Now showing items 21-40 of 42

    • A refinement of the rotation period of the roap star hr 3831 and the discovery of a significant phase lag between the times of pulsation and magnetic extrema and the time of mean-light extremum 

      Kurtz, Donald W.; Kanaan Neto, Antonio Nemer; Martinez, Peter; Tripe, P. (1992) [Journal article]
      HR 3831 is a rapidly oscillating Ap star with a pulsational period of 11.67 min. The amplitude of this pulsation ranges from O to about 5 mmag as a function of the rotational aspect of the star. We use 268 hr of new ...
    • The discovery of a new DAV star using IUE temperature determination 

      Kanaan Neto, Antonio Nemer; Kepler, Souza Oliveira; Giovannini Junior, Odilon; Diaz, M.P. (1992) [Journal article]
      We report the discovery of a new ZZ Ceti star observed on the assumption that most DA stars with temperature near 11,000 K are pulsators and on a temperature determination using lUE data. Even though BPM 37093 had already ...
    • The everchanging pulsating white dwarf GD358 

      Kepler, Souza Oliveira; Nather, R. Edward; Winget, Donald Earl; Nitta, Atsuko; Kleinman, Scot James; Metcalfe, Travis S.; Sekiguchi, Kazuhiro; Jiang, Xiaojun; Sullivan, Denis J.; Sullivan, Terry; Janulis, Rimvydas; Meistas, Edmundas G.; Kalytis, Romualdas; Krzesinski, Jerzy; Ogloza, Waldemar; Zola, Staszek; O'Donoghue, Darragh; Romero-Colmenero, Encarni; Martinez, Peter; Dreizler, Stefan; Deetjen, Jochen L.; Nagel, Thorsten; Schuh, Sonja L.; Vauclair, Gérard; Fu, Jianning Ning; Chevreton, Michel; Solheim, Jan-Eric; Gonzalez Perez, Jose Miguel; Johannessen, F.; Kanaan Neto, Antonio Nemer; Costa, Jose Eduardo da Silveira; Costa, Alex Fabiano Murillo da; Wood, Matthew A.; Silvestri, Nicole M.; Ahrens, T.J.; Jones, Aaron Kyle; Collins, A.E.; Boyer, M.; Shaw, James Scott; Mukadam, Anjum Shagufta; Klumpe, Eric W.; Larrison, Jesse; Kawaler, Steven D.; Riddle, Reed L.; Ulla, Ana; Bradley, Paul A. (2003) [Journal article]
      We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent ...
    • The pulsation modes of the pre-white dwarf PG 1159-035 

      Costa, Jose Eduardo da Silveira; Kepler, Souza Oliveira; Winget, Donald Earl; O'Brien, M. Sean; Kawaler, Steven D.; Costa, Alex Fabiano Murillo da; Giovannini Junior, Odilon; Kanaan Neto, Antonio Nemer; Mukadam, Anjum Shagufta; Mullally, Fergal; Nitta, Atsuko; Provencal, Judith L.; Shipman, Harry L.; Wood, Matthew A.; Ahrens, T.J.; Grauer, Albert D.; Kilic, Mukremin; Bradley, Paul A.; Sekiguchi, Kazuhiro; Crowe, Richard A.; Jiang, Xiaojun; Sullivan, Denis J.; Sullivan, Terry; Rosen, Rachel; Clemens, J. Christopher; Janulis, Rimvydas; O'Donoghue, Darragh; Ogloza, Waldemar; Baran, Andrzej; Silvotti, Roberto; Marinoni, S.; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Dreizler, Stefan; Schuh, Sonja L.; Deetjen, Jochen L.; Nagel, Thorsten; Solheim, Jan-Eric; Gonzalez Perez, Jose Miguel; Ulla, Ana; Barstow, Martin A.; Burleigh, Matt; Good, Simon A.; Metcalfe, Travis S.; Kim, Seung-Lee; Lee, H.; Sergeev, A.; Akan, Mustafa Can; Cakirli, Ö; Paparo, Margit; Virághalmy, Géza; Ashoka, B.N.; Handler, Gerald; Hürkal, Özlem; Johannessen, F.; Kleinman, Scot James; Kalytis, Romualdas; Krzesinski, Jerzy; Klumpe, Eric W.; Larrison, Jesse; Lawrence, T.; Meistas, Edmundas G.; Martinez, Peter; Nather, R. Edward; Fu, Jianning Ning; Pakstiene, Erika; Rosen, R.; Romero-Colmenero, Encarni; Riddle, Reed L.; Seetha, S.; Silvestri, Nicole M.; Vuckovic, Maja; Warner, B.; Zola, Staszek; Althaus, Leandro Gabriel; Córsico, Alejandro Hugo; Montgomery, Michael Houston (2008) [Journal article]
      Context. PG 1159-035, a pre-white dwarf with Teff ~_140 000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data obtained ...
    • The pulsations of PG 1351+489 

