Structure and evolution models of He core white dwarfs
Josep M. APARICIO & Gilles FONTAINE, Université de Montréal
We present the calculation of a series of evolutionary tracks of He core white dwarfs, from the loss of the hydrogen-rich envelope onwards.

Wide Field Imaging of Low Redshift Galaxy Clusters
W. A. BARKHOUSE & H.K.C. YEE, University of Toronto
O. LÓPEZ-CRUZ, Instituto Nacional de Astrofisica Optica y Eletronica
The advent of large format mosaic CCD cameras has given us the unprecedented ability to efficiently sample the galaxy population in low redshift galaxy clusters. We are presently conducting a photometric study of galaxy clusters in the redshift range of 0.02-0.04 with the 8k CCD mosaic camera on the KPNO 0.9m telescope. This telescope/detector combination, with a pixel scale of 0.42"/pix, provides a one square degree field of view, giving an areal coverage of 1-2h^-1 Mpc². These observations will allows us to determine the projected spatial distribution and luminosity function (LF) of cluster galaxies. With these data, will will test the cD format ion scenario based on the disruption of dwarf galaxies (Lopez-Cruz et al. 1996 ApJ, 475, L97) by: a) measuring LF's as a function of clustercentric radius, b) determining the spatial distribution of dwarf galaxies, and c) measuring the color gradients for dwarf galaxies, and the halos of cD and BCG's. We will report on the current progress of this project.

NGC 7129: SVS 13 and Other Stars
Pierre BASTIEN, R. HAJJAR¹ & D. NADEAU, Université de Montréal
¹aussi Université de Beyrouth
This paper is part of the Ph. D. thesis of Roger Hajjar. Polarimetric observations carried out at the Mont Megantic Observatory have revealed that SVS 13 has the highest linear polarization in NGC 7129. It also shows on polarization maps the largest disk as determined by the angular distance between the two null points, at the edges of the parallel vector pattern. At the distance of NGC 7129, 1.25 kpc, the disk has a size of approximately 5600 AU in the I band. The J band polarimetric map (from the CFHT) also show a large disk. The measured emissivity index, deduced from mm and submm continuum photometric measurements at the JCMT, Beta = 0.22, is compatible with what is found for Young Stellar Objects. We found 4 new infrared sources around SVS 13. A large number of infrared sources is also present around LkHalpha 234. They fall on or around a V-shaped enhanced emission ridge in the IR, also visible in H₂, giving insight on their star formation history. Based on this information, we confirm this scenario: The formation of BD+65^o 1638 triggered the formation of the other stars through shocked molecular gas by the stellar wind. It is still an ongoing process where now SVS 13 and LkHalpha 234 are triggering star formation.

A Survey of Planetary Nebulae in the Southern Galactic Bulge
Sylvie F. BEAULIEU, University of Cambridge
We present the results of a deep and uniform narrow-band Ha imaging survey for planetary nebulae in the southern galactic bulge. The goal of this survey was to obtain a sample of bulge tracers which have been used to study the dynamics of the Milky Way bulge.

Spectroscopie multi-fentes et etude du contenu stellaire de galaxies elliptiques appartenant a des amas
Isabelle BÉGIN, Université Laval
Ce projet de recherche consiste à étudier plus de 100 galaxies elliptiques appartenant à 7 amas differents. Ces galaxies ont été observées avec le spectrographe multi-fentes du TCFH. Le contenu stellaire des galaxies sera etudié et des modèles de synthèse spectrale developpés a l'Université Laval (Sonya Delisle) seront utilisés. De là, une comparaison entre les galaxies appartenant à des amas et celles du champ pourra être amorcée, ainsi qu'une comparaison entre les amas.

Observations Fabry-Perot de spirales tardives
Sébastien BLAIS-OUELLETTE & Claude CARIGNAN, Université de Montréal
Les galaxies spirales tardives semblent se situer à une transition quand à la relation entre les paramètres de la matière sombre et le type morphologique. Dans ces galaxies, les contributions lumineuses et sombres sont d'importance comparable bien avant le diamètre optique R_HO. Pour déterminer cette relation comme pour bien contraindre les paramètres de la distribution de masse, nous ajoutons a la grande sensibilité des données HI existantes, la haute résolution spatiale et spectrale de données Fabry-Perot pour un échantillon de galaxies spirales tardives.

Isotopic Anomalies of Platinum in the HgMn Star HR 7775
David BOHLENDER, HIA
Michael DWORETSKY & Chris JOMARON, UCL
High-resolution, high-S/N CFHT Gecko spectra have been obtained for the regions of the five strongest optical lines of Pt II in the spectrum of the cool HgMn star HR 7775. Model line profiles have been constructed based on isotopic and hyperfine structure laboratory analyses and abundances of the individual isotopes have been determined from spectrum synthesis. The total abundance of Pt is 4.46 dex greater than the adopted solar abundance. The isotopic composition is clearly non-terrestrial, with a pronounced relative enhancement of the heaviest isotope, 198Pt, and deficiencies of the isotopes lighter than 196Pt. The pattern of isotopic composition does not follow the widely-assumed fractionation formalism; the lighter isotopes are far more deficient than a single-parameter fractionation pattern would predict.

Cosmic parameters from the CMB
J. Richard BOND, CITA
A long-standing goal of theorists has been to constrain cosmological parameters that define the structure formation theory from CMB anisotropy experiments and large scale structure (LSS) observations. The status of this enterprise is described, using full Bayesian analysis for high weight CMB experiments such as COBE's DMR and Saskatoon 1995, approximate bandpower techniques for all other CMB experiments, and LSS density power spectrum amplitude estimates from cluster abundances and shape constraints from galaxy clustering observations. The initial fluctuation spectrum is not far off the scale invariant form (slope near unity) that inflation models prefer: e.g., for tilted Lambda CDM sequences of fixed 13 Gyr age, n_s = 1.01 +/- 0.05 for CMB experiments alone, and when LSS constraints are included as well. Open models are slightly preferred over $\Lambda$ models by the CMB data, but are much less likely than $\Lambda$ models when LSS information is included. The $\Lambda$ values found are the same as those obtained using high redshift Type I supernovae.

Liquid Mirror Telescopes: A progress report
Ermanno F. BORRA, Université Laval
I briefly review the status of the LMT project. In a nutshell, liquid mirrors do work. Optical shop tests show that the optical qualities are very high (diffraction limit). The largest LM built so far (in the Laval lab; see poster by Tremblay) ) has a diameter of 3.7-m. Several liquid mirror telescopes have been built and operated for several years. The largest working LMT (operated by NASA) has a diameter of 3.0 meters and has given so far over 100 nights of deep sky images. Several articles dealing with astronomical results are currently being written up (see poster by Cabanac). A 6-m LMT is presently being built at UBC. The future of the technology looks bright, promising very large diameters and greater versatility. A novel corrector design shows that fields of regard as large as 20 degrees (with 20 arcminute corrected patches) should be feasible. In the laboratory, efforts to develop novel reflecting liquids are also very encouraging. Heading the calls by the national granting agencies, we are also successfully exploring industrial applications that exploit the unique qualities of LMs (e.g. large diameters at low cost). A 3-D scanner using a LM as its main optical element has been demonstrated.

A New Generation of White Dwarfs Evolutionary Models
Pierre BRASSARD & Gilles FONTAINE, Université de Montréal
We present a new generation of white dwarfs models incorporating the latest developments of the constitutive physics. These are evolutive models especially designed for cooling, spectral evolution and seismological studies.

A Search of Peculiar Objects with the NASA Orbital Debris Observatory 3-m Liquid Mirror Telescope.
Rémi CABANAC & Ermanno BORRA, Université Laval
Mario BEAUCHEMIN, Centre canadien de télédétection
The NASA Orbital Debris Observatory (NODO) survey uses a transit 3-m liquid miror telescope to observe a strip of sky in 20 narrow band filters. In this article we analyse a subset of data from the 1996 season. The catalog consist of 18,000 objects with V between 10 and 19 in 10 narrow-band filters from 500nm to 950nm. We first demonstrate the reliability of the data by fitting Bahcall-Soneira model of the Galaxy to the NODO star counts. We then perform a hierarchical clustering analysis in order to extract objects showing peculiar energy distributions. This is the first time in optical astronomy that a paper demonstrates astronomical research with a new type of optics.

HI in Dwarf Spheroidal Galaxies
Claude CARIGNAN, Université de Montréal
HI has now been detected in the field of 3 Local Group Dwarf Spheroidal galaxies: Tucana, Sculptor and Phoenix. While, as will be described, the HI in the field of Tucana is probably not associated with the galaxy but is probably a component of the Magellanic Stream, the spatial and velocity coincidence of the gas mapped in the field of Sculptor suggest that it is most likely associated with the dwarf. As for Phoenix, it is difficult to make any conclusion about the origin of the gas since no optical velocity is yet available

A roAp Star Survey in the Northern Hemisphere
François CHAGNON & Jaymie MATTHEWS, University of British Columbia
Philippe EENENS, Universidad de Guanajato, Mexico
The rapidly oscillating Ap stars represent powerful objects to test asteroseismology due to their high-overtone p-mode pulsations. As only 3 of these stars are known in the Northern Hemisphere, where we can use very good spectroscopic sites, it is of vital importance to find more roAp stars in order to apply the techniques of asteroseismology. A photometric search for such roAp stars in the Northern Hemisphere was conducted by Chagnon, Matthews and Eenens at the "Observatorio Astronomico Nacional", Mexico. The results of this search will be presented, along with some new photometric data of a recently discovered roAp.

The core regions of nearby Seyfert galaxies
Scott CHAPMAN, University of British Columbia
Simon MORRIS, DAO
An emerging model for active galaxies suggests that if most galaxies possess a supermassive black hole in their cores, then the AGN are simply the ones which can channel fuel effectively down to the nucleus. Within the zoo of the AGN types, the nearby Seyfert galaxies are perhaps the best suited to try to answer the questions surrounding this hypothesis - specifically, how does the core fueling take place? Although less powerful than more distant AGNs like quasars and radio-galaxies, their proximity allows the central regions of the active nuclei to be probed up to a scale of a few tens of parsec in the visible and near-infrared wavelength domains. We have obtained adaptive optics images and IFU spectra of a sample of nearby Seyfert galaxies using mainly the CFHT. The detailed morphology and colour gradients in the core regions of Seyfert galaxies may then provide clues as to how the activity was triggered and continues to be fueled.

