31 research outputs found
An Empirical Planetesimal Belt Radius-Stellar Luminosity Relation
Resolved observations of millimetre-sized dust, tracing larger planetesimals,
have pinpointed the location of 26 Edgeworth-Kuiper belt analogs. We report
that a belt's distance to its host star correlates with the star's
luminosity , following with a low
intrinsic scatter of 17%. Remarkably, our Edgeworth-Kuiper belt in the
Solar System and the two CO snow lines imaged in protoplanetary disks lie close
to this - relation, suggestive of an intrinsic relationship
between protoplanetary disk structures and belt locations. To test the effect
of bias on the relation, we use a Monte Carlo approach and simulate
uncorrelated model populations of belts. We find that observational bias could
produce the slope and intercept of the - relation, but is unable
to reproduce its low scatter. We then repeat the simulation taking into account
the collisional evolution of belts, following the steady state model that fits
the belt population as observed through infrared excesses. This significantly
improves the fit by lowering the scatter of the simulated -
relation; however, this scatter remains only marginally consistent with the one
observed. The inability of observational bias and collisional evolution alone
to reproduce the tight relationship between belt radius and stellar luminosity
could indicate that planetesimal belts form at preferential locations within
protoplanetary disks. The similar trend for CO snow line locations would then
indicate that the formation of planetesimals and/or planets in the outer
regions of planetary systems is linked to the volatility of their building
blocks, as postulated by planet formation models
A gap in the planetesimal disc around HD 107146 and asymmetric warm dust emission revealed by ALMA
While detecting low mass exoplanets at tens of au is beyond current
instrumentation, debris discs provide a unique opportunity to study the outer
regions of planetary systems. Here we report new ALMA observations of the
80-200 Myr old Solar analogue HD 107146 that reveal the radial structure of its
exo-Kuiper belt at wavelengths of 1.1 and 0.86 mm. We find that the
planetesimal disc is broad, extending from 40 to 140 au, and it is
characterised by a circular gap extending from 60 to 100 au in which the
continuum emission drops by about 50%. We also report the non-detection of the
CO J=3-2 emission line, confirming that there is not enough gas to affect the
dust distribution. To date, HD 107146 is the only gas-poor system showing
multiple rings in the distribution of millimeter sized particles. These rings
suggest a similar distribution of the planetesimals producing small dust grains
that could be explained invoking the presence of one or more perturbing
planets. Because the disk appears axisymmetric, such planets should be on
circular orbits. By comparing N-body simulations with the observed visibilities
we find that to explain the radial extent and depth of the gap, it would be
required the presence of multiple low mass planets or a single planet that
migrated through the disc. Interior to HD 107146's exo-Kuiper belt we find
extended emission with a peak at ~20 au and consistent with the inner warm belt
that was previously predicted based on 22m excess as in many other
systems. This warm belt is the first to be imaged, although unexpectedly
suggesting that it is asymmetric. This could be due to a large belt
eccentricity or due to clumpy structure produced by resonant trapping with an
additional inner planet
The SHARDDS survey: limits on planet occurrence rates based on point sources analysis via the Auto-RSM framework
In the past decade, HCI surveys provided new insights about the frequency and
properties of substellar companions at separation larger than 5 au. In this
context, our study aims to detect and characterise potential exoplanets and
brown dwarfs within debris disks, by considering the SHARDDS survey, which
gathers 55 Main Sequence stars with known bright debris disk. We rely on the
AutoRSM framework to perform an in-depth analysis of the targets, via the
computation of detection maps and contrast curves. A clustering approach is
used to divide the set of targets in multiple subsets, in order to reduce the
computation time by estimating a single optimal parametrisation for each
considered subset. The use of Auto-RSM allows to reach high contrast at short
separations, with a median contrast of 10-5 at 300 mas, for a completeness
level of 95%. Detection maps generated with different approaches are used along
with contrast curves, to identify potential planetary companions. A new
planetary characterisation algorithm, based on the RSM framework, is developed
and tested successfully, showing a higher astrometric and photometric precision
for faint sources compared to standard approaches. Apart from the already known
companion of HD206893 and two point-like sources around HD114082 which are most
likely background stars, we did not detect any new companion around other
stars. A correlation study between achievable contrasts and parameters
characterising HCI sequences highlights the importance of the strehl, wind
speed and wind driven halo to define the quality of high contrast images.
