Pierre Bergeron

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We present the first detailed study of the properties (temperatures, gravities, and masses) of the NGC 6791 white dwarf population. This unique stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H] ∼ +0.4) open clusters in our Galaxy, and has a color-magnitude diagram (CMD) that exhibits both a red giant clump and a much hotter(More)
A detailed photometric and spectroscopic analysis of cool (Teff < ∼ 12, 000 K) white dwarf stars is presented. The sample has been drawn from the Yale Parallax Catalog and from a proper-motion survey in the southern hemisphere. Optical BV RI and infrared JHK photometry, as well as spectroscopy at Hα, have been secured for a sample of 152 white dwarfs. The(More)
The effect of substratum heterogeneity on the distribution and abundance of sessile epibenthos was studied between May 1980 and September 1981, in a mid-intertidal shore subject to severe annual ice scouring during winter In summer, low abundances of organisms were associated with smooth regular surfaces whereas high abundances were associated with higher(More)
Byers and Dunn (Reports, 9 November 2012, p. 802) claimed that predation on offspring reduced the potential for sexual selection in pronghorn. We argue that the potential for sexual selection is not affected by random offspring mortality when relative reproductive success is considered and increases when measured with the opportunity for selection, a metric(More)
BACKGROUND Rapidly occurring changes within the health care systems are creating an opportunity to re-orient the relationships between their different sectors. In order to know the locus of responsibility for various types of preventive activities, we undertook an inquiry on eight areas in six countries from Europe and North America. METHODS An inquiry(More)
We report on spectroscopy of the white-dwarf companion of the millisecond radio pulsar PSR J1012+5307. We find strong Balmer absorption lines, as would be expected for a cool DA white dwarf. The profiles are much narrower than usual, however, and lines are seen up to H12, indicating that the companion has a low gravity and hence a low mass. This is(More)
Enhancing effective preventive interventions to address contemporary public health problems requires improved capacity for applied public health research. A particular need has been recognized for capacity development in population health intervention research to address the complex multidisciplinary challenges of developing, implementing, and evaluating(More)
We report limits in the planetary-mass regime for companions around the nearest single white dwarf to the Sun, van Maanen’s star (vMa 2), from deep J-band imaging with Gemini North and Spitzer Infrared Array Camera (IRAC) mid-IR photometry. We find no resolved common proper motion companions to vMa 2 at separations from 3 to 45 arcsec, at a limiting(More)
We have obtained spectra of the yellow giant S1040 in the open cluster M67 using the Goddard High-Resolution Spectrograph (GHRS) and the Faint Object Spectrograph on the Hubble Space Telescope. S1040 is a single-lined spectroscopic binary with a 42.8d period that occupies a “red straggler” position in the M67 color-magnitude diagram (CMD), 0.2 mag blueward(More)