ABSTRACT Results of an analysis of the BRITE-Constellation and Solar Mass Ejection Imager photometry and radial-velocity observations, archival and new, of two single-lined spectroscopic binary (SB) systems ν Centauri and γ Lupi are reported. In the case of γ Lup AB, a visual binary, an examination of the light-time effect shows that component A is the SB. Both ν Cen and γ Lup exhibit light variations with the orbital period. The variations are caused by the reflection effect, i.e. heating of the secondary’s hemisphere by the early-B main sequence (MS) primary component’s light. The modelling of the light curves augmented with the fundamental parameters of the primary components obtained from the literature photometric data and Hipparcos parallaxes, shows that the secondary components are pre-MS stars, in the process of contracting on to the MS. ν Cen and γ Lup A are thus found to be non-eclipsing counterparts of the B2 IV eclipsing binary (and a β Cephei variable) 16 (EN) Lac, the B5 IV eclipsing binary (and an SPB variable) μ Eri, and the recently discovered Large Magellanic Cloud nascent eclipsing binaries.

ABSTRACT Results of an analysis of the BRITE-Constellation photometry of the SB1 system and ellipsoidal variable π5 Ori (B2 III) are presented. In addition to the orbital light-variation, which can be represented as a five-term Fourier cosine series with the frequencies forb, 2forb, 3forb, 4forb, and 6forb, where forb is the system’s orbital frequency, the star shows five low-amplitude but highly significant sinusoidal variations with frequencies fi (i = 2, .., 5, 7) in the range from 0.16 to 0.92 d−1. With an accuracy better than 1σ, the latter frequencies obey the following relations: f2 − f4 = 2forb, f7 − f3 = 2forb, f5 = f3 − f4 = f7 − f2. We interpret the first two relations as evidence that two high-order ℓ = 1, m = 0 gravity modes are self-excited in the system’s tidally distorted primary component. The star is thus an ellipsoidal SPB variable. The last relations arise from the existence of the first-order differential combination term between the two modes. Fundamental parameters, derived from photometric data in the literature and the Hipparcos parallax, indicate that the primary component is close to the terminal stages of its main-sequence (MS) evolution. Extensive Wilson–Devinney modelling leads to the conclusion that best fits of the theoretical to observed light curves are obtained for the effective temperature and mass consistent with the primary’s position in the HR diagram and suggests that the secondary is in an early MS evolutionary stage.

We present possible explanations of pulsations in early B-type main sequence stars which arise purely from the excitation of gravity modes. There are three stars with this type of oscillations detected from the BRITE light curves: $\kappa$ Cen, a Car, $\kappa$ Vel. We show that by changing metallicity or the opacity profile it is possible in some models to dump pressure modes keeping gravity modes unstable. Other possible scenario involves pulsations of a lower mass companion.

Using BRITE photometric data for several close binary systems we address the problem of damping pulsations in close binary systems due to proximity effects. Because of small number statistics, no firm conclusion is given, but we find pulsations in three relatively close binaries. The pulsations in these binaries have, however, very low amplitudes.

We present results of a search for identification of modes responsible for the six most significant frequency peaks detected in the rapidly rotating slowly pulsating B-type (SPB) star mu Eridani. All published and some unpublished photometric data are used in our new analysis. The mode identification is carried out with the method developed by Daszynska-Daszkiewicz et al. employing the phases and amplitudes from multiband photometric data and relying on the traditional approximation for the treatment of oscillations in rotating stars. Models consistent with the observed mean parameters are considered. For the five frequency peaks, the candidates for the identifications are searched amongst unstable modes. In the case of the third frequency, which is an exact multiple of the orbital frequency, this condition is relaxed. The systematic search is continued up to a harmonic degree l = 6. Determination of the angular numbers, (l, m), is done simultaneously with the rotation rate, V-rot, and the inclination angle, i, constrained by the spectroscopic data on the projected rotational velocity, V(rot)sin i, which is assumed constant. All the peaks may be accounted for with g-modes of high radial orders and the degrees l <= 6. There are differences in some identifications between the models. For the two lowest-amplitude peaks the identifications are not unique. None the less, the equatorial velocity is constrained to a narrow range of (135, 140) km s(-1). Our work presents the first application of the photometric method of mode identification in the framework of the traditional approximation and we believe that it opens a new promising direction in studies of SPB stars.

A multisite photometric campaign for the beta Cephei and eclipsing variable 16 Lacertae is reported. 749 h of high-quality differential photoelectric Stromgren, Johnson and Geneva time series photometry were obtained with 10 telescopes during 185 nights. After removing the pulsation contribution, an attempt was made to solve the resulting eclipse light curve by means of the computer program EBOP. Although a unique solution was not obtained, the range of solutions could be constrained by comparing computed positions of the secondary component in the Hertzsprung-Russell diagram with evolutionary tracks. For three high-amplitude pulsation modes, the uvy and the Geneva UBG amplitude ratios are derived and compared with the theoretical ones for spherical-harmonic degrees l <= 4. The highest degree, l = 4, is shown to be incompatible with the observations. One mode is found to be radial, one is l = 1, while in the remaining case l = 2 or 3. The present multisite observations are combined with the archival photometry in order to investigate the long-term variation of the amplitudes and phases of the three high-amplitude pulsation modes. The radial mode shows a non-sinusoidal variation on a time-scale of 73 yr. The l = 1 mode is a triplet with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and 29.1 yr. The amplitude and phase of the l = 2 or 3 mode vary on time-scales of 380.5 d and 43 yr. The light variation of 2 And, one of the comparison stars, is discussed in the appendix.

MOST time-series photometry of mu Eri, an SB1 eclipsing binary with a rapidly-rotating SPB primary, is reported and analyzed. The analysis yields a number of sinusoidal terms, mainly due to the intrinsic variation of the primary, and the eclipse light-curve. New radial-velocity observations are presented and used to compute parameters of a spectroscopic orbit. Frequency analysis of the radial-velocity residuals from the spectroscopic orbital solution fails to uncover periodic variations with amplitudes greater than 2 km/s. A Rossiter-McLaughlin anomaly is detected from observations covering ingress. From archival photometric indices and the revised Hipparcos parallax we derive the primary's effective temperature, surface gravity, bolometric correction, and the luminosity. An analysis of a high signal-to-noise spectrogram yields the effective temperature and surface gravity in good agreement with the photometric values. From the same spectrogram, we determine the abundance of He, C, N, O, Ne, Mg, Al, Si, P, S, Cl, and Fe. The eclipse light-curve is solved by means of EBOP. For a range of mass of the primary, a value of mean density, very nearly independent of assumed mass, is computed from the parameters of the system. Contrary to a recent report, this value is approximately equal to the mean density obtained from the star's effective temperature and luminosity. Despite limited frequency resolution of the MOST data, we were able to recover the closely-spaced SPB frequency quadruplet discovered from the ground in 2002-2004. The other two SPB terms seen from the ground were also recovered. Moreover, our analysis of the MOST data adds 15 low-amplitude SPB terms with frequencies ranging from 0.109 c/d to 2.786 c/d.

Precision asteroseismology uses the observed effective temperature and luminosity or surface gravity in selecting evolutionary models for analysis. In the case of the primary component of mu Eri, an SPB variable, the surface gravity and luminosity can be derived from the parameters of the SB1 eclipsing system. We examine how the surface gravity and luminosity so derived help to select the evolutionary models suitable for asteroseismic analysis.

We present results of a CCD variability search in the field of the young open cluster NGC 6834. We discover 15 stars to be variable in light. The brightest, a multiperiodic Gamma Doradus-type variable is a foreground star. The eight fainter ones, including a Gamma Cassiopeiae-type variable, two Lambda Eridani-type variables, an ellipsoidal variable, an EB-type eclipsing binary, and three variable stars we could not classify, all have E(B-V) within proper range, thus fulfilling the necessary condition to be members. One of the three unclassified variables may be a non-member on account of its large angular distance from the center of the cluster. Four of the six faintest variable stars, which include two eclipsing binaries and two very red stars showing year-to-year variations, are certain non-members. One of the remaining two faintest variable stars, an EA-type eclipsing binary may be a member, while the faintest one, a W Ursae Majoris-type variable, is probably a non-member. For 6937 stars we provide the V magnitudes and (V-I)_C color indices on the standard system. Because of nonuniform reddening over the cluster's face, a direct comparison of these data with theoretical isochrones is not possible. We therefore obtain E(B-V) from available UBV photometry, determine the lower and upper bound of E(B-V) for NGC 6834, and then fit properly reddened Padova isochrones to the data. Assuming HDE 332843, an early-F supergiant, to be a member we get log (age/yr) = 7.70, V_0 - M_V = 12.10 mag. For 103 brightest stars in our field we obtained the alpha index, a measure of the equivalent widths of the Halpha line. We find Halpha emission in five stars, including the Gamma Cas-type variable and the two Lambda Eri-type variables.

