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Yale University Department of Astronomy New Haven, Connecticut 06520 735 Yale University Department of Astronomy New Haven, Connecticut 06520 1. PERSONNEL Astronomy 110a Birth, Life, and Death of Stars. Charles Bailyn FACULTY AND RESEARCH STAFF, 1994-1995 Astronomy 111b Frontier and Controversies Professors: Pierre Demarque, Richard B. Larson, Augustus in Astrophysics C. Bailyn Oemler, Jr., Sabatino Sofia, William F. van Altena, and Astronomy 120b Galaxies and the Universe. R. Zinn Robert J. Zinn Astronomy 130b Life in the Universe. Professor Emeritus: Boris Garfinkel Assistant Professors: Sabatino Sofia Charles Bailyn, Paolo Coppi, Jeffrey Kenney, and Bradley Astronomy 220b Galaxies and Cosmology. Schaefer ~primary appointment in Physics! A. Oemler Senior Research Scientist ~Emeritus!: E. Dorrit Hoffleit Astronomy 250b Observational Astronomy. Research Scientist: Terrence Girard William van Altena Associate Research Scientist: Imants Platais Astronomy 310b Galactic & Extragalactic Department of Energy, Distinguished Postdoctoral Fellow: Astronomy. Richard Larson T.J. Lydon Astronomy 350a Stellar Astrophysics. Research Affilate: M. W. Schaefer Pierre Demarque Hubble Fellow: C. Deliyannis Postdoctoral Fellows: X. Guo, Astronomy 418b Stellar Dynamics. Jeffery Kenney Elliot Horch, Y.-C. Kim, and R. Me´ndez Astronomy 450b Cosmology. Augustus Oemler Associate in Research: John T. Lee and Vera Kozhurina- Astronomy 490a Independent Projects Platais in Astronomy. Faculty Visiting Fellows: A. Upgren and Hai-Wa Wu Research As- Astronomy 491b Independent Projects sistant: Y. Li in Astronomy. Faculty Members of the Yale Southern Observatory scientific staff in Graduate Teaching San Juan, Argentina included: M. R. Cesco, R. A. Gil Hutton, H. S. Le´pez, J. A. Torres, J. G. Sanguin, J. A. I. The Following graduate courses were Vicentela and C. E. Lo´pez; in July 1994 M. A. De Lau- offered during the year: rentis joined the group. C. E. Lo´pez continued as the YSO Astronomy 518b Stellar Dynamics. Coordinator in Argentina. Jeffery Kenney Astronomy 550a Stellar Astrophysics. ADMINISTRATIVE ASSIGNMENTS Pierre Demarque Chairman: Sabatino Sofia Astronomy 570a High Energy Astrophysics. Director of Graduate Studies: Robert J. Zinn P. Coppi Director of Undergraduate Studies: Charles Bailyn Astronomy 580a Research. Faculty Oemler and Zinn served as Yale’s astronomer members on Astronomy 580b Research. Faculty the board of the WIYN Corporation, where Oemler chaired Astronomy 600b Cosmology. Augustus Oemler the WIYN Scientific Advisory Committee. There were 17 graduate students in the department during the year. Two were awarded the PhD degree: Rene´ Me´ndez SPECIAL HONORS for the thesis ‘‘Semi-Empirical Model for the Distribution if In November 1994, C. E. Lo´pez received the Argentine Star-Counts, Colors and Kinematical Properties of Stars in National Award ‘‘Dr. Eduardo Braun Menendez’’ for his ar- the Milky Way’’ and Xinjian Guo for the thesis ‘‘Galactic ticle ‘‘Star Tales: A Journey Through the Solar System.’’ Structure, Kinematics and Chemical Abundance from UBV On March 1 Hoffleit was invited to deliver the prestigious Photometry and Absolute Proper Motions to B 5 22.5 To- Glover Memorial Lecture for 1995 at Dickinson College, wards the SGP.’’ Carlysle, PA. She delivered two talks, the first open to the public, ‘‘A Century of Women in Astronomy,’’ the second for the Physis Department, ‘‘The Development of Spectroscopy 3. PROGRESS AND PROBLEMS for Discovering the Physical Properties of Stars.’’ For these This year significant events have taken place in the De- she was presented the Glover Medal. partment. First, there was the dedication of the WIYN tele- scope in October 1994, followed by extensive testing and fine tuning, with regular scientific operations beginning in early Summer. It has been widely judged that the WIYN is 2. TEACHING the ‘‘finest ground-based imaging telescope’’ currently in ex- Undergraduate Teaching istence. The scheduled observing program entails the partici- The Following undergraduate courses were taught during pation of a large fraction of the Faculty and graduate students the year: in our Department. 736 ANNUAL REPORT A second significant development in our Department has tion in plate-overlap methods in the region of the Orion been the joint implementation with the Physics Department Nebula Cluster, and the ongoing Van Vleck parallax pro- of a teaching and research program in High Energy Astro- gram. physics. Besides carrying out the work in X-ray and Gamma- Kozhurina-Platais and Girard have continued to use the ray astronomy originally planned, the observing program has PDS in playback mode to generate coronograph masks. Two been greatly expanded by the initiation of an international sets of masks were provided to C. Ftaclas ~Hughes Danbury collaboration to carry out a deep survey of astronomical ob- Optical Systems! and collaborators who successfully used jects near the equator. The collaboration membership in- these in coronographic observations from the Infra-Red Tele- cludes Astronomers and Physicists at Yale and Indiana, plus scope Facility in Hawaii. Along with other targets, the