      Redaelli, Maurício; Kepler, Souza Oliveira; Costa, Jose Eduardo da Silveira; Winget, Donald Earl; Handler, Gerald; Castanheira, Bárbara Garcia; Kanaan Neto, Antonio Nemer; Fraga, Luciano; Henrique, P.; Giovannini Junior, Odilon; Provencal, Judith L.; Shipman, Harry L.; Dalessio, J.; Thompson, S. E.; Mullally, Fergal; Brewer, M. M.; Childers, D.; Oksala, M. E.; Rosen, Rachel; Wood, Matthew A.; Reed, M. D.; Walter, B.; Strickland, Willie; Chandler, Dean W.; Watson, Todd K.; Nather, R. Edward; Montgomery, Michael Houston; Bischoff-Kim, Agnès; Hansen, Carl J.; Nitta, Atsuko; Kleinman, Scot James; Claver, C.F.; Brown, Tim; Sullivan, Denis J.; Kim, Seung-Lee; Chen, Wen-Ping; Yang, M.; Shih, Chia-You; Zhang, X; Jiang, Xiaojun; Fu, Jianning Ning; Seetha, S.; Ashoka, B.N.; Marar, T.M. Krishnan; Baliyan, Kiran S.; Vats, Hari Om; Chernyshev, A.V.; Ibbetson, Peter A.; Leibowitz, Elia M.; Hemar, Shirley; Sergeev, A.; Andreev, M.; Janulis, Rimvydas; Meistas, Edmundas G.; Moskalik, Pawel; Pajdosz, Gabriel; Baran, Andrzej; Winiarski, M.; Zola, Staszek; Ogloza, Waldemar; Siwak, Michal; Bognár, Zsófia; Solheim, Jan-Eric; Sefako, R.; Buckley, David A.H.; O'Donoghue, Darragh; Nagel, Thorsten; Silvotti, Roberto; Bruni, I.; Fremy, J. R.; Vauclair, Gérard; Chevreton, Michel; Dolez, Noël; Pfeiffer, Ben; Barstow, Martin A.; Creevey, o; Kawaler, Steven D.; Clemens, J. Christopher (2011) [Journal article]
      PG 1351+489 is one of the 20DBVs – pulsating helium-atmospherewhite dwarf stars – known and has the simplest power spectrum for this class of star, making it a good candidate to study cooling rates. We report accurate ...
    • The unusual helium variable AM Canum Venaticorum 

      Provencal, Judith L.; Winget, Donald Earl; Nather, R. Edward; Robinson, E.L.; Solheim, Jan-Eric; Clemens, J. Christopher; Bradley, Paul A.; Kleinman, Scot James; Kanaan Neto, Antonio Nemer; Claver, C.F.; Hansen, Carl J.; Marar, T.M. Krishnan; Seetha, S.; Ashoka, B.N.; Leibowitz, Elia M.; Meistas, Edmundas G.; Bruvold, A.; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Barstow, Martin A.; Sansom, A.E.; Tweedy, R.W.; Fontaine, Gilles; Bergeron, Pierre; Kepler, Souza Oliveira; Wood, Matthew A.; Grauer, Albert D. (1995) [Journal article]
      The unusual variable star AM CVn has puzzled astronomers for over 40 years. This object, both a photometric and spectroscopic variable, is believed to contain a pair of hydrogen-deficient white dwarfs of extreme mass ratio, ...
    • The ZZ Ceti red edge 

      Kanaan Neto, Antonio Nemer; Kepler, Souza Oliveira; Winget, Donald Earl (2002) [Journal article]
      With a time-series CCD photometric survey, we have demonstrated clearly that the observed red edge for the ZZ Ceti stars instability strip at 11 000 K is real, with the pulsation amplitude decreasing at least by a factor ...
    • Thirty-five new pulsating DA white dwarf stars 

      Mukadam, Anjum Shagufta; Mullally, Fergal; Nather, R. Edward; Winget, Donald Earl; Von Hippel, Theodore A.; Kleinman, Scot James; Nitta, Atsuko; Krzesinski, Jerzy; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Koester, Detlev; Sullivan, Denis J.; Homeier, Derek; Thompson, S. E.; Reaves, David Earl; Cotter, C.; Slaughter, D.; Brinkmann, Jon (2004) [Journal article]
      We present 35 new pulsating DA (hydrogen atmosphere) white dwarf stars discovered from the Sloan Digital Sky Survey (SDSS) and the Hamburg Quasar Survey (HQS). We have acquired high-speed time series photometry of preselected ...
    • Two new pulsating low-mass pre-white dwarfs or SX Phoenicis stars? 

