Tennessee State University
Center of Excellence in Information Systems
Nashville, Tennessee 37209

This report covers the interval October 1, 2006 through September 30, 2007.

The astrophysics program in the TSU Center of Excellence concentrates on photometry and spectroscopy of cool giants, chromospherically active stars, solar-type stars, planetary-candidate host stars, binary and multiple stars, and pulsating variables, as well as building and managing robotic telescopes and applying automation to astronomy. Astronomy staff in 2006-07 were Geoffrey S. Burks, Michael R. Busby, Joel A. Eaton, Francis C. Fekel, Gregory W. Henry, and Michael H. Williamson. Student research assistants were Sharina Haynes, Daniel Henry and Julie Henry.

During the spring of 2007, the Center of Excellence offices were moved from their temporary location in Holland Hall to the new Research and Sponsored Programs Building on the west side of TSU's main campus.

OBSERVING FACILITIES

Center of Excellence astronomers operate several automatic telescopes at Fairborn Observatory in the Patagonia mountains of southern Arizona. Fairborn is a non-profit Educational Corporation directed by Lou Boyd and dedicated to the advancement of automated astronomy. Operational TSU telescopes include the T2 0.25 m automatic photoelectric telescope (APT) for Johnson VRI photometry, the T3 0.40 m APT for Johnson BV photometry, the T4 0.75 m APT for Stromgren by photometry, the T8, T10, T11, and T12 0.80 m APTs, also for Stromgren by photometry, and the T13 2.0 m automatic spectroscopic telescope (AST) for high-resolution echelle spectroscopy. The T2 0.25 m APT was decomissioned at the start of the 2007 Summer Shutdown to make room for newer APTs.

During the most recent observing year (2006 September - 2007 July), the T2 0.25 m APT collected 6550 group observations during 247 nights, mostly of the unusual Be variable star gamma Cas and the quintuple eclipsing system HD 71663 (LO Hya). The T2 APT was decommissioned at the end of this observing year in 2007 July. In its 19 years of automated operation, the T2 APT collected 121,590 group observations of variable stars. The T3 0.40 m APT collected 16,808 group observations, primarily of chromospherically active single and binary stars and gamma Doradus candidates, on 250 nights. In its 20 years of operation, it has collected 281,319 group observations. The T4 0.75 m APT acquired 7,510 group observations of solar-type stars on 247 nights. It has collected a total of 92,155 group observations in 15 years of operation. The T8 0.80 m APT made 10,856 group observations of solar-type stars on 247 nights. In 12 years of operation, it has collected a total of 93,151 group observations. The T10 0.80 m APT made a total of 11,214 group observations of solar-type stars on 249 nights. In 7 years of operation, it has collected a total of 69,116 group observations. The T11 0.80 m APT made a total of 11,283 group observations of solar-type stars on 251 nights. In its 7 years of operation, it has collected a total of 67,337 group observations. The T12 0.80 m APT made a total of 13,420 group observations of planetary candidate stars on 249 nights. In its 7 years of operation, it has collected a total of 75,154 group observations. Finally, the T13 2.0 m AST collected 6661 high-dispersion echelle spectra on 273 nights; it has acquired a total of 33,650 spectra in its first 4 full years of operation. Further information about the APTs and the AST can be found on the Web at http://schwab.tsuniv.edu and http://astro.tsuniv.edu, respectively.

Henry and CoI P. Butler (Carnegie Instituion of Washington) marked the second year of their National Science Foundation (NSF) Major Research Instrumention (MRI) grant to construct three new 0.8 m APTs for their planetary search program. L. Boyd at Fairborn Observatory is building the telescopes, from designs very similar to the existing T10, T11, and T12 APTs. All mechanical and electronic parts necessary to build the telescope mounts, two-channel photometers, and control systems are in hand. Final assembly can begin when the three primary and secondary mirror sets are delivered by Star Instruments, now located in Atlanta, Georgia. Meanwhile, the roll-off roof enclosure was completed on site at Carnegie's Las Campanas Observatory (LCO) in Chile, where two of the APTs will be located. M. Roth (LCO Director) has begun the search for a senior-level technician to be shared by LCO and the APT project.

