Dreizler, Stefan

[["dc.bibliographiccitation.firstpage","1039"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","1046"],["dc.bibliographiccitation.volume","486"],["dc.contributor.author","Bean, Jacob L."],["dc.contributor.author","Benedict, G. Fritz"],["dc.contributor.author","Charbonneau, David"],["dc.contributor.author","Homeier, Derek"],["dc.contributor.author","Taylor, D. C."],["dc.contributor.author","McArthur, Barbara E."],["dc.contributor.author","Seifahrt, Andreas"],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Reiners, Ansgar"],["dc.date.accessioned","2018-11-07T11:12:17Z"],["dc.date.available","2018-11-07T11:12:17Z"],["dc.date.issued","2008"],["dc.description.abstract","We present time series photometry for six partial transits of GJ 436b obtained with the Fine Guidance Sensor instrument on the Hubble Space Telescope (HST). Our analysis of these data yields independent estimates of the host star's radius R- = 0.505(-0.029) (+0.020) R-circle dot, and the planet's orbital period P = 2.643882(-0.000058)(+0.000060) d, orbital inclination i = 85.80 degrees(-0.25 degrees),(+ 0.21 degrees), mean central transit time T-c = 2 454 455.279241(-0.00025)(+0.00026) HJD, and radius Rp = 4.90(-0.33)(+ 0.45) R-circle plus. The radius we determine for the planet is larger than the previous findings from analyses of an infrared light curve obtained with the Spitzer Space Telescope. Although this discrepancy has a 92% formal significance (1.7s), it might be indicative of systematic errors that still influence the analyses of even the highest-precision transit light curves. Comparisons of all the measured radii to theoretical models suggest that GJ 436b has a H/ He envelope of similar to 10% by mass. We point out the similarities in structure between this planet and Uranus and Neptune and discuss possible parallels between these planets' formation environments and dynamical evolution. We also find that the transit times for GJ 436b are constant to within 10s over the 11 planetary orbits that the HST data span. However, the ensemble of published values exhibits a long-term drift and our mean transit time is 128 s later than that expected from the Spitzer ephemeris. The sparseness of the currently available data hinders distinguishing between an error in the orbital period or perturbations arising from an additional object in the system as the cause of the apparent trend. Assuming the drift is due to an error in the orbital period we obtain an improved estimate for it of P = 2.643904 +/- 0.000005 d. This value and our measured transit times will serve as important benchmarks in future studies of the GJ 436 system."],["dc.identifier.doi","10.1051/0004-6361:200810013"],["dc.identifier.fs","513377"],["dc.identifier.isi","000258326500046"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9395"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53628"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","A Hubble Space Telescope transit light curve for GJ 436b"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A149"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","588"],["dc.contributor.author","Kamann, Sebastian"],["dc.contributor.author","Husser, T.-O."],["dc.contributor.author","Brinchmann, Jarle"],["dc.contributor.author","Emsellem, Eric"],["dc.contributor.author","Weilbacher, Peter M."],["dc.contributor.author","Wisotzki, Lutz"],["dc.contributor.author","Wendt, M."],["dc.contributor.author","Krajnovic, Davor"],["dc.contributor.author","Roth, M. M."],["dc.contributor.author","Bacon, Roland"],["dc.contributor.author","Dreizler, Stefan"],["dc.date.accessioned","2018-11-07T10:16:10Z"],["dc.date.available","2018-11-07T10:16:10Z"],["dc.date.issued","2016"],["dc.description.abstract","We present a detailed analysis of the kinematics of the Galactic globular cluster NGC 6397 based on more than similar to 18 000 spectra obtained with the novel integral field spectrograph MUSE. While NGC 6397 is often considered a core collapse cluster, our analysis suggests a flattening of the surface brightness profile at the smallest radii. Although it is among the nearest globular clusters, the low velocity dispersion of NGC 6397 of < 5 km s(-1) imposes heavy demands on the quality of the kinematical data. We show that despite its limited spectral resolution, MUSE reaches an accuracy of 1 km s(-1) in the analysis of stellar spectra. We find slight evidence for a rotational component in the cluster and the velocity dispersion profile that we obtain shows a mild central cusp. To investigate the nature of this feature, we calculate spherical Jeans models and compare these models to our kinematical