Papers by Austin Gulliver
Monthly Notices of the …, Jan 1, 1997
Monthly Notices of the Royal …, Jan 1, 1997
Monthly Notices of The Royal Astronomical Society, 1998
Elemental abundances of the early A stars epsilon Ser, 29 Vul and sigma Aqr are derived consisten... more Elemental abundances of the early A stars epsilon Ser, 29 Vul and sigma Aqr are derived consistently with previous studies of this series using spectrograms obtained with Reticon and CCD detectors. The derived abundances confirm that epsilon Ser is a definite Am star. 29 Vul shows evidence for a weakly operating Am star phenomenon. sigma Aqr, a hot Am star
Astronomy & Astrophysics, 2014
Context. The study of rotational velocity distributions for normal stars requires an accurate spe... more Context. The study of rotational velocity distributions for normal stars requires an accurate spectral characterization of the objects in order to avoid polluting the results with undetected binary or peculiar stars. This piece of information is a key issue in the understanding of the link between rotation and the presence of chemical peculiarities. Aims. A sample of 47 low v sin i A0-A1 stars (v sin i < 65km s −1 ), initially selected as main-sequence normal stars, are investigated with high-resolution and high signal-to-noise spectroscopic data. The aim is to detect spectroscopic binaries and chemically peculiar stars, and eventually establish a list of confirmed normal stars. Methods. A detailed abundance analysis and spectral synthesis is performed to derive abundances for 14 chemical species. A hierarchical classification, taking measurement errors into account, is applied to the abundance space and splits the sample into two different groups, identified as the chemically peculiar stars and the normal stars.
The Astrophysical Journal, 1981
Publications of the Astronomical Society of the Pacific, 1990
... LINE IDENTIFICATION AUSTIN F. GULLIVER AND JOACHIM G. STADEL Department of Physics and Astron... more ... LINE IDENTIFICATION AUSTIN F. GULLIVER AND JOACHIM G. STADEL Department of Physics and Astronomy, Brandon University, Brandon, MB R7A ... 034 based on the improved wavelengths of Iglesias and Velasco (1964) and the presence ofmost of the other members of ...
Physica Scripta, 1999
In the last 25 years the quality of data obtained from astronomical spectrographs has drastically... more In the last 25 years the quality of data obtained from astronomical spectrographs has drastically improved due to the wide spread use of electronic detectors, especially Charge Coupled Devices (CCDs) whose quantum efficiencies are approaching unity throughout much of the optical region. The typical signal-to-noise ratio (S/N) for a high dispersion spectrogram has increased from about 25 with photographic plates to between 100 and 300 with CCDs. Several reduction and analysis problems which were usually ignored at S/N = 25 must now be considered in detail, for example, scattered light in the spectrograph. Further, spectrum synthesis techniques are becoming more the norm, especially for the best understood types of stars. We examine the data needs from the perspective of spectrum synthesis and consider gf values, line damping parameters, hyperfine structure, and isotopic shifts. Proper interpretation of stellar spectra requires good quality atomic data. This is equally true for the sharp-lined stars and those with moderate rotational velocities, although the latter lack the resolution of the former. Astrophysical gf values can be important supplements to laboratory and theoretical values in obtaining the thousands of accurate and precise gf values needed to synthesize the optical region spectra of stars hotter than the Sun. The telluric spectrum, which our atmosphere superimposes upon stellar spectra, and specialized types of analyses such as those of interstellar lines and magnetic fields have their own data needs.
The Astrophysical Journal Supplement Series, 1977
... Houziaux, L. 1962, Pub. ASP, 74, 250. Kiess, M., Krogdahl, W., Bidelman, W., and Hall, RG 194... more ... Houziaux, L. 1962, Pub. ASP, 74, 250. Kiess, M., Krogdahl, W., Bidelman, W., and Hall, RG 1946, Pub. AAS, 10, 227. AUSTIN F. GULLIVER: Dominion Astrophysical Canada Kriz, S., and Harmanec, P. 1975, Bull. Astr. Inst. Czechoslovakia, 26, 65. Limber, DN 1969, Ap. ...
High-resolution optical spectra (UES/WHT) of the extreme metal-poor post-AGB star HR 4049 were ob... more High-resolution optical spectra (UES/WHT) of the extreme metal-poor post-AGB star HR 4049 were obtained at four different orbital phases. The spectra cover the wavelength region from 3650Å to 10850Å at a resolution of R = 5.2 × 10 4 . These observations are supplemented with four high-resolution spectra of the NaI D1 & D2 and CaII K lines at R ≈ 10 5 (CAT/CES). The optical spectrum shows 217 spectral lines: the Balmer series (Hα -H35), the Paschen series (P9 -P23), NI, OI and numerous CI lines. We show that the lines of Hα, Hβ, Hγ and NaI D show significant changes in profile between different observation dates. Nine components were identified in the profile of the NaI D lines of which three are circumstellar and six interstellar. The stronger CI lines are asymmetric and we derive a post-AGB mass-loss oḟ M= 6 ± 4 × 10 −7 M ⊙ yr −1 from the asymmetry. The [OI] 6300Å line has been detected in emission at the system velocity and we argue that the emission is from an almost edge-on disk with a radius of about 20 R * .