Helioseismologie de la tachocline solaire
Paul CHARBONNEAU, High Altitude Observatory, NCAR
La tachocline est une région de forte rotation différentielle située directement sous la zone convective du soleil. Je décrirai quelques inversion hélioséismiques récentes visant a determiner la structure de la tachocline, et discuterai brièvement les conséquences de ces résultats pour les modèles de la dynamo solaire.

Theory of Pulsating Subdwarf B Stars: A Set of Testable Predictions
S. CHARPINET, G. FONTAINE, P. BRASSARD, Université de Montréal
P. CHAYER (Berkeley), F.J. ROGERS, C.A. IGLESIAS (LLNL), B. DORMAN(NASA/GSFC)
Pulsating subdwarf B (sdB) stars, now called EC14026 stars after the class prototype (Kilkenny et al. 1997, MNRAS 285, 640), were first theoretically predicted from stellar pulsation theory (Charpinet et al. 1996, ApJ Letters 471, L103). The identified mechanism destabilizing these stars, a kappa-mechanism associated to local accumulations of iron due to heavy metal diffusion processes (Charpinet et al. 1997, ApJ Letters 484, L123), also reveals several characteristics for excited acoustic modes that can be tested. In this paper, we summerize these theoretical predictions to allow confrontations with observed pulsators.

La Trousse d'exploration du système solaire: un outil pédagogique pour les écoles
Pierre CHASTENAY, Planétarium de Montréal
La Trousse d'exploration du système solaire est une valise pédagogique autonome destinée aux élèves du niveau préscolaire et des premier et deuxième cycles du primaire. Elle se compose de trois unités indépendantes qui abordent chacune un thème précis. Le «Loto des planètes» est un jeu de mémoire qui permet aux participants d'apprendre à reconnaître et à nommer les principaux objets qui composent le système solaire : le Soleil, les planètes et leurs principaux satellites, les astéroïdes et les comètes. L'activité «Le système solaire à l'échelle» permet aux enfants de construire un modèle à l'échelle du diamètre du Soleil et des planètes, puis un modèle des distances qui les séparent dans l'espace. Enfin, l'activité «Le cadran solaire» permet aux élèves de construire un cadran solaire simple et d'apprendre à lire l'heure à l'aide du Soleil. La Trousse d'exploration du système solaire circule dans les écoles de la région de Montréal depuis janvier 1998 et devrait être disponible dans toutes les régions du Québec dès septembre 1998.

The Mode Switch of the RR Lyrae Star V79 in M3
Christine M. CLEMENT, University of Toronto
A recent investigation of variable stars in the globular cluster M3 by Clement, Hilditch, Kaluzny and Rucinski (1997, ApJ 489, L55) revealed that the RR Lyrae variable V79 had switched modes. Their observations, obtained in 1996, showed that V79 was a double-mode (RRd) variable with the first overtone mode dominating, but all previously published data (1962 and earlier) had indicated that the star was a fundamental mode (RRab) pulsator with an irregular light curve. They considered the mode switch to be observational evidence for blueward evolution of horizontal branch stars in the Oosterhoff type I cluster M3. Subsequently, Corwin, Carney and Allen (1998, IBVS 4548) confirmed that V79 was an RRd star with the first overtone dominating, based on observations that they made in 1992 and 1993.
Meanwhile, in a study of V79 on M3 photographs in the Sternberg Observatory plate collection, Goranskij (1980, Astronomical Circular 1111, 6) showed that the pulsation period of V79 decreased substantially and its B amplitude varied between 1956 and 1976, but he was unable to detect any oscillations in the first overtone mode.
An analysis of approximately 1000 observations of V79 made in the Soviet Union between 1950 and 1991 is presented here. It appears that the mode switch took place in late 1991 or early 1992. However, prior to the switch, the star exhibited chaotic behaviour.

Near-Infrared Observations of the Metal-Poor Inner Spheroid Globular Cluster NGC6287
Tim DAVIDGE, Canadian Gemini Project Office/HIA/UBC
Deep JHK images are used to probe the stellar content of the metal-poor ([Fe/H] ~ -2) globular cluster NGC6287, which van den Bergh (1993, ApJ, 411, 173) suggests may be one of the oldest objects in the Galaxy. The data, which extend to the main sequence turn-off, are used to investigate the metallicity, distance, reddening, and age of this cluster.

Fundamental Parameters of Low-mass Stars From Broad-band Photometry
P.C. DAWSON, Trent University
C.A.P. KRAWCHUCK & M. M. DE ROBERTIS, York University
A rigorous method for computing effective surface temperatures and metallicities of low-mass stars (M less than 0.6 solar masses) using broad-band photometry and the most recent (NextGen) model atmospheres (Allard et al. 1997) is presented.
In particular, temperatures and metallicities are determined for YY Gem, CM Dra, and a sample of low-metallicity halo objects. These results are compared with those obtained using the previous version of Allard's model atmospheres (Allard and Hauschildt 1995). Preliminary indications are that the NextGen models give rise to systematically cooler temperatures. In addition, we discuss an extension of this method to measure directly radii and masses of low-mass stars both within a cluster environment and the field.

Observations and Analysis of the light curves of three SX Phoenicis stars: XX Cyg, DY Peg and BL Cam.
M. BLAKE, H. KHOSRAVANI, P. DELANEY, J. MARSHALL, B. HESSMAN, S. ROESS, C. HOMECKO, C. HARROP, S. HOFFMAN, N. NUNES, S. VIRANI, K. WEISZ, D. CRAIG, C. HANN, York University
Since the summer of 1997, as part of a long term monitoring program, the 60 cm telescope of the York University Observatory has been used to observe three SX Phoenicis stars. An HPC-1 CCD has been used to obtain differential photometry on these stars and sample light curves are included. The analysis has yielded several times of minimum light and in conjunction with the literature, O-C plots for all three stars have been produced. A discussion of the problems incurred in obtaining the data in a bright urban environment is included.

The Youngest Stars of the Sculptor Dwarf Spheroidal Galaxy
Serge DEMERS, Université de Montréal
Paolo BATTINELLI, Osservatorio Astronomico di Roma
The discovery of neutral hydrogen in the periphery of Sculptor by Carignan et al. (1998) has incited us to look for young stars associated with the region of largest HI velocity dispersion. This small area, located 15 arcmin from the center of Sculptor, was imaged in December 1997 with the Tek 2K CCD attached to the CTIO 1.5 m telescope. The CMD reveals nearly 200 blue stars brighter than the populous turnoff seen at V = 23. Isochrone fittings imply that these stars, if they are not blue stragglers, are 1 Gyr and older. These blue stars are distributed, in the field observed, like the bulk of the stars and do not appear associated with the gas.

Formation d'étoiles et propriétés physiques des galaxies starburst
Daniel DEVOST, Université Laval/STScI
Les flambées de formation stellaire observées dans les galaxies starburst produisent des étoiles massives qui enrichissent le MIS via leur vents stellaires. Je vais explorer de facon quantitative l'effet de ces épisodes de formation stellaire sur le MIS des galaxies starburst.

Massive close binaries & Spectral evolutionary synthesis of young starbursts.
Dany DIONNE & Carmelle ROBERT, Université Laval
The evolution of massive close binaries (MCB) form massive stars at ages where these should be missing if one considered only single stars in a instantaneous starburst. We evaluate the impact of the MCB on the equivalent width of several spectral lines.

KIR: First Light
R. DOYON & N. St-LOUIS, Université de Montréal
C. ROBERT, D. DEVOST, J.-R. ROY & L. DRISSEN, Université Laval
KIR is the 1024x1024 high-resolution near-infrared camera used with the adaptive optics bonnette of the CFHT. First light on KIR was obtained on December 8th 1997 on a program devoted to starburst galaxies. The seeing conditions were excellent (0.6-0.7") with typical spatial resolution of 0.2-0.3". Preliminary analysis of these observations will be presented.

Etoiles de faible masse dans NGC 3603
Laurent DRISSEN, Université Laval
Anthony MOFFAT, Université de Montréal
Eva GREBEL, UCO/Lick Observatory
NGC 3603 est un amas jeune et très compact qui ionise la plus lumineuse region HII géante de notre Galaxie. Cet amas contient 3 étoiles Wolf-Rayet ainsi qu'une douzaine d'étoiles O3. Nous présenterons des images HST/WFPC2 de cet amas indiquant clairement la présence d'étoiles pré-séquence principale de masse inférieure à celle du Soleil.

Modeling the Diversity of Outer Planetary Systems
Martin James DUNCAN, Queen's University
It has been made clear in the last few years that the dynamical structure of extra-solar planetary systems can vary significantly from system to system. In order to better understand the range of possible systems, we present the results of a set of bottom-up numerical simulations designed to generate plausible giant planet systems from a large number of planetary embryos. Our simulations produced systems stable for at least a billion years with a wide range of characteristics, including some reminiscent of our own planetary system. The number of planets ranged from one to seven. Many systems contained only Uranus-mass objects. We constructed systems that were more compact than our own and systems that were much less compact with planets on very eccentric orbits. Perhaps most surprisingly, we constructed systems that were stable for at least a billion years despite undergoing macroscopic orbital changes on much shorter timescales.

The CADC Services/Les Services du CCDA
Daniel DURAND, Institut Herzberg d'Astrophysique/CNRC
David BOHLENDER, HIA/NRC
David SHADE, HIA/NRC
After many years of existence, the CADC is now an important international service for astronomers. This poster will present an overview of the different services offered by the CADC as well as a presentation of futur services.

The abundances gradient of early-type spirals
Yvan DUTIL, Université Laval
The measurment of interstellar abundances in early-type galaxies is challenging. The Hii regions are small and faint, and the nebular dianostic lines are weak if abundances are high. By the use of spectroscopic imagery and multi-slit spectroscopy to overcome some of these difficulties, I derived the abundances profiles for seven early type galaxies. It appear than the early-type galaxies shows similar abundance profiles than the strongly barred late type! This is consistent with the scenario of the morphological evolution of disk galaxies by the action of a bar.

