Bull. A. A. S., Vol. 31, 538, 1999

Tennessee State University
Center of Excellence in Information Systems
Nashville, Tennessee 37203-3401

This report covers the interval October 1, 1997, through September 30, 1998. The astrophysics program in the Center of Excellence at TSU continues to concentrate on understanding magnetic activity in cool stars, managing robotic telescopes, and applying automation to astronomy. Astronomy staff in 1997-98 were Michael R. Busby, Joel A. Eaton, Francis C. Fekel, and Gregory W. Henry. Marino Alvarez (Coll. of Education), Sallie L. Baliunas (CfA), and Douglas S. Hall (Vanderbilt University) continued as adjunct staff. Ezell Allen, Stephen Henry, Sterling Langley, Rahsaan Long, Kenneth McDavis, Fred Northern, Jason Ruffus, Richard Tantaris, Kedrick Vaughns, LaKeisha Warnsley, and Tamara Williams served as student assistants in the astrophysics program. Williams graduated with highest honors in physics, Tantaris received his masters degree in electrical engineering, and Eaton was named Researcher of the Year for TSU.

1 OBSERVING FACILITIES

The Center of Excellence continues to operate four Automatic Photometric Telescopes (APTs) at Fairborn Observatory, including the Fairborn 10-inch, run in collaboration with S. Baliunas, the Vanderbilt/Tennessee State 16-inch in collaboration with D. Hall, and the SAO/TSU 30-inch and TSU/SAO 32-inch telescopes in collaboration with Baliunas. We have now completed the second year of operation at the new observatory site in the Patagonia Mountains near Washington Camp, Arizona. In spite of the influence of the recent El Nino weather pattern, the four telescopes were able to observe on well over 200 nights over the past year.

Construction continues at Fairborn on the three new 32-inch APTs as well as the new 24-inch automatic imaging telescope (AIT), all mentioned in last year's report. All optical elements as well as most mechanical components have now been fabricated and delivered to Fairborn, where assembly is taking place. Integration and testing is anticipated this fall and winter.

Construction also continues on the TSU 2-m automatic spectroscopic telescope. This instrument will have a single-channel fiber-coupled echelle spectrograph with three resolutions (3 x 10⁴, 10⁵, and 2 x 10³); please refer to our last two reports for a further description of it. The Manufacturing Technology Center (Y12 plant) at Oak Ridge National Lab, our principal manufacturer, has delivered all of the major parts of the mount, and we are now assembling the telescope in the State of Tennessee's hangar at the Nashville airport. Mechanical integration should be complete by the end of 1998. The enclosure for the telescope and associated instrumentation has been erected at Fairborn Observatory by Sierrita Mining and Ranching Co. The basic control system is being developed at TSU with Andre Hedrick (Vanderbilt Univ.) serving as primary consultant. See our web site (http://coe.tsuniv.edu/eaton/eng_t13_over.html) for more details. Students working on the 2-m telescope development/instrumentation over the past year were Allen, McDavis, Northern, Vaughns, and Warnsley (weather station), Long and Ruffus (guide camera), Langley (enclosures and telescope integration), Brown and Tantaris (control system).

During the past year (4Q97-3Q98), the Fairborn 10-inch APT collected 8,028 new group observations during 240 nights, mostly of semi-regular variable stars. In its twelve years of operation, the Fairborn-10 has collected a total of 73,052 group observations. This year the Vanderbilt/Tennessee State 16-inch collected 17,111 group observations of chromospherically active single and binary stars on 237 nights. In its eleven years of operation, it has collected 131,174 group observations. The SAO/TSU 30-inch APT acquired 6,679 group observations of lower-main-sequence stars on 238 nights. It has collected a total of 29,470 group observtions in six years of operation. Finally, the TSU/SAO 32-inch APT made 6,447 group observations of solar analogs on 230 nights. In its first three years of operation, it has collected a total of 13,722 group observations.

2 RESEARCH

Henry continues to make high-precision photometric observations of all the Sun-like stars suspected to have planetary companions based on precision radial-velocity surveys. Lack of photometric variability on the proposed planetary orbital periods in most of the stars have confirmed the likelihood that the radial-velocity variations are caused by planetary companions. However, no transits of any of the short-period planets have been detected thus far, in spite of the 50% probability that at least one should have been seen in the sample observed so far.

Henry is collaborating with Baliunas and R. Donahue (CfA) on an analysis of photometry and Ca II H & K spectroscopy of 18 Scorpii. This star most closely matches the Sun in its gross properties determined from its photometric colors and spectroscopic abundances. The analysis shows that 18 Sco also closely matches the Sun in its surface magnetic activity and photometric variability. A paper is being prepared for publication.