Eaton (with CoI's Henry and J. Hall and G. W. Lockwood of Lowell Observatory) has another NSF Major Research Instrumention (MRI) grant for building a dedicated Ca II H&K spectrograph to observe the solar-type stars Henry is monitoring with the APTs. The Mt. Wilson/Lowell H-K programs will effectively move to the TSU Automatic Spectroscopic Telescope and become its primary program within 2-3 years.

TSU and Vanderbilt astronomers have collaborated to place a new 0.36 m telescope for automated imaging on the roof of Vanderbilt's Dyer Observatory. The telescope (referred to as the Dyer-14 or D14) was funded by a NASA New Technology grant from Marshall Space Flight Center. It consists of a Celestron C-14 f/11 optical tube assembly, an Astro-Physics GTO 1200 telescope mount, an Optec TCF-S focuser, and an SBIG ST-1001E CCD camera with 1024x1024 24-micron pixels. The resulting field of view is 21 x 21 arcminutes at 1.26 arcseconds per pixel. Dyer Observatory superintendent R. Alvey designed and built an enclosure to house the telescope. Williamson at TSU developed the necessary hardware and software (in C under Linux) to automate the enclosure and control the mount, CCD camera, and focuser. Williamson and Henry developed data reduction procedures and software, and the telescope has been conducting automated imaging operations for most of this past year. Typical measurement precision on good nights is in the range 0.005 - 0.010 mag for stars with V = 9 - 12 mag. The primary observing program for this first year of operation has been the brightness measurements of a couple dozen M dwarf stars suspected of having low-mass planetary companions; the primary result has been the successful measurement of several stellar rotation periods.

RESEARCH

Binary and Multiple Stars

Fekel and Tomkin (Univ. of Texas) are obtaining spectra of about 40 known spectroscopic binaries with orbital periods greater than 5 days. Such stars are likely targets of various optical interferometers that are in operation, and some of the top priority systems are now being observed with the CHARA interferometric array. The new radial velocities will be used to determine significantly improved orbital elements so that good three-dimensional orbital solutions can be determined. The second spectroscopic orbit paper from this project, which discusses 3 stars (HR 2962, HD 214686, and 16 Psc), will shortly be submitted for publication. The three systems are double-lined spectroscopic binaries with mid- to late-F spectral types. The systems have periods ranging from 22 to 45 days, and the orbits of all three have significant eccentricities. The minimum masses for the 6 components have accuracies of about 1 per cent.

Another star in this project, HR 8257, is being analyzed by Fekel and Tomkin in collaboration with A. Boden (Cal. Tech.) and W. Torres (CfA). Interferometric observations with the Palomar Testbed Interferometer (PTI) are in hand and spectroscopic observations are finished. A three-dimensional orbit with masses, parallax, and the evolutionary status of the components has been computed. The components are solar abundance, early-F stars on the main sequence. Although both components are slowly rotating, and so might be expected to be Am stars, neither one is.

Fekel and several collaborators are continuing spectroscopic observation of about 20 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.) and USNO observers. Several also have astrometric observations obtained with the PTI. From this multiple star sample Fekel, along with B. Lane (MIT), M. Muterspaugh (Univ. of California) and others, has nearly finished work on two papers that deal with the quadruple systems 88 Tau A and mu Ori. Radial velocities combined with high precision astrometry from the PTI allow the mutual inclinations of the orbits (some with periods as short as 4 days) to be compared. For both star systems the subsystems are not coplanar with the outer orbit. Recent theoretical work predicts that the distribution between the relative inclinations of the inner and outer orbits peaks at 40 and 140 degrees. A comparison of this prediction with the handful of systems currently known to have well determined relative inclinations, produces inconclusive results.

Fekel, in collaboration with K. Hinkle (NOAO), R. Joyce (NOAO) and P. Wood (Australian National Univ.), has continued a program of high-resolution infrared spectroscopy to obtain orbital elements of over 50 southern symbiotic binaries. Out of nearly 200 known symbiotics, there currently are only about 30 systems with well-determined orbital elements. Significantly increasing the number of orbits will provide statistics on a greatly expanded sample of symbiotic binaries. Since the destruction of Mt. Stromlo Observatory in 2003, southern symbiotic stars north of $-$45 degrees have been observed with the Kitt Peak National Observatory coude feed telescope.

