Papers by Robert Lamontagne
The Journal of the Royal Astronomical Society of Canada. Royal Astronomical Society of Canada
The Astronomical Journal, 1986
A survey aimed at improving significantly the statistics of white dwarfs and hot subdwarfs in the... more A survey aimed at improving significantly the statistics of white dwarfs and hot subdwarfs in the southern hemisphere is presented. In this first report, emphasis is put on the colorimetric part of the survey which had been started at CTIO in 1984 September. In this initial effort, which corresponds to a sky coverage of ≡1000 deg2 centered on the south
The Astronomical Journal, 2000
Results for the south Galactic cap region of the survey of blue sub-Montre al-Cambridge-Tololo lu... more Results for the south Galactic cap region of the survey of blue sub-Montre al-Cambridge-Tololo luminous stars are presented. This region overlaps the 840 deg2 region studied almost three decades ago by Slettebak & Brundage. We present a list of equatorial coordinates, photographic photometry, and spectroscopic identiÐcations, as well as Ðnding charts, for 188 blue objects brighter [(U[B) pg ¹ [0.6] than in this area. Completeness of the survey and comparisons with other similar e †orts are B pg \ 16.5 discussed.
The Astrophysical Journal, 1990
The Astrophysical Journal, 1985
... 1984b), and that line is, at best, weak in our own spectra; we thus adopt the sdB classificat... more ... 1984b), and that line is, at best, weak in our own spectra; we thus adopt the sdB classification for that object. ... The resulting fits are displayed in Figure 3. b) Abundance Ana!ysis Model calculations with the atmospheric parameters summarized above were performed to determine ...
White Dwarfs: Advances in Observation and Theory, 1993
Feige 55 is a relatively bright blue star with y = 13.59 and b-y = - 0.167 (Bergeron et al. 1984)... more Feige 55 is a relatively bright blue star with y = 13.59 and b-y = - 0.167 (Bergeron et al. 1984), previously classified as a B subdwarf by Greenstein and Sargent (1974). A recent moderate resolution (~ 12A) optical spectrum, obtained as part of another program, showed it to be a white dwarf of the DAO subclass. The spectra of these stars are characterized by broad Balmer lines together with a sharp He II λ 4686 feature (Wesemael, Green, and Liebert 1985; Holberg et al. 1989). This is apparent in Figure 1 where we compare our observation of Feige 55 with that of another DAO star, PG 1210+533.
The Astrophysical Journal, 1993
A detailed analysis of the optical spectrum of the DAO white dwarf Feige 55 is presented. We show... more A detailed analysis of the optical spectrum of the DAO white dwarf Feige 55 is presented. We show that the atmospheric parameters obtained from fits to the H-beta line and to higher Balmer lines, respectively, are discrepant. This problem is akin to that reported in previous analyses of hot DAO central stars of planetary nebulae. Model atmosphere calculations are used
The Astronomical Journal, 1995
THE ASTRONOMICAL JOURNAL VOLUME 109, NUMBER 2 FEBRUARY 1995 ThE ENIGMATIC WN8 STARS: INTENSIVE PH... more THE ASTRONOMICAL JOURNAL VOLUME 109, NUMBER 2 FEBRUARY 1995 ThE ENIGMATIC WN8 STARS: INTENSIVE PHOTOMETRY OF FOUR SOUThERN STARS ON TIME SCALES FROM 30 MIN TO 3 MONThS IGOR ANTOKHIN,1'2 JEAN-FRANç0Is BERTRAND,' ...
The Astronomical Journal, 1993
Publications of the Astronomical Society of the Pacific, 1993
Astrophysics and Space Science, 2004
We have secured FUSE observations for a sample of hot, hydrogen-rich subdwarf B stars. The main o... more We have secured FUSE observations for a sample of hot, hydrogen-rich subdwarf B stars. The main objective of this project is to map in a more detailed way than has been done in the past pattern of heavy element abundances in sdB stars in order to understand the competing roles of gravitational settling, radiative element support, and mass loss in their photospheres. We present abundances analyses for a subsample of four objects and compare these results with predictions of the parameter-free version of the radiative levitation theory.
