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Tisdall P.,University College Dublin | Hanlon L.,University College Dublin | Murphy D.,University College Dublin | Topinka M.,University College Dublin | And 6 more authors.
Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias | Year: 2014

We report on a gamma-ray blazar optical monitoring programme that is underway that can provide both short-term and long-term optical variability data for key southern hemisphere sources. Ten sources are being monitored in this programme, with a focus on PKS 2155-304 and PKS 2005-489 during the austral winter of 2013. Both sources were monitored with 3 filters (V, R and I) and over 20,000 images were taken over a period of 5 months. Preliminary analysis of some of this data indicates no major flaring episodes in the optical band. Source


Semaan T.,University Paris Diderot | Martayan C.,University Paris Diderot | Fremat Y.,University Paris Diderot | Hubert A.-M.,University Paris Diderot | And 4 more authors.
Proceedings of the International Astronomical Union | Year: 2010

First we investigate the spectral and photometric properties (colours, magnitudes)of a sample of faint Be stars observed in the first exoplanet fields of CoRoT (IR1, LRA1 and LRC1). We determine the fundamental parameters by fitting ESO-FLAMES/GIRAFFE spectra with synthetic models taking account for non-LTE effects. After that we correct these parameters from fast rotation effects. We also study the location of each star in the (logL vs logT) HR diagram. Second we start to analyse the CoRoT light curves to investigate further the possible correlation between the pulsating properties and the fundamental parameters of the stars. © International Astronomical Union 2011. Source


Beck P.G.,Catholic University of Leuven | Kambe E.,Okayama Astrophysical Observatory | Hillen M.,Catholic University of Leuven | Corsaro E.,Catholic University of Leuven | And 36 more authors.
Astronomy and Astrophysics | Year: 2015

Context. Red giants are evolved stars that exhibit solar-like oscillations. Although a multitude of stars have been observed with space telescopes, only a handful of red giant stars were targets of spectroscopic asteroseismic observing projects. Aims. We search for solar-like oscillations in the two bright red giant stars γ Psc and θ1 Tau from a time series of ground-based spectroscopy and determine the frequency of the excess of oscillation power νmax and the mean large frequency separation Δν for both stars. Seismic constraints on the stellar mass and radius will provide robust input for stellar modelling. Methods. The radial velocities of γ Psc and θ1 Tau were monitored for 120 and 190 days, respectively. Nearly 9000 spectra were obtained. To reach accurate radial velocities, we used simultaneous thorium-argon and iodine-cell calibration of our optical spectra. In addition to the spectroscopy, we acquired interferometric observations of γ Psc for an independent estimate of the radius. We also analysed 22 days of observations of θ1 Tau with the MOST satellite. Results. The frequency analysis of the radial velocity data of γ Psc revealed an excess of oscillation power around 32 μHz and a large frequency separation of 4.1 ± 0.1 μHz. θ1 Tau exhibits oscillation power around 90 μHz, with a large frequency separation of 6. 9 ± 0.2 μHz. Scaling relations indicate that γ Psc is a star of about 1 M⊙ and 10 R⊙. The object θ1 Tau appears to be a massive star of about 2.7 M⊙ and 10 R⊙. The radial velocities of both stars were found to be modulated on timescales much longer than the oscillation periods. Conclusions. The estimated radii from seismology are in agreement with interferometric observations and also with estimates based on photometric data. While the mass of θ1 Tau is in agreement with results from dynamical parallaxes, we find a lower mass for γ Psc than is found in the literature. The long periodic variability agrees with the expected timescales of rotational modulation. © ESO 2015. Source


Frew D.J.,Macquarie University | Stanger J.,Sydney Girls High School | Fitzgerald M.,Macquarie University | Parker Q.,Macquarie University | And 16 more authors.
Publications of the Astronomical Society of Australia | Year: 2011

We present new imaging data and archival multiwavelength observations of the little-studied emission nebula K 1-6 and its central star. Narrow-band images in Hα (+[N II]) and [O III] taken with the Faulkes Telescope North reveal a stratified, asymmetric, elliptical nebula surrounding a central star which has the colours of a late G or early K-type subgiant or giant. GALEX ultraviolet images reveal a very hot subdwarf or white dwarf coincident in position with this star. The cooler, optically dominant star is strongly variable with a period of 21.312±0.008 days, and is possibly a high-amplitude member of the RS CVn class, although an FK Com classification is also possible. Archival ROSAT data provide good evidence that the cool star has an active corona. We conclude that K 1-6 is most likely an old bona fide planetary nebula at a distance of ∼1.0kpc, interacting with the interstellar medium, and containing a binary or ternary central star. The observations and data analyses reported in this paper were conducted in conjunction with Year 11 high school students as part of an Australian Research Council Linkage Grant science education project, denoted Space To Grow, conducted jointly by professional astronomers, educational researchers, teachers, and high-school students. © Astronomical Society of Australia 2011. Source


Ripa J.,Sungkyunkwan University | Ahmad S.,University Paris - Sud | Barrillon P.,University Paris - Sud | Brandt S.,Technical University of Denmark | And 37 more authors.
EAS Publications Series | Year: 2013

The Ultra-Fast Flash Observatory (UFFO), which will be launched onboard the Lomonosov spacecraft, contains two crucial instruments: UFFO Burst Alert & Trigger Telescope (UBAT) for detection and localization of Gamma-Ray Bursts (GRBs) and the fast-response Slewing Mirror Telescope (SMT) designed for the observation of the prompt optical/UV counterparts. Here we discuss the in-space calibrations of the UBAT detector and SMT telescope. After the launch, the observations of the standard X-ray sources such as pulsar in Crab nebula will provide data for necessary calibrations of UBAT. Several standard stars will be used for the photometric calibration of SMT. The celestial X-ray sources, e.g. X-ray binaries with bright optical sources in their close angular vicinity will serve for the cross-calibration of UBAT and SMT. © EAS, EDP Sciences 2013. Source

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