High-resolution optical spectra (UES/WHT) of the extreme metal-poor post-AGB star HR 4049 were ob... more High-resolution optical spectra (UES/WHT) of the extreme metal-poor post-AGB star HR 4049 were obtained at four different orbital phases. The spectra cover the wavelength region from 3650 ûA to 10850 ûA at a reso- lution of R = 5.2 × 104. These observations are supple- mented with four high-resolution spectra of the NaI D1 & D2 and CaII K lines
showed that the distribution of rotational velocities for A0-A1 stars is bimodal although all kno... more showed that the distribution of rotational velocities for A0-A1 stars is bimodal although all known peculiar and/or binary stars had been excluded from their sample. We present here the preliminary results of the abundance analysis for 47 A0-A1 "normal" main sequence stars selected with v sin i slower than 65 km s −1 . These high signal-to-noise spectra collected withÉLODIE and SOPHIE (OHP) will allow us to obtain a clean sample of low v sin i normal A0-A1 stars and search for intrinsic slow rotators.
The Astrophysical Journal, 2002
The variability of the Hg II λ3984 line in the primary of the binary star α And was discovered th... more The variability of the Hg II λ3984 line in the primary of the binary star α And was discovered through the examination of high-dispersion spectra with signal-to-noise ratios greater than 500. This first definitively identified spectrum variation in any mercury-manganese star is ...
The Astrophysical Journal, 1991
... V STAR VEGA AUSTIN F. GULLIVER Department of Physics and Astronomy, Brandon University, Brand... more ... V STAR VEGA AUSTIN F. GULLIVER Department of Physics and Astronomy, Brandon University, Brandon, Manitoba, Canada R7A 6A9 SAUL J. ADELMAN ... A further important development is the modification of the RET72 and PLOTFITS routines (Hill &amp; Fisher 1986) to allow ...
The Astronomical Journal, 1975
Nature Physics, 2007
The formation of long-lasting structures at the surfaces of stars is commonly ascribed to the act... more The formation of long-lasting structures at the surfaces of stars is commonly ascribed to the action of strong magnetic fields. This paradigm is supported by observations of evolving cool spots in the Sun 1 and active late-type stars 2 , and stationary chemical spots in the earlytype magnetic stars 3 . However, results of our seven-year monitoring of mercury spots in non-magnetic early-type star α Andromedae show that the picture of magnetically-driven structure formation is fundamentally incomplete. Using an indirect stellar surface mapping technique, we construct a series of 2-D images of starspots and discover a secular evolution of the mercury cloud cover in this star. This remarkable structure formation process, observed for the first time in any star, is plausibly attributed to a non-equilibrium, dynamical evolution of the heavy-element clouds created by atomic diffusion 4 and may have the same underlying physics as the weather patterns on terrestrial and giant planets.
Astronomische Nachrichten, 2008
This series of high quality elemental abundance analyses of mostly Main Sequence normal and pecul... more This series of high quality elemental abundance analyses of mostly Main Sequence normal and peculiar B, A, and F stars defines their properties and provides data for the comparison with analyses of somewhat similar stars and with theoretical predictions. Most use high dispersion and high S/N (≥ 200) spectrograms obtained with CCD detectors at the long camera of the 1.22-m Dominion Astrophysical Observatory telescope's coudé spectrograph. Here we expand the range of stars examined to include two relatively quiescent F supergiants. ν Her (F2 II) and 41 Cyg (F5 Ib-II) are analyzed as consistently as possible with previous studies. These LTE fine analyses use the ATLAS9 and the WIDTH9 programs of R. L. Kurucz. High signal-to-noise spectrograms and high quality atomic data were employed. The derived values of these photometrically constant stars are somewhat different with the abundances of ν Her being somewhat metal-poor and those of 41 Cyg being crudely solar-like. Our analyses indicate that the basic results of Luck & Wepfer (1995) who also studied ν Her and 41 Cyg are not likely to be significantly changed by new studies of all their stars.
Arxiv preprint astro-ph/ …, 1995
High-resolution optical spectra (UES/WHT) of the extreme metal-poor post-AGB star HR 4049 were ob... more High-resolution optical spectra (UES/WHT) of the extreme metal-poor post-AGB star HR 4049 were obtained at four different orbital phases. The spectra cover the wavelength region from 3650Å to 10850Å at a resolution of R = 5.2 × 10 4 . These observations are supplemented with four high-resolution spectra of the NaI D1 & D2 and CaII K lines at R ≈ 10 5 (CAT/CES). The optical spectrum shows 217 spectral lines: the Balmer series (Hα -H35), the Paschen series (P9 -P23), NI, OI and numerous CI lines. We show that the lines of Hα, Hβ, Hγ and NaI D show significant changes in profile between different observation dates. Nine components were identified in the profile of the NaI D lines of which three are circumstellar and six interstellar. The stronger CI lines are asymmetric and we derive a post-AGB mass-loss oḟ M= 6 ± 4 × 10 −7 M ⊙ yr −1 from the asymmetry. The [OI] 6300Å line has been detected in emission at the system velocity and we argue that the emission is from an almost edge-on disk with a radius of about 20 R * .
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Papers by Austin Gulliver