scholarly journals Doppler Imaging of Starspots

1983 ◽  
Vol 71 ◽  
pp. 379-385
Author(s):  
Steven S. Vogt ◽  
G. Donald Penrod
Keyword(s):  
Doppler Imaging ◽  
Stellar Disk ◽  
Doppler Velocity ◽  
High Signal ◽  
Line Profiles ◽  
Signal To Noise ◽  
Rs Cvn Stars ◽  
Spot Model ◽  
Very High ◽  
General Appearance

ABSTRACTWe discuss a newly-developed technique for spatially resolving starspots on some of the more rapidly rotating RS CVn stars. Basically, the method uses high resolution, very high signal-to-noise spectral line profiles and exploits the Doppler velocity correspondence between position across the stellar disk and wavelength position across a rotationally broadened line profile to synthesize an image of the star, showing the location, sizes, and shapes of its starspots. Though still in a developmental stage, the technique is already yielding information about the structure and general appearance of starspots. Examples of Doppler Imaging observations of HR 1099 will be presented, along with a movie showing the behavior of synthetic line profiles generated from a computer spot model.

scholarly journals The first Doppler imaging of the active binary prototype RS Canum Venaticorum

2020 ◽  
Vol 492 (3) ◽  
pp. 3647-3656 ◽  
Author(s):  
Yue Xiang ◽  
Shenghong Gu ◽  
U Wolter ◽  
J H M M Schmitt ◽  
A Collier Cameron ◽  
...  
Keyword(s):  
High Resolution ◽  
Differential Rotation ◽  
Binary Star ◽  
Doppler Imaging ◽  
High Signal ◽  
Line Profiles ◽  
Signal To Noise ◽  
Spot Pattern ◽  
Deconvolution Technique ◽  
Modelling Studies

ABSTRACT We present the first Doppler images of the prototypical active binary star RS Canum Venaticorum, derived from high-resolution spectra observed in 2004, 2016 and 2017, using three different telescopes and observing sites. We apply the least-squares deconvolution technique to all observed spectra to obtain high signal-to-noise line profiles, which are used to derive the surface images of the active K-type component. Our images show a complex spot pattern on the K star, distributed widely in longitude. All star-spots revealed by our Doppler images are located below a latitude of about 70°. In accordance with previous light-curve modelling studies, we find no indication of a polar spot on the K star. Using Doppler images derived from two consecutive rotational cycles, we estimate a surface differential rotation rate of ΔΩ = −0.039 ± 0.003 rad d−1 and α = ΔΩ/Ωeq = −0.030 ± 0.002 for the K star. Given the limited phase coverage during those two rotations, the uncertainty of our differential rotation estimate is presumably higher.

scholarly journals Photospheric molecular line profiles in cool stars

1981 ◽  
Vol 59 ◽  
pp. 119-124
Author(s):  
S.T. Ridgway ◽  
E.D. Friel
Keyword(s):  
Spectral Lines ◽  
High Spectral Resolution ◽  
High Signal ◽  
Line Profiles ◽  
Signal To Noise ◽  
Molecular Line ◽  
Ejection Process ◽  
Cool Stars ◽  
Mass Ejection ◽  
Selection Of

AbstractSpectral lines of the ΔV=2 rotation vibration bands of CO are well suited for study of photospheric motions and the mass ejection process in cool stars. We have obtained high spectral resolution (1.8 km/sec) and high signal-to-noise (>102) line profiles for a selection of K and M giants. These profiles are being studied for evidence of gas motions in the photosphere and near circumstellar regions.

Anti-Vibration Sub Allows A Very High Signal-To-Noise Ratio And Improves Borehole Quality

2013 ◽  
Author(s):  
Paul Christian Bates ◽  
Chakib Bouziane ◽  
Denise Nicholl ◽  
Reina Teelken ◽  
Mohammed Zuki Bin Bidi ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
High Signal ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Very High

scholarly journals A Precise CN Measurement of the Microwave Background at 1.32 mm

1990 ◽  
Vol 139 ◽  
pp. 392-393
Author(s):  
David M. Meyer ◽  
Katherine C. Roth ◽  
Isabel Hawkins
Keyword(s):  
Cosmic Microwave Background ◽  
Brightness Temperature ◽  
High Signal ◽  
Microwave Background ◽  
Signal To Noise ◽  
Upper Limit ◽  
Vibrational Bands ◽  
Very High ◽  
Cmb Temperature ◽  
Line Strengths

