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We present and discuss the pulsational characteristics of the Delta Scuti star 38 Eri from photometric data obtained at two widely spaced epochs, partly from the ground (1998) and partly from space (MOST, 2011). We found 18 frequencies resolving the discrepancy among the previously published frequencies. Some of the frequencies appeared with different relative amplitudes at two epochs, however, we carried out investigation for amplitude variability for only the MOST data. Amplitude variability was found for one of three frequencies that satisfy the necessary frequency criteria for linear-combination or resonant-mode coupling. Checking the criteria of beating and resonant-mode coupling we excluded them as possible reason for amplitude variability. The two recently developed methods of rotational-splitting and sequence-search were applied to find regular spacings based only on frequencies. Doublets or incomplete multiplets with l=1, 2 and 3 were found in the rotational splitting search. In the sequence search method we identified four sequences. The averaged spacing, probably a combination of the large separation and the rotational frequency, is 1.724+/-0.092 d-1. Using the spacing and the scaling relation $\bar\rho = [0.0394, 0.0554]$ gcm$^{-3}$ was derived. The shift of the sequences proved to be the integer multiple of the rotational splitting spacing. Using the precise MOST frequencies and multi-colour photometry in a hybrid way, we identified four modes with l=1, two modes with l=2, two modes with l=3, and two modes as l=0 radial modes., Comment: 20 pages, 10 figures, accepted for publication in MNRAS

We present the results of a photometric variability survey in the young open cluster Stock 14 and the surrounding fields. In total, we detected 103 variable stars of which 88 are new discoveries. We confirm short-period, low-amplitude light variations in two eclipsing members of the cluster, HD 101838 and HD 101794. In addition, we find two new beta Cephei stars of which one, HD 101993, is also a member. The sample of pulsating cluster members is supplemented by one multimode slowly pulsating B-type star and several single-mode candidates of this type. The other pulsating stars in our sample are mostly field stars. In particular, we found fourteen delta Scuti stars including one gamma Dor/delta Sct hybrid pulsator. From our UBV photometry we derived new parameters of Stock 14: the mean reddening E(B-V) = 0.21 +/- 0.02 mag, the true distance modulus, 11.90 +/- 0.05 mag, and the age, 20 +/- 10 Myr. Finally, we use the new photometry to analyze changes of the 6.322-d orbital period of the bright eclipsing binary and the member of the cluster, V346 Cen. In addition to the known apsidal motion, we find that another effect, possibly light-time effect in a hierarchical system of a very long orbital period, affects these changes. The updated value of the period of apsidal motion for this system amounts to 306 +/- 4 yr. The open cluster Stock 14 was found to be a fairly good candidate for successful ensemble asteroseismology., Comment: 30 pages, 14 figures. Accepted for publication in Acta Astronomica

We report a multisite photometric campaign for the Beta Cep stars V2052 Oph and V986 Oph. 670 hours of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with eight telescopes on five continents during 182 nights. Frequency analyses of the V2052 Oph data enabled the detection of three pulsation frequencies, the first harmonic of the strongest signal, and the rotation frequency with its first harmonic. Pulsational mode identification from analysing the colour amplitude ratios confirms the dominant mode as being radial, whereas the other two oscillations are most likely l=4. Combining seismic constraints on the inclination of the rotation axis with published magnetic field analyses we conclude that the radial mode must be the fundamental. The rotational light modulation is in phase with published spectroscopic variability, and consistent with an oblique rotator for which both magnetic poles pass through the line of sight. The inclination of the rotation axis is 54o

Aims: We carried out high-resolution spectroscopy and BV(I)_C photometric monitoring of the two fastest late-type rotators in the nearby Beta Pictoris moving group, HD199143 (F7V) and CD-641208 (K7V). The motivation for this work is to investigate the rotation periods and photospheric spot patterns of these very young stars, with a longer term view to probing the evolution of rotation and magnetic activity during the early phases of main-sequence evolution. We also aim to derive information on key physical parameters, such as rotational velocity and rotation period. Methods: We applied maximum entropy (ME) and Tikhonov regularizing (TR) criteria to derive the surface spot map distributions of the optical modulation observed in HD199143 (F7 V) and CD-641208 (K7V). We also used cross-correlation techniques to determine stellar parameters such as radial velocities and rotational velocities. Lomb-Scargle periodograms were used to obtain the rotational periods from differential magnitude time series. Results: We find periods and inclinations of 0.356 days and 21.5deg for HD199143, and 0.355 days and 50.1deg for CD-641208. The spot maps of HD199143 obtained from the ME and TR methods are very similar, although the latter gives a smoother distribution of the filling factor. Maps obtained at two different epochs three weeks apart show a remarkable increase in spot coverage amounting to ~7% of the surface of the photosphere over a time period of only ~20 days. The spot maps of CD-641208 from the two methods show good longitudinal agreement, whereas the latitude range of the spots is extended to cover the whole visible hemisphere in the TR map. The distributions obtained from the first light curve of HD199143 show the presence of an extended and asymmetric active longitude with the maximum filling factor at longitude ~325degree., Comment: Accepted by A&A. 13 pages, 13 figures (4 online included), 5 Tables

We present results of a photometric study of the young southern open cluster Stock 14. This cluster is known to contain two eclipsing systems with presumed beta Cephei components, HD 101794 and HD 101838. We confirm variability due to pulsations and eclipses in both targets and announce the discovery of other variable stars in the observed field., Comment: 3 pages, 4 figures, Astronomische Nachrichten, HELAS IV Conference, Arecife, Lanzarote, Feb 2010, submitted

CONTEXT. The Lambda Bootis stars are a small spectroscopic subgroup of Population I A-type stars and show significant underabundances of metals. Many are Delta Scuti pulsators. AIMS. HD 210111 was selected for a detailed multisite pulsation study to determine whether its pulsation properties differ from those of normal A stars. METHODS. 262 hours of high-precision photometry were obtained at the SAAO and SSO observatories. RESULTS. 13 statistically significant pulsation frequencies were detected with very small photometric amplitudes from 1 to 7 millimag in the visual. A comparison with earlier 1994 measurements indicates a small increase in amplitude. As a byproduct, one of the comparison stars, HD 210571, was discovered to be a millimag variable with a frequency of 1.235 c/d and is probably a new Gamma Doradus variable. The observed wide range of excited frequencies from 12 to 30 c/d in HD 210111 can be explained with both the single- and double-star hypothesis. HD 210111 is in a similar evolutionary status to FG Vir, which also shows a wide range of excited frequencies with a similar frequency spacing near 4 c/d. This is interpreted as successive radial orders of the excited nonradial modes. In the double-star hypothesis previously evoked for HD 210111, the low and the high frequencies originate in different stars: here HD 210111 would resemble Theta^2 Tau. CONCLUSIONS. The pulsation of the Lambda Bootis star HD 210111 does not differ from that of normal Delta Scuti stars., Comment: 6 pages, 2 figures, 2 tables, submitted to A&A

We have carried out single and multi-site photometry of the three Beta Cephei stars Beta and 15 CMa as well as KZ Mus. For the two stars in CMa, we obtained 270 h of measurement in the Stromgren uvy and Johnson V filters, while 150 h of time-resolved Stromgren uvy photometry was acquired for KZ Mus. All three stars are multi-periodic variables, with three (Beta CMa) and four (15 CMa, KZ Mus) independent pulsation modes. Two of the mode frequencies of 15 CMa are new discoveries and one of the known modes showed amplitude variations over the last 33 years. Taken together, this explains the star's diverse behaviour reported in the literature fully. Mode identification by means of the amplitude ratios in the different passbands suggests one radial mode for each star. In addition, Beta CMa has a dominant l=2 mode while its third mode is nonradial with unknown l. The nonradial modes of 15 CMa, which are l <= 3, form an almost equally split triplet that, if physical, would imply that we see the star under an inclination angle larger than 55 degrees. The strongest nonradial mode of KZ Mus is l=2, followed by the radial mode and a dipole mode. Its weakest known mode is nonradial with unknown l, confirming previous mode identifications for the star's pulsations. The phased light curve for the strongest mode of 15 CMa has a descending branch steeper than the rising branch. A stillstand phenomenon during the rise to maximum light is indicated. Given the low photometric amplitude of this nonradial mode this is at first sight surprising, but it can be explained by the mode's aspect angle., Comment: 12 pages, 11 figures