data. This comparison shows that if a constant mass-to-light ratio is assumed, the addition of an intermediate-mass black hole with a mass of 600 M-circle dot brings the model predictions into agreement with our data, and therefore could be at the origin of the velocity dispersion profile. We further investigate cases with varying mass-to-light ratios and find that a compact dark stellar component can also explain our observations. However, such a component would closely resemble the black hole from the constant mass-to-light ratio models as this component must be confined to the central similar to 5 '' of the cluster and must have a similar mass. Independent constraints on the distribution of stellar remnants in the cluster or kinematic measurements at the highest possible spatial resolution should be able to distinguish the two alternatives."],["dc.identifier.doi","10.1051/0004-6361/201527065"],["dc.identifier.isi","000373207800161"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13437"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40984"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A131"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","598"],["dc.contributor.author","Khalafinejad, S."],["dc.contributor.author","von Essen, C."],["dc.contributor.author","Hoeijmakers, H. J."],["dc.contributor.author","Zhou, G."],["dc.contributor.author","Klocova, T."],["dc.contributor.author","Schmitt, J. H. M. M."],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Lopez-Morales, Mercedes"],["dc.contributor.author","Husser, T.-O."],["dc.contributor.author","Schmidt, T. O. B."],["dc.contributor.author","Collet, R."],["dc.date.accessioned","2018-11-07T10:27:40Z"],["dc.date.available","2018-11-07T10:27:40Z"],["dc.date.issued","2017"],["dc.description.abstract","Context. During primary transits, the spectral signatures of exoplanet atmospheres can be measured using transmission spectroscopy. We can obtain information on the upper atmosphere of these planets by investigating the exoplanets' excess sodium absorption in the optical region. However, a number of factors can affect the observed sodium absorption signature. We present a detailed model correcting for systematic biases to yield an accurate depth for the sodium absorption in HD 189733b. Aims. The goal of this work is to accurately measure the atomspheric sodium absorption light curve in HD 189733b, correcting for the effects of stellar differential limb-darkening, stellar activity, and a \"bump\" caused by the changing radial velocity of the exoplanet. In fact, owing to the high cadence and quality of our data, it is the first time that the last feature can be detected even by visual inspection. Methods. We use 244 high-resolution optical spectra taken by the UVES instrument mounted at the VLT. Our observations cover a full transit of HD 189733b, with a cadence of 45 s. To probe the transmission spectrum of sodium we produce excess light curves integrating the stellar flux in passbands of 1 angstrom, 1.5 angstrom, and 3 angstrom inside the core of each sodium D-line. We model the effects of external sources on the excess light curves, which correspond to an observed stellar flare beginning close to mid-transit time and the wavelength dependent limb-darkening effects. In addition, by characterizing the effect of the changing radial velocity and Doppler shifts of the planetary sodium lines inside the stellar sodium lines, we estimate the depth and width of the exoplanetary sodium feature. Results. We estimate the shape of the planetary sodium line by a Gaussian profile with an equivalent width of similar to 0.0023 +/- 0.0010 angstrom, thereby confirming the presence of sodium in the atmosphere of HD 189733b with excess absorption levels of 0.72 +/- 0.25%, 0.34 +/- 0.11%, and 0.20 +/- 0.06% for the integration bands of 1 angstrom, 1.5 angstrom, and 3 angstrom, respectively. Using the equivalent width of the planetary sodium line, we produce a first order estimate of the number density of sodium in the exoplanet atmosphere."],["dc.identifier.doi","10.1051/0004-6361/201629473"],["dc.identifier.isi","000394465000130"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14291"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43276"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Exoplanetary atmospheric sodium revealed by orbital motion Narrow-band transmission spectroscopy of HD 189733b with