16 research outputs found
Tracing snowlines and C/O ratio in a planet-hosting disk: ALMA molecular line observations towards the HD169142 disk
The composition of a forming planet is set by the material it accretes from
its parent protoplanetary disk. Therefore, it is crucial to map the chemical
make-up of the gas in disks to understand the chemical environment of planet
formation. This paper presents molecular line observations taken with the
Atacama Large Millimeter/submillimeter Array of the planet-hosting disk around
the young star HD 169142. We detect N2H+, CH3OH, [CI], DCN, CS, C34S, 13CS,
H2CS, H2CO, HC3N and c-C3H2 in this system for the first time. Combining these
data with the recent detection of SO and previously published DCO+ data, we
estimate the location of H2O and CO snowlines and investigate radial variations
in the gas phase C/O ratio. We find that the HD 169142 disk has a relatively
low N2H+ flux compared to the disks around Herbig stars HD 163296 and MWC 480
indicating less CO freeze-out and place the CO snowline beyond the millimetre
disk at ~150 au. The detection of CH3OH from the inner disk is consistent with
the H2O snowline being located at the edge of the central dust cavity at ~20
au. The radially varying CS/SO ratio across the proposed H2O snowline location
is consistent with this interpretation. Additionally, the detection of CH3OH in
such a warm disk adds to the growing evidence supporting the inheritance of
complex ices in disks from the earlier, colder stages of star formation.
Finally, we propose that the giant HD 169142 b located at 37 au is forming
between the CO2 and H2O snowlines where the local elemental make of the gas is
expected to have C/O=1.0.Comment: Accepted A&A 13th August 202
Investigating the asymmetric chemistry in the disk around the young star HD 142527
The atmospheric composition of planets is determined by the chemistry of the
disks in which they form. Studying the gas-phase molecular composition of disks
thus allows us to infer what the atmospheric composition of forming planets
might be. Recent observations of the IRS 48 disk have shown that (asymmetric)
dust traps can directly impact the observable chemistry, through radial and
vertical transport, and the sublimation of ices. The asymmetric HD 142527 disk
provides another good opportunity to investigate the role of dust traps in
setting the disk's chemical composition. In this work, we use archival ALMA
observations of the HD 142527 disk to obtain an as large as possible molecular
inventory, which allows us to investigate the possible influence of the
asymmetric dust trap on the disk's chemistry. We present the first ALMA
detections of [C I], 13C18O, DCO+, H2CO and additional transition of HCO+ and
CS in this disk. In addition, we have acquired upper limits for non-detected
species such as SO and CH3OH. For the majority of the observed molecules, a
decrement in the emission at the location of the dust trap is found. For the
main CO isotopologues continuum over-subtraction likely causes the observed
asymmetry, while for CS and HCN we propose that the observed asymmetries are
likely due to shadows cast by the misaligned inner disk. As the emission of the
observed molecules is not co-spatial with the dust trap and no SO or CH3OH are
found, thermal sublimation of icy mantles does not appear to play a major role
in changing the gas-phase composition of the outer disk in HD 142527 disk.
Using our observations of 13C18O and DCO+ and a RADMC-3D model, we determine
the CO snowline to be located beyond the dust traps, favouring cold gas-phase
formation of H2CO, rather than the hydrogenation of CO-ice and subsequent
sublimation.Comment: Accepted for publication in A&A on 12/04/202
An ALMA molecular inventory of warm Herbig Ae disks: I. Molecular rings, asymmetries and complexity in the HD 100546 disk
Observations of disks with the Atacama Large Millimeter/submillimeter Array
(ALMA) allow us to map the chemical makeup of nearby protoplanetary disks with
unprecedented spatial resolution and sensitivity. The typical outer Class II
disk observed with ALMA is one with an elevated C/O ratio and a lack of
oxygen-bearing complex organic molecules, but there are now some interesting
exceptions: three transition disks around Herbig Ae stars all show oxygen-rich
gas traced via the unique detections of the molecules SO and CH3OH. We present
the first results of an ALMA line survey at 337 to 357 GHz of such disks and
focus this paper on the first Herbig Ae disk to exhibit this chemical signature
- HD 100546. In these data, we detect 19 different molecules including NO, SO
and CH3OCHO (methyl formate). We also make the first tentative detections of
H213CO and 34SO in protoplanetary disks. Multiple molecular species are
detected in rings, which are, surprisingly, all peaking just beyond the
underlying millimeter continuum ring at 200 au. This result demonstrates a
clear connection between the large dust distribution and the chemistry in this
flat outer disk. We discuss the physical and/or chemical origin of these
sub-structures in relation to ongoing planet formation in the HD 100546 disk.
