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We present a detailed analysis of surface inhomogeneities on the K1-type sub-giant component of the rapidly rotating eclipsing binary KIC 11560447, using high-precision Kepler light curves spanning nearly four years, corresponding to about 2800 orbital revolutions. We precisely determine the system parameters using high-resolution spectra from the 2.1-m Otto Struve Telescope at the McDonald Observatory. We apply the maximum entropy method to reconstruct the relative longitudinal spot occupancy. Our numerical tests show that the procedure can recover large-scale random distributions of individually unresolved spots, and can track the phase migration of up to three major spot clusters. By determining the drift rates of various spotted regions in orbital longitude, we suggest a way to constrain surface differential rotation and show that the results are consistent with periodograms. The K1IV star exhibits two mildly preferred longitudes of emergence, indications of solar-like differential rotation, and a 0.5 to 1.3-year recurrence period in starspot emergence, accompanied by a secular increase in the axisymmetric component of spot occupancy., Accepted by MNRAS

Using high-precision photometry from the \textit{Kepler} mission, we investigate patterns of spot activity on the K1-type subgiant component of KIC 11560447, a short-period late-type eclipsing binary. We tested the validity of maximum entropy reconstructions of starspots by numerical simulations. Our procedure successfully captures up to three large spot clusters migrating in longitude. We suggest a way to measure a lower limit for stellar differential rotation, using slopes of spot patterns in the reconstructed time-longitude diagram. We find solar-like differential rotation and recurrent spot activity with a long-term trend towards a dominant axisymmetric spot distribution during the period of observations., Comment: 2 pages, 1 figure, IAU Symposium 340: Long-Term Datasets for the Understanding of Solar and Stellar Magnetic Cycles

Photometric and spectroscopic techniques have proven to be effective ways to measure the properties of dark, cool starspots on magnetically active stars. Recently, a technique was introduced using atomic line depth ratios (LDRs) to measure starspot properties. Carefully reproducing this technique using a new set of spectroscopic observations of active stars, we find that the LDR technique encounters difficulties, specifically by overestimating spot temperatures (because the atomic lines blend with titanium oxide absorption in cooler spots) and by not tightly constraining the filling factor of spots. While the use of LDRs for active star studies has great promise, we believe that these concerns need to be addressed before the technique is more widely applied.

We present measurements of starspot parameters (temperature and filling factor) on five highly active stars, using absorption bands of TiO, from observations made between 1998 March and 2001 December. We determined starspot parameters by fitting TiO bands using spectra of inactive G and K stars as proxies for the unspotted photospheres of the active stars and spectra of M stars as proxies for the spots. For three evolved RS CVn systems, we find spot filling factors between 0.28 and 0.42 for DM UMa, 0.22 and 0.40 for IN Vir, and 0.31 and 0.35 for XX Tri; these values are similar to those found by other investigators using photometry and Doppler imaging. Among active dwarfs, we measured a lower spot temperature (3350 K) for EQ Vir than found in a previous study of TiO bands, and for EK Dra a lower spot temperature (~3800 K) than found through photometry. For all active stars but XX Tri, we achieved good phase coverage through a stellar rotational period. We also present our final, extensive grid of spot and nonspot proxy stars.

We present results from a study of starspots on active stars using a pair of vibrational-rotational absorption lines of the OH molecule near 1.563 μm. We detect excess OH absorption due to dark, cool starspots on several active stars of the RS CVn and BY Dra classes. Our results for the single-lined spectroscopic binaries II Pegasi, V1762 Cygni, and λ Andromedae augment those from a previous study that used a less sensitive detector. In this study, we were able for the first time to use molecular absorption features to measure starspot properties on double-lined spectroscopic binaries. Measuring the equivalent widths of these OH lines in inactive giant and dwarf stars of spectral types G, K, and M, we find that the total equivalent width of the line pair increases approximately linearly as effective temperature decreases from 5000 to 3000 K. We measure starspot filling factors by fitting the spectra of active stars with linear combinations of comparison star spectra representing the spot and nonspot regions of the star.

