7.7k citations · 25.2k across the 85 of their papers we have counts for
24 papers · 1 filter
Spectral analysis of 636 white dwarf - M star binaries from the Sloan Digital Sky Survey
René Heller, Derek Homeier, Stefan Dreizler +1
We present a catalog of 857 white dwarf (WD)-M binaries from the sixth data release (DR6) of the Sloan Digital Sky Survey (SDSS), most of which were previously identified. For 636…
Epsilon Indi Ba, Bb: a spectroscopic study of the nearest known brown dwarfs
Robert R. King, Mark J. McCaughrean, Derek Homeier +3
The discovery of Epsilon Indi Ba and Bb, a nearby binary brown dwarf system with a main-sequence companion, allows a concerted campaign to characterise the physical parameters of t…
A comparison of chemistry and dust cloud formation in ultracool dwarf model atmospheres
Ch. Helling, A. Ackerman, F. Allard +8
The atmospheres of substellar objects contain clouds of oxides, iron, silicates, and other refractory condensates. Water clouds are expected in the coolest objects. The opacity of…
Fifteen new T dwarfs discovered in the UKIDSS Large Area Survey
D. J. Pinfield, B. Burningham, M. Tamura +32
We present the discovery of fifteen new T2.5-T7.5 dwarfs (with estimated distances between ~24-93pc, identified in the first three main data releases of the UKIRT Infrared Deep Sky…
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition?
Philippe Delorme, Xavier Delfosse, Loic Albert +9
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-Fr…
A new period determination for the close PG1159 binary SDSSJ212531.92-010745.9
S. Schuh, I. Traulsen, T. Nagel +6
Methods to measure masses of PG1159 stars in order to test evolutionary scenarios are currently based on spectroscopic masses or asteroseismological mass determinations. One recent…
K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba
France Allard, Nicole F. Allard, Derek Homeier +3
T-type dwarfs present a broad and shallow absorption feature centred around 6950 A in the blue wing of the K doublet at 0.77 micron which resembles in depth and shape the satellite…
Alkali Line Profiles in Ultracool White Dwarfs
Derek Homeier, Nicole F. Allard, Christine M. S. Johnas +2
We present PHOENIX atmosphere models for metal-rich cool white dwarfs using improved line shapes for the Na I and K I resonance doublets. Profiles for collisional broadening due to…
Alkali Line Profiles in Degenerate Dwarfs
Derek Homeier, Nicole F. Allard, France Allard
Ultracool stellar atmospheres show absorption by alkali resonance lines severely broadened by collisions with neutral perturbers. In the coolest and densest atmospheres, such as th…
A high resolution spectral atlas of brown dwarfs
A. Reiners, D. Homeier, P. H. Hauschildt +1
We present a UVES/VLT high resolution atlas of three L dwarfs and one T dwarf system, spectral classes at which most of the objects are brown dwarfs. Our atlas covers the optical r…
Six New ZZ Ceti Stars from the SPY and the HQS Surveys
B. Voss, D. Koester, R. Østensen +3
We report on the discovery of six new ZZ Ceti stars. They were selected as candidates based on preparatory photometric observations of objects from the Hamburg Quasar Survey (HQS),…
Investigation of transit-selected exoplanet candidates from the MACHO survey
S. D. Huegelmeyer, S. Dreizler, D. Homeier +1
Context: Planets outside our solar system transiting their host star, i. e. those with an orbital inclination near 90 degree, are of special interest to derive physical properties…
Spectral analyses of eighteen hot H-deficient (pre-) white dwarfs from the Sloan Digital Sky Survey Data Release 4
S. D. Huegelmeyer, S. Dreizler, D. Homeier +4
Context: The Sloan Digital Sky Survey Data Release 4 has provided spectra of several new PG 1159 stars and DO white dwarfs. This increase in known hot H-deficient compact objects s…
Modelling Alkali Line Absorption and Molecular Bands in Cool DAZs
Derek Homeier, Nicole F. Allard, France Allard +4
Two peculiar stars showing an apparent extremely broadened and strong NaI D absorption have been discovered in surveys for cool white dwarfs by Oppenheimer et al. (2001) and Harris…
Phase-Resolved Infrared H- and K-band Spectroscopy of EF Eridani
Thomas E. Harrison, Steve B. Howell, Paula Szkody +3
We present new phase-resolved H and K-band spectroscopy of the ultra-short period magnetic cataclysmic variable EF Eri in its current, prolonged ``low'' state obtained using NIRI o…
Hot subdwarfs from the ESO Supernova Ia Progenitor Survey - I. Atmospheric parameters and cool companions of sdB stars
T. Lisker, U. Heber, R. Napiwotzki +4
We present the analysis of a high-resolution, high-quality sample of optical spectra for 76 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey (SPY). Effective temp…
Spectral Properties of Brown Dwarfs and Hot Jupiters
Derek Homeier, France Allard, Peter H. Hauschildt +3
Brown dwarfs bridge the gap between the stellar and planetary mass regimes. Evolving from conditions very similar to the lowest-mass stars, the atmospheres of older brown dwarfs cl…
Double degenerates and progenitors of supernovae type Ia
R. Napiwotzki, L. Yungelson, G. Nelemans +12
We report on systematic radial velocity surveys for white dwarf - white dwarf binaries (double degenerates - DDs) including SPY (ESO Supernovae Ia progenitor survey) recently carri…
Close binary EHB stars from SPY
R. Napiwotzki, C. A. Karl, T. Lisker +5
We present the results of a radial velocity (RV) survey of 46 subdwarf B (sdB) and 23 helium-rich subdwarf O (He-sdO) stars. We detected 18 (39%) new sdB binary systems, but only o…
Spectroscopic analysis of sdB stars from the ESO Supernova Ia Progenitor Survey
T. Lisker, U. Heber, R. Napiwotzki +3
We report on the analysis of high-resolution optical spectra for 77 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey. Effective temperature, surface gravity, and…
Methane and the Spectra of T Dwarfs
Derek Homeier, Peter H. Hauschildt, France Allard
We have updated our PHOENIX model atmospheres and theoretical spectra for ultracool dwarfs with new opacity data for methane based on line strength predictions with the STDS softwa…
Methane Opacities in T Dwarf Atmospheres
D. Homeier, P. H. Hauschildt, F. Allard
We present the current status of PHOENIX model atmospheres for dwarfs of the spectral type T, typical for older field brown dwarfs and low-mass brown dwarfs. The results are based…
Search for progenitors of supnernovae type Ia with SPY
R. Napiwotzki, N. Christlieb, H. Drechsel +13
We have started a large survey for double degenerate (DD) binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor su…
The stellar content of the Hamburg/ESO survey. I. Automated selection of DA white dwarfs
N. Christlieb, L. Wisotzki, D. Reimers +3
We describe automatic procedures for the selection of DA white dwarfs in the Hamburg/ESO objective-prism survey (HES). For this purpose, and the selection of other stellar objects…