Finally, planet detection and occurrence frequency maps are generated and show,
for the SHARDDS survey, a high detection rate between 10 and 100 au for
substellar companions with mass >10MJ
A Dust Trap in the Young Multiple System HD 34700
This is the author accepted manuscript. The final version is available from the American Astronomical Society via the DOI in this recordMillimeter observations of disks around young stars reveal substructures indicative of gas pressure
traps that may aid grain growth and planet formation. We present Submillimeter Array observations
of HD 34700- two Herbig Ae stars in a close binary system (Aa/Ab, ∼0.25 AU), surrounded by a
disk presenting a large cavity and spiral arms seen in scattered light, and two distant, lower mass
companions. These observations include 1.3 mm continuum emission and the 12CO 2-1 line at ∼ 0.
005
(178 AU) resolution. They resolve a prominent azimuthal asymmetry in the continuum, and Keplerian
rotation of a circumbinary disk in the 12CO line. The asymmetry is located at a radius of 155+11
−7
AU, consistent with the edge of the scattered light cavity, being resolved in both radius (72+14
−15 AU)
and azimuth (FWHM = 64◦+8
−7
). The strong asymmetry in millimeter continuum emission could be
evidence for a dust trap, together with the more symmetric morphology of 12CO emission and small
grains. We hypothesize an unseen circumbinary companion, responsible for the cavity in scattered
light and creating a vortex at the cavity edge that manifests in dust trapping. The disk mass has
limitations imposed by the detection of 12CO and non-detection of 13CO. We discuss its consequences
for the potential past gravitational instability of this system, likely accounting for the rapid formation
of a circumbinary companion. We also report the discovery of resolved continuum emission associated
with HD 34700B (projected separation ∼ 1850AU), which we explain through a circumstellar disk.National Science Foundation (NSF
Gas and dust around A-type stars at tens of Myr: signatures of cometary breakup
Discs of dusty debris around main-sequence stars indicate fragmentation of orbiting planetesimals, and for a few A-type stars, a gas component is also seen that may come from collisionally released volatiles. Here we find the sixth example of a CO-hosting disc, around the ∼30 Myr-old A0-star HD 32997. Two more of these CO-hosting stars, HD 21997 and 49 Cet, have also been imaged in dust with SCUBA-2 within the SCUBA-2 Survey of Nearby Stars project. A census of 27 A-type debris hosts within 125 pc now shows 7/16 detections of carbon-bearing gas within the 5–50 Myr epoch, with no detections in 11 older systems. Such a prolonged period of high fragmentation rates corresponds quite well to the epoch when most of the Earth was assembled from planetesimal collisions. Recent models propose that collisional products can be spatially asymmetric if they originate at one location in the disc, with CO particularly exhibiting this behaviour as it can photodissociate in less than an orbital period. Of the six CO-hosting systems, only β Pic is in clear support of this hypothesis. However, radiative transfer modelling with the ProDiMo code shows that the CO is also hard to explain in a proto-planetary disc context.JSG and PW thank the ERC for funding for project DiscAnalysis, under the grant FP7-SPACE-2011 collaborative project 284405. JPM is supported by a UNSW Vice-Chancellor's postdoctoral fellowship. MCW and LM acknowledge the support of the European Union through ERC grant 279973. The JCMT is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan, Academia Sinica Institute of Astronomy and Astrophysics, the Korea Astronomy and Space Science Institute, the National Astronomical Observatories of China and the Chinese Academy of Sciences (Grant No. XDB09000000), with additional funding support from the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ
Recommended from our members
An Empirical Planetesimal Belt Radius-Stellar Luminosity Relation
Resolved observations of millimetre-sized dust, tracing larger planetesimals, have pinpointed the location of 26 Edgeworth-Kuiper belt analogs. We report that a belt's distance to its host star correlates with the star's luminosity , following with a low intrinsic scatter of 17%. Remarkably, our Edgeworth-Kuiper belt in the Solar System and the two CO snow lines imaged in protoplanetary disks lie close to this - relation, suggestive of an intrinsic relationship between protoplanetary disk structures and belt locations. To test the effect of bias on the relation, we use a Monte Carlo approach and simulate uncorrelated model populations of belts. We find that observational bias could produce the slope and intercept of the - relation, but is unable to reproduce its low scatter. We then repeat the simulation taking into account the collisional evolution of belts, following the steady state model that fits the belt population as observed through infrared excesses. This significantly improves the fit by lowering the scatter of the simulated - relation; however, this scatter remains only marginally consistent with the one observed. The inability of observational bias and collisional evolution alone to reproduce the tight relationship between belt radius and stellar luminosity could indicate that planetesimal belts form at preferential locations within protoplanetary disks. The similar trend for CO snow line locations would then indicate that the formation of planetesimals and/or planets in the outer regions of planetary systems is linked to the volatility of their building blocks, as postulated by planet formation models
Biological support study, phase 1 Final report
Report produced under contract to the European Space AgencyAvailable from British Library Document Supply Centre- DSC:3425.929(ESA-CR-(P)--3618) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo