scholarly journals First Detection of a Frequency Multiplet in the Line Profile Variations of RR Lyrae: Towards an Understanding of the Blazhko Effect

2000 ◽  
Vol 176 ◽  
pp. 286-290 ◽  
Author(s):  
K. Kolenberg ◽  
C. Aerts ◽  
M. Chadid ◽  
D. Gillet
Keyword(s):  
Line Profile ◽  
Theoretical Models ◽  
Theoretical Modelling ◽  
Line Profiles ◽  
Multiplet Structure ◽  
Complete Understanding ◽  
Period Analysis ◽  
Essential Step ◽  
Rr Lyrae ◽  
Blazhko Effect

AbstractWe provide the first detection of a frequency multiplet in the line profile variations of RR Lyrae. Performing a period analysis on 669 high resolution line profiles obtained with the spectrograph ELODIE at OHP, we clearly detect a multiplet structure, with a separation equal to the Blazhko frequency, around the main frequency and its harmonics. The triplet components are very prominent; additional observations are needed to decide about the existence of a quintuplet. The complete understanding of the origin of the Blazhko effect still needs further theoretical modelling and better observations. Our detection of the frequency multiplet in the line profile variations is a first essential step towards a decisive confrontation between the theoretical models and the observations.

scholarly journals The Blazhko Effect Unravelled?

2002 ◽  
Vol 185 ◽  
pp. 414-415
Author(s):  
K. Kolenberg ◽  
C. Aerts ◽  
M. Chadid ◽  
D. Gillet
Keyword(s):  
Frequency Analysis ◽  
Strong Evidence ◽  
Fundamental Mode ◽  
Multiplet Structure ◽  
Main Frequency ◽  
Rr Lyrae ◽  
Non Linear ◽  
Blazhko Effect ◽  
Linear Effects

AbstractA detailed frequency analysis on ELODIE observations of the Blazhko star RR Lyrae (Chadid et al., 1999) clearly revealed the importance of non-linear effects upon the radial fundamental mode (with frequency fP), and a multiplet structure with a separation equal to the Blazhko frequency (f/B) around the main frequency and its harmonics. These results provided strong evidence for the presence of non-radial modes in the star. The identification of these non-radial modes is the following step in our work.

scholarly journals The Kinematics of Quasar Broad Emission Line Regions Using a Disk-Wind Model

2017 ◽  
Vol 34 ◽  
Author(s):  
Suk Yee Yong ◽  
Rachel L. Webster ◽  
Anthea L. King ◽  
Nicholas F. Bate ◽  
Matthew J. O’Dowd ◽  
...  
Keyword(s):  
Emission Line ◽  
Line Profile ◽  
Inclination Angle ◽  
Opening Angle ◽  
Line Profiles ◽  
Wind Model ◽  
Disk Wind ◽  
Reverberation Mapping ◽  
Broad Emission ◽  
Line Region

AbstractThe structure and kinematics of the broad line region in quasars are still unknown. One popular model is the disk-wind model that offers a geometric unification of a quasar based on the viewing angle. We construct a simple kinematical disk-wind model with a narrow outflowing wind angle. The model is combined with radiative transfer in the Sobolev, or high velocity, limit. We examine how angle of viewing affects the observed characteristics of the emission line. The line profiles were found to exhibit distinct properties depending on the orientation, wind opening angle, and region of the wind where the emission arises.At low inclination angle (close to face-on), we find that the shape of the emission line is asymmetric, narrow, and significantly blueshifted. As the inclination angle increases (close to edge-on), the line profile becomes more symmetric, broader, and less blueshifted. Additionally, lines that arise close to the base of the disk wind, near the accretion disk, tend to be broad and symmetric. Single-peaked line profiles are recovered for the intermediate and equatorial wind. The model is also able to reproduce a faster response in either the red or blue sides of the line profile, consistent with reverberation mapping studies.

scholarly journals The Blazhko Effect of the RR Lyrae Star FM Persei

2001 ◽  
Vol 113 (785) ◽  
pp. 835-838 ◽  
Author(s):  
Kevin M. Lee ◽  
Edward G. Schmidt
Keyword(s):  
Rr Lyrae ◽  
Blazhko Effect

scholarly journals Detecting shock waves in non-fundamental mode RR Lyrae using large sample of spectra in SDSS and LAMOST

2020 ◽  
pp. 181-186
Author(s):  
Xiao-Wei Duan ◽  
Xiao-Dian Chen ◽  
Li-Cai Deng ◽  
Fan Yang ◽  
Chao Liu ◽  
...  
Keyword(s):  
Shock Waves ◽  
Fundamental Mode ◽  
Variable Stars ◽  
Ionization Zone ◽  
Rr Lyrae Stars ◽  
Hydrogen Emission ◽  
Emission Signal ◽  
Rr Lyrae ◽  
Hydrogen Emission Lines ◽  
Blazhko Effect

Steps toward the nature inside RR Lyrae variables can not only improve our understanding of variable stars but also innovate the precision when we use them as tracers to map the structure of the universe. In this work, we develop a hand-crafted one-dimensional pattern recognition pipeline to fetch out the "first apparitions", the most prominent observational characteristic of shock. We report the first detection of hydrogen emission lines in the first-overtone and multi-mode RR Lyrae variables. We find that there is an anti-correlation between the intensity and the radial velocity of the emission signal, which is possibly caused by opacity changing in the helium ionization zone. Moreover, we find one RRd star with hydrogen emission that possibly shows Blazhko-type modulations. According to our discoveries, with an enormous volume of upcoming data releases of variable stars and spectra, it may become possible to build up the bridge between shock waves and big problems like the Blazhko effect in non-fundamental mode RR Lyrae stars.

Ca II Emission from Late-type Stars

1983 ◽  
Vol 5 (2) ◽  
pp. 152-157 ◽  
Author(s):  
L. E. Cram
Keyword(s):  
Line Profile ◽  
Strong Correlation ◽  
Velocity Fields ◽  
Line Profiles ◽  
Late Type ◽  
Wide Range ◽  
Cool Stars ◽  
Visual Magnitude ◽  
The Absolute ◽  
Emission Core

Two recent observational surveys of the Ca II resonance lines (Zarro and Rodgers 1983; Linsky et al. 1979) illustrate the great diversity of line profile shapes found in the spectra of cool stars. This diversity reflects a corresponding wide range in the underlying chromospheric properties of the stars. There are, however, three well-marked systematic trends in the shapes of Ca II line profiles which presumably reflect systematic trends in chromospheric properties. One of these, the Wilson-Bappu effect (Wilson and Bappu 1957), describes the strong correlation betweeen the width of the emission core (see Figure 1) and the absolute visual magnitude of the star. Despite much work, it is still not clear whether this is due primarily to systematic changes of velocity fields (e.g. Hoyle and Wilson 1958) or optical depths (e.g. Jefferies and Thomas 1959) in stellar chromospheres.

scholarly journals New Progress in Mode Detection and Identification in δ Scuti Stars by the Analysis of Line Profile Variations

2000 ◽  
Vol 176 ◽  
pp. 463-464
Author(s):  
L. Mantegazza ◽  
E. Poretti ◽  
M. Bossi ◽  
N. S. Nuñez ◽  
A. Sacchi ◽  
...  
Keyword(s):  
High Resolution ◽  
Line Profile ◽  
High Resolution Spectroscopy ◽  
Line Profiles ◽  
Powerful Technique ◽  
Mode Detection ◽  
Detection And Identification ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Nonradial Pulsation

Abstractδ Sct stars are among the most promising targets to perform ground-based asteroseismology. High resolution spectroscopy offers us a powerful technique to identify radial and nonradial pulsation modes, since we can easily detect oscillations and travelling features in the line profiles.

scholarly journals Bioinspired aerofoil adaptations: the next steps for theoretical models

2019 ◽  
Vol 377 (2159) ◽  
pp. 20190070 ◽  
Author(s):  
Lorna J. Ayton
Keyword(s):  
Experimental Data ◽  
Theoretical Models ◽  
Theoretical Modelling ◽  
Experimental Measurements ◽  
Far Field ◽  
Acoustic Analogy ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Theoretical Predictions ◽  
Field Noise

