Unravelling the baffling mystery of the ultrahot wind phenomenon in white dwarfs. (arXiv:1811.02922v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Reindl_N/0/1/0/all/0/1">Nicole Reindl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bainbridge_M/0/1/0/all/0/1">M. Bainbridge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Przybilla_N/0/1/0/all/0/1">N. Przybilla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Geier_S/0/1/0/all/0/1">S. Geier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prvak_M/0/1/0/all/0/1">M. Prvák</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Krticka_J/0/1/0/all/0/1">J. Krtička</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ostensen_R/0/1/0/all/0/1">R. H. Østensen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Telting_J/0/1/0/all/0/1">J. Telting</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Werner_K/0/1/0/all/0/1">K. Werner</a>
The presence of ultra-high excitation (UHE) absorption lines (e.g., O VIII)
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 ultra hot wind phenomenon.
The presence of ultra-high excitation (UHE) absorption lines (e.g., O VIII)
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 ultra hot wind phenomenon.
http://arxiv.org/icons/sfx.gif