Anchor's Away
Jayanne ENGLISH, Queen's University
A. Russel TAYLOR, University of Calgary
Judith A. IRWIN, Queen's University
We present preliminary results of a study of an anchor-like atomic hydrogen structure whose base occurs south of the Milky Way's mid-plane and which extends vertically (to more negative latitudes) ending in a "cap". These data were acquired as part of the Canadian Galactic Plane Survey project using the Dominion Radio Astrophysical Observatory's (DRAO) Synthesis Telescope (ST). By incorporating data from the 26m DRAO single-dish telescope the mosaic data cube has full information on all spatial scales down the to resolution limit of 1 arcminute. The velocity resolution is 0.82 km per sec. Although the projected extent of the "anchor" is only a few hundred parsecs, the anchor may be fountain-like, or represent the initial stages of a kpc-scale blowout structure. As either it could illuminate the processes by which gas in the Galaxy's halo is replenished and how the halo's energy input is maintained.

Study of the Gas and Dust Content in NGC 7129
Andreea FONT & George F. MITCHELL, Saint Mary's University
NGC 7129 is a molecular cloud containing photon heated gas (a PDR) and gas shocked by an outflow. Using SCUBA on the JCMT, we have obtain 850 $\mu$m and 450 $\mu$m continuum maps of the two overlapping fields. In order to compare gas and grain properties, we obtained C¹⁸O J = 3-2 spectra at a dozen positions in the same region. The line ratio ¹³CO/C¹⁸O has been used to find optical depth, excitation temperature, column densities and mass of the gas at each position. In the assumption that the gas and the dust are tightly coupled, one uses T_gas =T_dust to calculate dust masses. The frequency dependence of dust extinction ($\tau \sim \nu ^\beta$) is a clue of dust properties. We investigate spectral variation in dust properties by calculating $\beta$ from the 850 $\mu$m /450 $\mu$m flux ratio.

Observations of p-mode Pulsations in Hot B Subdwarfs
M. BILLERES, G. FONTAINE, P. BRASSARD, S. CHARPINET (U. de Montréal)
J. LIEBERT (U. of Arizona), R.A. SAFFER (Villanova U.), and G. VAUCLAIR (Observatoire Midi-Pyrénées)
We present some of the results of our ongoing search for pulsating stars of a new kind in asteroseismology, the EC14026 variables or pulsating sdB stars whose existence was predicted theoretically. Seven of these objects are now known. They are all multiperiodic pulsators showing excited p-modes. We discuss some of our observations of these objects. We also compare the class properties with further theoretical predictions described in a related paper

Cosmological hydrodynamic simulations with molecular hydrogen chemistry
Todd FULLER & Hugh COUCHMAN, University of Western Ontario
The first objects in CDM-like cosmologies form at a redshift of z ~ 10 - 30, have a baryonic mass of ~ 3 X 10⁴ M_o and virial temperatures of several hundred degrees. At this low temperature fragmentation and cooling is possible only through molecular hydrogen cooling. Numerical simulations of first object formation must therefore model H₂ chemistry. We have included the chemical reactions involving H, H⁺, H^-, H₂, H₂⁺ and e^- in our N-body gravitational + gasdynamic code. To test the code, we simulate a tophat collapse and compare with an analytic model. We report some preliminary results and discuss effects H₂ cooling has on object formation.

The Far Ultraviolet Spectroscopic Explorer Mission
Alex FULLERTON, University of Victoria/The Johns Hopkins University
The Far Ultraviolet Spectroscopic Explorer (FUSE) is a free-flying satellite that has been developed for NASA by a consortium of institutions under the leadership of the Johns Hopkins University. It is scheduled to be launched into low-earth orbit in late 1998 or early 1999. Over its lifetime of at least 3 years, it will obtain high-resolution (R ~ 30,000) spectra of many astronomical sources between 905 and 1195 Angstroms. Although this region is extraordinarily rich in atomic and molecular resonance lines, it has not been routinely accessible for nearly 20 years. Thus, results from FUSE are expected to have a significant impact on many current problems in interstellar, stellar, and extragalactic astrophysics.
This paper provides an brief overview of the FUSE mission, including instrumentation, operations, Science Team projects, and the Guest Investigator Program. As part of the cooperative agreement between NASA and the Canadian Space Agency (who provided the fine error sensors for FUSE), Canadian investigators have access to at least 5% of the total observing time. Consequently, FUSE represents a particularly valuable resource for the Canadian astronomical community.

HI Self-Absorption in the Canadian Galactic Plane Survey: First Results
Steven J. GIBSON & A. R. TAYLOR, University of Calgary
P. E. DEWDNEY, Herzberg Institute of Astrophysics
Neutral Hydrogen 21cm line emission is widely used to chart the warm and cool diffuse components of the interstellar medium. Less studied is the colder constituent revealed by HI self-absorption against background HI emission, though where detected, it has often shown a significant correlation with dense clouds of molecular gas and dust. While there is some evidence that HI self-absorption may be a more sensitive tracer of cold gas than CO emission, detailed examination of the exact relationships between these and other ISM constituents requires both high angular resolution and an unbiased sample.
The ongoing Canadian Galactic Plane Survey (CGPS) meets these criteria to an unprecedented degree, permitting the comparison of HI, CO, and dust features at arcminute scales over hundreds of square of degrees of the Milky Way. We will present the first results of an investigation of neutral Hydrogen self-absorption features in the CGPS dataset.

Introduction and latest results from the Laval wide field survey of old and peculiar HII Regions
Steve GODBOUT, Gilles JONCAS & Laurent DRISSEN, Université Laval
A survey is now underway at the Observatoire astronomique du Mont Mégantic which will focus mainly on the kinematics of the ionized gas of old and peculiar galactic HII regions as well that of the local neutral hydrogen. The end result should give us a better understanding of the energy exchange between these two phases of the interstellar medium and help pinpoint the scales at which this process takes place. An extragalactic base of comparison will also be built using the same kind of data from M33. We will outline the instrumentation used, affiliation with the CGPS and present preliminary results from optical data of M33 obtained at the CFHT.

Bayesian Detective Work With a 20 Year Time Series of LSI+61d303 Periodic Radio Outbursts
P. C. GREGORY, University of British Columbia
M. PERACAULA & A. R. TAYLOR, University of Calgary
The early-type binary LSI+61d303 is an interesting radio, X-ray and probable gamma-ray source. At radio wavelengths it exhibits periodic outbursts with a 26.5 day period as well as a longer term modulation of the outburst peaks of approximately 4 years. There has been increasing evidence for a change in the period of the system. We will present a Bayesian analysis of 20 years of radio observations including the Green Bank -NASA radio monitoring data which provides a new insight into the properties of the system.

WFPC2/H-alpha Imagery of the Nebula M1-67 : A Clumpy Wolf-Rayet Wind Imprinting Itself on the Nebular Structure?
Yves GROSDIDIER & A.F.J. MOFFAT, Université de Montréal
G. JONCAS, Université Laval
A. ACKER, Obs. de Strasbourg
With HST/WFPC2 we have obtained a deep, net H-alpha image of the relatively young ejection-type nebula M1-67 around the runaway population-I WR star WR124 (WN8). This image shows a wealth of complex details, some of which have never been seen before in such a nebula. In particular, besides large arcs of nebulosity extending chaotically in many directions yet with no overall global shell structure to the nebula, we note the presence of numerous bright, resolved knots of emission often surrounded by what appear to be their own local ``wind'' bubbles. Is this the first direct evidence of spatially resolved clumps being ejected from the wind of a hot central star?

The Globular Clusters of The Fornax dSph Galaxy: A view From Space
Eduardo HARDY, NRAO/MMA Project
R. BUONANNO & C. CORSI, Roma
F. FUSI-PECCI, Bologna
R. ZINN, Yale University
N. SUNTZEFF, CTIO
Color-magnitude diagrams were constructed for four of the five Globular Clusters of the Fornax dSph galaxy from observations with HST. These diagrams reach well below the main-sequence turn-off and allow a study of the age and the HB morphology of these clusters essentially free of distance effects. The second parameter effect exists in the metal-poor cluster system of Fornax and is probably unrelated to age. A correlation was found, however, between HB morphology and central density.

IDEFIX, un imageur polarimétrique pour l'OMM
Olivier HERNANDEZ, Université de Montréal
L'Observatoire du Mont Mégantic se dote d'un imageur polarimétrique. Idefix est un instrument qui permettra d'obtenir deux images de polarisation perpendiculaire de façon simultanée sur le CCD Loral. Le champ de chaque image sera de plus de deux minutes d'arc et cela permettra l'étude d'étoiles très jeunes. Grâce à un choix de 4 filtres BVRI, une étude en longueur d'onde pourra être effectuée. Enfin, autant les polarisations linéaire et circulaire pourront être étudiées grâce aux lames demi-ondes ou quart d'onde placée à l'entrée d'Idefix. Les premières lumières sont prévues pour le mois de juin......

Innovations in Altair, the Gemini adaptive optics system
Glen HERRIOT & Simon MORRIS, HIA/NRC
Altair includes some interesting new design ideas, because of the infrastructure provided by the Gemini Observatory and because of the decision to put Altair's deformable mirror at an image of the plane 6.5 km in front of the telescope.

HST Studies of Second-Parameter Globular Clusters in the Outer Galactic Halo
P. B. STETSON, J. E. HESSER, S. VAN DEN BERGH DAO/HIA/NRC
M. BOLTE, J. A. JOHNSON, UCO/Lick
W. E. HARRIS, McMaster University
D. A. VANDENBERG, U. Victoria
R. A. BELL, U. Maryland
H. E. BOND, L. FULLTON, STScI
G. G. FAHLMAN & H. B. RICHER, UBC
We have observed Palomar 3, Palomar 4 and Eridanus with WFPC2 on HST. These three are classic examples of the "second parameter" anomaly because of their red horizontal-branch morphologies in combination with their low-to-intermediate metallicities. Our (V,I) color-magnitude diagrams (CMDs) reach V (limit) ~27.8 and clearly delineate the subgiant and turnoff regions and about three magnitudes of the unevolved main sequence. The slopes and dereddened colours of the giant branches are consistent with published [Fe/H] estimates that rank the clusters (Pal 3, Eri, Pal 4) in order of increasing metallity, with all three falling near or between the abundance values of the classic nearby halo clusters M3 and M5. From differential fits of their CMDs, we find that the three outer-halo clusters differ from those of the nearby ones in a way that is consistent with the distant objects being younger by ~1.5-2 Gyr. This inferred age difference could be smaller (< 1 Gyr) if either [Fe/H] or [alpha/Fe] for the outer-halo clusters is significantly lower than we have assumed. Possible age spreads of order 1 Gyr among both the nearby and outer-halo clusters may also be present.