The extended introduction in this paper reviews the theoretical modelling of leading- and trailing-edge noise, various bioinspired aerofoil adaptations to both the leading and trailing edges of blades, and how these adaptations aid in the reduction of aerofoil–turbulence interaction noise. Attention is given to the agreement between current theoretical predictions and experimental measurements, in particular, for turbulent interactions at the trailing edge of an aerofoil. Where there is a poor agreement between theoretical models and experimental data the features neglected from the theoretical models are discussed. Notably, it is known that theoretical predictions for porous trailing-edge adaptations do not agree well with experimental measurements. Previous works propose the reason for this: theoretical models do not account for surface roughness due to the porous material and thus omit a key noise source. The remainder of this paper, therefore, presents an analytical model, based upon the acoustic analogy, to predict the far-field noise due to a rough surface at the trailing edge of an aerofoil. Unlike previous roughness noise models which focus on roughness over an infinite wall, the model presented here includes diffraction by a sharp edge. The new results are seen to be in better agreement with experimental data than previous models which neglect diffraction by an edge. This new model could then be used to improve theoretical predictions for far-field noise generated by turbulent interactions with a (rough) porous trailing edge. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

scholarly journals MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’

2019 ◽  
Vol 490 (3) ◽  
pp. 4154-4165 ◽  
Author(s):  
M E Shultz ◽  
C Johnston ◽  
J Labadie-Bartz ◽  
V Petit ◽  
A David-Uraz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Light Curve ◽  
Line Profile ◽  
Longitudinal Magnetic Field ◽  
Stellar Structure ◽  
Line Profiles ◽  
Dipole Strength ◽  
Rotational Modulation ◽  
Brightness Modulation

ABSTRACT HD 62658 (B9p V) is a little-studied chemically peculiar star. Light curves obtained by the Kilodegree Extremely Little Telescope (KELT) and Transiting Exoplanet Survey Satellite (TESS) show clear eclipses with a period of about 4.75 d, as well as out-of-eclipse brightness modulation with the same 4.75 d period, consistent with synchronized rotational modulation of surface chemical spots. High-resolution ESPaDOnS circular spectropolarimetry shows a clear Zeeman signature in the line profile of the primary; there is no indication of a magnetic field in the secondary. PHOEBE modelling of the light curve and radial velocities indicates that the two components have almost identical masses of about 3 M⊙. The primary’s longitudinal magnetic field 〈Bz〉 varies between about +100 and −250 G, suggesting a surface magnetic dipole strength Bd = 850 G. Bayesian analysis of the Stokes V profiles indicates Bd = 650 G for the primary and Bd < 110 G for the secondary. The primary’s line profiles are highly variable, consistent with the hypothesis that the out-of-eclipse brightness modulation is a consequence of rotational modulation of that star’s chemical spots. We also detect a residual signal in the light curve after removal of the orbital and rotational modulations, which might be pulsational in origin; this could be consistent with the weak line profile variability of the secondary. This system represents an excellent opportunity to examine the consequences of magnetic fields for stellar structure via comparison of two stars that are essentially identical with the exception that one is magnetic. The existence of such a system furthermore suggests that purely environmental explanations for the origin of fossil magnetic fields are incomplete.

scholarly journals Oblique Pulsator Model for the Blazhko Effect of RR Lyrae Stars

1995 ◽  
Vol 155 ◽  
pp. 42-43
Author(s):  
Hiromoto Shibahashi ◽  
Masao Takata
Keyword(s):  
Rotation Axis ◽  
Oscillation Mode ◽  
Stellar Rotation ◽  
Rr Lyrae Stars ◽  
Aspect Angle ◽  
Rr Lyrae ◽  
Quadrupole Component ◽  
Blazhko Effect ◽  
Apparent Variation ◽  
Lyrae Stars

AbstractBy assuming that the RR Lyrae stars have fairly strong dipole magnetic fields with the symmetry axis oblique to the rotation axis of the star, we show that the oscillation mode which would be a pure radial oscillation in absence of the magnetic field has a quadrupole component, which is axisymmetric with respect to the magnetic axis. The aspect angle of the quadrupole component changes due to the stellar rotation, and this apparent variation is interpreted as the Blazhko effect in RR Lyrae stars.

scholarly journals Measurement of line profiles

1986 ◽  
Vol 118 ◽  
pp. 401-412
Author(s):  
David F. Gray
Keyword(s):  
Spectral Line ◽  
High Precision ◽  
Line Profile ◽  
Line Profiles ◽  
Spectral Line Profile ◽  
The University

The basic requirements for high precision spectral line profile measurements are reviewed, with the observatory at the University of Western Ontario serving to illustrate several of the points.

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