We undertook a time-series photometric multi-site campaign for the rapidly oscillating Ap star HD 99563 and also acquired mean light observations over two seasons. The pulsations of the star, that show flatter light maxima than minima, can be described with a frequency quintuplet centred on 1557.653 microHertz and some first harmonics of these. The amplitude of the pulsation is modulated with the rotation period of the star that we determine with 2.91179 +/- 0.00007 d from the analysis of the stellar pulsation spectrum and of the mean light data. We break the distorted oscillation mode up into its pure spherical harmonic components and find it is dominated by the l=1 pulsation, and also has a notable l=3 contribution, with weak l=0 and 2 components. The geometrical configuration of the star allows one to see both pulsation poles for about the same amount of time; HD 99563 is only the fourth roAp star for which both pulsation poles are seen and only the third where the distortion of the pulsation modes was modelled. We point out that HD 99563 is very similar to the well-studied roAp star HR 3831. Finally, we note that the visual companion of HD 99563 is located in the Delta Scuti instability strip and may thus show pulsation. We show that if the companion was physical, the roAp star would be a 2.03 solar mass object, seen at a rotational inclination of 44 degrees, which then predicts a magnetic obliquity of 86.4 degrees., Comment: 10 pages, 6 figures, accepted for publication by MNRAS

We have carried out a three-site photometric campaign for the Beta Cephei star Theta Ophiuchi from April to August 2003. 245 hours of differential photoelectric uvy photometry were obtained during 77 clear nights. The frequency analysis of our measurements resulted in the detection of seven pulsation modes within a narrow frequency interval between 7.116 and 7.973 c/d. No combination or harmonic frequencies were found. We performed a mode identification of the individual pulsations from our colour photometry that shows the presence of one radial mode, one rotationally split l=1 triplet and possibly three components of a rotationally split l=2 quintuplet. We discuss the implications of our findings and point out the similarity of the pulsation spectrum of Theta Ophiuchi to that of another Beta Cephei star, V836 Cen., Comment: 8 pages, 6 figures

The second multisite photometric campaign devoted to Nu Eri is reported. For Nu Eri, analysis of the new data adds four independent frequencies to the nine derived previously from the 2002-3 data, three in the range from 7.20 to 7.93 c/d, and a low one, equal to 0.614 c/d. Combining the new and the old data results in two further independent frequencies, equal to 6.7322 and 6.2236 c/d. Altogether, the oscillation spectrum is shown to consist of 12 high frequencies and two low ones. The latter have u amplitudes about twice as large as the v and y amplitudes, a signature of high radial-order g modes. Thus, the suggestion that Nu Eri is both a Beta Cephei and an SPB star, put forward on the basis of the first campaign's data, is confirmed. 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, Mu 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, Xi Eri, is confirmed to be a Delta Scuti variable. To the frequency of 10.8742 c/d seen already in the first campaign's data, another one, equal to 17.2524 c/d, is added., Comment: 13 pages, 8 figures, MNRAS, in press

Extensive photometric multisite campaigns of the Delta Scuti variable FG Vir are presented. For the years 2003 and 2004, 926 hours of photometry at the millimag precision level were obtained. The combinations with earlier campaigns lead to excellent frequency resolution and high signal/noise. A multifrequency analysis yields 79 frequencies. This represents a new record for this type of star. The modes discovered earlier were confirmed. Pulsation occurs over a wide frequency band from 5.7 to 44.3 c/d with amplitudes of 0.2 mmag or larger. Within this wide band the frequencies are not distributed at random, but tend to cluster in groups. A similar feature is seen in the power spectrum of the residuals after 79 frequencies are prewhitened. This indicates that many additional modes are excited. The interpretation is supported by a histogram of the photometric amplitudes, which shows an increase of modes with small amplitudes. The old question of the 'missing modes' may be answered now: the large number of detected frequencies as well as the large number of additional frequencies suggested by the power spectrum of the residuals con rms the theoretical prediction of a large number of excited modes. FG Vir shows a number of frequency combinations of the dominant mode at 12.7162 c/d (m = 0) with other modes of relatively high photometric amplitudes. The amplitudes of the frequency sums are higher than those of the differences. A second mode (20.2878 c/d) also shows combinations. This mode of azimuthal order m = -1 is coupled with two other modes of m = +1., Comment: 12 pages, 6 figures, 4 tables, accepted by Astronomy and Astrophysics