Events in the Star Forming Region Cepheus A
Victor A. HUGHES, Queen's University
A monitoring of the star forming region Cepheus A, over a period of 13 years, using the VLA, has shown up a number of events which are associated with the early stages of star formation. The events are unique in that no other region has been monitored for a period as long as this, whether it is a star forming region or not. They include the demonstration of a jet, showing both the Mach and jet shocks, a source that shows two diverging radio sources, two sources that can appear and disappear in periods of 100 days and which have brightness temperatures of 10**6 to 10**9 K, and an object which contains three individual components which appear to be in orbit.
An attempt will be made to put these observations into perspective as regards protostar formation.

Resolution of QSOs with AOB on CFHT
John HUTCHINGS, David CRAMPTON & Simon MORRIS, DAO/HIA/NRC
We will present the results of AOB imaging of QSOs, in passbands from I to K. The high resolution and signal obtainable have led to new results on QSO host galaxies and environments.

Orbital Motion in the Symbiotic Nova HM Sge
H. T. KENNY, Royal Military College
A. R. TAYLOR, University of Calgary
HM Sge is a D-type symbiotic star system, which exhibited a symbiotic nova eruption beginning in 1975. VLA images at 5 and 22.5 GHz are presented with data extending from 1982 to 1998. The morphology and evolution of the radio emission is analysed in terms of a model which considers the effects of both colliding winds (Kwok, Purton and Fitzgerald 1978; Girard and Willson 1987; and Kenny 1995), and differential ionization (STB model: Seaquist, Taylor and Button 1984; Taylor and Seaquist 1984). The outer shell, of radius $\sim$ 2$''$, is characterized by a ratio of mass loss rate to velocity of $\dot{M}_c/v_c = $ $5.1 \pm 0.3 \times 10^{-8}D^{3/2}_{\rm kpc}$ [$M_\odot$ yr$^{-1}$][km s$^{-1}$]$^{-1}$. The inner shell, of radius $\sim 0.''3$, is characterize by a value which is $\sim$ 4 times larger, {\it i.e.} $\dot{M}_c/v_c = $ $1.9 \pm 0.9 \times 10^{-7}D^{3/2}_{\rm kpc}$ [$M_\odot$ yr$^{-1}$][km s$^{-1}$]$^{-1}$.
At 22.5 GHz, the radio morphology includes two features which evolve in separation and position angle. This evolution is analysed in terms of a model of orbital colliding winds. The fitted orbital elements indicate a highly inclined orbit ($i = 78^\circ \pm 4^\circ$) with a period of 80$\pm^{60}_{20}$ yr, and a binary separation of 24$\pm^{10}_{5}$ AU for a total system mass of 2 $M_\odot$. Spectral analysis (STB model) suggests an angular binary separation of $\sim 0.''1$, which yields a distance of 300$\pm^{130}_{65}$ pc. A distance as high as 750 pc may be obtained if the present mass loss characteristics of the cool component have returned to their pre-outburst values, represented in the outer shell.

Near-IR [FeII] Line Emission in Nearby Star-Forming Galaxies and the Supernova Rate
K. LABRIE & C. J. PRITCHET, University of Victoria
Grain destruction behind supernova remnant (SNR) shock waves is believed to be the source of the near-IR [FeII] line emission observed in star-forming galaxies. The enhancement of the [FeII]$\lambda 1.644\mu m$/Pa$\beta$ ratio in SNRs compared to HII regions can be used to detect individual remnants in nearby galaxies.
Lumsden & Puxley (1995) observed a linear correlation between the expansion velocity of a sample of SNRs in M33 and their [FeII] flux. Through the Sedov solution, the expansion velocity of a remnant can be used to derive its age (i.e. time since the explosion).
High spatial resolution [FeII] mapping of nearby galaxies allows us to estimate the number of supernova remnants produced over a time interval calculated from the age estimates obtained from the iron flux of the individual SNRs. The supernova rate of the galaxy observed can then be calculated, without the need for multi-epoch observations.
We recently obtained, at CFHT, high spatial resolution near-IR narrow-band imaging of three nearby star-forming galaxies (NGC 1569, NGC 3738 and NGC 5253). Here we present our preliminary results.

Etude multi-spectrale du complexe Sharpless 247
France LALIBERTÉ, Université Laval
A partir de données radio du VLA, du DRAO et du FCRAO sur les gaz ionisé, atomique et moléculaire, il s'agira de déterminer les conditions physiques qui règnent dans ces gaz. En ionisant le gaz résiduel et donc en érodant le nuage moléculaire ayant servi à leur formation, les jeunes étoiles transfèrent une partie de leur énergie aux vestiges de gaz. A partir du champ de vitesses et des caractéristiques physiques des gaz (densité et température), il s'agira d'établir l'ampleur du transfert d'énergie mécanique étoile-gaz et les conditions de cohabitation des gaz.

The Dominion Radio Astrophysical Observatory
Tom L. LANDECKER, Dominion Radio Astrophysical Observatory/HIA/NRC
The Dominion Radio Astrophysical Observatory (DRAO) is part of the Herzberg Institute of Astrophysics, within the National Research Council. The principal fields of astronomical research at DRAO are interstellar medium studies, all aspects of research with space very-long-baseline interferometry, and solar radio astronomy. The themes of DRAO engineering and technical expertise are (a) the design and operation of aperture synthesis telescopes, (b) antennas, (c) digital signal processing systems, especially correlator systems, and (d) image processing.
The major facilities at DRAO are the Synthesis Telescope, the 26-m Telescope, and the telescopes of the Solar Radio Flux Monitoring Program. DRAO supports six major projects (a) the Canadian Galactic Plane Survey, (b) the operation of the Canadian correlator for the VSOP space VLBI mission, (c) the Solar Flux Monitoring program, (d) ACSIS, the development of a correlator for the focal plane arrays on the JCMT, (e) the program to define the future of Canadian Radio Astronomy, and (f) work to protect the radio astronomy spectrum allocations.

Discours du président/President's address
John LANDSTREET, University of Western Ontario

Mise en evidence des régions de formation d'étoiles à la péripherie de la galaxie spirale NGC 628
Mario LELIÈVRE, Université Laval
Discussion des résultats obtenus suite à la détection et à l'analyse des régions HII au-delà de R25 pour la galaxie spirale tardive NGC 628. Le but est d'étudier les processus de formation d'étoiles massives dans les régions du disque non affectées par l'onde de densité spirale. Au terme de cette étude, nous mettrons à l'épreuve certaines théories discutant de conditions particulières en densité de gaz nécessaire à la formation d'étoiles massives.

The mystery of Wolf-Rayet emission-line variability: A shocking behavior from a clumpy wind
Sébastien LÉPINE & Anthony F. J. MOFFAT, Université de Montréal
We present the results from a study of line-profile variability (lpv) in emission-lines of Wolf-Rayet stars. High resolution spectroscopic observations from CFHT shed new light on the behavior of these stochastic lpv. We show that these lpv are broadly consistent with line emission from a clumpy wind. However, strange behavior from the clumps suggest that the wind inhomogeneity arises in dramatic hydrodynamical events, which may be related to radiative instabilities generated by the intense radiation field from the underlying star.

Science with NGST
Simon LILLY, University of Toronto

Coherent Emission Mechanisms in Radio Pulsars
Maxim LYUTIKOV, CITA
A theory of pulsar radio emission generation, in which the observed waves are produced directly by maser-type plasma instabilities on the anomalous cyclotron-Cherenkov resonance $\, \omega-\, k_{\parallel} v_{\parallel} +\, \omega_B/\, \gamma_{res}=0$ and the Cherenkov-drift resonance $\, \omega-\, k_{\parallel} v_{\parallel} - k_{\perp} u_d =0$, is capable of explaining the main observational characteristics of pulsar radio emission. The instabilities are due to the interaction of the fast particles of the primary beam and from the tail of the distribution with the normal modes of a strongly magnetized one-dimensional electron-positron plasma. The waves emitted at these resonances are vacuum-like electromagnetic waves that may leave magnetosphere directly. The cyclotron-Cherenkov instability is responsible for core emission pattern and the Cherenkov-drift instability produces conal emission. The conditions for the development of the cyclotron-Cherenkov instability are satisfied for the both typical and millisecond pulsars provided that the streaming energy of the bulk plasma is not very high $\gamma_p = 5\div 10$. In a typical pulsar the cyclotron-Cherenkov and Cherenkov-drift resonances occur in the outer parts of magnetosphere at $ r_{res}\, \approx 10^9 {\rm cm}$. This theory can account for various aspects of pulsar phenomenology including the morphology of the pulses, their polarization properties and spectral behaviour.

Evolution des abondances chimiques dans les atmosphères d'étoiles naines blanches froides
Alain MALO, F. WESEMAEL, Université de Montréal
P. BERGERON, Lockheed Martin Canada
Les étoiles naines blanches montrent des changements dramatiques dans la composition chimique de leur enveloppe au cours de leur refroidissement, en particulier à T_eff~6000 K où on observe que les naines blanches de type non-DA se transforment en naines blanches de type DA. A ces températures, la majorité des étoiles froides peuvent être modélisées à l'aide d'atmosphères composées soit d'hydrogène soit d'hélium. Cependant, une demi-douzaine d'objets semblent caracterisés par des distributions d'énergie typiques d'atmosphères riches en hydrogène, alors que leur spectre ne montre pas la raie d'absorption H_alpha. Nous passons en revue les mécanismes proposés dans le but d'expliquer les propriétés de ces objets, et demontrons qu'aucun de ceux-ci n'arrive a reproduire adéquatement les observations.

HST Observations of the Lower Main Sequence of M55
Georgi MANDUSHEV, University of British Columbia
Archive single-field observations obtained with the WFPC2 camera on the Hubble Space Telescope were used for a photometric study of the lower main sequence of the metal-poor, sparse globular cluster M55. The cluster main sequence can be clearly seen to the faint limit of the photometry at I = 25.2, V-I = 3.2, although the number of stars on the MS drops sharply fainter than I = 23.0. This drop occurs brighter than the magnitude where the incompleteness of the data becomes significant and can be explained with the change in the slope of the mass-luminosity relation at very low masses. Comparison with the main-sequence mass function for another field at a larger distance from the cluster center indicates the presence of mass segregation.

