Isolated HAEBE stars are believed to represent an intermediate stage of objects between young stellar objects surrounded by massive, optically thick, gaseous and dusty disks and Vega like stars ...surrounded by debris disks. The star AB Aur is already known for being surrounded by an intermediate-stage dust disk emitting a fairly large infrared and (sub-)millimetric excess. Until now, the outer disk structure has only been resolved at millimeter wavelengths and at optical wavelength coronographic imaging. We have obtained 20 microns images which show an unexpected ellipse-shaped disk structure in emission at a distance of about 260 AU from the central star. Large azimuthal asymmetries in brightness can be noticed and the center of the ellipse does not coincide with the star. A simple, pure geometrical model based on an emission ring of uniform surface brightness, but having an intrinsic eccentricity succeeds in fitting the observations. These observations give for the first time clues on a very peculiar structure of pre-main-sequence disk geometry, i.e. a non uniform increase in the disk thickness unlike the common usual sketch of a disk with a constant flaring angle. They provide also valuable informations on the disk inclination as well as its dust composition; at such a large distance from the star, only transient heating of very small particles can explain such a bright ring of emission at mid-infrared wavelengths. Finally, the increase of thickness inferred by the model could be caused by disk instabilities; the intrinsic eccentricity of the structure might be a clue to the presence of a massive body undetected yet.
Submillimetre/TeraHertz (e.g. 200, 350, 450 microns) astronomy is the prime technique to unveil the birth and early evolution of a broad range of astrophysical objects. A major obstacle to carry out ...submm observations from ground is the atmosphere. Preliminary site testing and atmospheric transmission models tend to demonstrate that Dome C could offer the best conditions on Earth for submm/THz astronomy. The CAMISTIC project aims to install a filled bolometer-array camera with 16x16 pixels on IRAIT at Dome C and explore the 200-\(\mu\)m windows for potential ground-based observations.
Isolated HAEBE stars are believed to represent an intermediate stage of
objects between young stellar objects surrounded by massive, optically thick,
gaseous and dusty disks and Vega like stars ...surrounded by debris disks. The
star AB Aur is already known for being surrounded by an intermediate-stage dust
disk emitting a fairly large infrared and (sub-)millimetric excess. Until now,
the outer disk structure has only been resolved at millimeter wavelengths and
at optical wavelength coronographic imaging. We have obtained 20 microns images
which show an unexpected ellipse-shaped disk structure in emission at a
distance of about 260 AU from the central star. Large azimuthal asymmetries in
brightness can be noticed and the center of the ellipse does not coincide with
the star. A simple, pure geometrical model based on an emission ring of uniform
surface brightness, but having an intrinsic eccentricity succeeds in fitting
the observations. These observations give for the first time clues on a very
peculiar structure of pre-main-sequence disk geometry, i.e. a non uniform
increase in the disk thickness unlike the common usual sketch of a disk with a
constant flaring angle. They provide also valuable informations on the disk
inclination as well as its dust composition; at such a large distance from the
star, only transient heating of very small particles can explain such a bright
ring of emission at mid-infrared wavelengths. Finally, the increase of
thickness inferred by the model could be caused by disk instabilities; the
intrinsic eccentricity of the structure might be a clue to the presence of a
massive body undetected yet.
SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period ...extrasolar planets and circumstellar disks in the visible (450-900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5-10 AU) from nearby stars (less than 25 pc) with masses ranging from a few Jupiter masses to Super Earths (approximately 2 Earth radii, approximately 10 mass compared to Earth) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.