We present the results of an extensive observing campaign on the O7.5 III star Persei. The UV obser- vations were obtained with the International Ultraviolet Explorer. Per was monitored continuously in October 1994 during 10 days at ultraviolet and visual wavelengths. The ground-based optical observations include mag- netic eld measurements, H and He i 6678 spectra, and were partially covered by photometry and polarimetry. We describe a method to automatically remove the variable contamination of telluric lines in the groundbased spectra. The aim of this campaign was to search for the origin of the cyclical wind variability in this star. We determined a very accurate period of 2.086(2) d in the resonance lines of Si iv and in the subordinate Niv and H line proles. The epochs of maximum absorption in the UV resonance lines due to discrete absorption com- ponents (DACs) coincide in phase with the maxima in blue-shifted H absorption. This implies that the periodic variability originates close to the stellar surface. The phase velocity relation shows a maximum at 1400 km s 1 . The general trend of these observations can be well explained by the corotating interaction region (CIR) model. In this model the wind is perturbed by one or more xed patches on the stellar surface, which are most probably due to small magnetic eld structures. Our magnetic eld measurements gave, however, only a null-detection with a1 errorbar of 70 G in the longitudinal component. Some observations are more dicult to t into this picture. The 2-day period is not detected in the photospheric/transition region line He i 6678. The dynamic spectrum of this line shows a pattern indicating the presence of non-radial pulsation, consistent with the previously reported period of 3.5 h. The edge variability around 2300 km s 1 in the saturated wind lines of C iv and N v is nearly identical to the edge variability in the unsaturated Si iv line, supporting the view that this type of variability is also due to the moving DACs. A detailed analysis using Fourier reconstructions reveals that each DAC actually consists of 2 dierent components: a \fast" and a \slow" one which merge at higher velocities.

We present results from a study of starspot areas (fS) and temperatures (TS), primarily on active, single-lined spectroscopic binaries, determined using molecular absorption bands. Expanding upon our previous studies, we have analyzed multiorder echelle spectra of eight systems to simultaneously measure several different molecular bands and chromospheric emission lines. We determined starspot parameters by fitting the molecular bands of interest, using spectra of inactive G and K stars as proxies for the nonspotted photosphere of the active stars, and using spectra of M stars as proxies for the spots. At least two bands with different Teff sensitivities are required. We found that fitting bands other than the TiO 7055 and 8860 A features does not greatly extend the temperature range or sensitivity of our technique. The 8860 A band is particularly important because of its sharply different temperature sensitivity. We did not find any substantial departures from fS or TS that we have measured previously based on single-order spectra. We refined our derived spot parameters using contemporaneous photometry where available. We found that using M giants as spot proxies for subgiant active stars often underestimates fS needed to fit the photometry; this is presumably due to the increase in strength of the TiO bands with decreasing gravity. We also investigated correlations between fS and chromospheric emission, and we developed a simple method to measure nonspot temperature (TQ) solely from our echelle spectra.

We present results of a VLA 3.6 cm B-configuration study of a region around the Herbig Be star LkHα 101. We detect 16 sources down to 5 σ (rms) thresholds of 0.25 mJy. Most of the sources are thought to be young stellar objects associated with the star formation region. Six of the objects have optical counterparts, and at least two are weak-lined T Tauri stars. A large number exhibit high-amplitude variability, indicating that gyrosynchrotron emission from flares just above the photosphere is a primary cause of the emission. We discuss the distance to the star formation region as implied by the radio flux densities and Hipparcos data. We present evidence that the region may be located at a distance typical of the Taurus-Auriga star formation complex, not at the 800 pc suggested by previous studies.

