We have obtained spectroscopy and photometry of the chromospherically active, single-lined spectroscopic binaries HD 89546 and HD 113816. HD 89546 has a circular orbit with a period of 21.3596 days. Its primary has a spectral type of G9 III and is somewhat metal-poor with [Fe/H] ∼ -0.5. HD 113816 has an orbit with a period of 23.6546 and a low eccentricity of 0.022. Its mass function is extremely small, 0.0007 M⊙, consistent with a very low inclination. The primary is a slightly metal-poor K2 III. A decade or more of photometric monitoring with an automatic telescope demonstrates that both systems display brightness variations due to rotational modulation of the visibility of photospheric star spots, as well as light-curve changes resulting from the redistribution of star spots by differential rotation and long-term changes in the filling factor of the spots. We determined rotation periods for each season when the observations were numerous enough. Our mean rotation periods of 21.3 and 24.1 days for HD 89546 and HD 113816, respectively, confirm that the giants in each system are synchronously rotating. The orbital elements and properties of the giant components of these two systems, including levels of surface magnetic activity, are quite similar. However, the two rotational inclinations are rather different, 57° for HD 89546 and 13° for HD 113816. Thus the latter giant is seen nearly pole on. We analyzed the light curves for similarities and differences that result from viewing these two systems from quite different inclinations.

Our time series analysis of sixteen BV light curves of the chromospherically active binary V511 Lyr confirmed the 2. 7 rotation period uniquely. The seasonal periodicity changes of 3.8% indicated the presence of detectable surface differential rotation. The significant 2. 67455 periodicity in the light curve minimum epochs suggested that the strongest starspot formation in V511 Lyr was concentrated on one stable active longitude.

Recently acquired times of minimum for three RS CVn systems and one BY Draconis binary, all with periods under a day, are presented. Times of minimum for UV Psc, YY Gem, CG Cyg, and XY UMa have been measured for decades. These observations have been collected, and the O-C curves for each system have been examined for period changes. The O-C curves for UV Psc and YY Gem showed a linear deviation, and improved periods have been computed. CG Cyg and XY UMa, though, appear to have experienced true changes in their periods. An additional 11.0 yr periodic variation has been found in the O-C data of XY UMa. The mechanism for the period variations remains uncertain.

We have obtained new spectroscopy and photometry of the K0 IV, chromospherically active, single-lined spectroscopic binary HD 10909. Those observations show that the previously reported orbital and light variability periods are incorrect. HD 10909 has an orbital period of 30.1067 days and an eccentricity of 0.499. Its rotation period of 64.1 days is more than twice as long as its orbital period. The primary is situated near the base of the first-ascent red giant branch. Thus, its asynchronous rotation is likely the result of its recent evolution through the Hertzsprung gap, combined with its relatively long orbital period and high eccentricity.

As a case study of the solar-stellar connection, we have analysed a prolonged time series of BV photometry of the chromospherically active binary V815 Her. The surface dif- ferential rotation in the rapidly rotating G5v primary caused changes of 4.6% in the seasonal photometric rotation periods. This would imply a differential rotation coefficient of k=0:184, if the rotation of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, having k =0 :189 and the spectral-type of G2v. Our analysis of the primary and secondary minima of the seasonal light curves indicated that the regions of stronger activity have concentrated on one active longitude, which has maintained a constant rotation period of 1: d 79244 for about 14 years. No regular activity cycle was detected in the mean brightness changes of V815 Her.

We present multilongitude, multicolor photometry and simultaneous high-resolution, high signal-to-noise spectroscopy of the newly discovered γ Doradus variables HD 62454 and HD 68192. From combined Johnson and Strömgren data, we are able to identify five independent periods in HD 62454 and two stable periods in HD 68192. The data presented are sufficient to rule out all physically meaningful types of variations, with the one exception of the high-order, low-degree, nonradial gravity-mode pulsations that are believed to be at work in γ Doradus stars. We also find that HD 62454 is a double-lined spectroscopic binary and we present an orbital solution.

We rediscuss the unusual case of the slowly rotating late-type giant HR 1362, which exhibits a very unusual high level of magnetic activity. New BVRI photometry from two robotic telescopes from 1991 through 1998 together with previously published photometric data gives a very precise photometric period of 306.9+/-0.4 days. With the aid of high-resolution (R=120,000) optical spectra and the Hipparcos parallax we redetermine the absolute parameters of HR 1362 and find it to be a single G8IV-III star of 14 L. and a mass of 1.85 M. with T-eff=5125 K, log g=3.25, and solar abundances. Lithium is not significantly different from solar and we obtain log n(Li)=1.14 from a detailed spectrum synthesis including both isotopes at 6708 Angstrom. V sin i and macroturbulence are determined from fits of disk-integrated models to the observed line profiles as well as their Fourier transforms and are 1.5+/-0.5 kms(-1) and approximate to 5 km s(-1), respectively. The minimum radius from v sin i and P-rot is only then in agreement with the spectral classification and the bolometric luminosity from the Hipparcos parallax if the inclination of the stellar rotation axis is nearly 90 degrees. We concur with the arguments of Stepien (1993) that HR 1362 is an evolved Ap star, and therefore the magnetic field is possibly of galactic origin rather than dynamo generated.

