SONOMA STATE UNIVERSITY

Observatory Report 1993-94

(reprinted from the Bulletin of the American Astronomical Society (1995) 27, 1, 581)

This report, the Department's eighteenth, covers the period September 1993 through August 1994. More up-to-date information may be found at the Department of Physics and Astronomy pages. Reports from other years are also available.

I. PERSONNEL

The faculty consisted of professors Lynn R. Cominsky, John R. Dunning, Samuel L. Greene, Duncan E. Poland (Chair), Saeid Rahimi, Gordon G. Spear (Observatory Director), and Joseph S. Tenn. Cominsky was on sabbatical leave all year at the Stanford Linear Accelerator Center. Lecturer Norman Sperling also taught astronomy courses.

II. INSTRUCTION

A total of 367 students took Descriptive Astronomy, Introductory Observational Astronomy, Extraterrestrial Intelligence and Interstellar Travel, Frontiers in Astronomy, and Cosmology. The Department awarded 2 B.A. degrees and 5 B.S. degrees. (All degrees are in physics.) There were 42 physics majors in Spring 1994.

III. EQUIPMENT

Optical telescopes are mounted in a sliding-roof observatory on campus. Auxiliary instrumentation for the 0.36-m Schmidt-Cassegrain telescope includes a CCD camera, an f/10 guide scope, a 0.2-m f/3 Baker-Schmidt camera, wide field cameras, a slitless prism spectrograph, a dispersion grating spectrograph with a Hg-Ne comparison source, and a 0.5-angstrom H-alpha filter.

Epoch Instruments delivered a new, improved computer-controlled telescope system. The telescope is still a 0.25-m f/5 Newtonian, but the mounting and the drive system are far more robust than the earlier prototype. The control software now supports user-generated observing lists. The system points reliably to within 1-2 arcminutes on the sky. When it is used with the AstroLink CCD camera, the resulting images have a 20 arcminute field of view and a 2 arcsecond/pixel image scale. Reliable photometry is feasible for objects as faint as 16th magnitude.

The student-built Very Small Array (VSA) radio interferometer operates at 1420 MHz and consists of two 3-m parabolic dishes 80 m apart on the roof of the natural sciences building. The dishes are now fully steerable, and digital data are collected and analyzed with a Sun workstation.

Procedures were developed by Mallory Roberts ('94) to point and lock down the dishes. Roberts also developed analysis software and taught a seminar on basic radio astronomy. Students Daniel Hale, Greg Madruga, and Amanda Tunison aided with the software development. Students Robin Adams, Jorge Polanco, Naomi Owen, and Aaron Owen were also on the support team.

IV. RESEARCH

Cominsky worked in the Particle Astrophysics Group at the Stanford Linear Accelerator Center on projects involving X-rays and high-energy gamma-rays. She helped in the development of a ground data system for the Unconventional Stellar Aspect Experiment, which will be launched on the ARGOS satellite in 1995. She worked on designs for high-energy gamma-ray detectors using silicon strip technology. She presented results from the Compton Gamma Ray Observatory at the 2nd CGRO Symposium in September 1993. She also presented results from the ROSAT and Compton GRO satellites at the 4th Annual Astrophysics Conference in Maryland in October 1993. Cominsky and Andrew King of Leicester University proposed a new model to account for the unexpected X-ray emission from the PSR 1259-63 system near apastron. They calculated the emission expected from accretion onto the neutron star's magnetosphere (rather than onto the light cylinder) and showed that it was consistent with the discovery observations made by Cominsky, Roberts and Johnston (1994). This work has been accepted for publication in the Astrophysical Journal.

Preliminary results from analysis of HEAO A-1 data on galactic black hole and neutron star binary sources were presented at the June 1994 meeting of the American Astronomical Society by Cominsky, Roberts, and Stanford graduate students Andrew Lee and Dan Segel. Roberts, Cominsky, Spear, and student Naomi Owen presented results from the Very Small Array Sky Survey at this meeting. The Sky Survey resulted in the detection of 1420 MHz emission from ten radio sources.

Spear continued research on the variable sources observed by the IRAS mission. With support from the NASA Astrophysics Data Program, Spear and Matt Davis ('93) produced the first complete version of the IRAS Catalog of Variable Sources. The catalog includes positional associations of IRAS sources with objects in the 4th edition of the General Catalog of Variable Stars and subsequent namelists. Davis computerized the namelist catalogs and is analyzing the statistical distribution of variable star types. The active galaxy surveillance program continued. Spear, Miriam Carolin ('82), Christopher Espenlaub ('86), and Miriam Tobin ('90) observed NGC 5548, Mrk 421, Mrk 509, and NGC 7469 in V and R with the CCD system.

Spear continued to search for new variable stars in the anti-center region of the galaxy. Data have been obtained with the CCD camera for fields in MWF 97, MWF 109, and MWF 121. The search will be extended to additional fields with the computer-controlled telescope.

Tenn continued researching and writing a series of articles on the recipients of the Astronomical Society of the Pacific's Catherine Wolfe Bruce gold medal.

V. MISCELLANEOUS

The optical observatory was used 27 times, including 10 for public viewing nights, classes, and tours, and 17 for research. There were 382 visitors. The Very Small Array was used for more than 30 observations, some of 24-hour duration, for the sky survey.