We also investigate how similar and/or different the molecular make up of this
disk is to other chemically well-characterised Herbig Ae disks. The line-rich
data we present motivates the need for more ALMA line surveys to probe the
observable chemistry in Herbig Ae systems which offer unique insight into the
composition of disk ices, including complex organic molecules.Comment: Accepted to AJ, 25 pages, 11 figure
An ALMA molecular inventory of warm Herbig Ae disks: II. Abundant complex organics and volatile sulphur in the IRS 48 disk
The Atacama Large Millimeter/submillimeter Array (ALMA) can probe the
molecular content of planet-forming disks with unprecedented sensitivity. These
observations allow us to build up an inventory of the volatiles available for
forming planets and comets. Herbig Ae transition disks are fruitful targets due
to the thermal sublimation of complex organic molecule (COM) and likely
H2O-rich ices in these disks. The IRS 48 disk shows a particularly rich
chemistry that can be directly linked to its asymmetric dust trap. Here, we
present ALMA observations of the IRS 48 disk where we detect 16 different
molecules and make the first robust detections of H213CO, 34SO, 33SO and
c-H2COCH2 (ethylene oxide) in a protoplanetary disk. All of the molecular
emissions, aside from CO, are colocated with the dust trap and this includes
newly detected simple molecules such as HCO+, HCN and CS. Interestingly, there
are spatial offsets between different molecular families, including between the
COMs and sulphur-bearing species, with the latter being more azimuthally
extended and located radially further from the star. The abundances of the
newly detected COMs relative to CH3OH are higher than the expected protostellar
ratios, which implies some degree of chemical processing of the inherited ices
during the disk lifetime. These data highlight IRS 48 as a unique astrochemical
laboratory to unravel the full volatile reservoir at the epoch of planet and
comet formation and the role of the disk in (re)setting chemical complexity.Comment: Accepted to AJ, 21 pages, 7 figure
MINDS. JWST-MIRI Reveals a Dynamic Gas-Rich Inner Disk Inside the Cavity of SY Cha
SY Cha is a T Tauri star surrounded by a protoplanetary disk with a large
cavity seen in the millimeter continuum but has the spectral energy
distribution (SED) of a full disk. Here we report the first results from
JWST-MIRI Medium Resolution Spectrometer (MRS) observations taken as part of
the MIRI mid-INfrared Disk Survey (MINDS) GTO Program. The much improved
resolution and sensitivity of MIRI-MRS compared to Spitzer enables a robust
analysis of the previously detected H2O, CO, HCN, and CO2 emission as well as a
marginal detection of C2H2. We also report the first robust detection of
mid-infrared OH and ro-vibrational CO emission in this source. The derived
molecular column densities reveal the inner disk of SY Cha to be rich in both
oxygen and carbon bearing molecules. This is in contrast to PDS 70, another
protoplanetary disk with a large cavity observed with JWST, which displays much
weaker line emission. In the SY Cha disk, the continuum, and potentially the
line, flux varies substantially between the new JWST observations and archival
Spitzer observations, indicative of a highly dynamic inner disk.Comment: 19 pages, 10 figures, 5 tables, accepted for publication in Ap
MINDS. Abundant water and varying C/O across the disk of Sz 98 as seen by JWST/MIRI
MIRI/MRS on board the JWST allows us to probe the inner regions of
protoplanetary disks. Here we examine the disk around the classical T Tauri
star Sz 98, which has an unusually large dust disk in the millimetre with a
compact core. We focus on the HO emission through both its ro-vibrational
and pure rotational emission. Furthermore, we compare our chemical findings
with those obtained for the outer disk from Atacama Large
Millimeter/submillimeter Array (ALMA) observations. In order to model the
molecular features in the spectrum, the continuum was subtracted and LTE slab
models were fitted. The spectrum was divided into different wavelength regions
corresponding to HO lines of different excitation conditions, and the slab
model fits were performed individually per region. We confidently detect CO,
HO, OH, CO, and HCN in the emitting layers. The isotopologue
HO is not detected. Additionally, no other organics, including
CH, are detected. This indicates that the C/O ratio could be
substantially below unity, in contrast with the outer disk. The HO emission
traces a large radial disk surface region, as evidenced by the gradually
changing excitation temperatures and emitting radii. The OH and CO emission
are relatively weak. It is likely that HO is not significantly
photodissociated; either due to self-shielding against the stellar irradiation,