We undertook a multisite photometric campaign for the Beta Cephei star Nu Eridani. More than 600 hours of differential photoelectric uvyV photometry were obtained with 11 telescopes during 148 clear nights. The frequency analysis of our measurements shows that the variability of Nu Eri can be decomposed into 23 sinusoidal components, eight of which correspond to independent pulsation frequencies between 5 - 8 c/d. Some of these are arranged in multiplets, which suggests rotational m-mode splitting of nonradial pulsation modes as the cause. If so, the rotation period of the star must be between 30 - 60 d. One of the signals in the light curves of Nu Eri has a very low frequency of 0.432 c/d. It can be a high-order combination frequency or, more likely, an independent pulsation mode. In the latter case Nu Eri would be both a Beta Cephei star and a slowly pulsating B (SPB) star. The photometric amplitudes of the individual pulsation modes of Nu Eri appear to have increased by about 20 per cent over the last 40 years. So do the amplitudes of the dominant combination frequencies of the star. Among the latter, we only could identify sum frequencies with certainty, not difference frequencies, which suggests that neither light-curve distortion in its simplest form nor resonant mode coupling are their single cause. One of our comparison stars, Mu Eridani, turned out to be variable with a dominant time scale of 1.62 d. We believe that it is either an SPB star just leaving its instability strip or that its variations are of rotational origin., Comment: 10 pages, 5 figures

We have acquired between 127 and 150 h of time-resolved multicolour photometry for each of the three Beta Cephei stars IL Vel, V433 Car and KZ Mus over a time span of four months from two observatories. All three objects are multiperiodic with at least three modes of pulsation. Mode identification from the relative colour amplitudes is performed. We obtain unambiguous results for the two highest-amplitude modes of IL Vel (both are l=1) and the three strongest modes of KZ Mus (l=2,0 and 1), but none for V433 Car. Spectroscopy shows the latter star to be a fast rotator (v sin i = 240 km/s), whereas the other two have moderate v sin i (65 and 47 km/s, respectively). We performed model calculations with the Warsaw-New Jersey stellar evolution and pulsation code. We find that IL Vel is an object of about 12 Msun in the second half of its main sequence evolutionary track. Its two dipole modes are most likely rotationally split components of the mode originating as p1 on the ZAMS; one of these modes is m=0. V433 Car is suggested to be an unevolved 13 Msun star just entering the Beta Cephei instability strip. KZ Mus seems less massive (about 12.7 Msun) and somewhat more evolved, and its radial mode is probably the fundamental one. In this case its quadrupole mode would be the one originating as g1, and its dipole mode would be p1. It is suggested that mode identification of slowly rotating Beta Cephei stars based on photometric colour amplitudes is reliable; we estimate that a relative accuracy of 3% in the amplitudes is sufficient for unambiguous identifications. Due to the good agreement of our theoretical and observational results we conclude that the prospects for asteroseismology of multiperiodic slowly rotating Beta Cephei star are good., Comment: 16 pages, 16 figures, MNRAS, in press