Fekel, Hinkle, Joyce, Wood, and I. Howarth (Univ. College London) have finished work on the sixth paper in this series, which discusses the first spectroscopic orbits of M giants in two southern S-type symbiotic systems. Spectropolarimetric observations of the systems produce the orbital inclinations, providing greater constraints on the basic properties of the components than properties estimated from radial velocities alone. Of the two, V455 Sco has the longer orbital period, 1389 days, but has a circular orbit. The second symbiotic binary, SS 73-90, has an orbital period of 898 days and an eccentricity of 0.16. Both symbotics have inclination near 90 degrees and large mass function values, indicating that the systems should be eclipsing.

Chromospherically Active Stars

Fekel has continued his series of papers on chromospherically active stars. With T. Bolton (Univ. of Toronto) the orbital elements and some basic properties of HD 19485 = WZ Ari have been determined. The orbital period is 6.247854 days and the orbit is circular. The G5~V primary and K0~V secondary are chromospherically active. One star or possibly both are synchronously rotating. Based on the Hipparcos parallax and the magnitude differences derived in this work, we find that both components are approximately 1 mag above the zero age main sequence, a result that is inconsistent with the assumption that the components are coeval. We discuss some possible solutions to this anomaly, but none of them satisfactorily resolve the problem.

Extrasolar Planets

Henry is continuing to make photometric brightness measurements of planetary candidate host stars to search for additional planetary transits of bright stars and to confirm new planetary candidates, primarily in collaboration with the planet-search groups led by G. Marcy (Univ. of California) and P. Butler (Carnegie Institution of Washington). Major effort continued on the N2K (Next 2000 Stars) Project. This project uses the Lick, Keck, Magellan, and Subaru telescopes to search for short-period gas giant planets around a new sample of 2000 F - M metal-rich main sequence and subgiant stars brighter than V = 10.5. The goal is to find new short-period planets that transit host stars bright enough to allow detailed follow up observations both from the ground and from space. New orbits were published in the Astrophysical Journal by D. Fischer (San Francisco State Univ.) et al. for Jovian-mass planets orbiting the N2K stars HD 11506, HD 17156, HD 125612, HD 170469, and HD 231701. Periods for the five stars are 1405, 21.2, 510, 1145, and 142 days, respectively. All of the host stars have supersolar metallicity. Photometric observations were conducted for HD 11506, HD 17156, and HD 170469, and all three stars were found to have constant brightness. A transit search was carried out for HD 17156 but had covered just 25% of the search space by the time of publication. M. Barbieri (L'Observatoire Astronomique Marseille-Provence) et al. announced transits found in a search based on our published orbital parameters. The alignment of the eccentric (e=0.67) orbit favored the probability of transits. The planet experiences stellar insolation that varies by a factor of 26 throughout its 21.2 day orbit.

Two additional Jovian-mass planets from the N2K sample were announced in the Astrophysical Journal by S. Robinson (Univ. California Santa Cruz) et al. These two giant planets in orbit around HD 5319 and HD 75898 have minimum masses of 1.94 and 2.51 Mjup, periods of 675 and 418 days, semi-major axes of 1.75 and 1.19 AU, and small eccentricities. Therefore, these two new planets have orbits similar to the terrestrial planets in our solar system.

Transits in the G0 IV star HD 149026 were discovered with our T11 0.8m APT in 2005 May and reported in Sato et al. 2005. The transit depth in HD 149026 is only 0.003 mag, much shallower than any other transits found to date. The mass and radius of the planet, as constrained by the transit data, are 0.36 Mjup and 0.72 Rjup, respectively. Models of the planetary structure require a heavy element core with a mass of 60 - 70 Mearth and thus an unusual formation scenario. A. Wolf (California Institue of Technology) et al. have obtained 35 new radial velocity measurements with the Keck telescope, including 15 velocities taken during transit, and combined them with previous radial velocity and photometric data to derive a new best-fit model for the star-planet system. Their results confirmed the earlier mass and radius determinations of the planet and also allowed for the determination of the angle between the apparent stellar equator and the orbital plane, which they constrained to be 12 degrees with an uncertainty of similar size. This result seems to exclude truly strange formation scenarios, such as planet embryo collisions, that might result in large misalignments of the stellar equatorial and planetary orbital planes.

