COE Observatory Report 1994-1995

Bull. A. A. S., Vol. 28, 633, 1996

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

This report covers the interval October 1, 1994, through September 30, 1995. 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 1994-95 were Michael R. Busby, Joel A. Eaton, Francis C. Fekel (visiting scientist), and Gregory W. Henry. Sallie L. Baliunas (CfA) and Douglas S. Hall (Vanderbilt University) continued as adjunct staff. Cori Cantey, Paul Finley, and Brigette Tigner served as student assistants in the astrophysics program.

The Center of Excellence was chosen to be the home of a NASA University Research Center, the Center for Automated Space Science, through a NASA competition in Spring, 1995. This center is concentrating in advanced control systems and in automated astronomical observing. Research in control systems seeks to develop ways of controlling complicated structures, specifically those in space, by identifying their modes of vibration and using existing control mechanisms to counteract those vibrations. The emphasis in automated astronomy is to develop a system of coordinated telescopes, all run automatically by computers, that will carry out general observing programs flexibly under control of AI-based scheduling programs. These facilities will provide capabilities for aperture photometry, CCD imaging, and high-dispersion spectroscopy.


Our new Center for Automated Space Science within the Center of Excellence in Information Systems manages four automatic photometric telescopes (APTs). These include the Fairborn 10-inch in collaboration with S. Baliunas, the Vanderbilt/Tennessee State 16-inch in collaboration with D. Hall, the SAO/TSU 30-inch in collaboration with Baliunas, and a new TSU 32-inch. All four telescopes are housed at Mt. Hopkins in Arizona and maintained by Lou Boyd and Don Epand of Fairborn Observatory.

During the last half of 1994, Boyd upgraded the Fairborn 10-inch APT with a new micro-stepping, belt drive system for both axes and a new computer control system based on the Automatic Telescope Instruction Set (ATIS). Testing and debugging continued through the first quarter of 1995, and routine operations resumed thereafter. Because of downtime due to the upgrade, the Fairborn 10-inch collected only 2169 group observations, mostly of semi-regular variables, on 92 nights during its ninth year of operation (4Q94-3Q95). Now, however, with the more flexible scheduling capability offered by ATIS, complete sets of standard star and quality-control observations are being made each night. Therefore, the operation of the system can be monitored much more closely, as with our other APTs, to ensure optimal performance at all times. The Vanderbilt/Tennessee State 16-inch collected 12,917 group observations of chromospherically active stars on 220 nights during the past year, its eighth season of operation on Mt. Hopkins. The SAO/TSU 30-inch APT collected 5683 quartet groups containing lower-main-sequence stars on 228 nights during its second full year of operation.

The TSU 32-inch APT is currently undergoing final testing at the APT site. This telescope makes use of a new two-channel precision photometer designed by Boyd and a new ATIS93 control system written in C for Unix-based 486 computers by Epand. The ATIS93 control language incorporates new features that allow an external scheduler, located on a remote computer, to schedule and monitor the operation of the telescope in real time. Henry will use this telescope to make simultaneous Stromgren b and y measurements of luminosity changes in solar duplicate stars, which have ages and masses comparable to the Sun's. Early results have shown that the predicted sub-millimagnitude level of precision for a single nightly observation is achievable. It is expected that routine high-precision scientific observations will begin before the end of 1995.

Work on a new 20-inch Automated Imaging Telescope (AIT) has started through a joint TSU/CfA/Fairborn collaboration. This telescope will be located in a separate dome just outside the current roll-off-roof building at the APT site. TSU and CfA astronomers will share observing time on the new telescope, and Henry will manage the daily scheduling and quality-control operations.


Henry has continued his collaboration with the Computational Sciences Division at NASA Ames Research Center to develop an automated scheduling and management system for robotic telescopes. This system, called the Associate Principal Astronomer (APA) package, will combine AI-based scheduling of observations designed to maximize the precision and scientific usefulness of robotic telescope observations with automated quality control, data reduction, and telescope management features that will greatly simplify the operation of these telescopes. The APA will run on a single workstation or high-end personal computer and will be capable of simultaneously managing the operation of several multi-user robotic telescopes in real time over the Internet. Preliminary simulations have shown that AI scheduling can significantly improve the performance of existing APTs. Henry has submitted two papers on this subject to the proceedings of the Workshop on New Observing Modes for the Next Century, held in Hilo, Hawaii in July 1995. As soon as final testing of the 32-inch APT is completed, testing of the scheduling capabilities of the APA will begin on that telescope.