Cominsky spoke on the PSR1259-63 results in the Stanford University Center for Space Sciences and Astrophysics seminar series and at the UC Berkeley Center for Extreme Ultraviolet Astrophysics. She gave a colloquium entitled "X-ray Binary Pulsars" at the Stanford Linear Accelerator Center. She gave an invited lecture, "Dynamic Measurements of Stellar Mass Black Hole Candidates," at the Snowmass Summer Institute on Particle Physics, Astrophysics and Cosmology. She also presented an invited lecture, "X-ray Emission from Be-Binaries," at the Seventh Annual Marcel Grossman Conference at Stanford.

Spear participated in a summer workshop to evaluate astronomy laboratory exercises developed by Project CLEA (Contemporary Laboratory Experiences in Astronomy) at Gettysburg College. Scripts for the next generation of computer simulations for introductory astronomy laboratory courses were developed.

Tenn presented an invited lecture at the January meeting of the American Association of Physics Teachers in San Diego. He organized a session, "How California Astronomers Changed Our View of the Universe," at the annual meeting of the American Association for the Advancement of Science in San Francisco. As chair of the Astronomical Society of the Pacific history committee, he organized sessions on the Lowell Observatory in twentieth century astronomy and on the history of planetary astronomy for the ASP annual meeting in Flagstaff.

The Department presented its "What Physicists Do" public lecture series, under Tenn's direction, for the 46th and 47th semesters. Visiting speakers on astronomical topics were Dorrit Hoffleit (Yale U.), Claire Max (Lawrence Livermore National Lab), Roger Malina (U. of California at Berkeley), Sallie Baliunas (Harvard-Smithsonian CfA), Dan Nottingham (Boston U.), Paul Hodge (U. of Washington), and Hank Crawford (Lawrence Berkeley Lab).

VI. PUBLICATIONS

Cominsky, L. 1994, "The Evolutionary Status of PSR 1259-63," in The Evolution of X-ray Binaries, eds. S. S. Holt & C. S. Day (New York: Amer. Inst. of Physics), 291.

Cominsky, L., Roberts, M. & Finger, M. 1994, "An April 1991 Outburst from 4U0115+63 observed by BATSE," in The Second Compton Symposium, College Park, MD, 1993, eds. C. E. Fichtel, N. Gehrels, & J. P. Norris (New York: Amer. Inst. of Physics), 294.

Cominsky, L., Roberts, M., & Johnston, S. 1994, "Detection of X-ray Emission from the PSR 1259-63/SS2883 Binary System," Astrophysical Journal, 427, 978.

Cominsky, L., Roberts, M., & Johnston, S. 1994, "Detection of X-rays from the Be-Star/Radio Pulsar PSR1259-63," in Interacting Binary Stars, ed. A.W. Shafter, ASP Conference Series, Vol. 56, 424.

Cominsky, L., Roberts, M., Lee, A. & Segel, D. 1994, "HEAO A-1 Archival Observations of Galactic X-ray Binaries," Bulletin of the American Astronomical Society, 26, 872.

Finger, M., Cominsky, L. R., Wilson, R. B., Harmon, B. A. & Fishman, G. J. 1994, "Hard X-ray Observations of A0535 +26," in The Evolution of X-ray Binaries, eds. S. S. Holt & C. S. Day (New York: Amer. Inst. of Physics), 459.

Hertz, P., Ly, Y., Wood, K. S. & Cominsky, L. R. 1994, "ROSAT Measurement of the Evolving Orbital Period in the Low Mass X-ray Binary EXO 0748-676," in The Evolution of X-ray Binaries, eds. S. S. Holt & C. S. Day (New York: Amer. Inst. of Physics), 363.

Hertz, P., Ly, Y., Wood, K. S. & Cominsky, L. R. 1994, "Evidence Against Secular Evolution in the Orbital Period of the Low Mass X-ray Binary EXO 0748-676," in The Soft X-ray Cosmos: ROSAT Science Symposium, College Park, MD, November 1993, eds. E. M. Schlegel & R. Petre (New York: Amer. Inst. of Physics), 80.

Roberts, M., Owen, N., Spear, G. & Cominsky, L. 1994, "The Very Small Array Sky Survey," Bulletin of the American Astronomical Society, 26, 859.

Tenn, Joseph S. 1993, "Henry Norris Russell: The Twentieth Bruce Medalist," Mercury, 22, 5, 19.

Tenn, Joseph S. 1993, "Highlights of California Astronomy from the 1880s to the 1980s," American Association of Physics Teachers Announcer, 23, 96.

Tenn, Joseph S. 1993, "Robert G. Aitken: The Twenty-First Bruce Medalist," Mercury, 22, 6, 20.

Tenn, Joseph S. 1994, "Herbert Hall Turner: The Twenty-Second Bruce Medalist," Mercury, 23, 1, 16.

Tenn, Joseph S. 1994, "Walter S. Adams: The Twenty-Third Bruce Medalist," Mercury, 23, 2, 20.

Tenn, Joseph S. 1994, "Frank Schlesinger: The Twenty-Fourth Bruce Medalist," Mercury, 23, 3, 26.

Tenn, Joseph S. 1994, "Max Wolf: The Twenty-Fifth Bruce Medalist," Mercury, 23, 4, 27.

Tenn, Joseph S., Cominsky, Lynn R. & Spear, Gordon G. 1993, "Yes, There Are Jobs in Astronomy," American Association of Physics Teachers Announcer, 23, 50.

Joseph S. Tenn
1994-11-10