Listar Ciencias Exactas y Naturales por tema "Accretion, accretion disks"

Mostrando ítems 1-12 de 12

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

      Koester, Detlev; Kepler, Souza Oliveira (2015) [Artículo de periódico]
      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 ...

    • 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) [Artículo de periódico]
      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 ...

    • Double-peaked profiles : ubiquitous signatures of disks in the broad emission lines of active galactic nuclei 

      Storchi-Bergmann, Thaisa; Schimoia, Jáderson da Silva; Peterson, Bradley M.; Elvis, Martin; Denney, Kelly D.; Eracleous, Michael; Nemmen, Rodrigo S. (2017) [Artículo de periódico]
      Broad (10,000 km s−1), double-peaked emission-line profiles of Balmer lines emitted by active galactic nuclei (AGN) are thought to originate in the outer parts of an accretion disk surrounding a nuclear supermassive black ...

    • Elliptical accretion disks in active galactc nuclei 

      Eracleous, Michael; Livio, Mario; Halpen, Jules P.; Storchi-Bergmann, Thaisa (1995) [Artículo de periódico]
      We present a calculation of the profiles of emission lines originating in a relativistic, eccentric disk, and show examples of the resulting model profiles. Our calculations are motivated by the fact that in about one­ ...

    • Evidence for a precessing accretion disk in the nucleus of NGC 1097 

      Storchi-Bergmann, Thaisa; Eracleous, Michael; Ruiz, Maria Teresa; Livio, Mario; Wilson, Andrew S.; Filippenko, Alexei V. (1997) [Artículo de periódico]
      We present new spectroscopic observations of the LINER (and now Seyfert 1) nucleus of NGC 1097, and discuss the evolution of its broad, double-peaked Balmer lines. When originally discovered in 1991, the red peak of the ...

    • Evidence of a starburst within 9 parsecs of the active nucleus of NGC 1097 

      Storchi-Bergmann, Thaisa; Nemmen, Rodrigo S.; Spinelli, Patrícia Figueiro; Eracleous, Michael; Wilson, Andrew S.; Filippenko, Alexei V.; Livio, Mario (2005) [Artículo de periódico]
      We report evidence of a recent burst of star formation located within 9 pc of the active nucleus of NGC 1097. The observational signatures of the starburst include UV absorption lines and continuum emission from young stars ...

    • Evolution of the nuclear accretion disk emission in NGC 1097 : getting closer to the black hole 

      Storchi-Bergmann, Thaisa; Nemmen, Rodrigo S.; Eracleous, Michael; Halpern, Jules P.; Wilson, Andrew S.; Filippenko, Alexei V.; Ruiz, Maria Teresa; Smith, Robert Christopher; Nagar, Neil M. (2003) [Artículo de periódico]
      We study the evolution of the broad, double-peaked H emission-line profile of the LINER/Seyfert 1 nucleus of NGC 1097, using 24 spectra obtained over a time span of 11 years—from 1991 November through 2002 October. While ...

    • Long-term profile variability in active galactic nucleus with double-peaked Balmer emission lines 

      Lewis, K.T.; Eracleous, Michael; Storchi-Bergmann, Thaisa (2010) [Artículo de periódico]
      An increasing number of active galactic nuclei (AGNs) exhibit broad, double-peaked Balmer emission lines, which represent some of the best evidence for the existence of relatively large-scale accretion disks in AGNs. A set ...

    • Radiatively inefficient accretion flow in the nucleus of NGC 1097 

      Nemmen, Rodrigo S.; Storchi-Bergmann, Thaisa; Yuan, Feng; Eracleous, Michael; Terashima, Yuichi; Wilson, Andrew S. (2006) [Artículo de periódico]
      We present a model for the accretion flow around the supermassive black hole in the LINER nucleus of NGC 1097 that fits the optical to X-ray spectral energy distribution (SED). The X-ray segment of the SED is based on ...

    • Short timescale monitoring of the X-ray, UV, and broad double-pead emission line of the nucleus of 1097 

      Schimoia, Jáderson da Silva; Storchi-Bergmann, Thaisa; Grupe, Dirk; Eracleous, Michael; Peterson, Bradley M.; Baldwin, Jack A.; Nemmen, Rodrigo S.; Winge, Claudia (2015) [Artículo de periódico]
      Recent studies have suggested that the short-timescale (<~ 7 days) variability of the broad (∼10,000 km s-ˡ) doublepeaked Hα profile of the LINER nucleus of NGC 1097 could be driven by a variable X-ray emission from a ...

    • Short timescale variations of the Hα double-peaked profile of the nucleus of NGC 1097 

      Schimoia, Jáderson da Silva; Storchi-Bergmann, Thaisa; Nemmen, Rodrigo S.; Winge, Claudia; Eracleous, Michael (2012) [Artículo de periódico]
      The broad (FWHM ∼ 10,000 km s-ˡ) double-peaked Hα profile from the LINER/Seyfert 1 nucleus of NGC 1097 was discovered in 1991 and monitored for the following 11 years. The profile showed variations attributed to the rotation ...

    • 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) [Artículo de periódico]
      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, ...