J. Aparicio, P. Bergeron, R. Distefano, T. P. Stecher
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...
The Masses of Population II White Dwarfs (2009)
Kalirai, Jason S., Davis, D. Saul, Richer, Harvey B., Bergeron, P., Catelan, Marcio, Hansen, Brad M. S., ...
Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on...
Parameter-free Stark Broadening of Hydrogen Lines in DA White Dwarfs (2009)
We present new calculations for the Stark broadening of the hydrogen line profiles in the dense atmospheres of white dwarf stars. Our improved model is based on the unified theory of Stark broadening...
A Photometric Analysis of ZZ Ceti Stars: A Parameter-Free Temperature Indicator? (2009)
Bergeron, P., Leggett, S. K., Harris, H. C.
We present a model atmosphere analysis of optical VRI and infrared JHK photometric data of about two dozen ZZ Ceti stars. We first show from a theoretical point of view that the resulting energy...
A Determination of the Luminosity Function of DA White Dwarfs from the Kiso Survey (2009)
We rederive the luminosity function for the sample of DA white dwarfs from the Kiso Schmidt ultraviolet excess survey (KUV stars) using the spectroscopic method where the atmospheric parameters (Teff...
The Luminosity Function for White Dwarfs in the SuperCOSMOS Sky Survey (2009)
Rowell, N. R., Hambly, N. C., Bergeron, P.
We present the techniques and early results of our program to measure the luminosity function for White Dwarfs in the SuperCOSMOS Sky Survey. Our survey covers over three quarters of the sky to a...
We present improved calculations for the Stark broadening of hydrogen lines in dense plasmas typical of white dwarf atmospheres. Our new model is based on the unified theory of Stark broadening from...
A spectroscopic analysis of the DBA (or DAB) white dwarf KUV 02196+2816 is presented. The observed hydrogen and helium line profiles are shown to be incompatible with model spectra calculated under...
Subasavage, John P., Jao, Wei-Chun, Henry, Todd J., Bergeron, P., Dufour, P., Ianna, Philip A., ...
We present accurate trigonometric parallaxes for 20 new members of the 25 pc white dwarf sample as part of the DENSE project (Discovery and Evalution of Nearby Stellar Embers,...
The triple system HIP96515: a low-mass eclipsing binary with a DB white dwarf companion (2009)
Huelamo, N., Vaz, L. P. R., Torres, C. A. O., Bergeron, P., Melo, C. H. F., Quast, G. R., ...
HIP96515A is a double-lined spectroscopic binary with a visual companion (HIP96515B) at 8.6 arcsec. It is included in the SACY catalog as a potential young star and classified as an eclipsing binary...
The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397 (2009)
Winget, D. E., Kepler, S. O., Campos, Fabiola, Montgomery, M. H., Girardi, Leo, Bergeron, P., ...
We explore the physics of crystallization in the deep interiors of white dwarf stars using the color-magnitude diagram and luminosity function constructed from proper motion cleaned Hubble Space...
Spectroscopic analysis of DA white dwarfs from the McCook & Sion catalog (2008)
Gianninas, A., Bergeron, P., Ruiz, M. T.
For some years now, we have been gathering optical spectra of DA white dwarfs in an effort to study and define the empirical ZZ Ceti instability strip. However, we have recently expanded this survey...
Cool White Dwarfs Identified in the Second Data Release of the UKIRT Infrared Deep Sky Survey (2008)
Lodieu, N., Leggett, S. K., Bergeron, P., Nitta, A.
We have paired the Second Data Release of the Large Area Survey of the UKIRT Infrared Deep Sky Survey with the Fifth Data Release of the Sloan Digital Sky Survey to identify ten cool white dwarf...
Subasavage, John P., Henry, Todd J., Bergeron, P., Dufour, P., Hambly, Nigel C.
We present medium resolution spectroscopy and multi-epoch VRI photometry for 21 new nearby (< 50 pc) white dwarf systems brighter than V ~ 17. Of the new systems, ten are DA (including a wide double...
Burleigh, M. R., Clarke, F. J., Hogan, E., Brinkworth, C. S., Bergeron, P., Dufour, P., ...
We report limits in the planetary-mass regime for companions around the nearest single white dwarf to the Sun, van Maanen's star (vMa2), from deep J-band imaging with Gemini North and Spitzer...
Burleigh, M. R., Clarke, F. J., Hogan, E., Brinkworth, C. S., Bergeron, P., Dufour, P., ...
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 IRAC...
We determine the ratio of helium- to hydrogen-atmosphere white dwarf stars as a function of effective temperature from a model atmosphere analysis of the infrared photometric data from the Two Micron...
We present a comparative study of effective temperatures determined from the hydrogen Balmer lines and from the UV energy distribution for 140 DA white dwarfs drawn from the IUE archive. Our results...
Kalirai, Jasonjot S., Bergeron, P., Hansen, Brad M. S., Kelson, Daniel D., Reitzel, David B., Rich, R. Michael, ...
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...
Evidence for a merger of binary white dwarfs: the case of GD 362 (2007)
Garcia-Berro, E., Loren-Aguilar, P., Pedemonte, A. G., Isern, J., Bergeron, P., Dufour, P., ...