      Corti, Mariela Alejandra; Kanaan Neto, Antonio Nemer; Córsico, Alejandro Hugo; Kepler, Souza Oliveira; Althaus, Leandro Gabriel; Koester, Detlev; Sánchez Arias, J. P. (2016) [Journal article]
      Context. The discovery of pulsations in low-mass stars opens an opportunity to probe their interiors and determine their evolution by employing the tools of asteroseismology. Aims. We aim to analyse high-speed photometry ...
    • Understanding the cool DA white dwarf pulsator G29-38 

      Kleinman, Scot James; Nather, R. Edward; Winget, Donald Earl; Clemens, J. Christopher; Bradley, Paul A.; Kanaan Neto, Antonio Nemer; Provencal, Judith L.; Claver, C.F.; Watson, Todd K.; Yanagida, K.; Nitta, Atsuko; Dixson, James S.; Wood, Matthew A.; Grauer, Albert D.; Hine, B.P.; Fontaine, Gilles; Liebert, James; Sullivan, Denis J.; Wickramasinghe, D.T.; Achilleos, Nicholas; Marar, T.M. Krishnan; Seetha, S.; Ashoka, B.N.; Meistas, Edmundas G.; Leibowitz, Elia M.; Moskalik, Pawel; Krzesinski, Jerzy; Solheim, Jan-Eric; Bruvold, A.; O'Donoghue, Darragh; Kurtz, Donald W.; Warner, B.; Martinez, Peter; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Barstow, Martin A.; Kepler, Souza Oliveira; Giovannini Junior, Odilon; Augusteijn, T.; Hansen, Carl J.; Kawaler, Steven D. (1998) [Journal article]
      The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical ...
    • A Whole Earth Telescope campaign on the pulsating subdwarf B binary system PG 1336-018 (NY Vir) 

      Kilkenny, Dave; Reed, M. D.; O'Donoghue, Darragh; Kawaler, Steven D.; Mukadam, Anjum Shagufta; Kleinman, Scot James; Nitta, Atsuko; Metcalfe, Travis S.; Provencal, Judith L.; Watson, Todd K.; Sullivan, Denis J.; Sullivan, Terry; Shobbrook, Robert R.; Jiang, Xiaojun; Joshi, Santosh; Ashoka, B.N.; Seetha, S.; Leibowitz, Elia M.; Ibbetson, Peter A.; Mendelson, Haim; Meistas, Edmundas G.; Kalytis, Romualdas; Alisauskas, Darius; Martinez, Peter; Van Wyk, Francois; Stobie, Robert S.; Marang, Fred; Zola, Staszek; Krzesinski, Jerzy; Ogloza, Waldemar; Moskalik, Pawel; Silvotti, Roberto; Piccioni, Adalberto; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Dreizler, Stefan; Schuh, Sonja L.; Deetjen, Jochen L.; Solheim, Jan-Eric; Gonzalez Perez, Jose Miguel; Ulla, Ana; Ostensen, Roy; Manteiga, Minia; Suarez, Olga; Burleigh, Matt; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Giovannini Junior, Odilon (2003) [Journal article]
      We present results from a multisite (‘Whole Earth Telescope’) photometric campaign on PG 1336−018, the close eclipsing binary system containing a pulsating subdwarf B (sdB) star. The main part of the campaign (1999 April) ...
    • Whole earth telescope observations and seismological analysis of the cool zz ceti star gd 154 

      Pfeiffer, Ben; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Fremy, J. R.; Barstow, Martin A.; Belmonte, J.A.; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Giovannini Junior, Odilon; Fontaine, Gilles; Bergeron, Pierre; Wesemael, F.; Grauer, Albert D.; Nather, R. Edward; Winget, Donald Earl; Provencal, Judith L.; Clemens, J. Christopher; Bradley, Paul A.; Dixson, James S.; Kleinman, Scot James; Watson, Todd K.; Claver, C.F.; Matzeh, Tsevi; Leibowitz, Elia M.; Moskalik, Pawel (1996) [Journal article]
      This paper presents the results of high speed photometric observations of the cool variable DA white dwarf (DAV) GD 154 obtained with the Whole Earth Telescope. GD 154 is one of the coolest pulsating DA white dwarfs and ...
    • Whole Earth Telescope observations and seismological analysis of the pre-white dwarf pg 2131+066 

      Kawaler, Steven D.; O'Brien, M. Sean; Clemens, J. Christopher; Nather, R. Edward; Winget, Donald Earl; Watson, Todd K.; Yanagida, K.; Dixson, James S.; Bradley, Paul A.; Wood, Matthew A.; Sullivan, Denis J.; Kleinman, Scot James; Meistas, Edmundas G.; Leibowitz, Elia M.; Moskalik, Pawel; Zola, Staszek; Pajdosz, Y.; Krzesinski, Jerzy; Solheim, Jan-Eric; Bruvold, A.; O'Donoghue, Darragh; Katz, M.; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Barstow, Martin A.; Kanaan Neto, Antonio Nemer; Kepler, Souza Oliveira; Giovannini Junior, Odilon; Provencal, Judith L.; Hansen, Carl J. (1995) [Journal article]
      As transition objects between the asymptotic giant branch (AGB) and cooling white dwarfs, the PG 1159 stars are key objects for understanding the late stages of stellar evolution. The pulsations exhibited by many members ...
    • Whole earth telescope observations of am canum venaticorum-discoseismology at last 

      Solheim, Jan-Eric; Provencal, Judith L.; Bradley, Paul A.; Vauclair, Gérard; Barstow, Martin A.; Kepler, Souza Oliveira; Fontaine, Gilles; Graver, A.D.; Winget, Donald Earl; Marar, T.M. Krishnan; Leibowitz, Elia M.; Enanvelsen, P.I.; Chevreton, Michel; Dolez, Noël; Kanaan Neto, Antonio Nemer; Bergeron, Pierre; Claver, C.F.; Clemens, J. Christopher; Kleinman, Scot James; Hine, B.P.; Seetha, S.; Shoka, B.N.; Mazeh, Tsevi; Sansom, A.E.; Tweedy, P.W.; Meistas, Edmundas G.; Bruvold, A.; Massacand, C.N. (1998) [Journal article]
      We report the results of 143.2 hours of time-series photometry over a 12 day period for AM CVn (= HZ 29) as part of the Whole Earth Telescope (WET) project.ˡ This star is believed to be an ultra-short period cataclysmic ...
    • Whole Earth Telescope observations of BPM 37093 : a seismological test of crystallization theory in white dwarfs 

      Kanaan Neto, Antonio Nemer; Nitta, Atsuko; Winget, Donald Earl; Kepler, Souza Oliveira; Montgomery, Michael Houston; Metcalfe, Travis S.; Oliveira, H.; Fraga, Luciano; Costa, Alex Fabiano Murillo da; Costa, Jose Eduardo da Silveira; Castanheira, Bárbara Garcia; Giovannini Junior, Odilon; Nather, R. Edward; Mukadam, Anjum Shagufta; Kawaler, Steven D.; O'Brien, M. Sean; Reed, M. D.; Kleinman, Scot James; Provencal, Judith L.; Watson, Todd K.; Kilkenny, Dave; Sullivan, Denis J.; Sullivan, Terry; Shobbrook, Bob; Jiang, Xiaojun; Ashoka, B.N.; Seetha, S.; Leibowitz, Elia M.; Ibbetson, Peter A.; Mendelson, Haim; Meistas, Edmundas G.; Kalytis, Romualdas; Alisauskas, Darius; O'Donoghue, Darragh; Buckley, David A.H.; Martinez, Peter; Van Wyk, Francois; Stobie, Robert S.; Marang, Fred; Van Zyl, L.; Ogloza, Waldemar; Krzesinski, Jerzy; Zola, Staszek; Moskalik, Pawel; Breger, M.; Stankov, A.; Silvotti, Roberto; Piccioni, Adalberto; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Deetjen, Jochen L.; Dreizler, Stefan; Schuh, Sonja L.; Gonzalez Perez, Jose Miguel; Ostensen, Roy; Ulla, Ana; Manteiga, Minia; Suarez, Olga; Burleigh, Matt; Barstow, Martin A. (2005) [Journal article]
      BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 Mʘ) to theoretically crystallize while still inside the ZZ Ceti instability strip (Teff ~ 12 000 K). As a consequence, ...
    • Whole Earth Telescope observations of the DAV white dwarf G226-29 

