The white dwarf has a
circumstellar disk despite being 3 billion years old. The
infrared excess in the spectrum was first interpreted as two separate rings. Later it was however found that this feature is caused by
silicate dust in a single ring, lying between 36 and 54.1 RWD and having a mass of 5.4 × 1019 g. It may be a
debris disk created from an asteroid broken apart by the star's gravity. The mass of heavy elements in the
convective zone of the white dwarf is currently 1.22 × 1022 g, which is the lower limit of the parent body mass. This parent body would be larger than 225 km. One work used photometry of the
Astrophysical Observatory of Javalambre of the J-PLUS survey to predict a 89.7% chance of the white dwarf having absorption due to
calcium. Later 13 heavy elements were found in
spectroscopic observations with
Lick Observatory,
Magellan Baade Telescope and
Keck I telescope. The lack of molecular
CH suggests a body depleted in carbon-volatiles. The composition is
earth-like, with an enhanced abundance of
siderophilic elements. The researchers interpret this as a massive differentiated rocky body with a large core (mass fraction of 55%) that got accreted. It is only the 5th white dwarf with detected
strontium, showing that this element is preferably detected in cooler white dwarfs. Strontium has a short sinking time of around 35,000 years, showing that accretion is ongoing on LSPM J0207+3331. It is also only the second white dwarf with calcium
H+K line core emission, likely originating in the upper atmosphere of the white dwarf. The researchers suggest this hints at additional physical processes that require future investigation. Models predict only a low rate of asteroids to be disrupted by an old white dwarf. The 1 Gyr simulations by Debes et al. found that only one asteroid per simulation was disrupted 200 Myrs after the white dwarf has formed. The presence of a disk around a 3 Gyr white dwarf sets new demands for models that seek to explain dust around white dwarfs.
Two-ring model An early interpretation was that the disk did compose of two rings. Newer analysis interpret the 11.6 μm emission in
WISE data as silicate emission.
James Webb Space Telescope spectroscopy is needed to confirm this interpretation and to study the
mineralogy of the parent body. The inner disk is optically thick with an inner radius of and an outer radius of . The outer disk is optically thin. It is located near the
Roche radius at around and has a mass of a small
asteroid or
comet. This suggests that the outer disk formed relative recently from a tidal disruption of such a small body. If this outer disk is confirmed, it would be the first known dusty white dwarf with a two-component ring system. Alternatively the gap in the disk could be explained by a dense
exoplanet orbiting inside the disk and clearing a gap, or a planet orbiting outside the disk and opening a gap via
resonant dynamics. Due to the inner edge of the inner disk being located near the
sublimation radius of
fayalite and
iron, it is suggested that the inner disk is composed of these materials. It is however not excluded that
forsterite is a component of the inner disk. == See also ==