GD 362 is a massive white dwarf with a spectrum suggesting a H-rich atmosphere which also shows very high abundances of Ca, Mg, Fe and other metals. However, for pure H-atmospheres the diffusion...
Subasavage, John P., Henry, Todd J., Bergeron, P., Dufour, P., Hambly, Nigel C., Beaulieu, Thomas D.
We present spectra for 33 previously unclassified white dwarf systems brighter than V = 17 primarily in the southern hemisphere. Of these new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We...
Dufour, P., Bergeron, P., Liebert, James, Harris, H. C., Knapp, G. R., Hall, Patrick B., ...
We present a detailed analysis of a large spectroscopic and photometric sample of DZ white dwarfs based on our latest model atmosphere calculations. We revise the atmospheric parameters of the...
Breton, R. P., Roberts, M. S. E., Ransom, S. M., Kaspi, V. M., Durant, M., Bergeron, P., ...
PSR J1744-3922 is a binary pulsar exhibiting highly variable pulsed radio emission. We report on a statistical multi-frequency study of the pulsed radio flux variability which suggests that this...
A Progress Report on the Empirical Determination of the ZZ Ceti Instability Strip (2006)
Gianninas, A., Bergeron, P., Fontaine, G.
Although the Sloan Digital Sky Survey has permitted the discovery of an increasing number of new ZZ Ceti stars, recent published analyses have shown that there are still many relatively bright (V <...
We review the available near- and mid-infrared photometry for white dwarfs obtained from the Two Micron All-Sky Survey (2MASS) and by the Spitzer Space Telescope. Both data sets have recently been...
The Mass Distribution of White Dwarfs: An Unwavering Obsession (2006)
Bergeron, P., Gianninas, A., Boudreault, S.
We discuss some of our current knowledge of the mass distribution of DA and non-DA stars using various methods for measuring white dwarf masses including spectroscopic, trigonometric parallax, and...
Near-Infrared Photometric Analyses of White Dwarf Stars (2006)
We review the available near- and mid- infrared photometry data sets for white dwarfs from the Two Micron All-Sky Survey (2MASS) Point Source Catalog and the Spitzer Space Telescope. These data sets...
Model Atmosphere Analysis of the Weakly Magnetic DZ White Dwarf G165-7 (2006)
Dufour, P., Bergeron, P., Schmidt, G. D., Liebert, James, Harris, H. C., Knapp, G. R., ...
A reanalysis of the strongly metal-blanketed DZ white dwarf G165-7 is presented. An improved grid of model atmospheres and synthetic spectra is used to analyze BVRI, JHK, and ugriz photometric...
Fontaine, G., Brassard, P., Bergeron, P., Randall, S. K.
We present a quantitative and homogeneous analysis of the broadband multicolor photometric data sets gathered so far on rapidly pulsating hot B subdwarf stars. This concerns seven distinct data sets...
Mapping the ZZ Ceti Instability Strip: Discovery of 6 New Pulsators (2006)
Gianninas, A., Bergeron, P., Fontaine, G.
As part of an ongoing program to map better the empirical instability strip of pulsating ZZ Ceti white dwarfs, we present a brief progress report based on our last observing season. We discuss here...
Anderson, Brian L., Bergeron, P.
RMA and USATHAMA have been tasked with developing a preliminary conceptual design for the Northwest Boundary Contamination Control System. Specific tasks included in this program follow: (1) Provide...
The Potential of Multi-Colour Photometry for Pulsating Subdwarf B Stars (2005)
Randall, S. K., Fontaine, G., Brassard, P., Bergeron, P.
We investigate the potential of multi-colour photometry for partial mode identification in both long- and short-period variable subdwarf B stars. The technique presented is based on the fact that the...
Towards an Empirical Determination of the ZZ Ceti Instability Strip (2005)
Gianninas, A., Bergeron, P., Fontaine, G.
We present atmospheric parameters for a large sample of DA white dwarfs that are known to be photometrically constant. For each star, we determine the effective temperature and surface gravity by...
A Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs (2005)
Dufour, P., Bergeron, P., Fontaine, G.
We present an analysis of spectroscopic and photometric observations of cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of...
Analysis of DA White Dwarfs from the McCook & Sion Catalog (2005)
Gianninas, A., Bergeron, P., Dufour, P.
The Sloan Digital Sky Survey has already doubled the number of spectroscopically identified white dwarfs. However, there remains a wealth of white dwarfs in the McCook & Sion catalog for which little...
Comparison of White Dwarf Mass Determinations (2005)
White dwarf masses can be determined in several ways. Here we compare masses obtained from Balmer line spectroscopy with those derived from trigonometric parallax measurements for an ensemble of cool...
Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs (2005)
Dufour, P., Bergeron, P., Fontaine, G.
We present an analysis of spectroscopic and photometric data for cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of the...
On the Interpretation of High Velocity White Dwarfs as Members of the Galactic Halo (2005)
Bergeron, P., Ruiz, Maria Teresa, Hamuy, M., Leggett, S. K., Currie, M. J., ...
