Browsing Exact and Earth Sciences by Subject "White dwarfs"

Now showing items 1-20 of 95

    • 2006 Whole Earth Telescope observations of GD358 : a new look at the prototype DBV 

      Provencal, Judith L.; Montgomery, Michael Houston; Kanaan Neto, Antonio Nemer; Shipman, Harry L.; Childers, D.; Baran, Andrzej; Kepler, Souza Oliveira; Reed, M. D.; Zhou, Ai-Ying; Eggen, J.; Watson, Todd K.; Winget, Donald Earl; Thompson, S. E.; Riaz, B.; Nitta, Atsuko; Kleinman, Scot James; Crowe, Richard A.; Slivkoff, Jay; Sherard, P.; Purves, Norman G.; Binder, Philippe M.; Knight, R.; Kim, Seung-Lee; Chen, Wen-Ping; Yang, M.; Lin, Hung-Chin; Lin, Chien-Cheng; Chen, C.-W.; Jiang, Xiaojun; Sergeev, A.; Mkrtichian, David; Andreev, M.; Janulis, Rimvydas; Siwak, Michal; Zola, Staszek; Koziel-Wierzbowska, Dorota; Stachowski, G.; Paparo, Margit; Bognár, Zsófia; Handler, Gerald; Lorenz, Denise; Steininger, Bruno; Beck, Paul; Nagel, Thorsten; Kusterer, D.; Hoffman, A.; Reiff, E.; Kowalski, R.; Vauclair, Gérard; Charpinet, Stéphane; Chevreton, Michel; Solheim, Jan-Eric; Pakstiene, Erika; Fraga, Luciano; Dalessio, J. (2009) [Journal article]
      We report on the analysis of 436.1 hr of nearly continuous high-speed photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth Telescope (WET) during the 2006 international observing run, designated ...

    • About the existence of warm H-rich pulsating white dwarfs 

      Althaus, Leandro Gabriel; Córsico, Alejandro Hugo; Uzundag, Murat; Vuckovic, Maja; Baran, Andrzej; Bell, Keaton; Camisassa, María E.; Calcaferro, Leila Magdalena; De Gerónimo, Francisco Cesar; Kepler, Souza Oliveira; Silvotti, Roberto (2020) [Journal article]
      Context. The possible existence of warm (Teff ∼ 19 000 K) pulsating DA white dwarf (WD) stars, hotter than ZZ Ceti stars, was predicted in theoretical studies more than 30 yr ago. These studies reported the occurrence of ...

    • Analysis of cool DO-type white dwarfs from the Sloan Digital Sky Survey data release 10 

      Reindl, Nicole; Rauch, Thomas; Werner, Klaus; Kepler, Souza Oliveira; Gänsicke, Boris; Fusillo, Nicola Pietro Gentile (2014) [Journal article]
      We report on the identification of 22 new cool DO-type white dwarfs (WDs) detected in data release 10 (DR10) of the Sloan Digital Sky Survey (SDSS). Among them, we found one more member of the so-called hot-wind DO WDs, ...

    • An empirical test of the theory of crystallization in stellar interiors 

      Winget, Donald Earl; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Montgomery, Michael Houston; Giovannini Junior, Odilon (1997) [Journal article]
      Our theoretical calculations indicate that the massive pulsating DA white dwarf, BPM 37093, has a crystallized ion interior. Our estimates for the crystallized mass fraction depend on our assumption for the interior ...

    • An observational limit to the evolutionary time scale of the 13,000 K white dwarf G117-B15A 

      Kepler, Souza Oliveira; Vauclair, Gérard; Dolez, Noël; Chevreton, Michel; Barstow, Martin A.; Nather, R. Edward; Winget, Donald Earl; Provencal, Judith L.; Clemens, J. Christopher; Fontaine, Gilles (1990) [Journal article]
      Nature has provided us with a way of measuring the evolutionary time scale of some stars through aster­ oseismology, i.e., the study of stellar interiors through their intrinsic variations in brightness. By measuring the ...

    • Asteroseismological study of massive ZZ Ceti stars with fully evolutionary models 

      Romero, Alejandra Daniela; Kepler, Souza Oliveira; Córsico, Alejandro Hugo; Althaus, Leandro Gabriel; Fraga, Luciano (2013) [Journal article]
      We present the first asteroseismological study for 42 massive ZZ Ceti stars based on a large set of fully evolutionary carbon–oxygen core DA white dwarf models characterized by a detailed and consistent chemical inner ...