Henry made high-precision photometric observations of the single G0 V star HD 166435 with the 32-inch APT in order to seek transits of a suspected new planetary companion of the star in a 3.8-day orbit. The planet was suspected on the basis of radial-velocity variations and was to be announced at the Protostars and Planets IV meeting in Santa Barbara, CA. Rather than detecting a transit of a planetary companion, Henry found that the radial-velocity variations were the result of starspots on the surface of the star rotating with a 3.8-day period and, hence, the planet did not exist. A paper in collaboration with D. Queloz and M. Mayor (Geneva Observatory) is in preparation.

Henry, Fekel, and Hall are collaborating with A. Kaye (Los Alamos National Laboratory) on the analysis of time-series photometry and spectroscopy of the new Gamma Doradus star HR 8330. The star was discovered to be photometrically variable when used as a comparison star on the 30-inch APT. The study concludes that the observed photometric and spectroscopic variations result from non-radial pulsations rather than starspots, but the star is unusual in that only one pulsation period (2.6 days) is observed. A paper has been submitted to Monthly Notices of the Royal Astronomical Society. Additional Gamma Dor candidate stars, also discovered as variable comparison stars, are under observation with the 16-inch APT.

Henry collaborated with the Palomar Testbed Interferometer Group in a study of the double-lined spectroscopic binary iota Pegasi. The known spectroscopic orbit and spectral types of the components suggested the possibility of eclipses, but the new interferometric orbital and component diameter determinations predicted a near miss. Photometric observations confirmed the lack of eclipses, but also revealed iota Peg to be a low-amplitude variable star. The results have been accepted for publication in the Astrophysical Journal.

Henry and Hall have collaborated with K. Strassmeier (University of Vienna) on an analysis of long-term photometric and spectroscopic observations of the G8 giant EK Eri. This single, slowly rotating star is unusual for its high level of magnetic activity and photometric variability. Twenty years of photometry reveal large changes in amplitude and mean magnitude as well as signficant changes in the ~300-day photometric period, which is taken to be the rotation period. EK Eri appears to be overactive by two orders of magnitude for its rotation rate when compared to other G and K giants. Its magnetism, therefore, may arise from a source other than the dynamo mechanism, an idea proposed earlier by K. Stepien (Warsaw University).

Henry, Fekel, and S. Henry continue an analysis of photometric variability in a sample of 200 G and K giant stars, formerly used as comparision stars for solar analogs being observed with the 30-inch and 32-inch APTs. They find low-level variability is ubiquitous among these stars, so, as a class, they are unsuitable as comparison stars for high-precision photometry. Fekel and Eaton have made complementary spectroscopic observations of these stars, and a detailed paper on the results is in preparation.

Tantaris completed his Master's Thesis on the development of an optimal scheduling algorithm for automatic telescopes. The algorithm, which uses dynamic-programming-based decision theory, was analytically proven to produce the optimal schedule when asked to order a set of observations to minimize air mass. However, the execution of the prototype routine requires too much computer time to be practical for scheduling our APTs. Therefore, Tantaris is working on implementing and experimentally verifying a sliding-window approach to calculating the optimal schedule piecemeal, which should drastically reduce the required computation time.

Eaton continued his program of monitoring about 100 G, K, and M stars with luminosity classes I, II, and III at H-alpha to look for variations in the blueshifted cores of these lines, discussed in last year's report, presenting an interim report on the project in Munich last October.

Fekel, in collaboration with C. Scarfe (Univ. of Victoria) and others, is continuing spectroscopic observation of about 25 close multiple systems and a half dozen speckle binaries to obtain fundamental parameters. For most of the systems speckle observations have been obtained by the CHARA group (Georgia State Univ.). Combined spectroscopic and visual orbits usually produce orbital parallaxes more accurate than the trigonometric parallaxes obtained by the Hipparcos satellite, providing an important independent check on the Hipparcos results. The quadruple system HR 3337 = ADS 6828AB, having a visual period of 53 years, continues to be followed closely as it goes through periastron passage during the next couple years.

For over a decade Fekel has monitored the radial velocities of about 30 slowly rotating B and A stars, which are candidates for early-type velocity standards. A paper on the current status of the project was presented at IAU Colloquium 170. A bootstrap procedure has been used to tie the velocities of the early-type stars to the IAU late-type velocity system. Most of the early- and mid-B type stars have variable velocities. However, about two-thirds of the slowly rotating late-B and A-type stars appear to have constant velocities. Unfortunately, omicron Peg = HR 8641, which was used as a primary standard for several years, has been found to be a low-amplitude velocity variable with a period of 10.8 years.

Fekel, in collaboration with K. Strassmeier, M. Weber, and A. Washuttl (Univ. of Vienna), has determined the orbital elements for 10 chromospherically active binaries. One system, HU Vir, is actually a triple system, while a second, IM Peg, is suspected of being triple.

Henry and Fekel, in collaboration with S. Balachandran (Univ. of Maryland), have continued to observe HDE 233517, a rapidly rotating, chromospherically active, single K giant with a dust disk and evidence of mass loss. Photometric observations show low-amplitude light variability with a period of 47.9 days. This post-main-sequence giant is lithium rich. Abundances of both the 6707 Å and 6103 Å lines result in a super-meteoritic abundance of log n(Li) = 4.0, if it is assumed that only ⁷Li is present.

Fekel and L. Watson (Univ. of Canterbury) have searched for additional lithium-rich giants similar to HDE 233517. They observed the lithium and H-alpha lines of a sample of 39 infrared-excess giants but found no lithium-rich giants that were not previously known. The star whose properties are most similar to those of HDE 233517 is HD 219025, a previously known lithium-rich giant.

PUBLICATIONS

Ambruster, C. W., Brown, A., Fekel, F. C., Guinan, E. F., & Fabian, D. 1998, ``Rotation-Activity Relations for Cool Zero Age Main-Sequence (ZAMS) Stars,'' in ASP Conf. Ser. 154, The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue & J. A. Bookbinder (San Francisco: ASP), p. 1205.

Balachandran, S. C., Henry, G. W., & Fekel, F. C. 1998, ``The Li-Rich Giant HD 233517,''in ASP Conf. Ser. 154, The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue & J. A. Bookbinder (San Francisco: ASP), p. 879

Baliunas, S. L., Donahue, R. A., Soon, W., & Henry, G. W. 1998, ``Activity Cycles in Lower Main Sequence and Post Main Sequence Stars: The HK Project,'' in ASP Conf. Ser. 154, The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue & J. A. Bookbinder (San Francisco: ASP), p. 153

Berdyugina, S. V., Jankov, S., Ilyin, I., Tuominen, I., & Fekel, F. C. 1998, ``The Active RS CVn Binary II Peg I. Stellar and Orbital Parameters,'' A&A, 334, 863

Barlow, D. J., Scarfe, C. D., & Fekel, F. C. 1998, ``Physical Properties of the Binary Star 12 Persei,'' AJ, 115, 2555

Eaton, J. A. 1998, ``Variations of Winds of Cool Giants in H-alpha,'' in Cyclical Variability in Stellar Winds, eds. L. Kaper & A. W. Fullerton (Springer), p. 82

Fekel, F. C. 1997, ``Chromospherically Active Stars. XVI. The Double-Lined Binary 42 Capricorni,'' AJ, 114, 2747

Fekel, F. C., Eitter, J. J., De Madeiros, J.-R., & Kirkpatrick, J. D. 1998, ``Chromospherically Active Stars. XVII. The Double-Lined Binary 54 Camelopardalis = AE Lyncis,'' AJ, 115, 1153

Fekel, F. C. & Henry, G. W. 1998, ``Variability in K Giants,'' in ASP Conf. Ser. 154, The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue & J. A. Bookbinder (San Francisco: ASP), p. 755

Henry, G. W. 1998, ``Automatic Telescope Search for Extrasolar Planets,'' in NASA University Research Centers Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and Education, eds. T. L. Coleman et al. (Albuquerque: TSI Press), p. 679

Henry, S. M. & Henry, G. W. 1998, ``Brightness Changes in Sun-Like Stars,'' in NASA University Research Centers Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and Education, eds. T. L. Coleman et al. (Albuquerque: TSI Press), p. 889

Kaye, A., Bagnulo, W. G., Hall, D. S., & Henry, G. W. 1998, ``A New Look at the Gamma Doradus Phenomenon,'' in ASP Conf. Ser. 154, The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue & J. A. Bookbinder (San Francisco: ASP), p. 773

Kaye, A. B., Bagnuolo, W. G., Hall, D. S., & Henry, G. W. 1998, ``Recent Periodic Variations in Three Gamma Doradus Variables,'' in A Half Century of Stellar Pulsation Interpretation: A Tribute to Arthur N. Cox, ASP Conference Series Volume 135, eds. P. A. Bradley & J. A. Guzik (Provo: ASP), p. 497

Strassmeier, K. G., Fekel, F. C., Gray, D. F., Hatzes, A. P., Schmitt, J. H. M. M., & Solanki, S. K. 1998, ``Evolved Stars: What Happens to Activity Off the Main Sequence,'' in ASP Conf. Ser. 154, The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue & J. A. Bookbinder (San Francisco: ASP), p. 257

Tantaris, R. N. 1998, ``Optimal Scheduling of a Multi-User, Multi-Tasking Automatic Robotic Telescope,'' in NASA University Research Centers Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and Education, eds. T. L. Coleman et al. (Albuquerque: TSI Press), p. 137

Williams, T. S. & Eaton, J. A. 1998, ``Random Spots on Chromospherically Active Stars,'' in NASA University Research Centers Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and Education, eds. T. L. Coleman et al. (Albuquerque: TSI Press), p. 690