Search

New multicolour photometric observations were carried out on 22 nights in three observation missions between 2015 October and 2016 February for eclipsing binary HIP 7666. High- and low-resolution spectroscopic observations were also carried out in the winters of 2015, 2016, and 2019, respectively. The fully phase-covered light curves and radial velocity curves are presented. All times of light minima are used to calculate the orbital period [2.372 2200(4) d] and new ephemerides. The photometric solution and stellar physical parameters are derived, showing that HIP 7666 is a detached binary with the absolute parameters M1 = 1.53(3) M⊙, R1 = 2.08(2) R⊙, log L1/L⊙ = 0.99(3), log g1 = 3.98(2), Mbol1 = 2.26(8), Teff,1 = 7100(100) K for the primary, and M2 = 1.23(3) M⊙, R2 = 1.06(2) R⊙, log L2/L⊙ = 0.13(4), log g2 = 4.47(2), Mbol2 = 4.4(1), Teff,2 = 6029(67) K for the secondary. The age of 1.69 Gyr and 1.755 Gyr are estimated from parsec isochrones and mesa evolutionary tracks, respectively. In Herzsprung–Russell (H–R) diagram, the primary component has evolved to the late stages, while the secondary still locates at the early stages of the main sequence. Frequency analysis yields three frequencies of f1 = 24.631(4) cd−1, f2 = 21.193(1) cd−1, and f3 = 28.07(7) cd−1. Comparisons between models and observations suggest that the primary component is most likely a p-mode non-radial δ Scuti oscillator.

Hydrogen atmosphere pulsating white dwarfs, also known as DAV stars, are the most abundant type of pulsating white dwarfs. High-temperature DAV stars in general exhibit a small number of pulsation modes and stable frequencies. G132–12 is one of the pulsating hydrogen atmosphere white dwarf stars which lies close to the blue edge of the instability strip. Previous researches reported that G132–12 might have only one pulsation mode with the period of 212.69 s. To study the pulsation properties of G132–12 in detail, we carried out a bi-site observation campaign in October 2019. Time series photometric data were collected during around 154 h in total. A Fourier analysis reveals three frequencies which are identified as the triplet of an l = 1 g-mode pulsation with the period of 212.499 s. The rotational period is derived as P rot = 35.0 ± 6.7 h and the inclination of the rotational axis to the line of sight is 70°. G132–12 could be an ideal target for measuring the cooling scale of this white dwarf star with only one excited pulsation mode detected.

We thank the anonymous referee for a careful reading of the manuscript. DLH acknowledges financial support from the Science and Technology Facilities Council (STFC) via grant ST/M000877/1. MSC acknowledges the support by FCT/MCTES through the research grants UIDB/04434/2020, UIDP/04434/2020, and PTDC/FIS-AST/30389/2017, and by FEDER - Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (grant: POCI01-0145-FEDER-030389). MSC is supported by national funds through FCT in the form of a work contract. VA was supported by a research grant (00028173) fromVILLUMFONDEN. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant agreement no.: DNRF106). The research leading to these results has received funding from the Research Foundation Flanders (FWO) by means of a senior postdoctoral fellowship to DMB with grant agreement No. 1286521N. This project has been supported by the Lendulet Program of the Hungarian Academy of Sciences, project No. LP2018-7/2020 and by the EU's MW-Gaia COST Action (CA18104). ASG acknowledges financial support from the Max Planck Society under grant 'Preparations for PLATO science' and from ALMA-CONICYT under grant #31170029. ZsB acknowledges the support by the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences. LFM acknowledges the financial support from the UNAM under grant PAPIIT IN100918. CCL acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC). DM acknowledges the support of the National Astronomical Research Institute of Thailand (NARIT). JPG acknowledges funding support from Spanish public funds for research from project PID2019-107061GB-C63 from the 'Programas Estatales de Generacion de Conocimiento y Fortalecimiento Cientifico y Tecnologico del Sistema de I+D+i y de I+D+i Orientada a los Retos de la Sociedad', and from the State Agency for Research through the Center of Excellence Severo Ochoa' award to the Instituto de Astrof ' isica de Andaluc ' ia (SEV2017-0709), all from the Spanish Ministry of Science, Innovation and Universities (MCIU). TRY acknowledges support from the NSF REU program, grant number PHY-1359195. The material is based upon work supported by NASA under award number 80GSFC21M0002. AD was supported by the UNKP-20-5 New National Excellence Program of the Ministry of Human Capacities and the J ' anos Bolyai Research Scholarship of the Hungarian Academy of Sciences. AD would like to thank the City of Szombathely for support under Agreement No. 67.177-21/2016. AGH acknowledges support from 'FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento' under project E-FQM-041-UGR18 by Universidad de Granada and from Spanish public funds (including FEDER funds) for research under project ESP2017-87676-C5-2-R. ARB acknowledges funding support from Spanish public funds for research through the research grant PRE2018-084322, through projects ESP2017-87676-C5-5-R and PID2019-107061GB-C63, and from the State Agency for Research through the `Center of Excellence Severo Ochoa' award to the Instituto de Astrof ' isica de Andaluc ' ia (SEV-2017-0709), all from the Spanish Ministry of Science, Innovation and Universities (MCIU). We are grateful to Sowgata Chowdhury, supported by Polish NCN grant 2015/18/A/ST9/00578, for conducting some spectroscopic observations that are reported in this work. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission directorate. Funding for the TESS Asteroseismic Science Operations Centre is provided by the Danish National Research Foundation (Grant agreement no.: DNRF106), ESA PRODEX (PEA 4000119301) and Stellar Astrophysics Centre (SAC) at Aarhus University. We thank the TESS team and staff and TASC/TASOC for their support of this work. This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement., We present the results of a systematic search for new rapidly oscillating Ap (roAp) stars using the 2-min cadence data collected by the Transiting Exoplanet Survey Satellite (TESS) during its Cycle 1 observations. We identify 12 new roAp stars. Amongst these stars we discover the roAp star with the longest pulsation period, another with the shortest rotation period, and six with multiperiodic variability. In addition to these new roAp stars, we present an analysis of 44 known roAp stars observed by TESS during Cycle 1, providing the first high-precision and homogeneous sample of a significant fraction of the known roAp stars. The TESS observations have shown that almost 60 per cent (33) of our sample of stars are multiperiodic, providing excellent cases to test models of roAp pulsations, and from which the most rewarding asteroseismic results can be gleaned. We report four cases of the occurrence of rotationally split frequency multiplets that imply different mode geometries for the same degree modes in the same star. This provides a conundrum in applying the oblique pulsator model to the roAp stars. Finally, we report the discovery of non-linear mode interactions in α Cir (TIC 402546736, HD128898) around the harmonic of the principal mode – this is only the second case of such a phenomenon., UK Research & Innovation (UKRI), Science & Technology Facilities Council (STFC), Science and Technology Development Fund (STDF) ST/M000877/1, Portuguese Foundation for Science and Technology, European Commission UIDB/04434/2020 UIDP/04434/2020 PTDC/FIS-AST/30389/2017, FEDER - Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao POCI-01-0145-FEDER-030389, European Commission, VILLUMFONDEN 00028173, Danmarks Grundforskningsfond DNRF106 FWO 1286521N, Lendulet Program of the Hungarian Academy of Sciences LP2018-7/2020, EU's MW-Gaia COST Action CA18104, Max Planck Society, Foundation CELLEX, ALMA-CONICYT 31170029, Hungarian Academy of Sciences, UNAM under grant PAPIIT IN100918, Natural Sciences and Engineering Research Council of Canada (NSERC), National Astronomical Research Institute of Thailand (NARIT), Spanish public funds the Spanish Ministry of Science, Innovation and Universities (MCIU) PID2019-107061GB-C63 PRE2018-084322 ESP2017-87676-C5-5-R, 'Programas Estatales de Generacion de Conocimiento y Fortalecimiento Cientifico y Tecnologico del Sistema de I+D+i y de I+D+i Orientada a los Retos de la Sociedad' from the Spanish Ministry of Science, Innovation and Universities (MCIU), State Agency for Research through the 'Center of Excellence Severo Ochoa' award from the Spanish Ministry of Science, Innovation and Universities (MCIU) SEV-2017-0709, National Science Foundation (NSF), NSF - Office of the Director (OD) PHY-1359195, National Aeronautics & Space Administration (NASA) 80GSFC21M0002, New National Excellence Program of the Ministry of Human Capacities UNKP-20-5, City of Szombathely 67.177-21/2016, 'FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento' by Universidad de Granada E-FQM-041-UGR18, Spanish public funds (FEDER) ESP2017-87676-C5-2-R, Polish NCN 2015/18/A/ST9/00578, NASA's Science Mission directorate, European Space Agency PEA 4000119301, Stellar Astrophysics Centre (SAC) at Aarhus University