diffi- scientists and engineers at the University of the Andes and cult binary Procyon A and B was successfully observed. The the Venezuelan National Observatory, both located in resulting separation measure will be combined with new par- Merida, Venezuela. Although the survey will provide photo- allax and orbital element determinations described elsewhere metric and spectroscopic information of all objects in that for the purpose of lowering the uncertainty in the mass esti- region of the sky, the primary interest of the Yale group is to mate of Procyon A. A set of masks was also produced for a detect gravitational lenses from quasar observations. It is ex- second team of coronograph operators represented by A. pected that within two years the project will have increased Crotts of Columbia University. the total number of known quasars ~and identified gravita- A. H. Lee, in collaboration with van Altena and Girard tional lenses! by approximately a factor of 100. This infor- designed an optical system for the PDS to illuminate and mation will allow us to address some of the most important relay the image of a star from the plate to a small CCD astrophysical questions of our time, such as the values of the camera. The goal of this project is to increase the throughput Hubble and of the Cosmological constants that are central to of the PDS for low signal-to-noise images where the scat- modern Cosmology. tered light in the direct imaging approach will not signifi- In the study of the Sun, this past year also saw the culmi- cantly degrade the derived image position in comparison nation of lengthy pursuits. From observations carried out by with the usual single channel scan system. Work is continu- the balloon-borne Solar Disk Sextant experiment in Septem- ing on improving the uniformity of the illumination system. ber 1992 and in Sepember 1994, we could establish that during this time interval the diameter of the Sun increased by 8 km. This value, far too small to be observed by any com- 4.3 The Solar Disk Sextant peting technique, explains the apparently contradictory re- The SDS is an instrument whose purpose is to make very sults obtained to date in the sense that all of the competing precise measurement of the solar radius at different orienta- techniques were measuring noise. The SDS also measured tions, and consequently the solar shape ~oblateness, limb os- the solar oblateness with unprecedented accuracy, and in the cillations, etc.!. The experiment is a joint effort between Yale process it disproved the recent claim that this quantity varied University and the Goddard Space Flight Center, and cur- as a function of the phase of the activity cycle. rently it is flown every year on stratospheric balloons to avoid the turbulence of the Earth’s atmosphere. It is contem- 4. FACILITIES plated that eventually the SDS will be flown on a spacecraft. The precision of the solar radius measurements made on the 4.1 The WIYN Telescope balloon-borne SDS have an rms distribution of less than 13 The WIYN telescope went into routine operation at the milli-arcseconds, with the noise primarily due to unevenness end of June 1995. This facility is a 3.5 meter alt-az telescope of the solar surface. During the period of this report, the SDS constructed on Kitt Peak by a consortium of Yale, the Uni- had one flight from Fort Sumner, NM, on September 26, versity of Wisconsin, Indiana University, and the National 1994. Optical Astronomy Observatories. Although some instrument development remains to be completed, it is now in use every night, with most time devoted to the two facility instruments: 5. RESEARCH a CCD camera, and the multiobject spectrograph, fed by the 5.1 Astrometry Hydra fiber positioner. Performance to date has been very satisfactory. Time lost to remaining problems has been mini- Guo, van Altena and T. Ingerson ~CTIO! finalized the mal, and the average image quality is excellent, with median modeling on the OFAD of the new Atmosphere Dispersion seeing of about 0.75 arc seconds. Correction ~ADC! on the CTIO 4-m telescope. Plate scale and distortion coefficients were obtained for the positioning 4.2 The PDS Microdensitometer of the fibers of the multi-fiber-fed Argus spectrograph, and for other imaging applications at the prime focus. The majority of the available PDS scanning time was de- Guo, T. Girard and van Altena also modeled the OFAD of voted to the Southern Proper Motion project and other, the 3.5-m WIYN telescope at the Nasmyth focus and ob- smaller, Yale astronomy department projects. The PDS has tained preliminary solutions for the positioning of the optical also been used by visiting researchers whose investigations fibers in the multi-fiber-fed Hydra spectrograph. have included scans of objective prism plates for galactic van Altena, R. Meyer and M. Yoshizawa ~Tokyo! began structure studies, a study of the Galactic bulge, an investiga- an investigation into the use of high time resolution multi- YALE UNIVERSITY 737 color astrometry as a method for compensating for atmo- the possibility of systematic effects on the derived magni- spheric turbulence as the principal limit to the accuracy of tudes.
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