The group of lambda Bootis type stars comprises late B- to early F-type, Population I objects which are basically metal weak, in particular the Fe group elements, but with the clear exception of C, N, O and S. The present work is a continuation of the studies by Paunzen et al. (1998, A&A, 335, 533), who presented first results on the pulsational characteristics of the lambda Bootis stars. Since then, we have observed 22 additional objects; we found eight new pulsators and confirmed another one. Furthermore, new spectroscopic data (Paunzen, 2001, A&A, 373, 633) allowed us to sort out misidentified candidates and to add true members to the group. From 67 members of this group, only two are not photometrically investigated yet which makes our analysis highly representative. We have compared our results on the pulsational behaviour of the lambda Bootis stars with those of a sample of delta Scuti type objects. We find that at least 70% of all lambda Bootis type stars inside the classical instability strip pulsate, and they do so with high overtone modes (Q < 0.020d). Only a few stars, if any, pulsate in the fundamental mode. Compared to the delta Scuti stars, the cool and hot borders of the instability strip of the lambda Bootis stars are shifted by about 25mmag, towards smaller (b-y)0. Using published abundances and the metallicity sensitive indices of the Geneva 7-colour and Stroemgren uvbybeta systems, we have derived [Z] values which describe the surface abundance of the heavier elements for the group members. We find that the Period-Luminosity-Colour relation for the group of lambda Bootis stars is within the errors identical with that of the normal delta Scuti stars. No clear evidence for a statistically significant metallicity term was detected., Comment: 14 pages, 8 figures, accepted by A&A

We have discovered both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a Gamma Doradus and a Delta Scuti star, which makes it the first pulsating star to be a member of two classes. The star is a single-lined spectroscopic binary with an orbital period of 3.10575 d and an eccentricity of 0.352. Weak pulsational signals are found in both the radial velocity and line-profile variations, allowing us to show that the two highest-amplitude Gamma Doradus pulsation modes are consistent with l=1 and |m|=1. In our 280 h of BVI multi-site photometry we detected ten frequencies in the light variations, one in the Delta Scuti regime and nine in the Gamma Doradus domain. Five of the Gamma Doradus frequencies are exact integer multiples of the orbital frequency. This observation leads us to suspect they are tidally excited. Results of theoretical modeling (stability analysis, tidal excitation) were consistent with the observations. We could not detect the secondary component of the system in infrared photometry, suggesting that it may not be a main-sequence star. Archival data of HD 209295 show a strong ultraviolet excess, the origin of which is not known. The orbit of the primary is consistent with a secondary mass of M > 1.04 Msun indicative of a neutron star or a white dwarf companion., Comment: 18 pages, 18 figures, accepted for publication in MNRAS, shortened abstract

We searched for Delta Scuti-type pulsations amongst known and candidate Gamma Doradus stars. We acquired 270 h of observations and monitored a total of 26 stars. One target, HD 209295, turned out to be a member of both classes of pulsating star. We classify six of our targets as new bona fide Gamma Doradus stars, nine more as good Gamma Doradus candidates, and three as ellipsoidal variables. The remainder comprise one Delta Scuti star and five unexplained variables. We revise the blue border of the Gamma Doradus phenomenon towards cooler temperatures. This new blue edge extends from a temperature of about 7550 K on the ZAMS to 7400 K one magnitude above it. Five bona fide Gamma Doradus stars we observed are located inside the Delta Scuti instability strip, but none of them exhibited observable Delta Scuti pulsations. We therefore suggest that Gamma Doradus stars are less likely to be Delta Scuti pulsators compared to other normal stars in the same region of the lower instability strip. In addition, we show that there is a clear separation between the pulsation constants Q of Delta Scuti and Gamma Doradus stars. The Gamma Doradus stars known to date all have Q>0.23 d., Comment: 12 pages, 9 figures. MNRAS, in press

We report the discovery of both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a gamma Doradus and a delta Scuti star, which makes it the first confirmed member of two classes of pulsating star. This object is located in a close binary system with an unknown, but likely degenerate companion in an eccentric orbit, and some of the gamma Doradus pulsation frequencies are exact integer multiples of the orbital frequency. We suggest that these pulsations are tidally excited. HD 209295 may be the progenitor of an intermediate-mass X-Ray binary., Comment: 4 pages, 1 figure, to appear in the proceedings of IAU Colloquium 185 "Radial and Nonradial Pulsations as Probes of Stellar physics", C.Aerts, T.Bedding and J.Christensen-Dalsgaard, eds