Polarimetric Variability of Binary Young Stars
Nadine MANSET & Pierre BASTIEN, Université de Montréal
Young stars are surrounded by accretion disks in which dust grains scatter and polarize stellar light. In binary systems, models predict this polarization will show phase-locked variations with a double sine behavior. About fifteen binary young stars have been observed at the Observatoire du Mont Megantic to seek for these polarimetric variations. Preliminary results show that a majority of binary young stars are variable polarimetrically, and some show phase-locked variations. If the existing models can be successfully applied to these young stars, observations will allow to find the orbital inclination. Since these systems are also spectroscopic binaries, the known inclination will then give the masses of the young stars, which is a very important parameter for testing evolutionnary models.

Dust Formation Episode in the Long-Period Binary WR137: Direct Imaging with HST/NICMOS 2
Sergey MARCHENKO, A.F.J. MOFFAT & Y. GROSDIDIER, Université de Montréal
We report preliminary results of medium-band (H' and K') direct imaging of the dust-forming binary WR 137 with the NICMOS-2 camera of HST. The images were obtained during periastron passage in this long- period (~13 y) binary. We have resolved, for the first time, IR-emitting dust in the close environment of HD 192641. The dust emission occurs in a few strong clumps within about 0.5" from the star and likely arises in the shock-cone zone where the winds collide. We estimate the mass of the resolved dust features to be 5(+7 -3) 10^-8 M_Sun.

Observations of Extrasolar Planets
Geoff MARCY, San Francisco State University
Eight candidate extrasolar planets have been identified by Keplerian Doppler shifts in their host stars. The masses (msini) lie between 0.5 and 7 Jupiter masses and the semimajor axes are less than 2.1 AU. For three of these companions (47 UMa, rho Crb, and 55 Cnc), their circular orbits must be primordial rather than tidally induced, indicating formation in a disk. Eccentric orbits may be explained by gravitational perturbations, either by companion stars, other planets, or disk resonances. The detections imply that 5% of Solar-type stars have giant planets within 2 AU. Orbital migration during the T Tauri disk phase provides a likely mechanism to explain the small orbits. New planet searches of 400 stars are underway at Keck and elsewhere, with the latest findings to be reported.

Aberrations du miroir primaire du mont Mégantic: Avons-nous un bon télescope?
Christian MAROIS & René RACINE, Université de Montréal
Dans le processus d'implantation d'un système d'optique adaptative, il est essentiel de connaître les limites intrinsèques du télescope. Les aberrations ainsi détectées permettent de fixer les performances futures du système et d'envisager des mesures de correction si cela s'avère nécessaire. Je présenterai donc les résultats de mes recherches dans le cadre de ma maîtrise avec le Dr. René Racine portant sur le miroir primaire du mont Mégantic.

Star Formation in Bar Environments
Pierre MARTIN, Télescope Canada-France-Hawaii
Daniel FRIEDLI, Université Laval
Galactic bars are the site of highly diversifed star formation activities. Along certain bars, no star formation is present while in others, numerous giant HII regions are seen. To better understand how massive star formation is triggered or quenched in bar environments, we describe a general study on the morphological and physical properties (i.e. density, excitation, abundances) of HII regions found along the bars of eleven spirals. These results were then used to investigate the star formation process along bars using performant numerical simulations. In a wider context, the implications of star forming activity along bars for AGN fueling and the evolution of barred spiral galaxies in general are briefly dicussed.

Mapping protostars with SCUBA: Extended Structure in RNO 43
Brenda C. MATTHEWS & Christine D. WILSON, McMaster University
We present the first SCUBA data of protostellar envelope structures. Data for six Class 0 sources are presented. The possibility that RNO 43 contains a disk or is an unresolved binary is discussed.

MOST: Probing Stellar Interiors With Canada's First Space Telescope
Jaymie MATTHEWS, University of British Columbia
The MOST (Microvariability & Oscillations of STars) mission would be a microsatellite carrying a 15-cm optical telescope in a polar low-Earth orbit. MOST is designed to detect rapid oscillations at the level of a few micromagnitudes in bright solar-type stars, as well as microvariability in a variety of stellar targets including Wolf-Rayet stars. One of the mission goals is to estimate the ages and global properties of some of the oldest metal-poor stars in the solar neighbourhood, setting independent lower limits on the age of the Universe.

PLASKET LECTURE:
Star Formation in Molecular Clouds and Globular Clusters
Dean E. McLAUGHLIN, UC Berkeley
The process of star formation is investigated in two complementary ways. First, a new model is developed for the internal structure of the dense cores of gas inside giant molecular clouds (GMCs), which are the main sites of star formation in the Galaxy today. This model, which posits that the total gas pressure in these cores varies logarithmically with density, allows for an explicit description of the significant nonthermal motions that support them, for a time, against their self-gravity. It is in good agreement with a range of observational data. This ``logotropic'' equation of state is used to explore the implications of turbulent initial conditions for the gravitational collapse of GMC cores.
Second, the collective properties of globular cluster systems (GCSs) in galaxy halos are used to gain some insight into the important phenomenon of clustered star formation. In particular, a theory is constructed for the globular cluster luminosity function (GCLF). The GCLF is considered as having been built up by collisions between gaseous protocluster ``cores'' within much larger (but subgalactic) ``supergiant molecular clouds'' in the halos of protogalaxies. Observations of the GCLFs in the Milky Way, M31, and M87 are used to constrain basic ingredients of the model, and the implications for present-day cluster formation are discussed.

The Distribution of Mass in the Core of Virgo and Dynamics of the Globular Cluster System Around M87
Dean E. McLAUGHLIN, UC Berkeley
Radial velocities for a sample of 205 globular clusters around M87, recently obtained by Cohen & Ryzhov (1997), are used to investigate the dynamics of the globular cluster system (GCS) of this cD galaxy. Previous analyses of similar (but sparser) data have made a priori assumptions on some property of the GCS (e.g., isotropic orbits) in order to use the cluster velocities to constrain the dark matter density profile in the core of Virgo. Here, we instead refer to the distribution of stars and gas in M87 to construct a mass model for the Virgo cluster independently of any data on the GCS. This is then used, along with the observed GCS density profile, to solve the Jeans equation for the GCS velocity dispersion as a function of radius in M87. The orbital anisotropy of the cluster system is a free parameter in this approach, and is constrained by comparing model line-of-sight velocity dispersions with the data of Cohen & Ryzhov.

The Kinetic Temperature (as a Function of Position) in the Circumstellar Envelopes of Be Stars
Carol E. MILLAR & J. M. MARLBOROUGH, University of Western Ontario
We have investigated the temperature structure of the circumstellar envelopes for a range of Be stars from B0 to A0. The rates of energy gain and loss per unit volume were evaluated as a function of position throughout the envelope. The gas was assumed to gain energy from photoionization, collisional de-excitation of bound levels and free-free absorption; it loses energy by recombination, collisional excitation and free-free emission. The kinetic temperature at any location is determined by the condition that the ratio of energy gain to energy loss there be unity. We have applied this approach to the PM model (Poeckert-Marlborough) and to the disk model (Waters). Initially, we tested the appropriateness of the envelope temperatures assumed. More importantly, we have determined the temperature structure throughout the envelope in a self consistent manner by balancing the rates of energy gain and energy loss at each point. The PM model, due to the exponential density distribution perpendicular to the equatorial plane, has a complex temperature distribution in the circumstellar envelope. The disk model, in contrast, yields a more uniform temperature distribution, because in this model the density is assumed to be constant on surfaces of constant radial distance from the central star.

Searching the Galaxy for Wolf-Rayet Stars
A.F.J. MOFFAT (UdeMontréal), M.M. SHARA (STScI), L.F. SMITH (U. Sydney), V.S. NIEMELA (La Plata), M. POTTER (STScI), R. LAMONTAGNE (UdeM)
We have just completed an optical Schmidt plate survey and spectroscopic confirmation of the Southern Milky Way for new WR stars as faint as 19th mag. The 31 newly detected WR stars are amongst the reddest and/or most distant known in the Galaxy. They clearly demonstrate an increasing number ratio of WN to WC with increasing Galactocentric distance. The total number of known Galactic WR stars now stands at over 200. We use a simple Galactic model to predict the total number of Galactic WR stars that should be discovered in future IR surveys in the whole Galaxy.

Spectrophotometric Models Applied to Spiral Galaxies
Mercedes MOLLÁ, Eduardo HARDY & Dominique BEAUCHAMP, Université Laval
We use the results of chemical evolution models to calculate the radial distributions of the Mg2 and Fe52 spectral indices in spiral galaxy disks. In particular, we try to reproduce the behaviour of these indices in NGC 4303, NGC 4321 and NGC 4535.

Variabilité cyclique d'étoiles Wolf-Rayet apparemment isolées
Thierry MOREL & Nicole ST-LOUIS, Université de Montréal
Nous discutons de récentes observations photométriques et spectroscopiques illustrant le caractère strictement périodique - bien que fortement dépendant de l'epoque d'observation - des variations dans les étoiles Wolf-Rayet apparemment isolées WR 6 (3.77 j) et WR 134 (2.3 j). Nous présentons des arguments contre l'eventuelle association de ces deux étoiles avec un compagnon dégénéré (i.e., ``invisible'') et proposons que, à l'instar de certaines étoiles OB, la periodicité observée serait plutot induite par la modulation par rotation d'un vent largement anisotropique. Les mécanismes susceptibles d'engendrer une telle situation seront également discutés.

CITA LECTURE:
Migrating Planets
N. MURRAY & B. HANSEN, CITA
M. HOLMAN, CITA/Harvard CfA
S. TREMAINE, CITA/Princeton
A planet orbiting in a disk of planetesimals can experience an instability in which it migrates to much smaller orbital radii. Resonant gravitational interactions between the planet and planetesimals remove angular momentum from the planetesimals, thereby increasing their eccentricities. Subsequently, the planetesimals either collide with the planet or are ejected by close encounters with it; ejecting a planetesimal reduces the semimajor axis of the planet. If the surface density of planetesimals exceeds a critical value, corresponding to $\sim0.03$ solar masses of gas inside the orbit of Jupiter, the planet will migrate inward a large distance. This instability may explain the presence of Jupiter-mass objects in small orbits around nearby solar-type stars.