We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with periods around 4.7 min, making it the shortest period roAp star known to date. Four out of the five new roAp stars are multiperiodic. Three of these and the singly periodic one show the presence of rotational mode splitting. Individual frequencies are provided in all cases. In addition, seven previously known roAp stars are analysed. Additional modes of oscillation are found in some stars, while in others we are able to distinguish the true pulsations from possible aliases present in the ground-based data. We find that the pulsation amplitude in the TESS filter is typically a factor of 6 smaller than that in the B filter, which is usually used for ground-based observations. For four roAp stars we set constraints on the inclination angle and magnetic obliquity, through the application of the oblique pulsator model. We also confirm the absence of roAp-type pulsations down to amplitude limits of 6 and 13 \mumag, respectively, in two of the best characterized non-oscillating Ap (noAp) stars. We announce 27 new rotational variables along with their rotation periods, and provide different rotation periods for seven other stars. Finally, we discuss how these results challenge state-of-the-art pulsation models for roAp stars.© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society., This work was supported by FCT - Fundacao para a Ciencia e a Tecnologia through national funds and by FEDER through COMPETE02020 - Programa Operacional Competitividade e Internacionalizacao by these grants: UID/FIS/04434/2019, PTDC/FIS-AST/30389/2017 & POCI-01-0145-FEDER-030389. MC is supported in the form of work contract funded by national funds through FCT. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant agreement no.: DNRF106). DLH and DWK acknowledge financial support from the Science and Technology Facilities Council (STFC) via grant ST/M000877/1. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. LFM acknowledges support from the UNAM by the way of DGAPA project PAPIIT IN100918. The research leading to these results has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No670519: MAMSIE) and from the Fonds Wetenschappelijk Onderzoek -Vlaanderen (FWO) under the grant agreement G0H5416N (ERC Opvangproject). MS acknowledges the financial support of Postdoc@MUNI project CZ.02.2.69/0.0/0.0/16 027/0008360. EN acknowledges the Polish National Science Center grants no. 2014/13/B/ST9/00902. JCS acknowledges funding support from Spanish public funds for research under projects ESP2017-87676-2-2 and ESP2015-65712-C5-5-R, and from project RYC-2012-09913 under the 'Ramon y Cajal' program of the Spanish Ministry of Science and Education. AGH acknowledges funding support from Spanish public funds for research under projects ESP2017-87676-2-2 and ESP2015-65712-C5-5-R of the Spanish Ministry of Science and Education. AS, ZsB, and RSz acknowledge the financial support of the GINOP-2.3.2-15-2016-00003, K-115709, K-113117, K-119517, and PD-123910 grants of the Hungarian National Research, Development and Innovation Office (NKFIH), and the Lendulet Program of the Hungarian Academy of Sciences, project No. LP2018-7/2018. GH has been supported by the Polish NCN grant 2015/18/A/ST9/00578. MLM acknowledges funding support from Spanish public funds for research under project ESP2015-65712-C5-3-R. JPG acknowledges funding support from Spanish public funds for research under project ESP2017-87676-C5-5-R. MLM and JPG also acknowledges funding support from the State Agency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award for the Institute de Astrofisica de Andalucia (SEV-2017-0709). IS acknowledges funding support of NSF under projects DN 08-1/2016 and DN 18/13-12.12.2017. P. Kolaczek-Szymanski acknowledges support from the NCN grant no. 2016/21/B/ST9/01126. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program.