Henry, Eaton, and Fekel continued collaborating with Hall on interpretations of highly spotted chromospherically active stars, observed photometrically mostly with the VU/TSU telescope. During the past year, they published papers about the following stars: lambda And, zeta And, BM Cam, BL CVn, UV CrB, sigma Gem, V826 Her, V835 Her, V350 Lac, GX Lib, II Peg, V711 Tau, TZ Tri, EE UMa, and HD 181943.

Henry, Fekel, and Hall have completed an extensive photometric and spectroscopic survey of 66 chromospherically active stars with the 16-inch APT and the coude feed telescope on Kitt Peak. Variability was detected and its period determined for 47 of the stars, 41 of which are new variables. Because of advancements in the precision of robotic telescopes, many low-amplitude variables were found in this survey; almost two-thirds of the new variables had amplitudes less than or equal to 0.05 mag. The vsini, spectral type, and velocity variability of each star were determined, as well as new orbital periods for many of the binary systems. The rotational and orbital periods were compared to determine whether or not the spotted component of each binary system is rotating synchronously. The full results of this survey are being published in the December 1995 Astronomical Journal.

Henry has completed an analysis of the precision of 30-inch APT observations. After reprogramming the APT to make more extensive measurements of the sky background, he found the external precision of a single observation to be 0.0010 to 0.0012 mag for the more constant pairs of stars. Seasonal mean magnitudes could be determined to 0.0002 or better for these stars, thus making it possible to observe very small luminosity variations in solar-type stars. Henry is collaborating with Baliunas and R. Donahue of CfA on an analysis of rotation periods found in the first two years of observations with the 30-inch APT. Periods for over 40 stars have been found, including several for presumed constant comparison stars. A detailed paper is being prepared for the Publications of the Astronomical Society of the Pacific.

Henry spent several weeks at Lowell Observatory collaborating with Wes Lockwood in order to combine their photometric data for those Olin Wilson HK stars that they are jointly observing. This will make it possible to verify the subtle luminosity variations found in the Lowell data and extend the coverage of the APT observations back nearly a decade. Careful cross-calibrations of the pairs of stars common to both observing programs will continue over the next year.

As this report was being prepared, word came of the discovery of very small radial velocity variations in the old G2 star 51 Pegasi by M. G. Mayor of Geneva Observatory. Variations with a semi-amplitude of 70 m/sec and a period of 4.2 days have since been confirmed by other groups. This implies the existence of a Jupiter-sized or smaller planet in orbit 10 solar radii from the star. This star is one of the solar-type stars being observed with the 30-inch APT. Henry has analyzed the first two years of photometric data and finds no variation on the planetary orbital period greater than 0.0002 mag. This appears to eliminate pulsations as the cause of the radial velocity variations and helps to confirm the presence of the planet around 51 Pegasi. The mean magnitude of 51 Peg was also constant from one year to the next to 0.0001 mag or so.

Eaton, Henry, and Fekel have investigated the effect of having large numbers (10-40) of moderately large starspots (7-15 deg radius) randomly spread over a differentially rotating star. They find that this hypothesis produces light variation very similar to the light curves of RS CVn binaries, provided there are 10-40 spots on average and provided these spots have a finite lifetime. The effect of differential rotation is to arrange the many spots into temporary groupings that look like two or three very large spots. These patterns are maintained for times inversely proportional to the amount of differential rotation. Finite spot lifetimes lead to apparent photometric cycles by assuring that at any one time there will be fewer or more spots on the star than the long-term average. Evolution of these spot patterns, as determined in traditional two-spot analyses, can give a surprisingly accurate determination of the surface differential rotation but not of spot lifetimes. Furthermore, in one case investigated, the random spots showed their groupings at two preferred longitudes, as sometimes seen in two-spot analyses.

Eaton and Henry have used photometry from the 16-inch APT, high-dispersion spectra from NSO, and ultraviolet spectra from IUE to estimate the number of spots and active regions on the cool component of the chromospherically active binary SZ Psc. They find that significant dimming by spots is seen at all phases in this star, that the spots producing this dimming are probably moderately small (so as not to distort optical spectral lines more than observed), that the flux from active regions (C IV lambda 1550) is roughly constant with phase, and that flux of chromospheric Mg II emission is proportional to unspotted area visible, not to the projected area of spots. The cool, more massive K star seems even closer to its Roche lobe than previously thought, which makes the system important for binary evolution.

Eaton has continued his analyses of zeta Aurigae binaries as probes of stellar chromospheres and winds. During the period of this report, he published analyses of IUE observations of 31 Cyg at 31 times during the atmospheric eclipse of 1992/93 and of the archival IUE spectra of delta Sge. He observed AL Vel (K0 II+B9.5 V) with IUE during the eclipse of April 1995, finding a pronounced atmospheric eclipse with strong absorption once again.