A venir
Daniel NADEAU, Université de Montréal

A Thermal Mass-Transfer Model for Supersoft X-Ray Sources
Lorne A. NELSON & M.-P. PORTELANCE, Bishop's University
We analyze a binary model for the recently identified class of objects known as Supersoft X-ray Sources. According to this model, a subgiant companion fills its Roche lobe and loses matter onto a C-O white dwarf accretor. We show that the donor loses mass on its Kelvin timescale and that this rate of accretion onto the degenerate dwarf is sufficiently high to ensure that stable nuclear burning occurs on its surface (i.e., the mass of the degenerate companion can increase). Using population synthesis techniques, we compare the theoretically expected number of supersoft sources with that which is actually observed and investigate the possibility that these sources are the progenitors of Type Ia supernovae.

Fueling a Starburst in M83: Observations of CI and CO
Glen PETITPAS & Christine WILSON, McMaster University
I present CI, CO J=4-3, and CO J=3-2 maps of the barred spiral galaxy M83 taken at the James Clerk Maxwell Telescope. Observations indicate a double peaked structure which is consistent with gas inflow along the bar collecting at the inner Lindblad resonance. This structure suggests that nuclear starbursts can occur even in galaxies where this inflow/collection occurs, in contrast to previous studies of barred spiral galaxies. However, the observations also suggest that the double peaked emission may be the result of a rotating molecular ring oriented nearly perpendicular to the main disk of the galaxy. The CO J=4-3 data indicate the presence of warm gas in the nucleus that is not apparent in the lower-J CO observations, which suggests that CO J=1-0 emission may not be a reliable tracer of molecular gas in starburst galaxies. The CI/CO J=4-3 line ratios indicate that the CO J=4-3 emission is originating in the same hot photon-dominated regions as the CI emission. The CO J=4-3/J=3-2 line ratios are higer along an arc of active star forming regions which likely indicates optically thin gas created by the high temperatures caused by star forming regions in the nucleus of this starburst galaxy.

Superposition de populations dans la galaxie starburst IRAS 0833 : triplet de calcium
Anne PELLERIN, Université Laval
Le triplet de calcium est un indicateur d'étoiles Supergéantes Rouges (SGR).Il s'agit ici de comparer les populations jeunes du starburst nucléaire de IRAS 0833 avec celles de SGR et de discuter ensuite des superpositions possibles de populations stellaires.

Une nouvelle région HII bipolaire dans le Cygne
Serge PINEAULT, Université Laval
Des données couvrant une gamme importante du spectre électromagnetique, allant du radio (continu et raie a 21 cm de l'hydrogène neutre) au visible en passant par l'infrarouge, sont utilisées pour déterminer les propriétés physiques d'une région HII bipolaire récemment découverte à partir d'observations obtenues avec le télescope a synthèse d'ouverture de l'Observatoire fédéral de radioastrophysique (DRAO) à Penticton. Une source compacte (mais non ponctuelle) centrale est possiblement associée à la région circumstellaire affectée par le vent de l'étoile centrale.

The effect of metallicity on the winds of O stars
Stéphanie PLANTE, Université Laval
In order to quantify the effect of metallicity on the winds of massive stars, we have determined mass-loss rates and terminal velocities for a sample of 29 LMC and SMC O stars and compared those values with results from galactic stars. We derived the desired quantities with the help of HST UV spectra, optical spectra obtained at the CASLEO observatory and atmosphere models. We used the Schmutz \& Hubeny code, which reproduce the hydrogen and helium signatures present in the optical spectral range, to determine the mass-loss rate, luminosity and temperature of each of the stars. Terminal velocities have been calculated with the SEI code (Groenewegen et al. 1989), which synthesized the UV P-Cygni profiles formed in the dense winds of O stars. Radiation-driven wind theory predicts a strong dependence of the mass-loss rate with metallicity: $\dot{M}\propto Z^{0.8}$. Based on our observations, this dependence is not that strong, especially for giant and supergiant O stars. We also find that the terminal velocities are almost insensitive to metallicity; O stars from the SMC, LMC and Milky Way have similar v$_{\infty}.

Origin and observables of the Cosmic Web
D. POGOSYAN, J. R. BOND, CITA
L. KOFMAN, IfA, U. Hawaii
Observations indicate galaxies are distributed in a filament-dominated web-like structure. Numerical experiments at high and low redshift of viable structure formation theories also show filament-dominance. We have showed that the final state web is actually present in embryonic form in the overdensity pattern of the initial fluctuations, and is largely defined by the position and primordial tidal fields of rare events in the medium, with the strongest filaments between nearby peaks (clusters at low redshift, galaxies at high redshift) whose tidal tensors are nearly aligned. Here the web theory is used to craft N-body and hydrodynamical simulations which confront observations probing low redshift cluster-cluster bridges by weak gravitational lensing, X-rays and the Sunyaev-Zeldovich effect. Our results indicate that lensing at moderate redshift can probe the filaments best among these three observational strategies, but also that the SZ effect will be useful for probing the outskirts of clusters.

Quadrupole moments of rotating neutron stars
Bill LAARAKKERS & Eric POISSON, University of Guelph
Numerical models of rotating neutron stars (with realistic equations of state) are used to compute the star's quadrupole moment as a function of its mass and angular momentum. A quadratic relation between quadrupole moment and angular momentum is revealed for the entire relevant range of angular momenta.

Helical Fields and Filamentary Molecular Clouds
Ralph PUDRITZ & Jason FIEGE, McMaster University
Molecular clouds are observed to be filamentary structures that are supported by magnetic fields and non-thermal (MHD) turbulence of some sort. Most theoretical models for self-gravitating filaments have featured magnetic fields that are aligned with the long axis of the filaments. However, observations suggest that some of these clouds could be wrapped by helical magnetic fields (Heiles 1987). We present a new and more general model for filamentary molecular clouds that incorporates the important possible role of helical fields.

"Shall We Dance?", Said the Jester
René RACINE, Université de Montréal
"conferencier-dessert" ou "fou de la cours"
We've all eaten our cake and wish we have it. Finely dressed company sits in a luxuriously appointed room, each gentleperson(?) endowed with precious jewels, yet sitting pat on its(?) chair and ogling with envy the neighbours' riches. "Shall we dance?" said the court jester, he alone daring to come close to jewels he did not mint, wishing to capture their glow yet having to offer in exchange but exquisitly honed "badinage". Inspired by such boldness, others soon followed suite, so much the room became aglow with sparkles from jewels which all could relish in.
So is it perhaps with telescopes we each built, wherever they may sit. Hasn't time come for a jester to inspire opening one to others so they do the same unto all, for the greater benefit of science ?

Calculating reionization: the effect of diffuse Pop III stars
Alexei RAZOUMOV, University of British Columbia
Recombination of the Universe at z ~ 1000 gave rise to the cosmic dark age which lasted until "moderate" reshifts. However, all of the observable Universe is almost entirely ionized and transparent to radiation. The details of reionization are closely related to the growth of structure between redshifts 30 and 10, with light coming from the first generation of stars and quasars. A numerical scheme for the 3D time-dependent radiative transfer is being developed, to be merged with an existing cosmological hydrodynamical code. Prior work in the field usually focused either on 1D problems, or on using some local approximation (self-shielding, local optical depth). In this work we present a method to solve the moment equations of the radiation field allowing for a complex geometry of ray propagation. Hopefully, this technique will allow us to compute the growth of ionized bubbles from collapsed objects into a clumpy medium.

SCUBA Observations of the Lightcurves of Ceres, Vesta and Pallas
Russel O. REDMAN, Henry E. MATTHEWS & Paul FELDMAN, NRC
Lightcurves of the major asteroids Ceres and Vesta have been measured at wavelengths of 0.45, 0.85 and 2.0 mm using SCUBA on the JCMT. It is anticipated that a similar set of lightcurves of Pallas will also be available by the time of the meeting. These lightcurves will be used to probe the structure and physical properties of the asteroids' regoliths.

Dating Stellar Systems with White Dwarfs
Harvey RICHER, Greg FAHLMAN, Joanne ROSVICK, Paul HICKSON & Gordon WALKER, University of British Columbia
The age of stellar systems remains an important and difficult parameter to measure. We have been testing the cooling times of white dwarfs to see if this technique offers accuracy similar to that of isochrone fitting in age determination. We report on a few such tests. The ultimate goal is to use the coolest white dwarfs of population II to provide an age of the Universe.

Spectroscopie UV de galaxies starburst
Carmelle ROBERT, Université Laval

Atomic Hydrogen near the Cygnus Loop
Robert S. ROGER, Dominion Radio Astrophysical Observatory
Denis LEAHY, University of Calgary
21-cm HI-line observations of the Cygnus Loop have been made with DRAO's Synthesis Telescope and 26-m Telescope. Spectral line maps for 128 channels with 1.65 km/s velocity separation were constructed for a 6 degree square field encompassing the supernova remnant. A number of features are detected in and around the Cygnus Loop but no features are clearly identified with the interior of the remnant. However, several features have interior edges closely matching the outer boundary of the SNR. These provide evidence for the wall of the cavity into which the Cygnus Loop is hypothesized to be expanding.

Science verification of the Gemini Telescope instruments
Jean-René ROY, Université Laval
Four early-use phases of the Gemini instruments are planned: 1) on-telescope acceptance, 2) scientific commissioning, 3) shared-risks use, and 4) full use. Science verification is part of commissioning. Several science programs, proposed by the instruments scientists, the Gemini astronomers and the national project scientists are being designed to achieve the goals of science verification. These programs are to establish the instrument capabilities, to demonstrate fundamental science objectives, and illustrate the capabilities of the instruments by doing science. It will also serve for Gemini and national support staff training, and refinement of observational and data processing techniques. In summary, the science verification phase will exercise the whole Gemini environment, minus the intervention the Telescope Time Allocation evaluation. I will illustrate this phase by presenting some of the plans for the science verification of the Gemini Multi-Object Spectrograph built by Canada and the United Kingdom.

High spatial density of the disk population contact binaries
Slavek RUCINSKI, Canada-France-Hawaii-Telescope Co.
Analysis of the OGLE micro-lensing survey data in terms of the presence of contact binaries of the WUMa-type has permitted derivation of the luminosity function for these objects from a volume-limited (3 kpc) sample to absolute magnitude of Mv = 5.5. With (large) sampling-volume corrections, the function can be approximately estimated to fainter levels, down to the short-period end of the contact binary sequence at Mv = 7.5. Comparison of the luminosity function with that for the main sequence stars gives a high apparent frequency of occurrence of the WUMa-type binaries of one such a system for about 100 - 120 main sequence stars. This frequency is the apparent one and does not take into account missed systems with low orbital inclinations; the correction for those would increase the frequency by 1.5 - 2 times. When compared with the frequency of binary stars in the galactic field, derived by Duquennoy and Mayor (1991) and extrapolated to the shortest orbital periods, the contact binary stars show a large excess in the period range of 0.25 - 0.6 day suggesting that many (or all) originated from close binary systems with somewhat longer periods which lost large amounts of their angular momenta.

The Orbits of Two Giant Binary Stars
Colin SCARFE, University of Victoria
HD 90512 and HD 121212 are both single-spectrum binary stars, whose primaries are giants. Their orbital elements have been determined from radial velocities obtained with the DAO 1.2 m telescope and coude radial velocity spectrometer. Their periods are near 100 days and their orbital eccentricities are low. Thus they provide two new points near the boundary between circular and eccentric orbits in the period-eccentricity diagram for binaries containing giants.

The discovery of an open cluster associated with two Wolf-Rayet stars
Steve SHORLIN, University of Western Ontario
David G. TURNER, Saint Mary's University
CCD photometry reveals a very young open cluster, at a distance of 12.6kpc, associated with two Wolf-Rayet stars: WR 38 and WR 38a. WR 38 is the first WR star of spectral subtype WC4 to be found in a Galactic open cluster and its estimated absolute magnitude is far brighter than has become accepted for WC4 stars in our Galaxy. The absolute magnitude estimate for WR 38a confirms what is known about other stars of spectral subtype WN6.

Lyman-alpha Fluorescent Excitation of FeII in Active Galactic Nuclei
T. A. Aaron SIGUT, University of Western Ontario
Anil K. PRADHAN, Ohio State University
We have calculated FeII emission line strengths for Active Galactic Nuclei Broad-Line Regions using precise radiative transfer and Iron Project atomic data. We improve the treatment of all previously considered excitation mechanisms for the FeII emission, continuum fluorescence, collisional excitation, fluorescence by self-overlap among the iron lines, and fluorescent excitation by Lyman-alpha. We demonstrate that Lyman-alpha fluorescence is of fundamental importance in determining the strength of the FeII emission. In addition to enhancing the ultraviolet and optical FeII flux, Lyman-alpha fluorescence also results in significant near-infrared FeII emission in the 8500-9500 Angstrom wavelength range. New observations are suggested to probe this effect in strong FeII emitting quasars.

Vents en collision dans Gamma Velorum/ Colliding Winds in Gamma Velorum
Nicole St-LOUIS, Université de Montréal
La preuve de l'existence de vents stellaires en collision dans le système binaire WR+O Gamma Velorum a été obtenue par l'entremise d'une importante série de spectres optiques. Les caractéristiques du choc déduites de l'analyse de ces spectres seront présentées.
Evidence for the presence of colliding winds in the WR=+O binary system Gamma Velorum Has been obtained through an extensive series of optical spectra. The charateristics of the shock region deduced from the spectra will be presented.

HI in the field of the dwarf spheroidal galaxy Phoenix
Julie ST-GERMAIN & Claude CARIGNAN, Université de Montréal
We present new results of a mosaic of the HI emission in the field of the dwarf spheroidal galaxy Phoenix done with the Australia Telescope Compact Array. HI emission is seen in four different velocity components (-23, 0, 56, 140 km/s). While the component at 0 km/s is of galactic origin and the one at 140 km/s is probably related to the Magellanic Stream, one of the two other components could be associated with Phoenix. However, optical velocities are needed to verify whether this is the case.

Cosmic microwave background as a probe of cosmic topology
Tarun SOURADEEP, CITA
The measurements of CMB anisotropy have opened up a window for probing the global topology of the universe on length scales comparable to and beyond the Hubble radius. We have developed a new method for calculating the CMB anisotropy in models with nontrivial topology and apply it to open universe models with compact spatial topology. We conduct a Bayesian probability analysis for a selection of models which confronts the theoretical pixel-pixel temperature correlation function with the {\sc cobe--dmr} data. Our results demonstrate that strong constraints on compactness arise: if the universe is small compared to the `horizon' size, correlations appear in the maps that are irreconcilable with the observations. We have developed a new method for calculating the CMB anisotropy in models with nontrivial topology and apply it to open universe models with compact spatial topology. We conduct a Bayesian probability analysis for a selection of models which confronts the theoretical pixel-pixel temperature correlation function with the COBE-DMR data. Our results demonstrate that strong constraints on compactness arise: if the universe is small compared to the `horizon' size, correlations appear in the maps that are irreconcilable with the observations.

The Sun's Energy Output and the 10.7cm Flux
Kenneth Frank TAPPING, Herzberg Institute of Astrophysics/DRAO
The Sun's energy output has been measured over more than a solar activity cycle by orbiting radiometers. The National Research Council of Canada has made accurate measurements of the 10.7cm solar flux over the same period. The 10.7cm cm flux is an effective measure of the total magnetic flux in the lower solar atmosphere.In addition, there are connections between the Sun's total energy output and magnetic activity: sunspots cause dips and faculae enhancements. In a comparison between measurements of the energy output and the 10.7cm flux, each averaged over solar rotations, we find a strong, positive correlation. The processes modulating the Sun's energy output over timescales up to a solar cycle also modulate the density and magnetic field strength in the lower corona, where the 10.7cm emissions originate. There are signs of hysterisis between the energy output and 10.7cm flux between the rising and falling parts of the cycle. However, there is insufficient data to determine whether this is a systematic phenomenon.

The Canadian Galactic Plane Survey
A.R. TAYLOR, S. Gibson, D. Leahy, M. Peracaula, S. Dougherty (University of Calgary);
C. Carignan, & N. St-Louis (Universite de Montreal);    M. Fich (University of Waterloo);
N. Ghazzali, G. Joncas, S. Pineault & S. Mashchenko (Universite Laval);
J. Irwin, & J. English (Queen's University);    C. Heiles & M. Normandeau (University of California);
P. Martin, D. Johnstone, & S. Basu (Canadian Insititute for Theoretical Astrophysics);
W. McCutcheon (University of British Columbia);    D. Routledge, & F. Vaneldik (University of Alberta);
P. Dewdney, J. Galt, A. Gray, L. Higgs, L. Knee, T. Landecker, C. Purton, R.S. Roger, K. Tapping, B. Wallace, T. Willis (Herzberg Institute of Astrophysics);
C. Beichman (California Institute of Technology);    N. Duric (University of New Mexico);
D. Green (Cambridge University);    M. Heyer (University of Massachusetts);
H. Wendker (Hamburger Sternwarte);    Z. Xi-Zhen (Beijing Astronomical Observatory)

In April 1995 the Dominion Radio Astrophysical Observatory, in collaboration with a consortium of university astronomers, began a project to image the atomic hydrogen and radio continuum emission from the interstellar medium of the Milky Way galaxy. By constructing a mosaic of almost 200 synthesis fields, the survey will cover the region 75 < l < 145 degrees and -3 < b < +5 degrees, with angular resolution of 1'. The atomic hydrogen cube will yield a 3-dimenional images with spatial resolution of order 1 pc over regions several kiloparsec in extent. In the continuum, full Stokes I, Q, U and V images are produced at 1420 MHz and a Stokes I at 408 MHz.
Approximately 50% of the DRAO observations have now been completed, and the first complete mosaic images were created in December 1997. This paper presents a description of the survey project and highlights of the discoveries and results from these initial data products.

Spectroscopic study of binary B-type subdwarf (sdB) stars
Pascal THÉRIAULT, Robert LAMONTAGNE & F. WESEMAEL, Université de Montréal
The sdB stars are extended horizontal-branch members, having suffered important mass loss sometime on their evolutionary path. It is worth asking ourselves what role binarity might have in this scenario. Earlier photometric studies estimated that about 60% of the B-type subdwarfs are in binary systems, where the spectral type of the secondary, which resides either on the main-sequence or on the subgiant branch, ranges from late-G to early-M. In this work, we present optical spectra of several suspected binary sdB stars, which permit a deconvolution of the components of the system. Values for the parameters of each component are presented.

Baryon fraction variation in galaxy clusters
Eric TITTLEY & Hugh COUCHMAN, University of Western Ontario
The baryon fractions of clusters in n-body numerical simulations with hydrodynamics display remarkable variation depending on the mass of the clusters. This variation is found to be dependent on whether the clustering mechanism is hierarchical or non-hierarchical. In the case of hierarchical clustering, the mean baryon fractions of the clusters are bound by a fixed maximum fraction and a lower fraction which decreases with decreasing mass. In the non-hierarchical scenario, the mean baryon fractions are distributed about the lower bound seen in the hierarchical case. The baryon distribution within clusters differs between the two clustering scenarios, particularly in the vicinity of the virial radius. This may have implications for the cosmological baryon fraction estimations from X-ray observations of galaxy clusters which commonly extend out to approximately the virial radius.

3,7-m Liquid Mirror
Grégoire TREMBLAY & Ermanno BORRA, Université Laval
We have built a 3,7-m liquid mirror in our laboratory and we are currently testing it using a variety of optical shop tests. We will present the results we have obtained so far.

Monitoring Cepheid Period Changes from Saint Mary's University
David G. TURNER, Andrew J. HORSFORD & Joseph D. MACMILLAN Saint Mary's University
The 0.4-m telescope of the Burke-Gaffney Observatory at Saint Mary's was used with a CCD camera during the summers of 1996 and 1997 to image a selection of Cepheid variables in blue light. Seasonal light curves for each program star were constructed using the calculated magnitude differences of the Cepheids relative to reference stars in the same fields of view, and the data were then matched to existing light curve templates for each variable in order to establish O-C corrections to existing ephemerides. Examples of the results obtained for individual program stars are presented here. The long temporal baselines of O-C data that now exist for the observational histories of northern hemisphere Cepheids provide excellent material for studying their period changes. Such changes in turn are related directly to the rate at which the stars are evolving through the instability strip in the H-R diagram. From the results of our photometric monitoring it is possible to identify the probable crossing modes of our program objects with a fair degree of confidence. Extensive studies of a larger sample of Cepheids provide rather interesting revelations about the instability strip crossing modes of various objects. Some of the more controversial findings are described here.