New observations of the supernova remnant 3C391 are in the H2 2.12 micron and Fe II 1.64 micron narrow-band filters at the Palomar 200-inch telescope, and in the 5-15 micron CVF on ISOCAM. Shocked H2 ...emission was detected from the region 3C391:BML, where broad millimeter CO and CS lines had previously been detected. A new H2 clump was confirmed to have broad CO emission, demonstrating that the near-infrared H2 images can trace previously undetected molecular shocks. The Fe II emission has a significantly different distribution, being brightest in the bright radio bar, at the interface between the supernova remnant and the giant molecular cloud, and following filaments in the radio shell. The near-infrared Fe II and the mid-infrared 12-18 micron filter images are the first images to reveal the radiative shell of 3C391. The mid-infrared spectrum is dominated by bright ionic lines and H2 S(2) through S(7). There are no aromatic hydrocarbons associated with the shocks, nor is their any mid-infrared continuum, suggesting that macromolecules and very small grains are destroyed. Comparing 3C391 to the better-studied IC443, both remnants have molecular- and ionic-dominated regions; for 3C391, the ionic-dominated region is the interface into the giant molecular cloud, showing that the main bodies of giant molecular clouds contain significant regions with densities 100 to 1000/cm^3 and a small filling factor with higher-density. The molecular shocked region resolves into 16 clumps of H2 emission, with some fainter diffuse emission but with no associated near-infrared continuum sources. One of the clumps is coincident with a previously-detected OH 1720 MHz maser. These clumps are interpreted as a cluster of pre-stellar, dense molecular cores that are presently being shocked by the supernova blast wave.
Submillimetre/TeraHertz (e.g. 200, 350, 450 microns) astronomy is the prime
technique to unveil the birth and early evolution of a broad range of
astrophysical objects. A major obstacle to carry out ...submm observations from
ground is the atmosphere. Preliminary site testing and atmospheric transmission
models tend to demonstrate that Dome C could offer the best conditions on Earth
for submm/THz astronomy. The CAMISTIC project aims to install a filled
bolometer-array camera with 16x16 pixels on IRAIT at Dome C and explore the
200-$\mu$m windows for potential ground-based observations.
We calculate particle spectra and continuum photon emission from the Cassiopeia A supernova remnant (SNR). The particle spectra, ion and electron, result from diffusive shock acceleration at the ...forward SNR shock and are determined with a nonlinear Monte Carlo calculation. The calculation self-consistently determines the shock structure under the influence of ion pressure, and includes a simple parameterized treatment of electron injection and acceleration. Our results are compared to photon observations, concentrating on the connection between the Radio and GeV-TeV gamma-ray range, and to cosmic ray ion observations. We include new upper limits from the Cherenkov Array at Themis (CAT) imaging Cherenkov telescope and the Whipple 10m gamma-ray telescope at > 400 GeV. These new limits support the suggestion (e.g. Cowsik & Sarkar 1980; Allen et. al. 1997) that energetic electrons are emitting synchrotron radiation in an extremely high magnetic field (~ 1000 microGauss), far greater than values routinely assigned to the ISM, and help to constrain our model. The large magnetic field allows acceleration of cosmic ray ions to well above \(10^{15}\) eV per nucleon in the ~ 300 yr lifetime of Cas A.
New observations of the supernova remnant 3C391 are in the H2 2.12 micron and
Fe II 1.64 micron narrow-band filters at the Palomar 200-inch telescope, and
in the 5-15 micron CVF on ISOCAM. Shocked H2 ...emission was detected from the
region 3C391:BML, where broad millimeter CO and CS lines had previously been
detected. A new H2 clump was confirmed to have broad CO emission, demonstrating
that the near-infrared H2 images can trace previously undetected molecular
shocks. The Fe II emission has a significantly different distribution, being
brightest in the bright radio bar, at the interface between the supernova
remnant and the giant molecular cloud, and following filaments in the radio
shell. The near-infrared Fe II and the mid-infrared 12-18 micron filter
images are the first images to reveal the radiative shell of 3C391. The
mid-infrared spectrum is dominated by bright ionic lines and H2 S(2) through
S(7). There are no aromatic hydrocarbons associated with the shocks, nor is
their any mid-infrared continuum, suggesting that macromolecules and very small
grains are destroyed. Comparing 3C391 to the better-studied IC443, both
remnants have molecular- and ionic-dominated regions; for 3C391, the
ionic-dominated region is the interface into the giant molecular cloud, showing
that the main bodies of giant molecular clouds contain significant regions with
densities 100 to 1000/cm^3 and a small filling factor with higher-density. The
molecular shocked region resolves into 16 clumps of H2 emission, with some
fainter diffuse emission but with no associated near-infrared continuum
sources. One of the clumps is coincident with a previously-detected OH 1720 MHz
maser. These clumps are interpreted as a cluster of pre-stellar, dense
molecular cores that are presently being shocked by the supernova blast wave.
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