    • Asteroseismology of PG 1541 + 651 and BPM 31594 with TESS 

      Romero, Alejandra Daniela; Rosa, Gabriela Oliveira da; Kepler, Souza Oliveira; Bradley, Paul A.; Uzundag, Murat; Bell, Keaton; Hermes, James J.; Ramos, Gabriel Lauffer (2023) [Journal article]
      We present the photometric data from TESS for two known ZZ Ceti stars, PG 1541 + 651 and BPM 31594. Before TESS, both objects only had observations from short runs from ground-based facilities, with three and one period ...

    • Asteroseismology of ZZ Ceti stars with full evolutionary white dwarf models : II. The impact of AGB thermal pulses on the asteroseismic inferences of ZZ Ceti stars 

      De Gerónimo, Francisco Cesar; Althaus, Leandro Gabriel; Córsico, Alejandro Hugo; Romero, Alejandra Daniela; Kepler, Souza Oliveira (2018) [Journal article]
      Context. The thermally pulsing phase on the asymptotic giant branch (TP-AGB) is the last nuclear burning phase experienced by most low- and intermediate-mass stars. During this phase, the outer chemical stratification above ...

    • Asteroseismology of ZZ Ceti stars with fully evolutionary white dwarf models : I. the impact of the uncertainties from prior evolution on the period spectrum 

      De Gerónimo, Francisco Cesar; Althaus, Leandro Gabriel; Córsico, Alejandro Hugo; Romero, Alejandra Daniela; Kepler, Souza Oliveira (2017) [Journal article]
      Context. ZZ Ceti stars are pulsating white dwarfs with a carbon-oxygen core build up during the core helium burning and thermally pulsing Asymptotic Giant Branch phases. Through the interpretation of their pulsation periods ...

    • Bpm 24754 : a new southern zz ceti star 

      Giovannini Junior, Odilon; Kepler, Souza Oliveira; Kanaan Neto, Antonio Nemer; Costa, A.F.M.; Koester, Detlev (1998) [Journal article]
      We report the discovery of a new long{period ZZ Ceti star through the analysis of photometric time series gathered on 7 nights between 1995 and 1996. The light curve displays a periodic variation with a period of ~ 18 min ...

    • A comparative analysis of the observed white dwarf cooling sequence from globular clusters 

      Campos, Fabíola; Bergeron, Pierre; Romero, Alejandra Daniela; Kepler, Souza Oliveira; Ourique, Gustavo; Costa, Jose Eduardo da Silveira; Bonatto, Charles Jose; Winget, Donald Earl; Montgomery, Michael Houston; Pacheco, Thayse Adineia; Bedin, Luigi R. (2016) [Journal article]
      We report our study of features at the observed red end of the white dwarf cooling sequences for three Galactic globular clusters: NGC 6397, 47 Tucanae and M 4. We use deep colour– magnitude diagrams constructed from ...

    • Comparing the asteroseismic properties of pulsating pre-extremely low mass white dwarf and δ Scuti stars 

      Sánchez Arias, J. P.; Romero, Alejandra Daniela; Córsico, Alejandro Hugo; Pelisoli, Ingrid Domingos; Antoci, Victoria L.; Kepler, Souza Oliveira; Althaus, Leandro Gabriel; Corti, Mariela Alejandra (2018) [Journal article]
      Context. Pulsating extremely low-mass pre-white dwarf stars (pre-ELMV), with masses between ~0.15 M⊙ and ~0.30 M⊙, constitute a new class of variable stars showing g- and possibly p-mode pulsations with periods between 320 ...

    • Constraining the evolution of ZZ Ceti 

      Mukadam, Anjum Shagufta; Kepler, Souza Oliveira; Winget, Donald Earl; Nather, R. Edward; Kilic, Mukremin; Mullally, Fergal; Von Hippel, Theodore A.; Kleinman, Scot James; Nitta, Atsuko; Guzik, Joyce Ann; Bradley, Paul A.; Matthews, Jaymie M.; Sekiguchi, Kazuhiro; Sullivan, Denis J.; Sullivan, Terry; Shobbrook, Robert R.; Birch, P.; Jiang, Xiaojun; Xu, D.W.; Joshi, Santosh; Ashoka, B.N.; Ibbetson, Peter A.; Leibowitz, Elia M.; Ofek, Eran O.; Meistas, Edmundas G.; Janulis, Rimvydas; Alisauskas, Darius; Kalytis, Romualdas; Handler, Gerald; Kilkenny, Dave; O'Donoghue, Darragh; Kurtz, Donald W.; Muller, M.; Moskalik, Pawel; Ogloza, Waldemar; Zola, Staszek; Krzesinski, Jerzy; Johannessen, F.; Gonzalez Perez, Jose Miguel; Solheim, Jan-Eric; Silvotti, Roberto; Bernabei, S.; Vauclair, Gérard; Dolez, Noël; Fu, Jianning Ning; Chevreton, Michel; Manteiga, Minia; Suarez, Olga; Ulla, Ana; Cunha, Margarida S.; Metcalfe, Travis S.; Kanaan Neto, Antonio Nemer; Fraga, Luciano; Costa, Alex Fabiano Murillo da; Giovannini Junior, Odilon; Fontaine, Gilles; Bergeron, Pierre; O'Brien, M. Sean; Sanwal, Divas; Wood, Matthew A.; Ahrens, T.J.; Silvestri, Nicole M.; Klumpe, Eric W.; Kawaler, Steven D.; Riddle, Reed L.; Reed, M. D.; Watson, Todd K. (2003) [Journal article]
      We report our analysis of the stability of pulsation periods in the DAV star (pulsating hydrogen atmosphere white dwarf ) ZZ Ceti, also called R548. On the basis of observations that span 31 years, we conclude that the ...

    • Convection and rotation boosted prescription of magnetic braking application to the formation of extremely low-mass white dwarfs 

      Soethe, Leonardo Taynô Tosetto; Kepler, Souza Oliveira (2021) [Journal article]
      Extremely low-mass white dwarfs (ELM WDs) are the result of binary evolution in which a low-mass donor star is stripped by its companion leaving behind a helium-core white dwarf (WD). We explore the formation of ELM WDs ...

    • DB white dwarfs in the Sloan Digital Sky Survey data release 10 and 12 

      Koester, Detlev; Kepler, Souza Oliveira (2015) [Journal article]
      Aims. White dwarfs with helium-dominated atmospheres (spectral types DO, DB) comprise approximately 20% of all white dwarfs. There are fewer studies than of their hydrogen-rich counterparts (DA) and thus several questions ...

    • Direct measurement of a secular pulsation period change in the pulsating hot pre-white dwarf PG 1159-035 

      Costa, Jose Eduardo da Silveira; Kepler, Souza Oliveira; Winget, Donald Earl (1999) [Journal article]
      GW Vir (PG 1159[035) is the prototype of the class of multiperiodic, nonradially pulsating hot white dwarfs, and shows a strong pulsation mode at 516 s. All measurements to date of the secular variation of the 516 s pulsation ...

    • Discovery of a new AM CVn system with the Kepler satellite 

      Fontaine, Gilles; Brassard, P.; Green, Elisabeth M.; Charpinet, Stéphane; Dufour, Patrick; Hubeny, Ivan; Steeghs, Danny; Aerts, Conny; Randall, S. K.; Bergeron, Pierre; Guvenen, B.; O'Malley, C. J.; Van Grootel, Valérie; Ostensen, Roy; Bloemen, Steven; Silvotti, Roberto; Howell, Steve; Baran, Andrzej; Kepler, Souza Oliveira; Marsh, Tom; Montgomery, Michael Houston; Oreiro, Raquel; Provencal, Judith L.; Telting, John; Winget, Donald Earl; Zima, Wolfgang; Christensen-Dalsgaard, Jorgen; Kjeldsen, Hans (2011) [Journal article]
      We report the discovery of a new AM CVn system on the basis of broadband photometry obtained with the Kepler satellite supplemented by ground-based optical spectroscopy. Initially retained on Kepler target lists as a ...

    • Discovery of a new PG 1159 (GW Vir) pulsator 

      Kepler, Souza Oliveira; Fraga, Luciano; Winget, Donald Earl; Bell, Keaton; Córsico, Alejandro Hugo; Werner, Klaus (2014) [Journal article]
      We report the discovery of pulsations in the spectroscopic PG 1159 type pre-white dwarf SDSS J075415.12 + 085232.18. Analysis of the spectrum by Werner et al. indicated Teff = 120 000 ± 10 000 K, log g = 7.0 ± 0.3, mass ...

    • Discovery of an ultramassive pulsating white dwarf 

      Hermes, James J.; Kepler, Souza Oliveira; Castanheira, Bárbara Garcia; Gianninas, Alexandros; Winget, Donald Earl; Montgomery, Michael Houston; Brown, Warren R.; Harrold, Samuel T. (2013) [Journal article]
      We announce the discovery of themostmassive pulsating hydrogen-atmosphere white dwarf (WD) ever discovered, GD 518. Model atmosphere fits to the optical spectrum of this star show it is a 12,030 ± 210 K WD with a log g = ...

    • Discovery of five new massive pulsating white dwarf stars 

      Castanheira, Bárbara Garcia; Kepler, Souza Oliveira; Kleinman, Scot James; Nitta, Atsuko; Fraga, Luciano (2013) [Journal article]
      Using the SOuthern Astrophysical Research telescope (SOAR) Optical Imager at the SOAR 4.1 m telescope, we report on the discovery of five new massive pulsating white dwarf stars. Our results represent an increase of about ...