We present results of our 5-years-long program of ground-based spectroscopic and photometric observations of individual Kepler asteroseismic targets and the open clusters NGC6866 and NGC6811 from the Kepler field of view.We determined the effective temperature, surface gravity, metallicity, the projected rotational velocity and the radial velocity of 119 Kepler asteroseismic targets for which we acquired high-resolution spectra. For many of these stars the derived atmospheric parameters agree with Teff, log g, and [Fe/H] from the Kepler Input Catalog (KIC) to within their error bars. Only for stars hotter than 7000K we notice significant differences between the effective temperature derived from spectroscopy and Teff given in the KIC. For 19 stars which we observed photoelectrically, we measured the interstellar reddening and we found it to be negligible. Finally, our discovery of the delta Sct and gamma Dor pulsating stars in the open cluster NGC6866 allowed us to discuss the frequency of the occurrence of gamma Dor stars in the open clusters of different age and metallicity and show that there are no correlations between these parameters.

We summarize our ground-based program of spectroscopic and photometric observations of the asteroseismic targets of the Kepler space telescope. We have already determined atmospheric parameters, projected velocity of rotation, and radial velocity of 62 Kepler asteroseismic targets and 33 other stars in the Kepler field of view. We discovered six single-lined and two double-lined spectroscopic binaries, we determined the interstellar reddening for 29 stars in the Kepler field of view, and discovered three delta Sct, two gamma Dor and 14 other variable stars in the field of NGC 6866.

Kepler is a new NASA space mission that is scheduled for the launch in February 2009. We describe Kepler's scientific goals and the asteroseismic part of its investigation. Then, we present our program of ground-based spectroscopic and photometric observations of Kepler asteroseismic targets and we show results obtained by us in the first two years of its realization.

Reported are spectroscopic observations of 15 candidates for Kepler primary asteroseismic targets and 14 other stars in the Kepler field, carried out at three observatories (see the footnote). For all these stars, the radial velocities, effective temperature, surface gravity, metallicity, and the projected rotational velocity are derived from two separate sets of data by means of two independent methods. In addition, MK type is estimated from one of these sets of data. Three stars, HIP 94335, HIP 94734, and HIP 94743, are found to have variable radial-velocity. For HIP 94335 = FL Lyr, a well-known Algol-type eclipsing variable and a double-lined spectroscopic binary, the orbital elements computed from our data agree closely with those of Popper et al. For HIP 94734 and HIP 94743 = V2077 Cyg, which we discover to be single-lined systems, orbital elements are derived. In addition, from our value of the orbital period and the Hipparcos epoch photometry, HIP 94743 is demonstrated to be a detached eclipsing binary.

We report a multisite photometric campaign for the beta Cephei star 12 Lacertae. 750 h of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with nine telescopes during 190 nights. Our frequency analysis results in the detection of 23 sinusoidal signals in the light curves. Ten of those correspond to independent pulsation modes, and the remainder are combination frequencies. We find some slow aperiodic variability such as that seemingly present in several beta Cephei stars. We perform mode identification from our colour photometry, derive the spherical degree l for the five strongest modes unambiguously and provide constraints on l for the weaker modes. We find a mixture of modes of 0 <= l <= 4. In particular, we prove that the previously suspected rotationally split triplet within the modes of 12 Lac consists of modes of different l; their equal frequency splitting must thus be accidental.One of the periodic signals we detected in the light curves is argued to be a linearly stable mode excited to visible amplitude by non-linear mode coupling via a 2:1 resonance. We also find a low-frequency signal in the light variations whose physical nature is unclear; it could be a parent or daughter mode resonantly coupled. The remaining combination frequencies are consistent with simple light-curve distortions.The range of excited pulsation frequencies of 12 Lac may be sufficiently large that it cannot be reproduced by standard models. We suspect that the star has a larger metal abundance in the pulsational driving zone, a hypothesis also capable of explaining the presence of beta Cephei stars in the Large Magellanic Cloud.