      Kepler, Souza Oliveira; Giovannini Junior, Odilon; Wood, Matthew A.; Nather, R. Edward; Winget, Donald Earl; Kanaan Neto, Antonio Nemer; Kleinman, Scot James; Bradley, Paul A.; Provencal, Judith L.; Clemens, J. Christopher; Claver, C.F.; Watson, Todd K.; Yanagida, K.; Krisciunas, K.; Marar, T.M. Krishnan; Seetha, S.; Ashoka, B.N.; Leibowitz, Elia M.; Mendelson, Haim; Mazeh, Tsevi; Moskalik, Pawel; Krzesinski, Jerzy; Pajdosz, Y.; Zola, Staszek; Solheim, Jan-Eric; Emanuelsen, P.-I.; Dolez, Noël; Vauclair, Gérard; Chevreton, Michel; Fremy, J. R.; Barstow, Martin A.; Sansom, A.E.; Tweedy, R.W.; Wickramasinghe, D.T.; Ferrario, Lilia; Sullivan, Denis J.; Peet, A.J. van der; Buckley, David A.H.; Chen, A.-L. (1995) [Journal article]
      We observed G226-29 for 121 hr in 1992 February and confirm the presence of the three previously identified frequencies close to 109 s. We find no evidence of other pulsation periods down to our noise level of about 0.35 ...
    • Whole Earth Telescope observations of the DBV white dwarf GD 358 

      Winget, Donald Earl; Nather, R. Edward; Clemens, J. Christopher; Provencal, Judith L.; Kleinman, Scot James; Bradley, Paul A.; Claver, C.F.; Dixson, James S.; Montgomery, Michael Houston; Hansen, Carl J.; Hine, B.P.; Birch, P.; Candy, M.; Marar, T.M. Krishnan; Seetha, S.; Ashoka, B.N.; Leibowitz, Elia M.; O'Donoghue, Darragh; Warner, B.; Buckley, David A.H.; Tripe, P.; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Serre, T.; Garrido, R.; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Augusteijn, T.; Wood, Matthew A.; Bergeron, Pierre; Grauer, Albert D. (1994) [Journal article]
      We report on the analysis of 154 hours of early continuous high-speed photometry on the pulsating DB white dwarf (DBV) GD 358, obtained during the Whole Earth Telescope (WET) run of 1990 May. The power spectrum of the light ...
    • Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058−5234 

      Sullivan, Denis J.; Metcalfe, Travis S.; O'Donoghue, Darragh; Winget, Donald Earl; Kilkenny, Dave; Van Wyk, Francois; Kanaan Neto, Antonio Nemer; Kepler, Souza Oliveira; Nitta, Atsuko; Kawaler, Steven D.; Montgomery, Michael Houston; Nather, R. Edward; O'Brien, M. Sean; Bischoff-Kim, Agnès; Wood, Matthew A.; Jiang, Xiaojun; Leibowitz, Elia M.; Ibbetson, Peter A.; Zola, Staszek; Krzesinski, Jerzy; Pajdosz, Gabriel; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel (2008) [Journal article]
      We present the analysis of a total of 177 h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058−5234. The bulk of the observations (135 h) were obtained during a WET ...
    • Whole earth telescope observations of the interacting binary white dwarf v803 cen in its low state 

      O'Donoghue, Darragh; Wargau, W.; Warner, B.; Kilkenny, Dave; Martinez, Peter; Kanaan Neto, Antonio Nemer; Kepler, Souza Oliveira; Henry, G.W.; Winget, Donald Earl; Clemens, J. Christopher; Grauer, Albert D. (1990) [Journal article]
      Using a network of observatories in the southern hemisphere, high-speed photometry of the interacting binary white dwarf (IBWD) V803 Cen in its low state is presented. Because of the faintness of the system, the 1611-s ...
    • Whole earth telescope observations of the pulsating hot white dwarf PG 1707+427 

      Kawaler, Steven D.; Potter, E. M.; Vuckovic, Maja; O'Toole, Simon; Clemens, J. Christopher; O'Brien, M. Sean; Grauer, Albert D.; Nather, R. Edward; Moskalik, Pawel; Fontaine, Gilles; Wesemael, F.; Bergeron, Pierre; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Kleinman, Scot James; Watson, Todd K.; Barstow, Martin A.; Dind, Z. E.; Sansom, A.E.; Winget, Donald Earl; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Bradley, Paul A.; Dixson, James S.; Provencal, Judith L.; Bedding, T. R. (2004) [Journal article]
      We report on the analysis of multisite time-series photometry of the pulsating pre-white dwarf (GW Vir star) PG 1707+427, obtained by the Whole Earth Telescope collaboration. This is the last of the known GW Vir stars ...