Navegação por Autor "Koester, Detlev"
Resultados 1-20 de 33
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Analysis of IUE spectra of helium-rich white dwarf stars
(2006) [Artigo de periódico]We studied the class of DB white dwarf stars, using re-calibrated UV spectra for thirty four DBs obtained with the IUE satellite. By comparing the observed energy distributions with model atmospheres, we simultaneously ... -
Bpm 24754 : a new southern zz ceti star
(1998) [Artigo de periódico]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 ... -
DB white dwarfs in the Sloan Digital Sky Survey data release 10 and 12
(2015) [Artigo 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 74 new bright ZZ Ceti stars in the first three years of TESS
(2022) [Artigo de periódico]We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from the data obtained by the Transiting Exoplanet Survey Satellite mission, from Sectors 1 to 39, corresponding to the first 3 cycles. This ... -
Discovery of eleven new ZZ Ceti stars
(2006) [Artigo de periódico]We report the discovery of eleven new ZZ Cetis using telescopes at OPD (Observatório do Pico dos Dias/LNA) in Brazil, the 4.1 m SOAR (Southern Astrophysical Research) telescope at Cerro Pachon, Chile, and the 2.1 m Otto ... -
Discovery of seven ZZ Ceti stars using a new photometric selection method
(2006) [Artigo de periódico]We report the detection of non-radial g-mode oscillations in seven relatively bright (14.4 < B < 16.5) DA white dwarf stars from time-series photometry collected at the Nordic Optical Telescope (NOT) at Roque de Los Muchachos ... -
Evidence for temperature change and oblique pulsation from light curve fits of the pulsating white dwarf GD 358
(2010) [Artigo de periódico]Convective driving, the mechanism originally proposed by Brickhill for pulsating white dwarf stars, has gained general acceptance as the generic linear instability mechanism in DAV and DBV white dwarfs. This physical ... -
Evidence of spectral evolution on the white dwarf sample from the Gaia mission
(2020) [Artigo de periódico]Since the Gaia data release 2, several works have been published describing a bifurcation in the observed white dwarf colour−magnitude diagram for GBP−GRP>0. Some possible explanations in the literature include the existence ... -
Gemini spectra of 12 000 k white dwarf stars
(2006) [Artigo de periódico]We report signal-to-noise ratio (S/N) - ~100 optical spectra for four DA white dwarf stars acquired with the GMOS spectrograph of the 8-m Gemini north telescope. These stars have 18 < g < 19 and are around Teff ~ 12 000 ... -
Ground-based observation of ZZ Ceti stars and the discovery of four new variables
(2019) [Artigo de periódico]We perform ground-based photometric observations of 22 DA white dwarf stars, 10 already known ZZ Cetis and 12 candidates with atmospheric parameters inside the classical instability strip. We report on the discovery of ... -
HST observations of the pulsating white dwarf GD 358
(2005) [Artigo de periódico]We used time-resolved ultraviolet spectroscopy obtained with the FOS and STIS spectrographs of the Hubble Space Telescope (HST), together with archival IUE observations to measure the effective temperature (Teff), surface ... -
Magnetic white dwarfs in the SDSS and estimating the mean mass of normal DA and DB WDs
(2010) [Trabalho completo publicado em evento] -
Magnetic white dwarf stars in the Sloan Digital Sky Survey
(2013) [Artigo de periódico]To obtain better statistics on the occurrence of magnetism among white dwarfs, we searched the spectra of the hydrogen atmosphere white dwarf stars (DAs) in the Data Release 7 of the Sloan Digital Sky Survey (SDSS) for ... -
Mode identification of pulsating white dwarfs using the Hubble Space Telescope
(2000) [Artigo de periódico]We have obtained time-resolved ultraviolet spectroscopy for the pulsating DAV stars G226-29 and G185-32 and for the pulsating DBV star PG 1351+489 with the Hubble Space Telescope Faint Object Spectrograph to compare the ... -
New white dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 12
(2016) [Artigo de periódico]We report the discovery of 6576 new spectroscopically confirmed white dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 12. We obtain Teff, log g and mass for hydrogen atmospherewhite dwarf stars (DAs) ... -
New white dwarf stars in the Sloan Digital Sky Survey Data Release 10
(2015) [Artigo de periódico]We report the discovery of 9088 new spectroscopically confirmed white dwarfs and subdwarfs in the Sloan Digital Sky Survey Data Release 10. We obtain Teff, log g and mass for hydrogen atmosphere white dwarf stars (DAs) and ... -
Probing the structure of Kepler ZZ Ceti stars with full evolutionary models-based asteroseismology
(2017) [Artigo de periódico]We present an asteroseismological analysis of four ZZ Ceti stars observed with the Kepler spacecraft: GD 1212, SDSS J113655.17+040952.6, KIC 11911480, and KIC 4552982, based on a grid of full evolutionary models of DA white ... -
Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS : III. Asteroseismology of the DBV star GD 358
(2022) [Artigo de periódico]Context. The collection of high-quality photometric data by space telescopes, such as the completed Kepler mission and the ongoing TESS program, is revolutionizing the area of white-dwarf asteroseismology. Among the different ... -
SDSS DR7 white dwarf catalog
(2013) [Artigo de periódico]We present a new catalog of spectroscopically confirmed white dwarf stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and ... -
SDSS J124043.01+671034.68 : the partially burned remnant of a low-mass white dwarf that underwent thermonuclear ignition?
(2020) [Artigo de periódico]The white dwarf SDSS J124043.01+671034.68 (SDSS J1240+6710) was previously found to have an oxygen-dominated atmosphere with significant traces of neon, magnesium, and silicon. A possible origin via a violent late thermal ...