We present BV photometry and simultaneous high-resolution, high signal-to-noise ratio spectroscopy of the newly-discovered gamma Doradus variable HR 8330 taken during the 1997 and 1998 observing seasons. We calculate power spectra for the B- and V-band data sets and for the time series defined throughout the observing season at each point across the FeII lambda 4508.289 and the Ti II lambda 4501.278 line profiles to search for periodic variability. Period analysis reveals a single, 2.6-d period in both the photometric and the spectroscopic data, with a 237 degrees phase lag between them. Based on the location of HR 8330 in the HR diagram and the characteristics of its photometric and spectroscopic variations, we conclude that HR 8330 is a bona fide gamma Doradus-type pulsating variable.

We present a spot modeling analysis of the active late-type giant HK Lac using 30 years of photometry, including 600 new data points from the last six years. We have analyzed folded light curves and, when we had long continuous data sets, applied a new computer code for time-series modeling. The validity of the modeling results was tested as a function of the photometric noise. We have determined the unspotted brightness of HK Lac in the BV (RI)C bandpasses and obtained a spot temperature of ∆T = 1200 ± 100 K. Polar active regions were recovered throughout the modeling because no other scenario was able to describe both the mean light variability of over 0 . 25 accompanied by rotational modulation of similar amplitude. This result has gotten strong theoretical support recently (see Schussler 1996). The active regions preferably cluster around two orbital phases separated by ≈ 110. New spot appearences within active regions and, possibly, their interactions with the old ones could be the cause of rapid changes in the light curves.

We present 1985-1988 UBV and VRI photometry obtained at three different observatories and analyze it along with previously published 1982-1984 UBV photometry. New times of midprimary eclipse along with previously published times yield the improved orbital ephemeris T(pri.min.)=JD 2446674.185(+/-0.007)+27.(d)53707(+/-0.d00026)n. Periodogram analysis of previously published radial velocities, for both the K giant and the F subgiant, yields orbital ephemeris constants consistent with the one above, but of lesser precision. Fitting the seven years of photometry with a cos(2 theta) curve, after removing the eclipse points, yields 0.(m)021+/-0.(m)006 for the full amplitude of the ellipticity effect in V. Residuals from that cos(2 theta) fit give light curves which reveal continuing starspot variability, which had been seen in the 1982-1984 photometry. These residuals, in ten data groups, are analyzed with a two-spot light-curve fitting procedure. Six long-lived spots are identified, the largest producing a light loss of 0.(m)166 in V. Lifetimes were >2.85, 0.81, 1.88, 1.84, >0.58, and >0.45 yr. Rotation periods for these six spots have a mean of 27.(d)36+/-0.(d)06, thus confirming synchronous rotation, and a range which indicates a differential rotation coefficient of k=0.031. With respect to the value of 0.65 below which strong dynamo action is expected in a convective star, the Rossby number for the K giant, believed to be the spotted star, is 0.17, well below the threshold and so large starspots are expected. (C) 1996 American Astronomical Society.