Photoelectric intermediate-band b and y photometry of Uranus and Neptune obtained at each apparition since 1972, combined with broadband B and V photometry from 1950 to 1966, provide a record of planetary variability covering 2/3 of Uranus' 84-year orbital period and 1/3 of Neptune's 165-year orbital period. Almost all of the data were obtained with a dedicated 21-inch photometric telescope at Lowell Observatory. The data are quite homogeneous, with yearly uncertainties typically smaller than 0.01 mag (1%). The lightcurve of Uranus is sinusoidal with peaks at the solstices. The b amplitude slightly exceeds the expected 0.025 mag purely geometrical variation caused by oblateness as the planetary aspect changes, seen from Earth. The y amplitude is several times larger, indicating a strong equator-to-pole albedo gradient. The lightcurve is asymmetrical with respect to southern solstice, evidence of a temporal albedo variation. Neptune's post-1972 lightcurve exhibits a generally rising trend since 1972 interpreted by Sromovsky et al. [Sromovsky, L.A., Fry, P.M., Limaye, S.S., Baines, K.H., 2003. Icarus 163, 256–261] as a lagged sinusoidal seasonal variation. However, the 1950–1966 lightcurve segments are much fainter than expected, missing the proposed seasonal sinusoid by 0.1–0.2 mag. A major unknown component is therefore needed to explain Neptune's long-term variation. The apparent relationship between Neptune's brightness variation and the 11-year solar cycle seen in cycles 21–22 (1972–1996) has apparently now faded away. Further interpretation of the data in this paper will be found in a companion paper by Hammel and Lockwood [Hammel, H.B., Lockwood, G.W., 2005. Icarus. Submitted for publication].

We report on the second multisite photometric campaign devoted to ν Eridani (ν Eri). The campaign, carried out from 2003 September 11 to 2004 February 16, was very nearly a replica of the first campaign, 2002–2003: the five telescopes and photometers we used were the same as those in the first campaign, the comparison stars and observing procedure were identical, and the numbers and time baselines of the data were comparable. For ν Eri, analysis of the new data adds four independent frequencies to the nine derived previously from the 2002–2003 data: three in the range 7.20–7.93 d−1 and a low one, equal to 0.614 d−1. Combining the new and the old data results in two further independent frequencies, equal to 6.7322 and 6.2236 d−1. Altogether, the oscillation spectrum is shown to consist of 12 high and two low frequencies. The latter have u amplitudes about twice as large as the v and y amplitudes, a signature of high radial-order g modes. Thus, we confirm the suggestion, put forward on the basis of the data of the first campaign, that ν Eri is both a β Cephei and a slowly pulsating B (SPB) star. Nine of the 12 high frequencies form three triplets, of which two are new. The triplets represent rotationally split l= 1 modes, although in case of the smallest-amplitude one this may be questioned. Mean separations and asymmetries of the triplets are derived with accuracy sufficient for meaningful comparison with models. The first comparison star, μ Eri, is shown to be an SPB variable with an oscillation spectrum consisting of six frequencies, three of which are equidistant in period. The star is also found to be an eclipsing variable. The eclipse is a transit, probably total, the secondary is fainter than the primary by several magnitudes, and the system is widely detached. The second comparison star, ξ Eri, is confirmed to be a δ Scuti variable. To the frequency of 10.8742 d−1 seen already in the data of the first campaign, another, equal to 17.2524 d−1, is added.

We report a multisite photometric campaign for the Beta Cephei star 12 Lacertae. 750 hours of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with 9 telescopes during 190 nights. Our frequency analysis results in the detection of 23 sinusoidal signals in the light curves. Eleven of those correspond to independent pulsation modes, and the remainder are combination frequencies. We find some slow aperiodic variability such as that seemingly present in several Beta Cephei stars. We perform mode identification from our colour photometry, derive the spherical degree l for the five strongest modes unambiguously and provide constraints on l for the weaker modes. We find a mixture of modes of 0 <= l <= 4. In particular, we prove that the previously suspected rotationally split triplet within the modes of 12 Lac consists of modes of different l; their equal frequency splitting must thus be accidental. One of the periodic signals we detected in the light curves is argued to be a linearly stable mode excited to visible amplitude by nonlinear mode coupling via a 2:1 resonance. We also find a low-frequency signal in the light variations whose physical nature is unclear; it could be a parent or daughter mode resonantly coupled. The remaining combination frequencies are consistent with simple light-curve distortions. The range of excited pulsation frequencies of 12 Lac may be sufficiently large that it cannot be reproduced by standard models. We suspect that the star has a larger metal abundance in the pulsational driving zone, a hypothesis also capable of explaining the presence of Beta Cephei stars in the LMC.