We present very high signal-to-noise observations of the (1,0) and (0,0) vibrational bands of interstellar CN near 3580 and 3874 Å toward HD 21483. Corrected for saturation with a derived b-value of 1.29±0.05 km s-1, these CN line strengths yield excitation temperatures of 2.83±0.09 and 2.76±0.07 K for the J=1-2 and J=0-1 rotational transitions at 1.32 and 2.64 mm. In the absence of local CN excitation, these values represent the brightness temperature of the cosmic microwave background (CMB) radiation at these wavelengths. Millimeter observations have revealed no CN emission at 2.64 mm toward HD 21483 and allow us to set a 2σ upper limit of 0.11 K on the contribution of local processes to the J=0-1 excitation. Considering this limit and the lesser likelihood of local J=1-2 excitation, our observations indicate a CMB temperature of 2.83±0.09 K at 1.32 mm.

Electroionization study of ethylene: structures in the ionization and appearance curves

1987 ◽  
Vol 65 (7) ◽  
pp. 803-807 ◽  
Author(s):  
Pierre Plessis ◽  
Paul Marmet
Keyword(s):  
Carbon Atom ◽  
High Signal ◽  
Signal To Noise ◽  
Monoenergetic Electron ◽  
Text Production ◽  
Text Fragment ◽  
First Time ◽  
Fragmentation Processes ◽  
Fragment Production ◽  
Very High

Ionization-efficiency curves with very high signal-to-noise ratios for ethylene and all fragments consisting of at least one carbon atom are presented and analyzed. The curves are produced by monoenergetic electron impact and extend up to 10 eV above threshold. Most of the structures observed thus far by this method for these regions are reported here for the first time. Competition between [Formula: see text] production and [Formula: see text] and [Formula: see text] fragment production is clearly seen in the respective curves. Features occurring at the same energy in several of the curves indicate that these are due to a common progenitor, particularly the [Formula: see text] complex. The appearance of different fragmentation processes accounts for the onset-type structure found in some of the fragment-ion curves.

scholarly journals Effective Temperatures and Gravities for O-Type Stars Determined from High Precision Line Profiles and Wind-Blanketed Model Atmospheres

1988 ◽  
Vol 132 ◽  
pp. 127-130 ◽  
Author(s):  
B. Bohannan ◽  
S. A. Voels ◽  
D. C. Abbott ◽  
D. G. Hummer
Keyword(s):  
Spectral Type ◽  
Massive Stars ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Line Profiles ◽  
Astronomical Instrumentation ◽  
Signal To Noise ◽  
Effective Temperatures ◽  
Stellar Properties

Analysis of line profiles obtained with astronomical instrumentation capable of high signal-to-noise ratio spectroscopy have contributed significant new precision to the determination of the basic stellar parameters of hot, luminous, mass-loosing stars. Accurate measurement of such stellar properties as effective temperature and helium abundance for stars of spectral type O and early B is important not only to the physics of these stars but also to the environment in which they are located. The overall goals of the work we summarize here are to refine the spectral-type vs. temperature calibration for the most massive stars and to determine helium abundances for stars that are loosing mass at a rate sufficiently high to affect their evolution. Details of our procedures are described in the analysis of ξ Puppis by Bohannan et al. (1986).

scholarly journals Lineshape spectroscopy with a very high resolution, very high signal-to-noise crystal spectrometer

2016 ◽  
Vol 87 (6) ◽  
pp. 063501 ◽  
Author(s):  
P. Beiersdorfer ◽  
E. W. Magee ◽  
G. V. Brown ◽  
H. Chen ◽  
J. Emig ◽  
...  
Keyword(s):  
High Resolution ◽  
High Signal ◽  
Signal To Noise ◽  
Crystal Spectrometer ◽  
Very High

scholarly journals Spectroscopy of Cool Stars from IUE Data

1988 ◽  
Vol 132 ◽  
pp. 163-168
Author(s):  
P. G. Judge
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
High Signal ◽  
Line Profiles ◽  
Signal To Noise ◽  
High Quality ◽  
Atmospheric Structure ◽  
General Properties ◽  
Cool Stars ◽  
The Impact

After nine years of operation the IUE satellite continues to provide valuable spectra of cool stars from 1200 to 3100 Å. The impact of these spectra has been greatest in studies of the outer regions of the atmospheres, above the photospheres, allowing the general properties of stellar chromospheres, transition regions and winds to be established. After outlining these properties, I focus on studies based on high signal–to–noise echelle spectra (λ/Δλ ∼1.2 ×104) of single stars, showing how high quality emission line profiles have been used to derive constraints on the outer atmospheric structure, which in turn have been used to examine models of heating and mass loss.

Sign in / Sign up

Export Citation Format

Share Document