UVES"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","637"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","647"],["dc.bibliographiccitation.volume","434"],["dc.contributor.author","Karl, C. A."],["dc.contributor.author","Napiwotzki, R."],["dc.contributor.author","Heber, Ulrich"],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Koester, D."],["dc.contributor.author","Reid, I. Neill"],["dc.date.accessioned","2018-11-07T11:01:49Z"],["dc.date.available","2018-11-07T11:01:49Z"],["dc.date.issued","2005"],["dc.description.abstract","The sharp H alpha NLTE line cores of hydrogen- rich ( DA) white dwarfs allow their projected rotational velocities to be determined. High resolution optical spectra of 22 stars obtained with the Keck I telescope are matched by synthetic spectra computed from a grid of NLTE model atmospheres. In this paper, the third in a series on white dwarf rotation, we concentrate preferentially on DA white dwarfs with convective atmospheres, i. e. with T-eff < 14 000 K. Previous analyses found DA white dwarfs hotter than 14 000 K to be very slow rotators and rarely show any spectroscopically detectable rotation. For 19 of our programme stars we were able to derive projected rotational velocities or upper limits. No rotation could be detected for seven stars in our sample. However twelve stars show significant line broadening. In the case of the ZZ Ceti star G 117- B15A, the observed H alpha line profile cannot be matched by a rotationally broadened profile as its line core is too narrow. Combining our results with those from two similar studies, we have obtained information on the rotation or other line broadening mechanisms ( such as caused by magnetic fields) of 56 DA white dwarfs. The fraction of rotating DA white dwarfs whose line profiles can be matched for a vanishing projected rotation velocity is high for hot white dwarfs with radiative atmospheres ( 25 out of 28). Amongst the cool white dwarfs with presumedly convective atmospheres, only for a few stars ( 8 out of 22) has no additional line broadening to be invoked to explain their observed H alpha line profiles. We conjecture that the physics of H alpha line formation in convective DA white dwarf atmospheres is not yet sufficiently well understood and additional observational and theoretical efforts have to be made."],["dc.identifier.doi","10.1051/0004-6361:20041437"],["dc.identifier.fs","38253"],["dc.identifier.isi","000228326900024"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9867"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/51238"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","E D P Sciences"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Rotation velocities of white dwarfs - III. DA stars with convective atmospheres"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","498"],["dc.bibliographiccitation.journal","Memorie della Societa Astronomica Italiana"],["dc.bibliographiccitation.lastpage","504"],["dc.bibliographiccitation.volume","83"],["dc.contributor.author","Dreizler, S."],["dc.contributor.author","Beuermann, K."],["dc.contributor.author","Hesman, F. V."],["dc.date.accessioned","2019-07-10T08:14:09Z"],["dc.date.available","2019-07-10T08:14:09Z"],["dc.date.issued","2012"],["dc.description.abstract","In the recent years, several circum-binary planets orbiting post-common envelope systems have been announced. Some of the derived planetary parameters have been questioned by others. We therefore present an investigation of the current status in this dynamically evolving field. False positive scenarios for the eclipse time variations are therefore discussed. We also present an update on new measurements on NNSer and shortly address the quest for the frequency of planets in post-common envelope systems."],["dc.identifier.fs","596642"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9580"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/61448"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","0037-8720"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights.access","openAccess"],["dc.subject.ddc","530"],["dc.title","Evidence for planets in post-common envelope binaries"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","012048"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Journal of Physics. Conference Series"],["dc.bibliographiccitation.volume","172"],["dc.contributor.affiliation","S D Hügelmeyer, ; 1Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany"],["dc.contributor.affiliation","S Dreizler, ; 1Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany"],["dc.contributor.author","Hügelmeyer, S. D."],["dc.contributor.author","Dreizler, S."],["dc.date.accessioned","2019-07-09T11:52:44Z"],["dc.date.available","2019-07-09T11:52:44Z"],["dc.date.issued","2009"],["dc.date.updated","2022-02-19T14:35:34Z"],["dc.description.abstract","For a long time, no hydrogen-deficient white