A detailed analysis of 32 of the 38 halo white dwarf candidates identified by Oppenheimer et al. is presented, based on model atmosphere fits to observed energy distributions built from optical BVRI...
Discovery of Spectroscopic Variations in the DAB White Dwarf GD 323 (2005)
Pereira, C., Bergeron, P., Wesemael, F.
We report the discovery of spectroscopic variations in GD 323, the prototypical DAB white dwarf. Simultaneous optical spectroscopic observations over five consecutive nights of GD 323 and of PG...
Discovery of a Cool, Massive, and Metal-Rich DAZ White Dwarf (2004)
Gianninas, A., Dufour, P., Bergeron, P.
We report the discovery of a new metal-rich DAZ white dwarf, GD 362. High signal-to-noise optical spectroscopy reveals the presence of spectral lines from hydrogen as well as CaI, CaII, MgI, and FeI....
Liebert, J., Bergeron, P., Holberg, J. B
Spectrophotometric observations at high signal-to-noise ratio were obtained of a complete sample of 347 DA white dwarfs from the Palomar Green (PG) Survey. Fits of observed Balmer lines to synthetic...
A Helium White Dwarf of Extremely Low Mass (2004)
Liebert, James, Bergeron, P., Eisenstein, Daniel, Harris, H. C., Kleinman, S. J., Nitta, Atsuko, ...
We analyze the spectrum of an unusually-low mass white dwarf, SDSSJ123410.37-022802.9 (0335-264-52000), found in our recent, white dwarf catalog from the SDSS DR1 data release. Two independent, model...
Dahn, C. C., Bergeron, P., Liebert, J., Harris, H. C., Leggett, S. K.
By two different methods, we show that LHS 4033 is an extremely massive white dwarf near its likely upper mass limit for destruction by unstable electron captures. From the accurate trigonometric...
Bergeron, P., Fontaine, G., Billeres, M., Boudreault, S., Green, E. M.
We report the discovery of two new ZZ Ceti pulsators, LP 133-144 and HE 1258+0123, selected on the basis of model atmosphere fits to optical spectroscopic data. The atmospheric parameters for LP...
A Critical Examination of Halo White Dwarf Candidates (2002)
A detailed analysis of halo white dwarf candidates is presented, which is based on model atmosphere fits to observed energy distributions built from photoelectric or photographic magnitudes. Most of...
The True Incidence of Magnetism among Field White Dwarfs (2002)
Liebert, James, Bergeron, P., Holberg, J. B.
We study the incidence of magnetism in white dwarfs from three large and well-observed samples of hot, cool, and nearby white dwarfs in order to test whether the fraction of magnetic degenerates is...
Model Atmosphere Analysis of Two Very Cool White Dwarfs (2002)
A detailed analysis of the very cool white dwarfs SDSS 1337+00 and LHS 3250 is presented. Model atmosphere calculations with improved collision-induced absorptions by molecular hydrogen indicate that...
A spectroscopic analysis of the DAB white dwarf PG 1115+166 is presented. The observed hydrogen and helium line profiles are shown to be incompatible with model spectra calculated under the...
The Halo White Dwarf WD 0346+246 Revisited (2001)
The extreme helium-rich atmospheric composition determined for the halo white dwarf WD 0346+246 is reexamined. This solution is shown to be improbable from an astrophysical point of view when...
Bergeron, P., Leggett, S. K., Ruiz, Maria Teresa
A photometric and spectroscopic analysis of 152 cool white dwarf stars is presented. The discovery of 7 new DA white dwarfs, 2 new DQ white dwarfs, 1 new magnetic white dwarf, and 3 weak magnetic...
S1040 in M67: A Post-Mass-Transfer Binary with a Helium-Core White Dwarf (1997)
Landsman, W., Aparicio, J., Bergeron, P., Di Stefano, R., Stecher, T.
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...
The masses of the millisecond pulsar J1012+5307 and its white-dwarf companion (1996)
Van Kerkwijk, M. H., Bergeron, P., Kulkarni, S. R.
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...
MARTIN, J., CANO, N., DI-COSTANZO, J., RICHIERI, J. P., PIN, G., BERGERON, P., ...
Les fistules paraprothétiques sont des complications rares mais graves des prothèses aortiques abdomina'es. Le meilleur examen à visée diagnostique est l'endoscopie. Deux stades des lésions...
Untersuchungen zur Kinetik der Nitrifikation / (1978)
Proefschrift Universität Karlsruhe.
Hereditary C7 deficiency. Diagnosis and HLA studies in a French-Canadian family.
Delâge, J M, Bergeron, P, Simard, J, Lehner-Netsch, G, Prochazka, E
The serum of a 44-yr-old woman of French-Canadian descent having a B-27 positive ankylosing spondylitis was deficient in the seventh component of complement (C7) as determined by hemolytic and...
Hereditary C7 deficiency. Diagnosis and HLA studies in a French-Canadian family.
Delâge, J M, Bergeron, P, Simard, J, Lehner-Netsch, G, Prochazka, E
The serum of a 44-yr-old woman of French-Canadian descent having a B-27 positive ankylosing spondylitis was deficient in the seventh component of complement (C7) as determined by hemolytic and...