An increasing number of white dwarf stars show atmospheric chemical composition polluted by heavy elements accreted from debris disk material. The existence of such debris disks strongly suggests the presence of one or more planet(s) whose gravitational interaction with rocky planetesimals is responsible for their disruption by tidal effect. The ZZ Ceti pulsator and polluted DAZ white dwarf GD 133 is a good candidate for searching for such a potential planet. We started in 2011 a photometric follow-up of its pulsations. As a result of this work in progress, we used the data gathered from 2011 to 2015 to make an asteroseismological analysis of GD 133, providing the star parameters from a best fit model with $M$/$M_{\odot}$ = 0.630 $\pm$ 0.002, $T_{\rm eff}$ = 12400 K $\pm$ 70 K, log($M_{\rm He}/M$) = -2.00 $\pm$ 0.02, log($M_{\rm H}/M$) = -4.50 $\pm$ 0.02 and determining a rotation period of $\approx$ 7 days., 10 pages, 13 figures, accepted by MNRAS

Bi-site time-series photometric and high-resolution spectroscopic observations were made for the double-mode high-amplitude $\delta$ Scuti star VX\ Hya. The fundamental frequency $f_{0}=4.4763\ \rm{c\ days^{-1}}$, the first overtone $f_{1}=5.7897\ \rm{c\ days^{-1}}$ and 23 harmonics and linear combinations of $f_{0}$ and $f_{1}$ are detected by pulsation analysis. From the spectroscopic data, we get $\rm{[Fe/H] = -0.2\pm0.1\ dex}$. The period change rate of the fundamental mode is obtained by using the Fourier-phase diagram method, which gives the value of $(1/P_{0})(dP_{0}/dt)=(1.81\pm0.09) \times 10^{-7}\ \rm{yr}^{-1}$. With these results from the observations, we perform theoretical explorations with the stellar evolution code MESA, and constrain the models by fitting $f_{0}$, $f_{1}$, and $(1/P_{0})(dP_{0}/dt)$ within $3\sigma$ deviations. The results show that the period change of VX\ Hya could be ascribed to the evolutionary effect. The stellar parameters of VX\ Hya could be derived as: the mass $2.385\pm0.025\ M_{\odot}$, the luminosity $\log(L/L_{\odot})=1.93\pm0.02$ and the age $(4.43\pm0.13)\times 10^8$ years. VX\ Hya is found to locate at the post-main-sequence stage with a helium core and a hydrogen-burning shell on the H${-}$R diagram., Comment: 23 pages, 9 figures, 12 tables. ApJ version

Three optical telescopes located at the San Pedro M\'artir National Observatory were used for the first time to obtain multi-filter defocused photometry of the transiting extrasolar planets WASP-39b and WASP-43b. We observed WASP-39b with the 2.12m telescope in the U filter for the first time, and additional observations were carried out in the R and I filters using the 0.84m telescope. WASP-43b was observed in VRI with the same instrument, and in the i filter with the robotic 1.50m telescope. We reduced the data using different pipelines and performed aperture photometry with the help of custom routines, in order to obtain the light curves. The fit of the light curves (1.5--2.5mmag rms), and of the period analysis, allowed a revision of the orbital and physical parameters, revealing for WASP-39b a period ($4.0552947 \pm 9.65 \times 10^{-7}$ days) which is $3.084 \pm 0.774$ seconds larger than previously reported. Moreover, we find for WASP-43b a planet/star radius ($0.1738 \pm 0.0033$) which is $0.01637 \pm 0.00371$ larger in the i filter with respect to previous works, and that should be confirmed with additional observations. Finally, we confirm no evidence of constant period variations in WASP-43b., Comment: 13 pages, 7 figures, accepted in PASP, scheduled for the February 1, 2015 issue

We report the results of CCD photometric observations in the direction of the Coma Berenices and Upgren 1 open clusters with the aim at searching for new short-period variable stars. A total of 35 stars were checked for variability. As a result of this search the star designated in the SIMBAD database as Melotte 111 AV 1224 was found to be a new eclipsing binary star. Follow-up Str\"omgren photometric and spectroscopic observations allowed us to derive the spectral type, distance, reddening and effective temperature of the star. A preliminary analysis of the binary light curve was performed and the parameters of the orbital system were derived. From the derived physical parameters we conclude that Melotte 111 AV 1224 is most likely a W UMa eclipsing binary that is not a member of the Coma Berenices open cluster. On other hand, we did not find evidence of brightness variations in the stars NSV 5612 and NSV 5615 previously catalogued as variable stars in Coma Berenices open cluster., Comment: 9 pages, 9 figures, 4 tables, accepted for publication in New Astronomy

Asteroseismology is a unique tool to explore the internal structure of stars through both observational and theoretical research. The internal structure of pulsating hydrogen shell white dwarfs (ZZ Ceti stars) detected by asteroseismology is regarded as the representative of all DA white dwarfs. Observations for KUV~08368+4026, which locates in the middle of the ZZ Ceti instability strip, have been carried out in 1999 and from 2009 to 2012 with either single-site runs or multisite campaigns. Time-series photometric data of about 300 hours were collected in total. Through data reduction and analysis, 30 frequencies were extracted, including four triplets, two doublets, one single mode and further signals. The independent modes are identified as either l=1 or l=2 modes. Hence, a rotation period of $5.52\pm 0.22$ days was deduced from the period spacing in the multiplets. Theoretical static models were built and a best fit model for KUV~08368+4026 was obtained with $0.692\pm0.002$ solar mass, $(2.92\pm0.02)\times 10^{-3}$ solar luminosity and the hydrogen mass fraction of $10^{-4}$ stellar mass., 9 pages, 7 figures

Observations for the $\delta$ Scuti star AN Lyn have been made between 2008 and 2016 with the 85-cm telescope at Xinglong station of National Astronomical Observatories of China, the 84-cm telescope at SPM Observatory of Mexico and the Nanshan One meter Wide field Telescope of Xinjiang Observatory of China. Data in $V$ in 50 nights and in $R$ in 34 nights are obtained in total. The bi-site observations from both Xinglong Station and SPM Observatory in 2014 are analyzed with Fourier Decomposition to detect pulsation frequencies. Two independent frequencies are resolved, including one non-radial mode. A number of stellar model tracks are constructed with the MESA code and the fit of frequencies leads to the best-fit model with the stellar mass of $M = 1.70 \pm 0.05~\mathrm{M_{\odot}}$ , the metallicity abundance of $Z = 0.020 \pm 0.001$, the age of $1.33 \pm 0.01$ billion years and the period change rate $1/P\cdot \mathrm{d}P/\mathrm{d}t =1.06 \times 10^{-9} ~\mathrm{yr^{-1}} $, locating the star at the evolutionary stage close to the terminal age main sequence (TAMS). The O-C diagram provides the period change rate of $1/P \cdot \mathrm{d}P /\mathrm{d}t =4.5(8)\times10^{-7}~\mathrm{yr^{-1}}$. However, the period change rate calculated from the models is smaller in two orders than the one derived from the O-C diagram. Together with the sinusoidal function signature, the period variations are regarded to be dominated by the light-travel time effect of the orbital motion of a three-body system with two low-luminosity components, rather than the stellar evolutionary effect., Comment: 14 pages, 8 tables, 17 figures, accepted by mnras