dwarfs have been known that have effective temperature between 30 kK and < 45 kK, i. e. exceeding those of DB white dwarfs and having lower ones than DO white dwarfs. Therefore, this temperature range was long known as the DB-gap. Only recently, the SDSS provided spectra of several candidate DB-gap stars. First analyses based on model spectra calculated under the assumption of local thermodynamic equilibrium (LTE) confirmed that these stars had 30 kK < Teff < 45 kK (Eisenstein et al. 2006). It has been shown for DO white dwarfs that the relaxation of LTE is necessary to account for non local effects in the atmosphere caused by the intense radiation field. Therefore, we calculated a non-LTE model grid and re-analysed the aforementioned set of SDSS spectra. Our results confirm the existence of DB-gap white dwarfs."],["dc.identifier.doi","10.1088/1742-6596/172/1/012048"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/5873"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/60258"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","1742-6596"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","Goescholar"],["dc.rights.uri","https://goedoc.uni-goettingen.de/licenses"],["dc.subject.ddc","530"],["dc.title","Non-LTE spectral analyses of the lately discovered DB-gap white dwarfs from the SDSS"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","L5"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","609"],["dc.contributor.author","Reiners, A."],["dc.contributor.author","Ribas, I."],["dc.contributor.author","Zechmeister, M."],["dc.contributor.author","Caballero, J. A."],["dc.contributor.author","Trifonov, T."],["dc.contributor.author","Dreizler, S."],["dc.contributor.author","Morales, J. C."],["dc.contributor.author","Tal-Or, L."],["dc.contributor.author","Lafarga, M."],["dc.contributor.author","Quirrenbach, A."],["dc.contributor.author","Zapatero Osorio, M. R."],["dc.date.accessioned","2020-12-10T18:11:38Z"],["dc.date.available","2020-12-10T18:11:38Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1051/0004-6361/201732165"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/15629"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74089"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.intern","Merged from goescholar"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","The CARMENES search for exoplanets around M dwarfs"],["dc.title.alternative","HD147379 b: A nearby Neptune in the temperate zone of an early-M dwarf"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A103"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","561"],["dc.contributor.author","Ofir, Aviv"],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Zechmeister, Mathias"],["dc.contributor.author","Husser, Tim-Oliver"],["dc.date.accessioned","2018-11-07T09:46:40Z"],["dc.date.available","2018-11-07T09:46:40Z"],["dc.date.issued","2014"],["dc.description.abstract","Context. The primary goal of the Kepler mission is the measurement of the frequency of Earth-like planets around Sun-like stars. However, the confirmation of the smallest of Kepler's candidates in long periods around FGK dwarfs is extremely difficult or even beyond the limit of current radial velocity technology. Transit timing variations (TTVs) may offer the possibility for these confirmations of near-resonant multiple systems by the mutual gravitational interaction of the planets. Aims. We previously detected the second planet candidate in the KOI 1574 system. The two candidates have relatively long periods (about 114 d and 191 d) and are in 5: 3 resonance. We therefore searched for TTVs in this particularly promising system. Methods. The full Kepler data was detrended with the proven SARS pipeline. The entire data allowed one to search for TTVs of the above signals, and to search for additional transit-like signals. Results. We detected strong anti-correlated TTVs of the 114 d and 191 d signals, dynamically confirming them as members of the same system. Dynamical simulations reproducing the observed TTVs allowed us to also determine the masses of the planets. We found KOI 1574.01 (hereafter Kepler-87 b) to have a radius of 13.49 +/- 0.55 R-circle plus and a mass of 324.2 +/- 8.8 M-circle plus, and KOI 1574.02 (Kepler-87 c) to have a radius of 6.14 +/- 0.29 R-circle plus and a mass of 6.4 +/- 0.8 M-circle plus. Both planets have low densities of 0.729 and 0.152 g cm(-3), respectively, which is non-trivial for such cold and old (7-8 Gyr) planets. Specifically, Kepler-87 c is the lowest-density planet in the super-Earth mass range. Both planets are thus particularly amenable to modeling and planetary structure studies, and also present an interesting case where ground-based photometric follow-up of Kepler planets is very desirable. Finally, we also detected two more short-period super-Earth sized (<2 R-circle plus) planetary candidates in the system, making the relatively high multiplicity of this system notable against the general paucity of multiple systems in the presence of giant planets like Kepler-87 b."],["dc.identifier.doi","10.1051/0004-6361/201220935"],["dc.identifier.fs","606094"],["dc.identifier.isi","000330584000103"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/10901"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34933"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/279347."],["dc.relation.issn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","An independent planet search in the Kepler dataset II. An extremely low-density super-Earth mass planet around Kepler-87"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A6"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","553"],["dc.contributor.author","Husser, T.-O."],["dc.contributor.author","Wende-von Berg, S."],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Homeier, Derek"],["dc.contributor.author","Reiners, Ansgar"],["dc.contributor.author","Barman, T."],["dc.contributor.author","Hauschildt, P. H."],["dc.date.accessioned","2018-11-07T09:24:54Z"],["dc.date.available","2018-11-07T09:24:54Z"],["dc.date.issued","2013"],["dc.description.abstract","Aims. We present a new library of high-resolution synthetic spectra based on the stellar atmosphere code PHOENIX that can be used for a wide range of applications of spectral analysis and stellar parameter synthesis. Methods. The spherical mode of PHOENIX was used to create model atmospheres and to derive detailed synthetic stellar spectra from them. We present a new self-consistent way of describing micro-turbulence for our model atmospheres. Results. The synthetic spectra cover the wavelength range from 500 angstrom to 5.5 mu m with resolutions of R = 500 000 in the optical and near IR, R = 100 000 in the IR and Delta lambda = 0.1 angstrom in the UV. The parameter space covers 2300 K <= T-eff <= 12 000K, 0.0 <= log g <= +6.0, -4.0 <= [Fe/H] <= +1.0, and -0.2 <= [alpha/Fe] <= +1.2. The library is a work in progress and we expect to extend it up to T-eff = 25 000K."],["dc.identifier.doi","10.1051/0004-6361/201219058"],["dc.identifier.isi","000319858700006"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/10567"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29944"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","A new extensive library of PHOENIX stellar atmospheres and synthetic spectra"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","725"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","733"],["dc.bibliographiccitation.volume","450"],["dc.contributor.author","Werner, Katharina"],["dc.contributor.author","Nagel, T."],["dc.contributor.author","Rauch, T."],["dc.contributor.author","Hammer, N. J."],["dc.contributor.author","Dreizler, Stefan"],["dc.date.accessioned","2018-11-07T09:50:57Z"],["dc.date.available","2018-11-07T09:50:57Z"],["dc.date.issued","2006"],["dc.description.abstract","Aims. We present new medium-resolution high-S/N optical spectra of the ultracompact low-mass X-ray binaries 4U0614+091 and 4U1626-67, taken with the ESO Very Large Telescope. They are pure emission line spectra and the lines are identified as due to C II-IV and O II-III. Methods. Line identification is corroborated by first results from modeling the disk spectra with detailed non-LTE radiation transfer calculations. Hydrogen and helium lines are lacking in the observed spectra. Results. Our models confirm the deficiency of H and He in the disks. The lack of neon lines suggests an Ne abundance of less than about 10 percent ( by mass), however, this result is uncertain due to possible shortcomings in the model atom. These findings suggest that the donor stars are eroded cores of C/O white dwarfs with no excessive neon overabundance. This would contradict earlier claims of Ne enrichment concluded from X-ray observations of circumbinary material, which was explained by crystallization and fractionation of the white dwarf core."],["dc.identifier.doi","10.1051/0004-6361:20053768"],["dc.identifier.fs","45037"],["dc.identifier.isi","000236707400025"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9886"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/35812"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","VLT spectroscopy and non-LTE modeling of the C/O-dominated accretion disks in two ultracompact X-ray binaries"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]