Low(est) Noise Reticon Detection Systems

Walker, G. A. H.; Johnson, R.; Yang, Sean

doi:10.1016/s0065-2539(08)61619-4

Cited by 7 publications

(7 citation statements)

References 5 publications

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“…The signal processing electronics of the original RL1872F/30 Reticon diode array were replaced with a lower noise system in 1983.5 (Walker et al 1985) and some residual coma was eliminated from the spectrograph. These changes improved both the precision and observing e ciency and the three stars, UMa, 61 Cyg B, and HR 8832 were added to the program at that time.…”

Section: The Observationsmentioning

confidence: 99%

A Search for Jupiter-Mass Companions to Nearby Stars

Walker

Irwin

et al. 1995

Icarus

164

139

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Section: The Observationsmentioning

confidence: 99%

A Search for Jupiter-Mass Companions to Nearby Stars

Walker

Irwin

et al. 1995

Icarus

164

139

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“…Gamma Boo was among the stars selected. Time series observations were made with the Dominion Astrophysical Observatory 1.22-m telescope coudé spectrograph and 1872 Reticon detector (Walker et al 1985) on 1990 September 4 and December 29. The reciprocal dispersion of these observations was 10 Ä mm -1 (0.15 Â pixel -1 ) with spectral coverage of 284 A centered at A ~ 4500 A.…”

Section: Observation and Analysis Of Y Boomentioning

confidence: 99%

Detection of high-degree nonradial pulsations in Gamma Bootis

Kennelly¹,

Yang²,

Walker³

et al. 1992

PASP

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The line-profile variations of the rapidly rotating <5 Scuti star y Bootis can be explained by high-degree ( | m \ -10) nonradial pulsations (NRPs) with an apparent period of Ai-0.047 days. This same period was derived from two data sets taken three months apart wherein the amplitude increased by 30%. Such high-degree NRP cannot explain the apparent reversals previously observed by Auvergne et al. for this star in the cores of the hydrogen Balmer lines and Ca II K line. Our radialvelocity variations can be reconciled with their 0.25 day spectroscopic period if an amplitude of -1 km s -* is adopted, an order of magnitude less than previous measurements. We demonstrate that the presence of line-profile variations from high-degree modes probably limits the accuracy of radialvelocity measurements and may appear as bumps in the radial-velocity curve.

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“…The detector was a liquid-nitrogen-cooled RL1872F/30 Reticon. A description of the detector and data-reduction procedure can be found in Walker, Johnson, and Yang (1985). Both spectrographs were used in the first order and provided reciprocal dispersions of about 10 A mm -1 .…”

Section: Observationsmentioning

confidence: 99%

Line-profile variations and dimensions of the Be star Omicron Andromedae

Hill¹,

Walker²,

Yang³

et al. 1989

PASP

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In an earlier paper we showed that the Be star o And is at least quadruple. Here we report the discovery of subfeatures at ^ 0.5% of the continuum traveling through the rotationally broadened absorption lines of the primary. The linewidths also vary with a period of 0?79 which is half of the photometric period (when light variations are present). Associated variations in equivalent width are not observed. If the linewidth variations are due to € = 2 nonradial pulsation (NRP), then this suggests the photometric period corresponds to the period of rotation if the phase velocity of the NRP is small. Interpretation of the moving subfeatures is less clear. If they are due to NRP carried across the line of sight by stellar rotation, the subfeature velocities and accelerations are consistent with Irai =6 ± 2. The visibility of the subfeatures out to about 300 km s' 1 in the line wings together with their measured acceleration at the line center implies an equatorial radius of 21 ± 8 R 0 while spectrophotometry indicates a radius of 9 ± 2 R 0 . Further, the photometric period is consistent with the rotational period implied by the spectrophotometric radius and published values of v sin i and i while the subfeature velocities and accelerations imply a rotational period of 2.6 ± 0.4 days.The magnitude difference between o And A and o And B gives the apparent magnitude of component A as 3.8 ± 0.1. Projected rotational-velocity estimates in the literature and our measurements suggest v sin i = 243 ± 24 km s' 1 . The spectral type of o And A seems to be closer to B5 than B6 and the luminosity class is II-III. The spectrophotometric distance to o And is 188 ± 27 pc which makes the Aa-B and A-a separations about 70 and 11 AU, respectively. The radial velocity of the primary has not varied by more than ± 1 km s _1 in over a year which excludes a close companion of stellar mass as an explanation for the rapid photometric and spectroscopic variations.

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Low(est) Noise Reticon Detection Systems

Cited by 7 publications

References 5 publications

A Search for Jupiter-Mass Companions to Nearby Stars

A Search for Jupiter-Mass Companions to Nearby Stars

Detection of high-degree nonradial pulsations in Gamma Bootis

Line-profile variations and dimensions of the Be star Omicron Andromedae

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