Time-series, multi-color photometry and high-resolution spectra of the short period eclipsing binary V Tri were obtained by observations. The completely covered light and radial velocity curves of the binary system are presented. All times of light minima derived from both photoelectric and CCD photometry were used to calculate the orbital period and new ephemerides of the eclipsing system. The analysis of $O-C$ diagram reveals that the orbital period is $0.58520481\ days$, decreasing at a rate of $dP/dt=-7.80\times10^{-8} d\ yr^{-1} $. The mass transfer between the two components and the light time-travel effect due to a third body could be used to explain the period decrease. However, a semidetached configuration with the less-mass component filling and the primary nearly filling each of their Roche lobes was derived from the synthesis of the light and radial velocity curves by using the 2015 version of the Wilson-Devinney code. We consider the period decrease to be the nonconservative mass transfer from the secondary component to the primary and the mass loss of the system, which was thought to be an EB type while it should be an EA type (semi-detached Algol-type) from our study. The masses, radii and luminosities of the primary and secondary are $1.60\pm0.07 M_\odot$, $1.64\pm0.02 R_\odot$, $14.14\pm0.73 L_\odot$ and $0.74\pm0.02 M_\odot$, $1.23\pm0.02 R_\odot$, $1.65\pm0.05 L_\odot$, respectively., Comment: 11 pages, 6 figures, Accepted for publication by AJ

We present a photometric follow-up of transiting exoplanets HAT-P-3b and TrES-3b, observed by using several optical and near-infrared filters, with four small-class telescopes (D = 36--152cm) in the Northern Hemisphere. Two of the facilities present their first scientific results. New 10 HAT-P-3b light curves and new 26 TrES-3b light curves are reduced and combined by filter in order to improve the quality of the photometry. Combined light curves fitting is carried out independently by using two different analysis packages, allowing the corroboration of the orbital and physical parameters in the literature. Results find no differences in the relative radius with the observing filter. In particular, we report for HAT-P-3b a first estimation of the planet-to-star radius Rp/R* = 0.1112+0.0025-0.0026 in the B band which is coherent with values found in the VRIz'JH filters. Concerning TrES-3b, we derive a value for the orbital period of P = 1.3061862+-0.0000001 days which shows no linear variations over nine years of photometric observations., Comment: Accepted for publication in PASP; 9 pages, 6 figures, data will be published on CDS

We present long-term, multi-color photometric monitoring and spectroscopic observations of the short-period M-type eclipsing binary BX Tri. Six flare events were recorded in 4 years from 2014 to 2017. Three of them were detected on one night within an orbital cycle. The strongest one was identified on December 23, 2014. With the amplitudes of $\Delta$B=0.48 mag, $\Delta$V=0.28 mag, $\Delta$R=0.10 mag, $\Delta$I=0.02 mag, the total energy due to the flare event was measured to be 4.08 ($\pm$0.24) $\times$$10^{34}$ erg, exceeding the superflare level ($10^{34}$). Based on the observations, the evolutionary status of the binary system as well as the long-term orbital period changes were analyzed. It reveals that BX Tri is probably a semi-detached system with the primary component filling its Roche lobe. The extremely high occurrence of flare events of the binary could be related to the rapid mass transfer between components., Comment: 16 pages, 10figures; Accepted for publication in ApJ

Iliev, Ilian Kh/0000-0002-9811-449X; Fox-Machado, Lester/0000-0002-2781-873X; Dimitrov, Dinko/0000-0002-1667-5868; Balona, Luis/0000-0003-1241-9792; Shakhovskoy, Dmitry/0000-0002-3180-4621; , Antoniuk/0000-0003-2754-8925; CARBOGNANI, Albino/0000-0002-0737-7068; Achilova, Diyora/0000-0002-7645-9497, We present results of a multisite photometric campaign on the high-amplitude delta Scuti star KIC 6382916 in the Kepler field. The star was observed over a 85-d interval at five different sites in North America and Europe during 2011. Kepler photometry and ground-based multicolour light curves of KIC 6382916 are used to investigate the pulsational content and to identify the principal modes. High-dispersion spectroscopy was also obtained in order to derive the stellar parameters and projected rotational velocity. From an analysis of the Kepler time series, three independent frequencies and a few hundred combination frequencies are found. The light curve is dominated by two modes with frequencies f(1) = 4.9107 and f(2) = 6.4314 d(-1). The third mode with f(3) = 8.0350 d(-1) has a much lower amplitude. We attempt mode identification by examining the amplitude ratios and phase differences in different wavebands from multicolour photometry and comparing them to calculations for different spherical harmonic degree, l. We find that the theoretical models for f(1) and f(2) are in a best agreement with the observations and lead to value of l = 1 modes, but the mode identification of f(3) is uncertain due to its low amplitude. Non-adiabatic pulsation models show that frequencies below 6 d(-1) are stable, which means that the low frequency of f(1) cannot be reproduced. This is a further confirmation that current models predict a narrower pulsation frequency range than actually observed., NASANational Aeronautics & Space Administration (NASA); South African National Research Foundation (NRF)National Research Foundation - South Africa [73446]; South African National Research FoundationNational Research Foundation - South Africa; South African Astronomical ObservatoryNational Research Foundation - South Africa; Bulgarian NSFNational Science Fund of Bulgaria [DO 02-85, DO 02-362, DDVU 02/40-2010]; UNAMUniversidad Nacional Autonoma de Mexico [PAPIIT 104612]; CONACYTConsejo Nacional de Ciencia y Tecnologia (CONACyT) [118611]; European UnionEuropean Union (EU); Autonomous Region of the Aosta ValleyRegione Valle d'Aosta; Italian Department for Work, Health and Pensions; Regional Government of the Aosta Valley; Town Municipality of Nus; Mont Emilius Community; National Research Foundation of South AfricaNational Research Foundation - South Africa; [HDYF-051], The authors acknowledge the whole Kepler team for providing the unprecedented data sets that make these results possible. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. CU sincerely thanks the South African National Research Foundation (NRF) for the award of innovation post-doctoral fellowship, grant no. 73446. BU is supported by the project numbered HDYF-051. TG would like to thank NRF Equipment-Related Mobility Grant-2011 for travelling to carry out the photometric observations. LAB thanks the South African National Research Foundation and the South African Astronomical Observatory for generous financial support. IS and II gratefully acknowledge the partial support from Bulgarian NSF under grant DO 02-85. DD acknowledges for the support of grants DO 02-362 and DDVU 02/40-2010 of Bulgarian NSF. HAK acknowledges Carlos Vargas-Alvarez, Michael J. Lundquist, Garrett Long, Jessie C. Runnoe, Earl S. Wood and Michael J. Alexander for helping with the observations at WIRO. LFM acknowledges financial support from the UNAM under grant PAPIIT 104612 and from CONACYT by the way of grant 118611. MD, AC and DC are supported by grants provided by the European Union, the Autonomous Region of the Aosta Valley and the Italian Department for Work, Health and Pensions. The OAVdA is supported by the Regional Government of the Aosta Valley, the Town Municipality of Nus and the Mont Emilius Community. TEP acknowledges support from the National Research Foundation of South Africa. This study made use of IRAF Data Reduction and Analysis System and the Vienna Atomic Line Data Base (VALD) services. The authors thank Dr Zima for providing the FAMIAS code.

Exoplanetary transit observations were carried out for the first time with all the three telescopes at the San Pedro Mártir National Astronomical Observatory in Baja California, Mexico.We present preliminary results on WASP-39 and WASP-43, two Hot Jupiters known for the presence of a highly-inflated radius. Using the defocused photometry technique, we observed these systems, achieving photometric precision of ± 3–5mmag peak-to-valley. The preliminary fit of their lightcurves shows physical and orbital parameters consistent with published results.

The results of an observational campaign on the new $\delta$ Scuti pulsator \astrobj{HD~207331} are reported. The star was observed photometrically from August 26 to September 2, 2009 from the Observatorio San Pedro M\'artir (0.84-m telescope, Mexico) and the Observatorio del Teide (0.80-m telescope, Spain). An overall run of 53.8 h of useful data was collected from the two sites. Four oscillation frequencies for \astrobj{HD~207331} have been found above a 99\% confidence level. These results confirm the multiperiodic pulsation nature of the star suggested in previous observations with sparse data. Spectroscopic observations carried out in 2009 allowed us to derive its spectral type and luminosity class as well as to estimate its rotation rate. A simple comparison with models is performed., Comment: 6 pages, 5 figures, 3 tables, New Astronomy 15 (2010) 712-716

We present results on the second faintest pulsating subdwarf B (sdB) star, RAT J0455+1305, derived from photometric data obtained in 2009. It shows both short- and long-period oscillations, theoretically assigned as pressure and gravity modes. We identify six short-period frequencies (with one being a combination) and six long-period frequencies. This star is the fourth hybrid sdB star discovered so far which makes it of special interest as each type of mode probes a different part of the star. This star is similar to the sdB hybrid pulsator Balloon 090100001 in that it exhibits short-period mode groupings, which can be used to identify pulsation parameters and constrain theoretical models.

This paper presents a photometric and spectroscopic study of the short-period binary star Cl*~Melotte~111~AV~1224. Measurements in the $B$, $V$, and $R$ passbands obtained during three observing runs between 2014 and 2017 and medium-resolution spectra secured in 2014, are analyzed together with public data from the SuperWASP and LAMOST projects. Our light curves show marked asymmetry with a variable O'Connell effect. The SuperWASP photometry is used to derive a mean binary period of 0.345225 days. The analysis of the $(O-C)$ diagram reveals that the orbital period is decreasing at a rate of $dP/dt = -3.87 \times 10^{-6}$ days yr$^{-1}$, which may be caused by mass transfer from the more-massive component to the less-massive one. The system is found to be a single-lined spectroscopic binary with a systemic velocity, $\gamma = 1 \pm 3$ Km s$^{-1}$, and a semi-amplitude, K$_{1}$ = 21 $\pm$ 5 Km s$^{-1}$. The spectral classification and the effective temperature of the primary component are estimated to be K0V $\pm$ 1 and $5200 \pm 150$ K, respectively. The photometric and spectroscopic solutions reveal that Cl*~Melotte~111~AV~1224 is a low-mass ratio ($q=m_{2}/m_{1} \sim 0.11$), low-inclination ($\sim ~ 38^{\circ}$) near-contact system. The masses, radii and luminosity for the primary and secondary are estimated to be $1.02 \pm 0.06\, M_\odot$, $1.23 \pm 0.05\, R_\odot $, $1.01 \pm 0.06\, L_\odot$ and $0.11 \pm 0.08\, M_\odot$, $0.45 \pm 0.05\, R_\odot$, $0.10 \pm 0.06\, L_\odot$, respectively. The marginal contact, together with the period decrease, suggests that this binary system may be at a key evolutionary stage, as predicted by the theory of thermal relaxation oscillations., Comment: Accepted for publication in PASP; 11 pages, 11 figures, 8 tables

We present the results of a multisite photometric campaign on the pulsating sdB star Balloon 090100001. The star is one of the two known hybrid hot subdwarfs with both long- and short-period oscillations. The campaign involved eight telescopes with three obtaining UBVR data, four B-band data, and one Stromgren uvby photometry. The campaign covered 48 nights, providing a temporal resolution of 0.36microHz with a detection threshold of about 0.2mmag in B-filter data. Balloon 090100001 has the richest pulsation spectrum of any known pulsating subdwarf B star and our analysis detected 114 frequencies including 97 independent and 17 combination ones. The strongest mode (f_1) in the 2.8mHz region is most likely radial while the remaining ones in this region form two nearly symmetric multiplets: a triplet and quintuplet, attributed to rotationally split \ell=1 and 2 modes, respectively. We find clear increases of splitting in both multiplets between the 2004 and 2005 observing campaigns, amounting to 15% on average. The observed splittings imply that the rotational rate in Bal09 depends on stellar latitude and is the fastest on the equator. We use a small grid of models to constrain the main mode (f_1), which most likely represents the radial fundamental pulsation. The groups of p-mode frequencies appear to lie in the vicinity of consecutive radial overtones, up to the third one. Despite the large number of g-mode frequencies observed, we failed to identify them, most likely because of the disruption of asymptotic behaviour by mode trapping. The observed frequencies were not, however, fully exploited in terms of seismic analysis which should be done in the future with a larger grid of reliable evolutionary models of hot subdwarfs., accepted for publication in MNRAS