Photometric and spectroscopic variability of late-type stars frequently has been interpreted as evidence of magnetic activity. The standard picture of stellar activity – inherited from solar observations – includes cool, dark “spots” in the photosphere and hot, dense regions in the chromosphere and coronae. The immediate cause of each of these phenomena is a closed topology of the local magnetic field. Because stars appear as mere points of light, these localized phenomena have not been directly resolvable on stars other than the Sun. Most observed effects are produced by an asymmetric distribution of starspots. If the distribution is symmetric, it would escape detection by most current techniques of light-curve and line-profile modeling. Even more troubling, the stellar properties measured with these techniques describe only a difference between contrasting hemispheres, not an absolute measure.

Aims. We aim to reconstruct the first detailed surface maps of the W UMa-type contact binary system, SW Lac. These maps should reveal the distributions of dark, magnetically active spot regions on the component stars and enable us to compare these with the results of similar studies of other active stars.

Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by AURA, Inc. under cooperative agreement with the National Science Foundation. Guest Investigator with the International Ultraviolet Explorer satellite, which is sponsored and operated \jy Uic Na.(,k>jiitl Aeronautics and Space Administration, by the the Science Research Council of the United Kingdom, and by the European Space Agency. Visiting Astronomer, National Solar Observatory, National Optical Astronomy Observatories, which is operated by AURA, Inc. under cooperative agreement, with the National Science Foundation. (NASA-CR-199871) A MULTIWAVELENGTH N96-19048 CAMPAIGN OF ACTIVE STARS WITH INTERMEDIATE ROTATION RATES Final Report (Space Telescope Science Unclas Inst.) 54 p

A multi-epoch 5 GHz survey of candidate or confirmed weak T Tauri stars in the Taurus-Auriga molecular cloud complex was conducted with the Very Large Array. The stars were chosen from those having detectable X-ray or chromospheric emission, and weak-emission-line pre-main-sequence stars found by other means. Snapshots of 99 VLA fields containing 119 candidate stars were obtained with a sensitivity of 0.7 mJy; most fields were observed on two or three dates. Nine radio sources coincident with cataloged stars were found. One may be an RS CVn binary system; the other eight are pre-main-sequence stars. Three of the detected stars - HD 283447, V410 Tau, and FK X-ray 1 - were previously known radio sources. Five new detections are Herbig's Anon 1, Hubble 4, HDE 283572, Elias 12, and HK Tau/c. At least five of the sources are variable, and no linear or circular polarization was found. Several lines of evidence suggest that the radio-detected weak T Tauri stars are quite young, perhaps younger on average than nondetected stars. 54 refs.

Utilisation de calculs ab initio pour l'etude cinetique du detachement d'electron cause par un couplage non-Born-Oppenheimer des etats vibrationnels et electroniques de HCOCH 2 −

When viewed as a square two-indexed matrix, the array of atomic orbital-based, two-electron integrals (ij|kl) is a positive semidefinite array. Beebe and Linderberg showed, in 1977, that actual or near linear dependencies often exist within the types of atomic orbital basis sets employed in conventional quantum chemical calculations. In fact, large (i.e., higher quality) bases were shown to be substantially more redundant than smaller or more spatially separated bases. In situations where there exists significant basis near redundancy, the rank (r) of the (ij|kl) ≡ Vl,J matrix of integrals will be significantly smaller than the matrix dimension M. When this occurs, it proves computationally tractable to decompose the M-dimensional matrix V into components L (V = LLT) which contain all of the information needed to form the full V matrix. The Cholesky algorithm allow such a decomposition to be carried out and forms the basis of the work described here. The method is found to be highly successful in reducing the number of integrals and integral derivatives that must actually be calculated. In particular, results on the C2 molecule indicate that the algorithm can be superior to traditional methods of integral derivative generation if the orbital basis is large enough to contain appreciable near redundancy. In contrast, results on benzene with a more spatially delocalized basis show that conventional methods are preferred whenever substantial basis (near) redundancy is not present.

Utilisation de calculs ab initio pour l'etude cinetique du detachement d'electron cause par un couplage non-Born-Oppenheimer des etats vibrationnels et electroniques de HCOCH 2 −