Browsing by Subject "stars: oscillations"

Now showing 1 - 6 of 6
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    Open Access
    HD 12098 -A new northern hemisphere roAp star
    (2001) Girish, V; Seetha, S; Martinez, P; Joshi, S; Ashoka, B N; Kurtz, D W; Chaubey, U S; Gupta, S K; Sagar, R
    We present the analysis of 65 hours of high speed photometric observations of HD 12098 taken from State Observatory, Naini Tal and Gurushikhar Observatory, Mt. Abu on sixteen nights spanning from November 1999 to November 2000. HD 12098 is the first rapidly oscillating Ap star discovered from the "Naini Tal-Cape survey for northern hemisphere roAp stars". It is the 32nd in the complete list. HD 12098 exhibits one predominant mode of oscillation at
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    Open Access
    Hubble Space Telescope and Optical Observations of Three Pulsating Accreting White Dwarfs in Cataclysmic Variables
    (2007) Szkody, Paula; Mukadam, Anjum; Gänsicke, Boris T; Woudt, Patrick A; Solheim, Jan‐Erik; Nitta, Atsuko; Sion, Edward M; Warner, Brian; Sahu, D K; Prabhu, T; Henden, Arne
    Ultraviolet observations using the Solar Blind Channel on the Hubble Space Telescope provide light curves and low-resolution spectra of three pulsating white dwarfs in the cataclysmic variables SDSS J013132.39-090122.3, SDSS J161033.64-010223.3, and SDSS J220553.98+115553.7. The UV light curves show enhanced pulsation amplitudes over those from simultaneous and previous optical photometry, while the UV-optical spectra are fit with white dwarf temperatures near 15,000 K. These temperatures place the accreting white dwarfs outside the instability zone for noninteracting DAV white dwarfs and show that the instability strip is complex for accreting white dwarfs
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    On the nature of the cool component of MWC 560
    (2007) Gromadzki, M; Mikołajewska, J; Whitelock, P A; Marang, F
    Context.MWC 560 (V694 Mon) is one of the most enigmatic symbiotic system with a very active accretion-powered hot component. Such activity can be supported only by a luminous asymptotic giant branch star, i.e. a Mira or SR variable, with a high mass-loss rate. It is also a very unusual jet source because the jet axis lies practically parallel to the line of sight. Aims. The aims of our study are the determination of the evolutionary status of the cool component of MWC 560. Methods. Our methods involve analysis of near-IR JHKL and optical light curves. Results. The cool component of MWC 560 pulsates with a period of ∼340 days, and it is probably a red SR variable on the thermally pulsing AGB. The high mass-loss rate expected for such a star is sufficient to power the observed activity of the hot companion.
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    Preparing the COROT space mission: Incidence and characterisation ofpulsation in the lower instability strip
    (2003) Poretti, E; Garrido, R; Amado, P J; Uytterhoeven, K; Handler, G; Alonso, R; Martin, S; Aerts, C; Catala, C; Goupil, M J; Michel, E; Mantegazza, L; Mathias, P; Pretorius, M L; Belmonte, J A; Claret, A; Rodríguez, E; Suarez, J C; Vuthela, F F; Weiss, W W; Ballereau, D; Bouret, J C; Charpinet, S; Hua, T; LYftinger, T; Nesvacil, N; Van\'t Veer-Menneret, C
    By pursuing the goal to find new variables in the COROT field-of-view we characterised a sample of stars located in the lower part of the instability strip. Our sample is composed of stars belonging to the disk population in the solar neighbourhood. We found that 23% of the stars display multiperiodic light variability up to a few mmag in amplitude, i.e., easily detectable on a single night of photometry.
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    Open Access
    The Naini Tal -Cape survey for pulsations in chemically peculiarA-type stars: I. Methods and preliminary results
    (2001) Martinez, P; Kurtz, D W; Ashoka, B N; Chaubey, U S; Girish, V; Gupta, S K; Joshi, S; Kasturirangan, K; Sagar, R; Seetha, S
    A new survey for pulsating, chemically peculiar A- and F-type stars in the northern hemisphere has been initiated using the 1-m telescope at Uttar Pradesh State Observatory in Naini Tal. The survey is primarily structured to reveal high-overtone pulsations in chemically peculiar A-F stars, but it is also revealing low-overtone
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    Open Access
    The Nainital-Cape Survey: IV. A search for pulsational variability in 108 chemically peculiar stars⋆
    (2016) Joshi, S; Martinez, P; Chowdhury, S; Chakradhari, N K; Joshi, Y C; van Heerden, P; Medupe, T; Kumar, Y B; Kuhn, R B
    Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution.