massive than about 25 times the Sun’s mass
and thus not massive enough to be stripped
Wolf-Rayet stars. These authors instead suggest a history of mass loss through evolution in a binary system. Thus, binary environments appear to be important for some
core-collapse supernovae.
Figure 2.
Model of the
environment of V1247
Orionis includes a hot
optically thick inner
disk, a cool optically
thick outer disk, and
optically thin dust in the
gap between them.
For the study, the team used the integral
field unit of the Gemini Multi-Object Spectrograph (GMOS) on Gemini North as part of
Subaru exchange time, along with the SuperNova Integral Field Spectrograph at the
University of Hawai‘i 88-inch telescope, also
on Mauna Kea. They targeted nearby galaxies, where 1 arcsecond typically corresponds
to 230 light-years (70 parsecs), to distinguish
the progenitor star clusters. The data show
that other nearby clusters display a somewhat different history and metallicity from
the supernova site (Figure 1). These results
are published in The Astrophysical Journal,
and in a separate paper (pending), the team
applies identical techniques to the host environments of Type II supernovae.
ferometric analysis techniques, to determine
the disk orientation and geometry. Considering longer-baseline MIR interferometry in addition, a compact disk is evident, extending
over 0.2 AU. The inferred structure (Figure 2),
based on the full set of observations, shows a
hot inner disk, a cool outer disk, and optically thin carbon-rich dust in the gap between
them. The emission in the gap region appears
to be asymmetric, and the dependence on
observed wavelength implies that this is due
to density inhomogeneities, rather than the
presence of a single body like a planet.
Resolving a Stellar Disk at
Earth-Sun Distance Scales
Planets in the disks around young stars may
carve gaps or dynamically affect their environment. These so-called transitional and
pre-transitional disks are therefore interesting as important stages in the development
of planets. An international team led by
Stefan Kraus (Harvard-Smithsonian Center
for Astrophysics) used multiple telescopes,
including Gemini South, to resolve the disk
around V1247 Orionis on physical scales of
astronomical units (AU; the average EarthSun distance), finding asymmetries and unambiguous evidence for a gap in the disk.
The observations included an uncommon
use of Gemini’s Thermal Region Camera
Spectrograph (T-ReCS) for mid-infrared (MIR)
imaging, using short exposures and inter-
12
GeminiFocus
The persistence of the hot inner disk, with
material located at the dust sublimation
radius (corresponding to the hottest temperature where it can survive), rules out
some proposed methods of clearing gaps
in similar planetary disks, including photoevaporation, instabilities, and grain growth.
Instead, the authors conclude that dynamical clearing of the gap, due to developing
planetary or other companions, is the most
likely origin. Other well-studied transitional
and pre-transitional disks do not show evidence for such optically thin material close
to the star, which suggests that V1247 Orionis may show us an earlier stage of development. The complete results are published in
The Astrophysical Journal.
July2013