International audience; Context: The eclipsing delta Scuti star HD 172189 is a probable member of the open cluster IC 4756 and a promising candidate target for the CoRoT mission. Aims: The detection of pulsation modes is the first step in the asteroseismological study of the star. Further, the calculation of the orbital parameters of the binary system allows us to make a dynamical determination of the mass of the star, which works as an important constraint to test and calibrate the asteroseismological models. Methods: We performed a detailed frequency analysis of 210 hours of photometric data of HD 172189 obtained from the STEPHI XIII campaign. Results: We have identified six pulsation frequencies with a confidence level of 99% and a seventh with a 65% confidence level of 65%, in the range between 100-300 muHz. In addiction, three eclipses were observed during the campaign, allowing us to improve the determination of the orbital period of the system.

We report here the discovery of very low amplitude oscillations in the Pleiades star HD 23628. The 14-nights high quality light curve designates HD 23628 as a new member of the Scuti stars class. Amplitude spectra indicate a multi-periodic pulsation behaviour, and four pulsation frequencies have been detected so far. The frequency distribution suggests the presence of nonradial modes. Pulsation constant values of the four modes are distributed in the range corresponding to fundamental f to p4 radial modes.

The results of the tenth multi-site campaign of the STEPHI network are reported. The δ Scuti stars V624 Tau (HD 23156) and HD 23194, belonging to the Pleiades cluster, were observed photometrically for 34 days on three continents during 1999 November–December. An overall run of 343 hours of data was collected. Seven frequencies for V624 Tau and two frequencies for HD 23194 have been found above a 99% confidence level. These results greatly improve those found in previous studies with much less data. A preliminary comparison of observed and theoretical frequencies suggests that both stars may oscillate with radial and non-radial p modes of radial orders typical among δ Scuti stars.

Cool white dwarf stars often have mysteriously strong magnetic fields (because their coolness suggests that they are old, and magnetic fields should decline in strength with age) and unexplained brightness variations; here the magnetic field is shown to suppress atmospheric convection, inhibiting cooling evolution and causing dark spots. Most stars in the Universe will end their lives as burnt-out cores known as white dwarfs. Many old, isolated white dwarf stars with convecting atmospheres have stronger magnetic fields than young, convection-free ones, which is puzzling because the fields are expected to decay with time. In addition, some white dwarfs with strong fields vary in brightness with their rotation. Gennady Valyavin et al. report optical observations and analysis of the strongly-magnetic white dwarf WD1953-011. They find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. These strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, thereby inhibiting their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs. Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs1,2,3,4, which has been a puzzle because magnetic fields are expected to decay with time5,6 but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate7,8,9,10, which has been variously attributed to surface brightness inhomogeneities similar to sunspots8,9,10,11,12, chemical inhomogeneities13,14 and other magneto-optical effects15,16,17. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (muchfuss) aims to discover subdwarf-B stars with massive compact companions such as overmassive white dwarfs (M > 1.0 M_sun), neutron stars or black holes. From the 127 subdwarfs with substantial radial-velocity variations discovered in the initial survey, a number of interesting objects have been selected for extensive follow-up. After an initial photometry run with BUSCA revealed that FBS 0117+396 is photometrically variable both on long and short timescales, we chose it as an auxiliary target during a 6-night multi-color photometry run with Ultracam. Spectroscopy was obtained at a number of observatories in order to determine the binary period and obtain a radial-velocity amplitude. After establishing an orbital period of P = 0.252 d, and removing the signal associated with the irradiated hemisphere of the M-dwarf companion, we were able to detect ten pulsation periods in the Fourier spectrum of the light curve. Two pulsation modes are found to have short periods of 337 and 379 s, and at least eight modes are found with periods between 45 minutes and 2.5 hours. This establishes that FBS 0117+396 is an sdB+dM reflection binary, in which the primary is a hybrid pulsator, and the first one found with this particular melange of flavours., 11 pages, accepted for publication in A&A

The pulsating DA white dwarfs (ZZ Ceti stars) are $g$-mode non-radial pulsators. Asteroseismology provides strong constraints on their global parameters and internal structure. Since all the DA white dwarfs falling in the ZZ Ceti instability strip do pulsate, the internal structure derived from asteroseismology brings knowledge for the DA white dwarfs as a whole group. HS 0507+0434B is one of the ZZ Ceti stars which lies approximately in the middle of the instability strip for which we have undertaken a detailed asteroseismological study. We carried out multisite observation campaigns in 2007 and from December 2009 to January 2010. In total, 206 hours of photometric time-series have been collected. They have been analysed by means of Fourier analysis and simultaneous multi-frequency sine-wave fitting. In total, 39 frequency values are resolved including 6 triplets and a number of linear combinations. We identify the triplets as $\ell$=1 $g$-modes split by rotation. We derived the period spacing, the rotational splitting and the rotation rate. From the comparison of the observed periods with the theoretical periods of a series of models we estimate the fundamental parameters of the star: its total mass M$_{*}$/M$_{\odot}$ = 0.675, its luminosity L/L$_{\odot}$=3.5$\times 10^{-3}$, and its hydrogen mass fraction M$_{H}$/M$_{*}$= 10$^{-8.5}$., Comment: 12 pages,8 figures, accepted for publication in MNRAS

A search for new pulsating stars in the Coma Berenices open cluster was carried out. As a result of this search the cluster member Melotte 111 AV 1224 presented clear indications of photometric variability. In order to determine its physical parameters Str\"omgren standard indices and low-resolution spectra were acquired. In this work we present the preliminary results of these observations., Comment: To be published in conference proceedings of IAU Symposium 301: Precision Asteroseismology, held in Wroclaw, Poland, August 2013