Eaton has collected IUE spectra of 31 Cyg (K4 Ib + B3-4) and delta Sge (M1 II + B9.5 V) to search for signatures of magnetically channeled accretion. These observations cover a period of time designed to sample most rotational phases of the accreting B components.

Eaton has continued monitoring the H-alpha in eight cool supergiants with the McMath-Pierce solar telescope at NSO as a practical way of detecting phase dependence of chromospheres in zeta Aur binaries. The stars he is observing are zeta Aur (K4-5 Ib+B6), 31 Cyg (K4 Ib+B3-4), 32 Cyg (K4-5 Ib+B6-7), 22 Vul (G4 I+B7), 47 Cyg (K2 I+B3 V), 63 Cyg (K4 Ib-IIa), epsilon Peg (K2 Ib), and xi Cyg (K4-5 Ib-II). After 2.2 years of monitoring, there is no obvious phase dependence in the binaries, but all of these stars have shown changes in the strength of the blue wing of H-alpha, presumably resulting from episodes of enhanced mass loss in winds or from cyclic changes in strength or velocity structure of winds. Furthermore, this chromospheric feature changes with a timescale of years in some stars. Of the eight sample stars, the closest binary, 22 Vul, which is also the most rapid rotator, shows the greatest amount of chromospheric variation.

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.) Final analysis of several systems is underway. A new and improved analysis of the spectroscopic and visual orbits of the solar-type triple system HD 202908 = ADS 14839 is nearly finished. Twenty years of high-dispersion spectroscopic observations by four different groups are included in the analysis as well as recent speckle observations near periastron. Fekel and W. Hartkopf, B. Mason, and H. McAlister of the CHARA group are working on a combined visual and spectroscopic orbital solution of the F dwarf binary system 31 Ari. Fekel, Scarfe, and Barlow (Univ. of Victoria) now have a complete 13-year cycle of high-dispersion spectroscopic observations for HR 2130 and are updating the short- and long-period orbits of this late-B type triple system.

Fekel and S. Balachandran (National Air and Space Museum) are continuing their analysis of lithium in chromospherically active stars. They have also obtained spectra with the IUE satellite of chromospherically active metal-poor binaries. Preliminary UV results support ground-based findings that binaries with periods of 10 days or less have active chromospheres. The sample of metal-poor binaries are also being observed photometrically on the 16-inch APT. Initial results for some appear in the recently completed paper by Henry, Fekel, and Hall, mentioned earlier.

Fekel has continued work on the orbits of chromospherically active stars with several other collaborators including V. Dadonas (Vilnius Univ.) and R. F. Griffin (Cambridge Observatories). With B. Zuckerman, (UCLA). Fekel is examining the properties and evolutionary status of the IR excess source HDE 233517, which is chromospherically active and has an extremely strong lithium line, but may be a post-main-sequence giant rather than a pre-main-sequence star.


Choi, H.-J., Soon, W.H., Donahue, R.A., Baliunas, S.L., & Henry, G.W. 1995, ``A Study of Variability in a Sample of G and K Giants," PASP, 107, 744

Crews, L.J., Hall, D.S., Henry, G.W., Lines, R.D., Lines, H.C., & Fried, R.E. 1995, ``Starspots Found on the Ellipsoidal Variable V350 Lacertae=HR 8575," AJ, 109, 1346

Cristian, V.C., Donahue, R.A., Soon, W.H., Baliunas, S.L., & Henry, G.W. 1995, ``Pulsational Time Scales and Amplitudes in a Sample of Bright Semi-Regular Variable Stars," PASP, 107, 411

Donati, J.-F., Henry, G.W., & Hall, D.S. 1995, ``Activity, rotation and evolution of the RS CVn system lambda And," A&A, 293, 107

Drummond, M., Bresina, J., Edgington, W., Swanson, K., Henry, G., & Drascher, E. 1995, ``Flexible Scheduling of Automatic Telescopes over the Internet," in Robotic Telescopes: Current Capabilities, Present Developments, and Future Prospects for Automated Astronomy, eds. G.W. Henry and J.A. Eaton (Provo: ASP), p. 101

Drummond, M., Bresina, J., Swanson, K., Edgington, W., & Henry, G. 1994, ``The Associate Principal Astronomer Telescope Operations Model," in Proc. 3rd International Symp. on Artificial Intelligence, Robotics, and Automation for Space, JPL Publ. 94-23, p. 351

Eaton, J. A. 1995, ``H-Alpha Measurements for Cool Giants," AJ, 109, 1797

Eaton, J. A. 1995, ``The Rationale for an Automatic Spectroscopic Telescope," in Robotic Telescopes: Current Capabilities, Present Developments, and Future Prospects for Automated Astronomy, eds. G.W. Henry and J.A. Eaton (Provo: ASP), p. 226

Eaton, J.A., & Bell, C. 1994 ``The 1992/93 Eclipse of 31 Cygni," AJ, 108, 2276

Eaton, J.A., Hartkopf, W.I., McAlister, H.A., & Mason, B.D. 1995, ``Winds and Accretion in delta Sagittae," AJ, 109, 1856

Eaton, J.A., & Henry, G.W. 1994, ``New Times of Minimum for V444 Cygni," IBVS, No. 4061

Fekel, F.C., Dadonas, V., Sperauskas, J., Vaccaro, T.R., & Patterson, R. 1994, ``Chromospherically Active Stars. XIII. HD 30957: A Double Lined K Dwarf Binary," AJ, 108, 1936

Fekel, F.C., Henry, G.W., & Hall, D.S. 1995, ``Chromospherically Active Stars. XIV. A Rediscussion of the Properties and Evolutionary State of HD 181943," AJ, 109, 2821

Hall, D.S., Fekel, F.C., Henry, G.W., Eaton, J.A., Barksdale, W.S., Dadonas, V., Eker, Z., Kalv, P., Chambliss, C.R., Fried, R.E., Fortier, G.L., Landis, H.J., Louth, H.P., Powell, H.D., McFaul, T.G., Miles, R., Nielsen, P., Renner, T.R., Robb, S.P., Slauson, D.M., Stelzer, H.J., Wasson, R., & Wood, J.E. 1995, ``A Spectroscopic and Photometric Study of 12 BM Cam," AJ, 109, 1277

Hall, D.S., & Henry, G.W. 1994, ``1988-1991 Photometry of the Chromospherically Active Double-Lined Binary System HD 163621 = V835 Herculis," JApA, 15, 321

Hall, D.S., & Henry, G.W. 1994, ``The Law of Starspot Lifetimes," in Robotic Observatories, ed. M.F. Bode (Great Britain: Wiley), p. 49

Hall, D.S., & Henry, G.W. 1994, ``Suspected Variability of 5 Lacertae Confirmed," I.A.P.P.P. Comm., 58, 1

Henry, G. W. 1994, ``Remote Observing with Robotic Telescopes on Mt. Hopkins," Bull. AAS, 26, 1423

Henry, G. W. 1995, ``The Fairborn/TSU Robotic Telescope Model," in Robotic Telescopes: Current Capabilities, Present Developments, and Future Prospects for Automated Astronomy, eds. G.W. Henry and J.A. Eaton (Provo: ASP), p. 37

Henry, G. W. 1995, ``The Development of Precision Robotic Photometry," in Robotic Telescopes: Current Capabilities, Present Developments, and Future Prospects for Automated Astronomy, eds. G.W. Henry and J.A. Eaton (Provo: ASP), p. 44

Henry, G. W., Eaton, J. A., Hamer, J. W., & Hall, D.S. 1995, ``Starspot Evolution, Differential Rotation, and Magnetic Cycles in the Chromospherically Active Binaries lambda Andromedae, sigma Geminorum, II Pegasi, and V711 Tauri," ApJS, 97, 513

Henry, G. W., & Hall, D. S. 1994, ``The Quest for Precision Robotic Photometry," in Robotic Observatories, ed. M.F. Bode (Great Britain: Wiley), p. 41

Kaye, A.B., Hall, D.S., Henry, G.W., Eaton, J.A., Lines, R.D., Lines, H.C., Barksdale, W.S., Beck, S.J., Chambliss, C.R., Fried, R.E., Genet, R.M., Hopkins, J.L., Lovell, L.P., Louth, H.P., Montle, R.E., Renner, T.R., & Stelzer, H.J. 1995, ``Suspected Starspots found on the K Giants in Seven Ellipsoidal RS CVn-Type Binaries," AJ, 109, 2177

McAlister, H.A., Hartkopf, W.I., Mason, B.D., Fekel, F.C., Ianna, P.A., Tokovinin, A.A., Griffin, R.F., & Culver, R.B. 1995, ``Binary Star Orbits from Speckle Interferometry. VI. The nearby Solar-Type Speckle-Spectroscopic Binary HR 6697," AJ, 110, 366