Magnetism in Molecular Clouds: Monstrous Mayhem and Mild Madness
J. P. VALLÉE, NRC Canada/IHA    P. BASTIEN, Université de Montréal
In young clouds, the magnetic field is expected to be simple or at most to show mild madness (due to clump collisions, Alfven waves, etc). In old clouds, the magnetic field is expected to be complex and to show monstrous mayhem (due to starforming regions, bending magnetic lanes, etc).
We present new linear polarization observations at a wavelength of 800 microns of nearby dusty molecular clouds made with the James Clerk Telescope (JCMT) in Hawaii. The JCMT observations show that the magnetic field is often observed to be perpendicular to a cloud's elongation, constraining the possible geometries and time evolution. For extended clouds, the length scale of the magnetic field is of the order of the cloud itself or larger.
We assume that the polarization comes from emission by nonspherical grains aligned by a magnetic field, and that the direction of the tangential component of the magnetic field is given by perpendiculars to the observed position angles of the linear polarization.

A Detailed Investigation of the Environment of Active Galaxies
Marcel VANDALFSEN, McMaster University     M. M. DE ROBERTIS, York University
An analysis of some of the properties and environmental parameters of a sample of CfA Seyfert galaxies and a control sample of non-active galaxies is presented. To reduce selection effects, the two samples are well matched in redshift, luminosity and overall morphology. In particular, the distribution of host galaxy properties including disk and bulge scale radii and surface brightnesses are shown to be similar. The distribution of properties of the host galaxy "companions" -- galaxies in the field of a Seyfert or control galaxy out to a common projected distance -- are also illustrated. The distributions of relative companion frequency, projected separation (from the host), angular distribution, apparent magnitude difference from the host, and maximal tidal influence are found to be similar between both samples. Moreover, the frequency of "morphological disturbances" (bars, rings and distortions) between the Seyfert and control galaxies is found to be very similar. Though there is room for a more thorough investigation, nuclear activity does not appear to correlate with host-galaxy properties or the properties of the local environment.

Radiative Transfer and SPH Simulation
Serge VIAU & Pierre BASTIEN, Université de Montréal
In the SPH simulation of a collapsing cloud, the main advantage is that the code does not require a grid to compute spatial derivatives. Instead, we use point particles. Each particle possesses its own properties (mass, density, temperature) and those properties are smoothed out over an extended region by a given function called the kernel. The object of the research here is to add the radiative transfert to the energy conservation equation. This new version of SPH code will be very helpful to study the behavior of a molecular cloud during its collapse when we include the radiative transfer. For example, we are particularly interrested in te accretion disk. We think to be able to measure the distribution of the temperature along the disk.

Analysis of Two-Colour Data for Seyfert and Normal Galaxies
S. VIRANI & M. DE ROBERTIS, York University
A non-linear least-squares fitting algorithm was developed to determine the surface brightness structural parameters from a dataset consisting of 22 B and R images of Seyfert galaxies and 59 R images of non-active galaxies matched in redshift, luminosity and overall morphology. Rather than assume a de Vaucouleurs law, a more general relationship was used. In particular, the exponent for the bulge component was not adopted a priori.
Recent studies have shown that assuming an r^(1/n) "law", where n does not equal 4, may provide better fits than the standard r^(1/4) law. We will present results obtained from fitting a general Sersic form to our dataset. The best-fitting value for n is found to vary from values between 2 to 4. A comparison of the B and R data for the Seyferts, as well as the R data of the Seyferts and non-active sample, will be provided.

Spectropolarimetric observations of magnetic Ap stars
Gregg A. WADE, University of Western Ontario
Observations of circular and linear polarisation within the spectral lines of magnetic stars, obtained with an instrument such as the new MuSiCoS spectropolarimeter, provide a powerful means of constraining their surface magnetic field structure. In this talk I discuss recent spectropolarimetric observations of magnetic Ap stars, the detailed new magnetic maps that these data have made possible, and the implications of these maps on our understanding of the physical processes operating in stellar atmospheres.

BEALS LECTURE:
"CHALLENGES FOR THE NEW MILLENNIUM: Some Persistent Astronomical Mysteries"
Gordon WALKER, University of British Columbia
Carl Beals identified the strongest of the diffuse interstellar features sixty years ago and remained fascinated by them all his life. Their origin and signifcance still remain largely a mystery but satellites such as FUSE may provide crucial clues through better understanding of interstellar chemistry. Acquiring direct images and spectra of extra-solar planets has emerged as one of the greatest challenges for the new 8-m ground and space telescopes. I would like to talk about some of the efforts made together with my Montreal colleagues to meet the special problems of observing through the Earth's atmosphere and to speculate on our chance of success.

The Metallicity Dependence of the Cepheid Period-Luminosity Relation in the Near Infrared and a New Distance to M31
Tracy M. A. WEBB, D. L. WELCH, C. D. WILSON, Mc Master University
Peter STETSON, DAO
We present new JHK photometry for previously discovered M31 Cepheids, within the Baade and Swope fields I, III and IV. The data were obtained over six nights in August 1993 and three nights in October 1994 using the RedeyeN camera of the CFHT with conditions of FWHM=0.6 arcsec seeing. The Cepheids were chosen to be a subset of those observed by Freedman & Madore (1990) and were identified by optical finder charts and position on the JHK colour-colour plane. The total absorption at K is a factor of 4 lower than that for I, the longest wavelength in the previous study.
We present an improved distance modulus estimate for M31 and an investigation of the dependence of the Cepheid infrared P-L relation on metal abundance. Theoretical predictions and emperical studies of the latter are contradictory and the systematic errors affecting the calibration are expected to be much smaller in the infrared.

The Missing ISM of NGC 147 and M32
G. WELCH, Saint Mary's University    L. J. SAGE, Univ. of Maryland
We present the results of a search for CO(J=1-0) emission from NGC 147 and M32, two of the four dwarf elliptical companions of M31. Return of gas from evolved stars to the interstellar medium of these galaxies should have resulted in detections, but we find instead upper limits of 5500 and 6700 solar masses for NGC 147 and M32, respectively. Including an earlier HI limit, we find that the gaseous ISM of NGC 147 comprises less than 2% of what is expected. The large published HI mass limit for M32 prevents us from reaching a similarly extreme conclusion for it. These results stand in stark contrast to what is seen in NGC 185 and NGC 205, where the observed gas is approximately what is expected from stellar mass loss, though some of the gas in NGC 205 must have had an external origin. There are no obvious differences in masses or luminosities that would explain these results. The proposal that differences may be related to the recent interaction histories of the galaxies with M31 does not seem to be viable. These results may point to a fundamental gap in our understanding of galaxy evolution.

Les naines blanches variables de type V777 Her
F. WESEMAEL, Université de Montréal;    A. BEAUCHAMP, CAE Électronique Ltée;
P. BERGERON, Lockheed Martin Canada;    G. FONTAINE, Université de Montréal.
Les naines blanches de type V777 Her forment un groupe homogène d'étoiles variables à atmosphères composées d'hélium (types DB et DBA). Ces objets, en pulsation non radiale, sont tous caractérisés par des températures effectives de l'ordre de 20,000 K. Nous présentons une analyse spectroscopique détaillée des huit étoiles V777 Her connues, ainsi que d'un échantillon de 21 autres étoiles de même type spectral, toutes plus chaudes que 17,500 K. Les températures effectives déterminées permettent d'identifier les bornes de la bande d'instabilité des étoiles V777 Her, ainsi que de contraindre les analyses séismologiques de ces objets.

Large-Scale Structure of Molecular Gas in M17
C.D. WILSON, McMaster    J.E. HOWE, UMass    M.L. BALOGH, Victoria
Large-area CO maps of the molecular cloud M17 obtained at the JCMT have been used to study the CO line ratios and physical conditions in the cloud. The CO emission lines up to the J=3 level do not appear to be sensitive to small amounts of very hot gas. The 12CO/13CO line ratios correlate with the 13CO intensity, due primarily to variations in the column density from one position to another. Physical conditions (density, temperature) derived from globally averaged line ratios agree well with results obtained along individual lines-of-sight, which suggests that typical physical conditions can be measured successfully using global CO line ratios. The 12CO/13CO J=2-1 and J=3-2 line ratios indicate a systematic increase in these line ratios as we move to larger physical scales. These results suggest that emission from low column density "diffuse" molecular gas makes an important contribution to the CO emission in galactic disks.

The Globular Cluster System of Coma Elliptical Galaxy IC 4051
Sean C. WOODWORTH & W. E. HARRIS, McMaster University
We present a study of the globular cluster system in the giant elliptical galaxy IC 4051 in the Coma Cluster. The raw data consist of HST/WFPC2 images in F606W (V, 20500 seconds total) and F814W (I, 5200 seconds). Globular clusters are detected all the way in to the center of the galaxy, with a 50% completeness limit in the PC1 chip at V = 27.85 +/- 0.19 mag, and V = 28.41 +/- 0.23 mag in the WF chips. We have examined three properties of the globular cluster system: spatial distribution, colour distribution, and the cluster luminosity function. We find a mean colour V-I = 1.15 +/- 0.08 mag, which corresponds to a mean metallicity [Fe/H] = -0.29 implying a metal rich population. A study of the colour histogram does not show strong evidence for a bimodal colour distribution, unlike many other giant ellipticals and possibly indicating a single cluster formation epoch. The radial profile of clusters has been analyzed, showing evidence for a core radius within r = 6" (3 kpc) and a power law falloff of the cluster population at larger radii.

L'instrumentation de l'Observatoire du mont Megantic
Lamontagne, R. (UdM), Bastien, P. (UdM), Doyon, R. (UdM), Eversberg, T. (UdM), Nadeau, D. (UdM), Manset, N. (UdM), Moffat, A.F.J. (UdM), Roy, J.R. (UL), Vallee, P. (UdM)
Brève description des possibilités observationnelles en imagerie directe et fabry-perot, spectroscopie, polarimétrie et spectropolarimétrie dans les domaines visible et infrarouge a l'Observatoire du mont Mégantic.

Distribution de masse et matière sombre dans les galaxies/ Dark Matter and Mass Distribution in Galaxies
Claude CARIGNAN, Université de Montréal
Afin de pouvoir étudier la distribution de masse dans les galaxies spirales et les galaxies irregulières, il faut combiner aux observations HI donnant les informations cinématiques permettant de dériver les courbes de rotation, les profils de luminosité donnant la distribution de la composante stellaire. Une fois soustraites les composantes stellaire et gazeuse, la distribution de la matière sombre peut alors être étudiée. L'OMM a été utilisé pour obtenir ces données sur la photométrie de surface des galaxies étudiées.