or UV-shielding from small dust particles. The relative emitting strength of
the different identified molecular features point towards UV-shielding of
HO in the inner disk of Sz 98, with a thin layer of OH on top. The majority
of the organic molecules are either hidden below the dust continuum, or not
present. In general, the inferred composition points to a sub-solar C/O ratio
(<0.5) in the inner disk, in contrast with the larger than unity C/O ratio in
the gas in the outer disk found with ALMA.Comment: Submitted to A&A on May 25 2023. 18 pages, 11 figure
MINDS. The detection of CO with JWST-MIRI indicates abundant CO in a protoplanetary disk
We present JWST-MIRI MRS spectra of the protoplanetary disk around the
low-mass T Tauri star GW Lup from the MIRI mid-INfrared Disk Survey (MINDS) GTO
program. Emission from CO, CO, HO, HCN,
CH, and OH is identified with CO being detected for
the first time in a protoplanetary disk. We characterize the chemical and
physical conditions in the inner few au of the GW Lup disk using these
molecules as probes. The spectral resolution of JWST-MIRI MRS paired with high
signal-to-noise data is essential to identify these species and determine their
column densities and temperatures. The -branches of these molecules,
including those of hot-bands, are particularly sensitive to temperature and
column density. We find that the CO emission in the GW Lup disk is
coming from optically thick emission at a temperature of 400 K.
CO is optically thinner and based on a lower temperature of
325 K, may be tracing deeper into the disk and/or a larger emitting
radius than CO. The derived /
ratio is orders of magnitude higher than previously derived for GW Lup and
other targets based on \textit{Spitzer}-IRS data. This high column density
ratio may be due to an inner cavity with a radius in between the HO and
CO snowlines and/or an overall lower disk temperature. This paper
demonstrates the unique ability of JWST to probe inner disk structures and
chemistry through weak, previously unseen molecular features.Comment: 15 pages, 10 figures. Accepted to ApJ
Occurrence rate of hot Jupiters orbiting red giant stars
Context. Hot Jupiters form an enigmatic class of object whose formation pathways are not yet clear. Determining their occurrence rates as a function of orbit, planet and stellar mass, and system age can be an important ingredient for understanding how they form. To date, various hot Jupiters have been discovered orbiting red giant stars, and deriving their incidence would be highly interesting.
Aims. In this study our aim is to determine the number of hot Jupiters in a well-defined sample of red giants, estimate their occurrence rate, and compare it with that for A-, F-, and G-type stars.
Methods. A sample of 14474 red giant stars, with estimated radii between 2 and 5 R⊙, was selected using Gaia to coincide with observations by the NASA TESS mission. Subsequently, the TESS light curves were searched for transits from hot Jupiters. The detection efficiency was determined using injected signals, and the results further corrected for the geometric transit probability to estimate the occurrence rate.
Results. Three previously confirmed hot Jupiters were found in the TESS data, in addition to one other TESS object of interest, and two M-dwarf companions. This results in an occurrence rate of 0.37−0.09+0.29%. Due to the still large uncertainties, this cannot be distinguished from that of A-, F-, and G-type stars. We argue that it is unlikely that planet engulfment in expanding red giants plays an important role in this sample
MINDS. JWST/MIRI Reveals a Dynamic Gas-rich Inner Disk inside the Cavity of SY Cha
SY Cha is a T Tauri star surrounded by a protoplanetary disk with a large cavity seen in the millimeter continuum but has the spectral energy distribution of a full disk. Here we report the first results from JWST/Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) observations taken as part of the MIRI mid-INfrared Disk Survey (MINDS) GTO Program. The much improved resolution and sensitivity of MIRI-MRS compared to Spitzer enables a robust analysis of the previously detected H2O, CO, HCN, and CO2 emission as well as a marginal detection of C2H2. We also report the first robust detection of mid-infrared OH and rovibrational CO emission in this source. The derived molecular column densities reveal the inner disk of SY Cha to be rich in both oxygen- and carbon-bearing molecules. This is in contrast to PDS 70, another protoplanetary disk with a large cavity observed with JWST, which displays much weaker line emission. In the SY Cha disk, the continuum, and potentially the line, flux varies substantially between the new JWST observations and archival Spitzer observations, indicative of a highly dynamic inner disk.</p