46 research outputs found
Mid-Infrared Imaging of the Bipolar Planetary Nebula M2-9 from SOFIA
We have imaged the bipolar planetary nebula M2-9 using SOFIA's FORCAST
instrument in six wavelength bands between 6.6 and 37.1 . A bright
central point source, unresolved with SOFIA's 4-to-5 beam,
is seen at each wavelength, and the extended bipolar lobes are clearly seen at
19.7 and beyond. The photometry between 10 and 25 is well fit
by the emission predicted from a stratified disk seen at large inclination, as
has been proposed for this source by Lykou et al and by Smith and Gehrz. The
principal new results in this paper relate to the distribution and properties
of the dust that emits the infrared radiation. In particular, a considerable
fraction of this material is spread uniformly through the lobes, although the
dust density does increase at the sharp outer edge seen in higher resolution
optical images of M2-9. The dust grain population in the lobes shows that small
( 1 ) particles appear to be present in
roughly equal amounts by mass. We suggest that collisional processing within
the bipolar outflow plays an important role in establishing the particle size
distribution.Comment: 40 pages, 9 figures, 2 table
The disk of the eruptive protostar V900 Mon; a MATISSE/VLTI and MUSE/VLT perspective
In this work, we study the silicate dust content in the disk of one of the
youngest eruptive stars, V900 Mon, at the highest angular resolution probing
down to the inner 10 au of said disk, and study the historical evolution of the
system traced in part by a newly discovered emission clump. We performed
high-angular resolution mid-infrared interferometric observations of V900 Mon
with MATISSE/VLTI with a spatial coverage ranging from 38-m to 130-m baselines,
and compared them to archival MIDI/VLTI data. We also mined and re-analyzed
archival optical and infrared photometry of the star to study its long-term
evolution since its eruption in the 1990s. We complemented our findings with
integral field spectroscopy data from MUSE/VLT. The MATISSE/VLTI data suggest a
radial variation of the silicate feature in the dusty disk, whereby at large
spatial scales ( au) the protostellar disk's emission is dominated by
large-sized () silicate grains, while at smaller spatial scales
and closer to the star ( au), silicate emission is absent suggesting
self-shielding. We propose that the self-shielding may be the result of small
dust grains at the base of the collimated CO outflow previously detected by
ALMA. A newly discovered knot in the MUSE/VLT data, located at a projected
distance approximately 27,000 au from the star, is co-aligned with the
molecular gas outflow at a P.A. of () consistent with the
position angle and inclination of the disk. The knot is seen in emission in
H, [N II], and the [S II] doublet and its kinematic age is about 5150
years. This ejected material could originate from a previous eruption.Comment: 18 pages, 16 figures, accepted for publication by Astronomy &
Astrophysic
A dense disk of dust around the born-again Sakurai's object
In 1996, Sakurai's object (V4334 Sgr) suddenly brightened in the centre of a
faint Planetary Nebula (PN). This very rare event was interpreted as the
reignition of a hot white dwarf that caused a rapid evolution back to the cool
giant phase. From 1998 on, a copious amount of dust has formed continuously,
screening out the star which has remained embedded in this expanding high
optical depth envelope. The new observations, reported here, are used to study
the morphology of the circumstellar dust in order to investigate the hypothesis
that Sakurai's Object is surrounded by a thick spherical envelope of dust. We
have obtained unprecedented, high-angular resolution spectro-interferometric
observations, taken with the mid-IR interferometer MIDI/VLTI, which resolve the
dust envelope of Sakurai's object. We report the discovery of a unexpectedly
compact (30 x 40 milliarcsec, 105 x 140 AU assuming a distance of 3.5 kpc),
highly inclined, dust disk. We used Monte Carlo radiative-transfer simulations
of a stratified disk to constrain its geometric and physical parameters,
although such a model is only a rough approximation of the rapidly evolving
dust structure. Even though the fits are not fully satisfactory, some useful
and robust constraints can be inferred. The disk inclination is estimated to be
75+/-3 degree with a large scale height of 47+/-7 AU. The dust mass of the disk
is estimated to be 6 10^{-5} solar mass. The major axis of the disk (132+/-3
degree) is aligned with an asymmetry seen in the old PN that was
re-investigated as part of this study. This implies that the mechanism
responsible for shaping the dust envelope surrounding Sakurai's object was
already at work when the old PN formed.Comment: A&A Letter, accepte
A silicate disk in the heart of the Ant
We aim at getting high spatial resolution information on the dusty core of
bipolar planetary nebulae to directly constrain the shaping process. Methods:
We present observations of the dusty core of the extreme bipolar planetary
nebula Menzel 3 (Mz 3, Hen 2-154, the Ant) taken with the mid-infrared
interferometer MIDI/VLTI and the adaptive optics NACO/VLT. The core of Mz 3 is
clearly resolved with MIDI in the interferometric mode, whereas it is
unresolved from the Ks to the N bands with single dish 8.2 m observations on a
scale ranging from 60 to 250 mas. A striking dependence of the dust core size
with the PA angle of the baselines is observed, that is highly suggestive of an
edge-on disk whose major axis is perpendicular to the axis of the bipolar
lobes. The MIDI spectrum and the visibilities of Mz 3 exhibit a clear signature
of amorphous silicate, in contrast to the signatures of crystalline silicates
detected in binary post-AGB systems, suggesting that the disk might be
relatively young. We used radiative-transfer Monte Carlo simulations of a
passive disk to constrain its geometrical and physical parameters. Its
inclination (74 degrees 3 degrees) and position angle (5 degrees 5
degrees) are in accordance with the values derived from the study of the lobes.
The inner radius is 9 1 AU and the disk is relatively flat. The dust mass
stored in the disk, estimated as 1 x 10-5Msun, represents only a small fraction
of the dust mass found in the lobes and might be a kind of relic of an
essentially polar ejection process
A close halo of large transparent grains around extreme red giant stars
Intermediate-mass stars end their lives by ejecting the bulk of their
envelope via a slow dense wind back into the interstellar medium, to form the
next generation of stars and planets. Stellar pulsations are thought to elevate
gas to an altitude cool enough for the condensation of dust, which is then
accelerated by radiation pressure from starlight, entraining the gas and
driving the wind. However accounting for the mass loss has been a problem due
to the difficulty in observing tenuous gas and dust tens of milliarcseconds
from the star, and there is accordingly no consensus on the way sufficient
momentum is transferred from the starlight to the outflow. Here, we present
spatially-resolved, multi-wavelength observations of circumstellar dust shells
of three stars on the asymptotic giant branch of the HR diagram. When imaged in
scattered light, dust shells were found at remarkably small radii (<~ 2 stellar
radii) and with unexpectedly large grains (~300 nm radius). This proximity to
the photosphere argues for dust species that are transparent to starlight and
therefore resistant to sublimation by the intense radiation field. While
transparency usually implies insufficient radiative pressure to drive a wind,
the radiation field can accelerate these large grains via photon scattering
rather than absorption - a plausible mass-loss mechanism for lower-amplitude
pulsating stars.Comment: 13 pages, 1 table, 6 figure
The expanding dusty bipolar nebula around the nova V1280 Sco
V1280 Sco is one of the slowest dust-forming nova ever historically observed.
