TY  - JOUR
A1  - Reindl, Nicole
A1  - Bainbridge, M.
A1  - Przybilla, Norbert
A1  - Geier, Stephan
A1  - Prvak, M.
A1  - Krticka, Jiri
A1  - Ostensen, R. H.
A1  - Telting, J.
A1  - Werner, K.
T1  - Unravelling the baffling mystery of the ultrahot wind phenomenon in white dwarfs
JF  - Monthly notices of the Royal Astronomical Society
N2  - The presence of ultrahigh excitation (UHE) absorption lines (e.g. OVIII) in the optical spectra of several of the hottest white dwarfs poses a decades-long mystery and is something that has never been observed in any other astrophysical object. The occurrence of such features requires a dense environment with temperatures near 10(6) K, by far exceeding the stellar effective temperature. Here we report the discovery of a new hot wind white dwarf, GALEXJ014636.8+323615. Astonishingly, we found for the first time rapid changes of the equivalent widths of the UHE features, which are correlated to the rotational period of the star (P=0.242035 d). We explain this with the presence of a wind-fed circumstellar magnetosphere in which magnetically confined wind shocks heat up the material to the high temperatures required for the creation of the UHE lines. The photometric and spectroscopic variability of GALEXJ014636.8+323615 can then be understood as consequence of the obliquity of the magnetic axis with respect to the rotation axis of the white dwarf. This is the first time a wind-fed circumstellar magnetosphere around an apparently isolated white dwarf has been discovered and finally offers a plausible explanation of the ultrahot wind phenomenon.
KW  - stars: AGB and post-AGB
KW  - stars: evolution
KW  - stars: magnetic field
Y1  - 2018
U6  - https://doi.org/10.1093/mnrasl/sly191
SN  - 0035-8711
SN  - 1365-2966
VL  - 482
IS  - 1
SP  - L93
EP  - L98
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Reindl, Nicole
A1  - Finch, Nicolle L.
A1  - Schaffenroth, Veronika
A1  - Barstow, Martin A.
A1  - Casewell, Sarah L.
A1  - Geier, Stephan
A1  - Bertolami Miller, Marcelo Miguel
A1  - Taubenberger, Stefan
T1  - Revealing the true nature of Hen 2-428
JF  - Galaxies
N2  - The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines quantitative non-local thermodynamic (non-LTE) equilibrium spectral modelling, radial velocity analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations. Importantly, we find that the dynamical system mass that is derived by using all available He II lines does not exceed the Chandrasekhar mass limit. Furthermore, the individual masses of the two central stars are too small to lead to an SN Ia in case of a dynamical explosion during the merger process.
KW  - binaries: spectroscopic
KW  - stars: atmospheres
KW  - stars: abundances
KW  - supernovae
Y1  - 2018
U6  - https://doi.org/10.3390/galaxies6030088
SN  - 2075-4434
VL  - 6
IS  - 3
ER  - 
TY  - JOUR
A1  - Reindl, Nicole
A1  - Geier, Stephan
A1  - Ostensen, R. H.
T1  - Discovery of two bright DO-type white dwarfs
JF  - Monthly notices of the Royal Astronomical Society
N2  - We discovered two bright DO-type white dwarfs, GALEXJ053628.3+544854 (J0536+5448) and GALEXJ231128.0+292935(J2311+2929), which rank among the eight brightest DO-type white dwarfs known. Our non-LTE model atmosphere analysis reveals effective temperatures and surface gravities of T-eff = 80000 +/- 4600K and log g = 8.25 +/- 0.15 for J0536+5448 and T-eff = 69400 +/- 900K and log g = 7.80 +/- 0.06 for J2311+2929. The latter shows a significant amount of carbon in its atmosphere (C = 0.003(-0.002)(+0.005), by mass), while for J0536+5448 we could derive only an upper limit of C < 0.003. Furthermore, we calculated spectroscopic distances for the two stars and found a good agreement with the distances derived from the Gaia parallaxes.
KW  - stars: abundances
KW  - stars: atmospheres
KW  - white dwarfs
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty1875
SN  - 0035-8711
SN  - 1365-2966
VL  - 480
IS  - 1
SP  - 1211
EP  - 1217
PB  - Oxford Univ. Press
CY  - Oxford
ER  -