The Astronomical Journal, 2021
We present optical spectra of 144 white dwarfs detected in the Montreal-Cambridge-Tololo (MCT) co... more We present optical spectra of 144 white dwarfs detected in the Montreal-Cambridge-Tololo (MCT) colorimetric survey, including 120 DA, 12 DB, 4 DO, 1 DQ, and 7 DC stars. We also perform a model atmosphere analysis of all objects in our sample using the so-called spectroscopic technique, or the photometric technique in the case of DC white dwarfs. The main objective of this paper is to contribute to the ongoing effort of confirming spectroscopically all white dwarf candidates in the Gaia survey, in particular in the southern hemisphere. All our spectra are made available in the Montreal White Dwarf Database.
IAUC 5124 available at Central Bureau for Astronomical Telegrams.
We publish 159 CCD sequences obtained to calibrate the high galactic latitude plates taken for th... more We publish 159 CCD sequences obtained to calibrate the high galactic latitude plates taken for the Montreal-Cambridge-Tololo (MCT) survey. V magnitude and B−V and in some cases U−B colour indices were obtained for over one thousand stards ranging in V magnitude from 8 to 18 and located toward the south Galactic pole. Computer generated finding charts are included to permit easy identification of the stars
Voyager ultraviolet spectrometer observations of the subdwarf B or OB stars HD 205805, UV 1758+36... more Voyager ultraviolet spectrometer observations of the subdwarf B or OB stars HD 205805, UV 1758+36 and Feige 66 are presented. All three objects display the H I Layman series in absorption. These observations are combined with low dispersion IUE spectrophotometry and with Stroemgren photometry to construct virtually complete energy distributions, which extend over the range 950-5500 angstroms. Effective temperatures based on model atmosphere calculations for high gravity, hydrogen rich stars are determined. Our analyses yield T Sub e 28,200 + or - 1300 K for HD 205805, T sub e 31, 800 + or - 1100 K for UV 1758+36, and T sub e 35,700 + or - 1500 K for Feige 66. The importance of far ultraviolet observations below L sub alpha in reducing the uncertainties associated with the interstellar extinction and the degradation of the IUE sensitivity is emphasized.
We present a preliminary analysis of the FUSE spectra of MCT 0019-2441, a relatively He-poor sdO ... more We present a preliminary analysis of the FUSE spectra of MCT 0019-2441, a relatively He-poor sdO star. Among the handful of absorption features of photospheric origin present in the ultraviolet, we identify the O VI doublet at 1031.9 and 1037.6 Å, the S VI doublet at 933.4 and 944.5 Å, the Si IV triplet at 1122.5 and 1128.3 Å and some N IV lines. While synthetic spectra based on NLTE line blanketed model atmospheres can reproduce most line profiles, they fail to reproduce the O VI line profiles in a satisfactory manner. Possible solutions to this puzzle are considered.
Astronomy and Astrophysics Supplement Series, Jun 29, 1991
Photometry in different systems is presented for 14 Wolf-Rayet stars in the Large Magellanic Clou... more Photometry in different systems is presented for 14 Wolf-Rayet stars in the Large Magellanic Cloud and 4 Wolf-rayet stars in the Small Magellanic Cloud. All but two stars are spectroscopic binaries. Nine of the 16 binaries show phase-dependent variations due to wind transparency effects or, in one case, eclipses of the stars. In the former case, the shape of the light curve of 5 stars is used to derive the orbital inclination and the WR star mass loss rate.
The Journal of the Royal Astronomical Society of Canada Royal Astronomical Society of Canada, Sep 29, 1985
Astronomy and Astrophysics, Sep 29, 1982
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Papers by Robert Lamontagne