J. Winn (Massachusetts Institute of Technology) et al. refined the properties of HD 189733b from 8 new transits (4 observed with the T10 APT) and previously published radial velocities and photometric observations. Out-of-transit photometry from the APT also allowed explicit determination of the star's rotation period, Prot = 13.4 days. Knowledge of the stellar rotation period allowed explicit determination of the true (three-dimensional) angle between the stellar spin axis and the orbital axis, a first for any exo-planetary system. An upper bound on this (mis)alignment angle of 27 degrees was determined with 95% confidence. These new results were published in the Astronomical Journal for 2007 April.

Gamma Doradus Stars

Henry and Fekel are continuing their photometric and spectroscopic studies of candidate gamma Doradus stars, primarily with the T3 APT and the KPNO coude feed telescope. Most new identifications of gamma Doradus stars continue to come from this program.

Henry, Fekel, and S. Henry (Clemson Univ.) have completed the data analysis for their volume-limited survey of 114 gamma Doradus candidates chosen from the Hipparcos Catalog. There were 39 variable stars in the sample; 24 were confirmed to be gamma Doradus variables including 15 never before considered as candidates. The detailed results are being prepared for publication.

Solar-Type Stars

Henry continues his program of long-term study of photometric variations in a large sample of over 300 solar-type stars with the T3, T4, T8, T10, and T11 APTs. Photometric time series measurements now span 7 to 15 years. J. Hall and Lockwood continue to make new Ca II H & K measurements at Lowell of a modest subsample of the 300 stars. Full H & K coverage of the APT sample of stars must await completion of the H & K spectrograph funded by NSF for the TSU 2.0 m AST.

Hall, Henry, and Lockwood published a short paper in the AJ on the photometric and spectroscopic variations in the solar twin 18 Sco. Based on its spectroscopic properties, 18 Sco is one of a very small sample of stars that are essentially identical to the Sun. A full decade of HK observations from Lowell Observatory were compared to complementary brightness measurements made with the T8 0.8m APT at Fairborn. The star shows an ~7 yr chromospheric activity cycle and also a total brightness variability of 0.09% in phase with the chromospheric activity. Thus, 18 Sco not only has physical properties similar to the Sun's, it also displays chromospheric and photometric cycles of a similar length and amplitude as the Sun's. This lends some confidence that Sun-like stars may be used as proxies for the likely envelope of solar behavior on decadal to millennial timescales.

Hall Henry, and Lockwood have begun work on a new paper comparing Lowell H&K spectroscopy with Fairborn APT photometry for a much larger sample of 28 Sun-like stars to determine whether they also have activity cycles similar to the Sun's.

Miscellaneous

For over 15 years Fekel has monitored the radial velocities of about 30 slowly rotating B and A stars, which are candidates for early-type velocity standards. 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. The 9 stars with the most constant velocities are HR 153, HR 675, HR 1389, HR 2010, HR 2489, HR 5447, HR 7512, HR 7773, and HR 8404.

PUBLICATIONS

Berdyugina, S. V. and Henry, G. W. 2007, "Butterfly Diagram and Activity Cycles in HR 1099," Astrophysical Journal 659, L157

Biazzo, K., Frasca, A., Henry, G. W., Catalano, S., and Marilli, E. 2007, "Photospheric and Chromospheric Active Regions in Four Young, Solar-Type Stars," Astrophysical Journal 656, 474

Biazzo, K., Frasca, A., Marilli, E., Henry, G. W., Soydugan, F., Erdem, A., and Bakis, H. 2007, "First Simultaneous Photometric and Spectroscopic Analysis of the Active Star IT Com," Information Bulletin on Variable Stars, No. 5740

Butler, J., Myles, E. L., and Gary, T. 2007, "Perception of the Contributions of Astrobiologists from Minority Institutions," Astrobiology Vol. 5, No. 2, 232

Eaton, J. A. and Henry, G. W. 2007, "The Distribution of Activity on the RS CVn-Type Star SZ Piscium," Publications of the Astronomical Society of the Pacific 119, 259