view Abstract Citations (10) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Spectroscopic and Photometric Study of 12 BM Camelopardalis Hall, D. S. ; Fekelf, 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. Abstract Radial velocities from 1916.95 to 1991.95 and photometry from l979.25, both published and new in this paper, are presented and analyzed. A new solution of the radial velocity curve reveals a new period of 80.90 days and an eccentricity of e = 0.05 +/- 0.02, both very different from the 80.17 days and 0.35 found by Abt et al. (1969). An alternative solution with e = 0 is given because we cannot decide firmly whether or not the small eccentricity is real. We find V sin i = 11.3 +/- 0.3 km/s from Maidanak and 10 unequal depth. 0.048 mins and 0.026 mins. The orbital ephemeris for conjunction (K gisnt behind) is JD(hel.) 2,448,111.1 (+/- 0.4 days ) + 80.898 days (+/- 0.004 days ) E, consistent with both the radial velocities and the photometry. With the ellipticity effect removed, the light curve shows residual variability which we fit with a two-spot model. During the 13 years covered by photometry there were nine different starspots, the largest one producing a light loss of 0.19 mins. Rotation periods for the nine spots ranged from 78.6 +/- 0.5 days to 83.7 +/- 0.4 days from which we concluded that the K giant does rotate synchronously but with a differential rotation coefficient of k = 0.06 +/- 0.01. Lifetimes for the nine spots ranged from 1.1 to greater than 4.2 yr and were consistent with the empirical spot lifetime laws of Hall & Henry (1994). Use of the mass function, the orbital period, the V sin i, the two different ellipticity effect amplitudes, and various logical constraints led to ranges of possible masses, radii and inclinations. The most believable solution was around i = 90 deg, R1 = 24 solar radii, M1 = 1.1 solar mass, and M2 = 0.6 solar mass. THe Rossby number for the K giant is 0.48, small enough compared to the critical value of 0.65 to explain why, though rotating 'slowly', it does have large spots. Publication: The Astronomical Journal Pub Date: March 1995 DOI: 10.1086/117360 Bibcode: 1995AJ....109.1277H Keywords: Binary Stars; Light Curve; Radial Velocity; Starspots; Stellar Magnitude; Stellar Orbits; Stellar Rotation; Variability; Data Correlation; Ellipticity; Ephemerides; Orbital Elements; Periodic Variations; Stellar Spectrophotometry; Astronomy; STARS: GIANT; STARS: ROTATION full text sources ADS | data products SIMBAD (1)

High-resolution (Delta lambda < 0.4 Angstrom) echelle-Reticon spectra of 25 chromospherically active binaries in the H alpha region have been obtained at the University of Wisconsin Pine Bluff Observatory. H alpha profiles have been studied to search for excess emission which is not necessarily above the continuum, with 18 out of 25 stars found to have variable emission filling the core. The behavior of the H alpha excess is described, and the profiles of H alpha are presented for each star individually. Radial velocities measured from the metal lines in the H alpha order have been used to check the orbital phases in each corresponding ephemeris.

view Abstract Citations (7) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Starspots Found on the Ellipsoidal Variable V350 Lacertae = HR 8575 Crews, Lionel J. ; Hall, Douglas S. ; Henry, Gregory W. ; Lines, Richard D. ; Lines, Helen C. ; Fried, Robert E. Abstract It has been a puzzle why this chromospherically active, strong-dynamo K2 IV-III star is not known to have the large starspots characteristic of other such stars. Published individual radial velocities, which had never been analyzed, are used to derive an orbital solution. Combined with the one older existing orbital solution, this yields an improved orbital ephemeris: time of conjunction (K star behind) = JD 2445255.47 +/- 0.11 days and period = 17.75346 +/- 0.00016 days. All available photoelectric photometry, from 1970.9 to 1992.5, is collected A cos 2 theta fit of the ellipticity effect yields JD 2445255.60 +/- 0.06 days for a time of conjunction, 17.7523 +/- 0.0005 days for the period, and 0.084 mins for the peak-to-peak amplitude in V. With the ellipticity effect removed, the light curve does show measurable starspot variability in 15 of 16 data groups, the starspot wave amplitudes ranging between 0.03 mins and 0.08 mins. Ten starspots are identified and their rotation periods determined, the mean being 17.70 +/- 0.03 days (confirming synchronous rotation) and the range being Delta P/P = 0.017 +/- 0.006 (indicating differential rotation). There is a slow variation in mean brightness, almost 0.1 min in range and at least 2 decades in length. Publication: The Astronomical Journal Pub Date: March 1995 DOI: 10.1086/117366 Bibcode: 1995AJ....109.1346C Keywords: Binary Stars; Light Curve; Orbital Elements; Radial Velocity; Starspots; Stellar Orbits; Stellar Rotation; Variable Stars; Amplitudes; Angular Velocity; Brightness; Data Correlation; Ellipticity; Stellar Spectrophotometry; Astronomy; STARS: CHROMOSPHERES; STARS: INDIVIDUAL: HR 8575; STARS: VARIABLES: OTHER full text sources ADS | data products SIMBAD (1)

We studied seven different RS CVn-type binary star systems (zeta And, BL CVn, UV CrB, V826 Her, GX Lib, TZ Tri, and EE UMa) to look for suspected starspot activity. Each had been previously found variable due to the ellipticity effect. Although never established quantitatively, several had shown inklings of variability due to starspots. We determined, through analysis of all radial velocities available in the literature, a definitive orbital ephemeris for each. We analyzed all published photometry, as well as new photometry presented here. We removed the ellipticity effect by Fourier analysis and examined the remaining residuals for any variability characteristic of starspots, finding it in all seven, up to 0.09 mag in the extreme case. In the process, the photometry confirmed the best values for the orbital ephemerides and evaluated the depths of the two minima caused by ellipticity, slightly unequal due to the "pointed end" effect.