We performed multi-epoch high-spatial resolution observations of the
circumstellar dusty environment of V1280 Sco to investigate the level of
asymmetry of the ejecta We observed V1280 Sco in 2009, 2010 and 2011 using
unprecedented high angular resolution techniques. We used the NACO/VLT adaptive
optics system in the J, H and K bands, together with contemporaneous VISIR/VLT
mid-IR imaging that resolved the dust envelope of V1280 Sco, and SINFONI/VLT
observations secured in 2011. We report the discovery of a dusty
hourglass-shaped bipolar nebula. The apparent size of the nebula increased from
0.30" x 0.17" in July 2009 to 0.64" x 0.42" in July 2011. The aspect ratio
suggests that the source is seen at high inclination. The central source shines
efficiently in the K band and represents more than 56+/-5% of the total flux in
2009, and 87+/-6% in 2011. A mean expansion rate of 0.39+/-0.03 mas per day is
inferred from the VISIR observations in the direction of the major axis, which
represents a projected upper limit. Assuming that the dust shell expands in
that direction as fast as the low-excitation slow ejecta detected in
spectroscopy, this yields a lower limit distance to V1280 Sco of 1kpc; however,
the systematic errors remain large due to the complex shape and velocity field
of the dusty ejecta. The dust seems to reside essentially in the polar caps and
no infrared flux is detected in the equatorial regions in the latest dataset.
This may imply that the mass-loss was dominantly polar
Brightness and mass accretion rate evolution during the 2022 burst of EX~Lupi
EX Lupi is the prototype by which EXor-type outbursts were defined. It has experienced multiple accretion-related bursts and outbursts throughout the last decades, whose study have greatly extended our knowledge about the effects of these types of events. This star experienced a new burst in 2022. We used multi-band photometry to create color-color and color-magnitude diagrams to exclude the possibility that the brightening could be explained by a decrease in extinction. We obtained VLT/X-shooter spectra to determine the Lacc and Macc during the peak of the burst and after its return to quiescence using 2 methods: empirical relationships between line luminosity and Lacc, and a slab model of the whole spectrum. We examined the 130 year light curve of EX Lupi to provide statistics on the number of outbursts experienced during this period of time. Our analysis of the data taken during the 2022 burst confirmed that a change in extinction is not responsible for the brightening. Our two approaches in calculating the Macc were in agreement, and resulted in values that are 2 orders of magnitude above what had previously been estimated, thus suggesting that EX Lupi is a strong accretor even when in quiescence. We determined that in 2022 March the Macc increased by a factor of 7 with respect to the quiescent level. We also found hints that even though the Macc had returned to almost its pre-outburst levels, certain physical properties of the gas had not returned to the quiescent values. We found that the mass accreted during this three month event was 0.8 lunar masses, which is approximately half of what is accreted during a year of quiescence. We calculated that if EX Lupi remains as active as it has been for the past 130 years, during which it has experienced at least 3 outbursts and 10 bursts, then it will deplete the mass of its circumstellar material in less than 160000 yr
The disk of FU Orionis viewed with MATISSE/VLTI:First interferometric observations in <i>L</i> and <i>M</i> bands
The Nearby Evolved Stars Survey II: Constructing a volume-limited sample and first results from the James Clerk Maxwell Telescope
The Nearby Evolved Stars Survey (NESS) is a volume-complete sample of ∼850 Galactic evolved stars within 3 kpc at (sub-)mm wavelengths, observed in the CO J = (2–1) and (3–2) rotational lines, and the sub-mm continuum, using the James Clark Maxwell Telescope and Atacama Pathfinder Experiment. NESS consists of five tiers, based on distances and dust-production rate (DPR). We define a new metric for estimating the distances to evolved stars and compare its results to Gaia EDR3. Replicating other studies, the most-evolved, highly enshrouded objects in the Galactic Plane dominate the dust returned by our sources, and we initially estimate a total DPR of 4.7 × 10−5 M⊙ yr−1 from our sample. Our sub-mm fluxes are systematically higher and spectral indices are typically shallower than dust models typically predict. The 450/850 μm spectral indices are consistent with the blackbody Rayleigh–Jeans regime, suggesting a large fraction of evolved stars have unexpectedly large envelopes of cold dust
MATISSE, the VLTI mid-infrared imaging spectro-interferometer
GalaxiesStars and planetary systemsInstrumentatio