Eaton, J. A. and Shaw, F. G. 2007, "Properties of the Zeta Aur-Type Binary System 22 Vul = QS Vul," Astronomical Journal 133, 2669

Eaton, J. A. and Williamson, M. H. 2007, "The Tennessee State University Automatic Spectroscopic Telescope: Data Processing and Velocity Variation of Cool Giants," Publications of the Astronomical Society of the Pacific 119, 886

Fekel, F. C. and Bolton, C. T. 2007, "Chromospherically Active Stars. XXVI. The Double-Lined Late-Type Binary HD 19485 = WZ Arietis," Astronomical Journal 134, 2079

Fekel, F. C., Hinkle, K. H., Joyce, R. R., Wood, P. R., and Lebzelter, T. 2007, "Infrared Spectroscopy of Symbiotic Stars. V. First Orbits for Three S-Type Systems: Hen 2-173, CL Scorpii, and AS 270," Astronomical Journal 133, 17

Fekel, F. C. and Tomkin, J. 2007, "Spectroscopic Binary Candidates for Interferometers," in Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, Proceedings of IAU Symposium No. 240, eds. W. I. Hartkopf, E. F. Guinan, and P. Harmanec (United Kingdom: Cambridge University Press), p. 59

Fekel, F. C., Williamson, M., and Pourbaix, D. 2007, "The Spectroscopic and Astrometric Orbits of HR 672," Astronomical Journal 133, 2431

Fischer, D. A., Vogt, S. S., Marcy, G. W., Butler, R. P., ..., Henry, G. W., et al. 2007, "Five Intermediate-Period Planets from the N2K Sample," Astrophysical Journal 669, 1336

Hall, J. C., Henry, G. W., and Lockwood, G. W. 2007, "The Sun-Like Activity of the Solar Twin 18 Scorpii," Astronomical Journal 133, 2206

Henry, G. W., Fekel, F. C., and Henry, S. M. 2007, "Photometry and Spectroscopy of Eleven Gamma Doradus Stars," Astronomical Journal 133, 1421

Henry, S. M, Gillman, A. R., and Henry, G. W. 2005, "A Search for Transiting Neptune-Mass Extrasolar Planets in High-Precision Photometry of Solar-Type Stars," Astrobiology Vol. 5, No. 2, 208

Lane, B. F., Muterspaugh, M. W., Fekel, F. C., Williamson, M., Browne, S., Konacki, M., Burke, B. F., Colavita, M. M., Kulkarni, S. R., and Shao, M. 2007, "The Orbits of the Quadruple Star System 88 Tau A From Phases Differential Astrometry and Radial Velocity," Astrophysical Journal 669, 1209

Lockwood, G. W., Skiff, B. A., Henry, G. W., Henry, S. M., Radick, R. R., Baliunas, S. L., Donahue, R. A., and Soon, W. 2007, "Patterns of Photometric and Chromospheric Variation Among Sun-Like Stars: A 20-Year Perspective," Astrophysical Journal Supplement Series 171, 260

Robinson, S. E., Laughlin, G., Vogt, S. S., Fischer, D. A., Butler, R. P., Marcy, G. W., Henry, G. W., Driscoll, P., Takeda, G., and Johnson, J. A. 2007, "Two Jovian-Mass Planets in Earthlike Orbits," Astrophysical Journal 670, 1391

Simpson, E. K., Baliunas, S., and Henry, G. 2006, "Investigating the Rotation Periods of Exoplanet Host Stars, Bulletin of the American Astronomical Society 38, 1106

Winn, J. N., Holman, M. J., Henry, G. W., Roussanova, A., Enya, K., Yoshii, Y., Shporer, A., Mazeh, T., Johnson, J. A., Naarita, N., and Suto, Y. 2007, "The Transit Light Curve Project. V. System Parameters and Stellar Rotation Period of HD 189733," Astronomical Journal 133, 1828

Wolf, A. S., Laughlin, G., Henry, G. W., Fischer, D. A., Marcy, G., Butler, P., and Vogt, S. 2007, "A Determination of the Spin-Orbit Alignment and the Size of the Anomalously Dense Planet Orbiting HD 149026," Astrophysical Journal 667, 549