The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars. We propose three main groups to describe the observed variety in pulsating A-F type stars: gamma Dor, delta Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much larger fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities within the gamma Dor and delta Sct range, also between 5 and 10 c/d, which is a challenge for the current models. We find indications for the existence of delta Sct and gamma Dor stars beyond the edges of the current observational instability strips. The hybrid stars occupy the entire region within the delta Sct and gamma Dor instability strips, and beyond. Non-variable stars seem to exist within the instability strips. The location of gamma Dor and delta Sct classes in the (Teff,logg)-diagram has been extended. We investigate two newly constructed variables 'efficiency' and 'energy' as a means to explore the relation between gamma Dor and delta Sct stars. Our results suggest a revision of the current observational instability strips, and imply an investigation of other pulsation mechanisms to supplement the kappa mechanism and convective blocking effect to drive hybrid pulsations., Accepted for publication in Astronomy and Astrophysics (language edited version). 70 pages, 4 tables, 13 figures. The tables can be found as an appendix to the paper. The quality of the figures has been downgraded compared to the original

We present the recent discovery of a new subdwarf B variable (sdBV), with an exceptionally low surface gravity. Our spectroscopy of J20136+0928 places it at Teff = 32100 +/- 500, log(g) = 5.15 +/- 0.10, and log(He/H) = -2.8 +/- 0.1. With a magnitude of B = 12.0, it is the second brightest V361 Hya star ever found. Photometry from three different observatories reveals a temporal spectrum with eleven clearly detected periods in the range 376 to 566 s, and at least five more close to our detection limit. These periods are unusually long for the V361 Hya class of short-period sdBV pulsators, but not unreasonable for p- and g-modes close to the radial fundamental, given its low surface gravity. Of the ~50 short period sdB pulsators known to date, only a single one has been found to have comparable spectroscopic parameters to J20136+0928. This is the enigmatic high-amplitude pulsator V338 Ser, and we conclude that J20136+0928 is the second example of this rare subclass of sdB pulsators located well above the canonical extreme horizontal branch in the HR diagram., Comment: 5 pages, accepted for publication in ApJ Letters

"The preliminary results of a multisite photometric campaign on the Pleiades Delta Scuti variable V650 Tauri are reported. The star was observed photometrically for 14 days during 2008 November from three observatories distributed in Longitude around the Earth. As a result of the preliminary analysis we have detected in V650 Tauri at least nine oscillation frequencies above a 99% confidence level."

The discovery of non-radial pulsations (NRP) in the Be/X binaries of the Magellanic Clouds (MC, eg. Fabrycky 2005, Coe et al. 2005, Schmidtke & Cowley 2005) provided a new approach to understand these complex systems, and, at the same time, favoured the synergy between two different fields: stellar pulsations and X-ray binaries. This breakthrough was possible thanks to the MACHO and OGLE surveys. However, in our Galaxy, only two Be/X have been reported to show NRP: GROJ2058+42 (Kiziloglu et al. 2007) and LSI+61 235 (Sarty et al. 2009). Our objective is to study the short-term variability of Galactic Be/X binaries, compare them to the Be/X of the MC and to the isolated Galactic Be observed with CoRoT and Kepler. We present preliminary results of two Be/X stars, namely 4U0115+63 and SAXJ2103.5+4545 showing multiperiodicity and periodicity respectively, most probably produced by non-radial pulsations., 2 pages, 2 figures, IAUS 272 "Active OB stars: structure, evolution, mass loss and critical limits" conference, Paris, July 2010, submitted

The ZZ Ceti HS 0507+0434B is of special interest because it lies in a common proper motion system with HS 0507+0434A, another DA white dwarf of Teff = 20000 K. It lies in the middle of the instability strip and is a potentially useful pulsator to study the convection‐pulsation interaction. Its pulsation spectrum has shown 10 independent frequencies and a number of linear combinations. In an effort to better constrain its internal structure, we have performed new observations of HS 0507+0434B. We describe these new data obtained from mono‐site as well as multi‐site campaigns between 2007 and 2010. The analysis of these data reveals a complex behavior of the pulsator, with both frequency and amplitude variations on this 1.5 year time scale. We identify 7 l = 1 multiplets. We computed a grid of models and their l = 1 g‐modes. We then applied a χ2 fit method to derive a preliminary best fit model with: M*/M⊙ = 0.70, L/L⊙ = 3.5×10−3, Teff = 12080 K, MH/M* = 10−4.4.The ZZ Ceti HS 0507+0434B is of special interest because it lies in a common proper motion system with HS 0507+0434A, another DA white dwarf of Teff = 20000 K. It lies in the middle of the instability strip and is a potentially useful pulsator to study the convection‐pulsation interaction. Its pulsation spectrum has shown 10 independent frequencies and a number of linear combinations. In an effort to better constrain its internal structure, we have performed new observations of HS 0507+0434B. We describe these new data obtained from mono‐site as well as multi‐site campaigns between 2007 and 2010. The analysis of these data reveals a complex behavior of the pulsator, with both frequency and amplitude variations on this 1.5 year time scale. We identify 7 l = 1 multiplets. We computed a grid of models and their l = 1 g‐modes. We then applied a χ2 fit method to derive a preliminary best fit model with: M*/M⊙ = 0.70, L/L⊙ = 3.5×10−3, Teff = 12080 K, MH/M* = 10−4.4.

KUV 08368+4026 was considered a member of ZZ Ceti stars with large amplitudes and frequencies around a narrow range of 1.6 mHz and 2.0 mHz. As the first effort of asteroseismological study for KUV 08368+4026 since the discovery of its variability in 1996, a single‐site run in February of 2009 and a 3‐site observation campaign from December of 2009 to January of 2010 for KUV 08368+4026 were carried out in China and Mexico. More than 15,000 frames on 32 nights were obtained. 19 frequencies were distinguished in the datasets with 8 frequencies identified as independent modes. These results are helpful in determining stellar parameters including mass, rotation period, hydrogen mass fraction, and in constructing practical stellar and oscillation models, which will bring new knowledge about the internal structures of ZZ Ceti stars.

Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M$_{\sun}$) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M$_{\sun}$), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary., Comment: 7 pages, 5 figures, accepted for publication in A&A

Photometric $(ubvy-\beta$) and spectroscopic observations of the $\delta$ Scuti variables \astrobj{7 Aql} and \astrobj{8 Aql} are described. The Str\"omgren standard indices and physical parameters of both stars are derived. Spectral types of F0V and F2III have been assigned to \astrobj{7 Aql} and \astrobj{8 Aql} respectively considering the results from both spectroscopy and photometry. Differential $uvby$ light curves were also analyzed. A attempt of multicolour mode identification is carried out., Comment: 6 pages, 7 figures, 4 tables, accepted for publication in New Astronomy

The preliminary results of new photometric observations of the $\delta$ Scuti stars 7 Aql and 8 Aql are reported. 51 hr of $uvby-\beta$ photoelectric photometric data were obtained over the period June and July 2007 at the San Pedro M\'artir Observatory, Mexico. Period analyses confirm the three pulsation modes discovered in 8 Aql in the framework of the STEPHI 2003 multisite campaign. For the star 7 Aql we were able to detect only the main pulsation modes. The standard magnitudes of both stars are obtained. The frequency, amplitude and phases of the frequency modes in different filters are presented., Comment: Proceedings of the International Conference "Stellar Pulsation: Challenges for Theory and Observation", AIP Conf. Proc., Vol. 1170, issue 1, pp. 423-425

The preliminary results of a three-site CCD photometric campaign are reported. The $\delta$ Scuti variable V650 Tauri belonging to the Pleiades cluster was observed photometrically for 14 days on three continents during 2008 November. An overall run of 164 hr of data was collected. At least five significant frequencies for V650 Tauri have been detected., Comment: Proceedings of the International Conference "Stellar Pulsation: Challenges for Theory and Observation", AIP Conf. Proc., Vol. 1170, issue 1, pp. 426-428

In this preliminary work, the determination of physical parameters for the RR Lyrae stars CM, SW, SZ, and UY in Bootes from Stromgren uvby-\beta photometry is presented., Comment: Proceedings of the International Conference "Stellar Pulsation: Challenges for Theory and Observation", AIP Conf. Proc., Vol. 1170, issue 1, pp. 253-254

As a continuation of the study of the Delta Scuti stars 7 Aql and 8 Aql; new CCD photometric data were acquired in 2007. We present a period analysis on these data that confirm the dominant modes detected in each star in the framework of the STEPHI XII campaign in 2003., 9 pages, 7 figures, 2 tables; Accepted for publication in Communications in Asteroseismology, Vol 153, 2008

We present an analysis of the pulsation behaviour of the Delta Scuti stars 7 Aql (HD 174532) and 8 Aql (HD 174589) -- a new variable star -- observed in the framework of STEPHI XII campaign during 2003 June--July. 183 hours of high precision photometry were acquired by using four-channel photometers at three sites on three continents during 21 days. The light curves and amplitude spectra were obtained following a classical scheme of multi-channel photometry. Observations in different filters were also obtained and analyzed. Six and three frequencies have been unambiguously detected above a 99% confidence level in the range 0.090 mHz--0.300 mHz and 0.100 mHz-- 0.145 mHz in 7 Aql and 8 Aql respectively. A comparison of observed and theoretical frequencies shows that 7 Aql and 8 Aql may oscillate with p modes of low radial orders, typical among Delta Scuti stars. In terms of radial oscillations the range of 8 Aql goes from n=1 to n=3 while for 7 Aql the range spans from n=4 to n=7. Non-radial oscillations have to be present in both stars as well. The expected range of excited modes according to a non adiabatic analysis goes from n=1 to n=6 in both stars., Comment: 8 pages, 7 fugures, 5 tables, accepted for publication in Astronomical Journal

A comparison between the oscillation frequencies of six multi-periodic Delta Scuti stars of the Pleiades cluster and the eigenfrequencies of rotating stellar models that match the corresponding stellar parameters has been carried out. The assumption that all the stars considered have some common parameters, such as metallicity, distance or age, is imposed as a constraint. As a result, we have a best fit solution associated with a cluster metallicity of [Fe/H] ~ 0.067, an age between 70x10^6 and 100x10^6 yr and a distance modulus of mv-Mv=5.60-5.70 mag. All the stars were found to oscillate mainly in non-radial, low degree, low order p modes. Estimates of mass and rotation rates for each star are also obtained, Comment: 10 pages, 7 figures

We have obtained CCD photometry and medium-resolution spectroscopy of a number of δ Scuti and γ Doradus stars in the Kepler field-of-view as part of the ground-based observational efforts to support the Kepler space mission. In this work we present the preliminary results of these observations.

In the present work, we study correlations between stellar fundamental parameters and the oscillation amplitude for delta Scuti stars. We present this study for a sample of 17 selected delta Scuti stars belonging to 5 young open clusters. Taking advantage of properties of delta Scuti stars in clusters, we correct the photometric parameters of our objects for the effect of fast rotation. We confirm the benefit of applying such corrections in this kind of studies. In addition, the technique used for this correction allows us to obtain an estimation of stellar parameters like the angle of inclination and the rotation rate, usually not accessible. A significant correlation between the parameter i' (estimation of the angle of inclination of the star) and the oscillation amplitude is found. A discussion and interpretation of these a priori surprising results is proposed, in terms of a possible selection rule for oscillation modes of delta Scuti stars., 10 pages, 17 figures, article accepted by A&A

KIC10001893 is one out of 19 subdwarf-B (sdB) pulsators observed by the Kepler spacecraft in its primary mission. In addition to tens of pulsation frequencies in the g-mode domain, its Fourier spectrum shows three weak peaks at very low frequencies, which is too low to be explained in terms of g modes. The most convincing explanation is that we are seeing the orbital modulation of three Earth-size planets (or planetary remnants) in very tight orbits, which are illuminated by the strong stellar radiation. The orbital periods are P1=5.273, P2=7.807, and P3=19.48 hours, and the period ratios P2/P1=1.481 and P3/P2=2.495 are very close to the 3:2 and 5:2 resonances, respectively. One of the main pulsation modes of the star at 210.68 {\mu}Hz corresponds to the third harmonic of the orbital frequency of the inner planet, suggesting that we see, for the first time in an sdB star, g-mode pulsations tidally excited by a planetary companion. The extreme planetary system that emerges from the Kepler data is very similar to the recent discovery of two Earth-size planets orbiting the sdB pulsator KIC05807616 (Charpinet et al. 2011a)., Comment: 6 pages, 5 figures, accepted for publication in Astronomy and Astrophysics

Some results of the photometry multi-site observations of two δ Scuti stars, V624 Tau and HD 23194, are presented. The observations were carried out in the framework of a STEPHI network in 1999. We collected 343 hours of useful data and detected seven frequencies in V624 Tau and two frequencies in HD 23194.