time scale <lhr. The HeI λ6678 presents a blue-shifted asymmetric emission (red-winged) superimposed to the photospheric contribution.Furthermore the Hel photospheric line λ6678 of the B6 star o And has presented notable variations in its profile during the 2 observational campaigns, which do not seem correlated to the photometric period of 1.57 day.

scholarly journals New Spectroscopic Observations of Dwarf Nova BZ Ursae Majoris with Extremely Unusual Emission Lines Profiles

2004 ◽  
Vol 194 ◽  
pp. 269-269 ◽  
Author(s):  
V. V. Neustroev ◽  
S. V. Zharikov ◽  
A. Medvedev ◽  
A. Shearer
Keyword(s):  
Radial Velocity ◽  
Emission Line ◽  
Velocity Curve ◽  
Emission Lines ◽  
Radial Velocity Curve ◽  
Dwarf Nova ◽  
Preliminary Results ◽  
Spectroscopic Observations ◽  
Medium Resolution ◽  
Hα Emission

We present preliminary results of new spectroscopic observations of dwarf nova BZ UMa in quiescence. Fifty medium resolution spectra allow us to reproduce the radial velocity curve from the Hα emission line. We confirm that BZ UMa shows extremely unusual emission lines profiles, Unlike the classical single or the double-peaked profiles usually observed in spectra of dwarf novae, emission lines of BZ UMa consist of at least five peaks.

Rapid Variability of H α Emission Line in Be Stars

1994 ◽  
pp. 254-256
Author(s):  
B. G. Anandarao ◽  
A. Chakraborty ◽  
R. Swaminathan ◽  
B. Lokanadham
Keyword(s):  
Emission Line ◽  
Be Stars ◽  
Rapid Variability

scholarly journals Spectral Line Variations of Symbiotic Stars EG And, AG Dra, and BX Mon and Its Interpretation

2012 ◽  
Vol 8 (S290) ◽  
pp. 353-354
Author(s):  
Tae Seog Yoon ◽  
Soo Hyun Kim ◽  
Hyeonwoo Moon ◽  
Kyu-Seob Kim ◽  
Hyungil Oh
Keyword(s):  
High Resolution ◽  
Spectral Line ◽  
Emission Line ◽  
Emission Lines ◽  
Symbiotic Stars ◽  
Astronomy Observatory ◽  
Echelle Spectrograph ◽  
Balmer Lines ◽  
Hα Emission ◽  
Optical Astronomy

AbstractWe present some results obtained by high resolution spectroscopic observations for symbiotic stars EG And, AG Dra, and BX Mon in recent years which were performed with 1.8-m reflector and echelle spectrograph BOES at Bohyunsan Optical Astronomy Observatory, Youngcheon, South Korea. The variations of Hα emission line during a night and the variations of H Balmer lines and He I emission lines among several analyzed lines over months and years are shown and discussed.

scholarly journals Hα Survey of the Large Magellanic Cloud

1995 ◽  
Vol 149 ◽  
pp. 155-159 ◽  
Author(s):  
A. Laval ◽  
E. le Coarer ◽  
Y.P. Georgelin ◽  
M. Marcelin ◽  
P. Amram ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Emission Line ◽  
Large Magellanic Cloud ◽  
Central Core ◽  
Evolutionary Stage ◽  
Line Profiles ◽  
Fabry Perot ◽  
Hα Emission ◽  
Spherical Expansion ◽  
The One

AbstractThe LMC is being surveyed in the Hα emission line with a scanning Fabry-Perot interferometer, attached to the 36 cm telescope of the Observatoire de Marseille. The present results concern the kinematical mapping of bright nebulae; it shows that the kinetic energy involved in the gas motion is closely related to the evolutionary stage of the embedded stars. In particular, in the 30 Dor nebula, a few one-peaked line profiles remain at the boundaries of the shells, among the numerous split areas. The 50-100 pc shells exhibit a relatively usual spherical expansion, with velocities in the same range at the boundaries. On the contrary, the 10-20 pc shells of the central core show different velocities of the one-peak sides of the shells.

scholarly journals Variability of the Emission-Line Spectrum of the Nucleus of the Seyfert Galaxy NGC 7469

1975 ◽  
Vol 67 ◽  
pp. 605-609
Author(s):  
I. I. Pronik
Keyword(s):  
Emission Line ◽  
Seyfert Galaxy ◽  
Emission Lines ◽  
Time Variability ◽  
Variable Time ◽  
Balmer Lines ◽  
Hα Emission ◽  
Emission Line Spectrum ◽  
Hydrogen Lines ◽  
Ngc 7469

It is shown that the emission lines of the NGC 7469 nucleus spectrum are variable. Time variability of hydrogen lines is less than 20 days. The Hα emission line is at the profile base about a factor of two narrower than the Hγ line. Estimation of the density of hydrogen envelope, where Balmer lines wings were emitted, gives the value of about 108–109 cm−3.

scholarly journals High-Resolution Emission-Line Spectroscopy of Be Stars: Comparison of Hα and Weak Emission Lines

1987 ◽  
Vol 92 ◽  
pp. 208-210
Author(s):  
Reinhard W. Hanuschik
Keyword(s):  
High Resolution ◽  
Emission Line ◽  
Rotational Velocity ◽  
Outer Radius ◽  
Emission Lines ◽  
Be Stars ◽  
Line Profiles ◽  
Component Structure ◽  
Double Peak Structure ◽  
Disk Component

AbstractFor a number of bright southern Be stars, high-resolution, high S/N spectroscopy has been performed for Hα, Si II λ6371 and four Fe II emission lines. With the exception of four stars, both Hα and weak emission line profiles exhibit resolved double-peak structure. Peak separation increases with stellar projected rotational velocity. In many cases, Hα profiles (but not Fe II lines) show resolved fine-structure (inflections in the flanks) indicating a two-component structure of the disk. Envelope models with arbitrary density and rotational velocity laws have been fitted to the Fe II line profiles with satisfactory results. It is found that the innermost Hα disk component also emits the Fe II lines and has an average outer radius of 5 r*; density falls off as r-l.5 or more rapidly. The outer disk component emits the faint and narrow secondary component of Hα lines with average outer radius 20 r*. The envelopes of the four stars with a strong, dominating single peak both in Hα and Fe II either are dominated by strong radial motions or, more likely, have elliptical disk-like structure.

scholarly journals Emission-Line Variability and the Nature of the Broad-Line Region

1989 ◽  
Vol 134 ◽  
pp. 97-99
Author(s):  
B. M. Peterson
Keyword(s):  
Emission Line ◽  
Strong Correlation ◽  
Emission Lines ◽  
Broad Line ◽  
Rapid Variability ◽  
Broad Line Region ◽  
Line Region

Variability of the emission-line spectra of broad-line AGNs is now a well-established phenomenon (see Peterson 1988 for a review). The rapid variability of the emission lines and the strong correlation between continuum and line fluxes suggests broad-line region (BLR) dimensions too small to be consistent with theoretical estimates based on photoionization equilibrium considerations.

scholarly journals Hα KINEMATICS OF THE ISOLATED INTERACTING GALAXY PAIR KPG 486 (NGC 6090)

2020 ◽  
Vol 56 (1) ◽  
pp. 71-83
Author(s):  
M. M. Sardaneta ◽  
M. Rosado ◽  
M. Sánchez-Cruces
Keyword(s):  
Velocity Field ◽  
Emission Line ◽  
Kinematic Analysis ◽  
Rotation Curve ◽  
Dynamic Behaviour ◽  
Hydrogen Gas ◽  
Kinematic Parameters ◽  
Optical Images ◽  
Fabry Perot ◽  
Hα Emission

In optical images, the barely studied isolated interacting galaxy pair KPG 486 (NGC 6090) displays similar features to the Antennae (NGC 4038/39) galaxy pair. To compare the distribution of ionized hydrogen gas, morphology and kinematic and dynamic behaviour of both galaxy pairs, we present observations in the Hα emission line of NGC 6090 acquired with the scanning Fabry-Perot interferometer, PUMA. For each galaxy in NGC 6090 we obtained several kinematic parameters, its velocity field and its rotation curve. We also analysed some of the perturbations induced by their encounter. We verified the consistency of our results by comparing them with kinematic results from the literature. The comparison of our results on NGC 6090 with those obtained in a previous similar kinematic analysis of the Antennae highlighted great differences between these galaxy pairs.

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