Context.
Planet formation is a frequent process, but little observational constraints exist about the mechanisms involved, especially for giant planets at large separation. The NaCo-ISPY large ...program is a 120 night
L
′-band direct imaging survey aimed at investigating the giant planet population on wide orbits (
a
> 10 au) around stars hosting disks.
Aims.
Here we present the statistical analysis of a subsample of 45 young stars surrounded by protoplanetary disks (PPDs). This is the largest imaging survey uniquely focused on PPDs to date. Our goal is to search for young forming companions embedded in the disk material and to constrain their occurrence rate in relation to the formation mechanism.
Methods.
We used principal component analysis based point spread function subtraction techniques to reveal young companions forming in the disks. We calculated detection limits for our datasets and adopted a black-body model to derive temperature upper limits of potential forming planets. We then used Monte Carlo simulations to constrain the population of forming gas giant companions and compare our results to different types of formation scenarios.
Results.
Our data revealed a new binary system (HD 38120) and a recently identified triple system with a brown dwarf companion orbiting a binary system (HD 101412), in addition to 12 known companions. Furthermore, we detected signals from 17 disks, two of which (HD 72106 and T CrA) were imaged for the first time. We reached median detection limits of
L
′ = 15.4 mag at 2″.0, which were used to investigate the temperature of potentially embedded forming companions. We can constrain the occurrence of forming planets with semi-major axis
a
in 20–500 au and
T
eff
in 600–3000 K to be 21.2
-13.6
+24.3
%, 14.8
-9.6
+17.5
%, and 10.8
-7.0
+12.6
% for
R
p
= 2, 3, 5
R
J
, which is in line with the statistical results obtained for more evolved systems from other direct imaging surveys. These values are obtained under the assumption that extinction from circumstellar and circumplanetary material does not affect the companion signal, but we show the potential impact these factors might have on the detectability of forming objects.
Conclusions.
The NaCo-ISPY data confirm that massive bright planets accreting at high rates are rare. More powerful instruments with better sensitivity in the near- to mid-infrared are likely required to unveil the wealth of forming planets sculpting the observed disk substructures.
Context.
In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the ...circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question.
Aims.
We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets.
Methods.
We analyzed observations of six young stars (age 3.5–10 Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the H
α
filter (656 nm) and a nearby continuum filter (644.9 nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology.
Results.
We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both H
α
and the continuum. We derive new astrometry (
r
=62.8
−2.7
+2.1
mas and PA=(98.7±1.8)°) and photometry (ΔN_Ha = 6.3
−0.3
+0.2
mag, ΔB_Ha = 6.7 ± 0.2 mag and ΔCnt_Ha = 7.3
−0.2
+0.3
mag) for the companion in agreement with previous studies, and estimate its mass accretion rate (
Ṁ
≈ 1−2 × 10
−10
M
⊙
yr
−1
). A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142, and MWC 758 and calculate that processes involving H
α
fluxes larger than ~ 8 × 10
−14
–
10
−15
erg s
−1
cm
−2
(
Ṁ
> 10
−10
−10
−12
M
⊙
yr
−1
) can be excluded. Furthermore, flux upper limits of ~10
−14
−10
−15
erg s
−1
cm
−2
(
Ṁ
< 10
−11
–
10
−12
M
⊙
yr
−1
) are estimated within the gaps identified in the disks surrounding HD135344 B and TW Hya. The derived luminosity limits exclude H
α
signatures at levels similar to those previously detected for the accreting planet candidate LkCa15 b.
Context.
The occurrence rate of long-period (
a
≳ 50 au) giant planets around young stars is highly uncertain since it is not only governed by the protoplanetary disc structure and planet formation ...process, but also reflects both dynamical re-structuring processes after planet formation as well as possible capture of planets not formed in situ. Direct imaging is currently the only feasible method to detect such wide-orbit planets and constrain their occurrence rate.
Aims.
We aim to detect and characterise wide-orbit giant planets during and shortly after their formation phase within protoplanetary and debris discs around nearby young stars.
Methods.
We carry out a large
L
′-band high-contrast direct imaging survey for giant planets around 200 young stars with protoplanetary or debris discs using the NACO instrument at the ESO Very Large Telescope on Cerro Paranal in Chile. We use very deep angular differential imaging observations with typically >60° field rotation, and employ a vector vortex coronagraph where feasible to achieve the best possible point source sensitivity down to an inner working angle of about 100 mas. This paper introduces the NACO Imaging Survey for Planets around Young stars (NACO-ISPY), its goals and strategy, the target list, and data reduction scheme, and presents preliminary results from the first 2.5 survey years.
Results.
We achieve a mean 5
σ
contrast of Δ
L
′ = 6.4 ± 0.1 mag at 150 mas and a background limit of
L
′
bg
= 16.5±0.2 mag at >1.′′5. Our detection probability is >50% for companions with ≳8
M
Jup
at semi-major axes of 80–200 au and >13
M
Jup
at 30–250 au. It thus compares well to the detection space of other state-of-the-art high-contrast imaging surveys. We have already contributed to the characterisation of two new planets originally discovered by VLT/SPHERE, but we have not yet independently discovered new planets around any of our target stars. We have discovered two new close-in low-mass stellar companions around R CrA and HD 193571 and report in this paper the discovery of close co-moving low-mass stellar companions around HD 72660 and HD 92536. Furthermore, we report
L
′-band scattered light images of the discs around eleven stars, six of which have never been imaged at
L
′-band before.
Conclusions.
The first 2.5 yr of the NACO-ISPY survey have already demonstrated that VLT/NACO combined with our survey strategy can achieve the anticipated sensitivity to detect giant planets and reveal new close stellar companions around our target stars.
The circumstellar disk of PDS 70 hosts two forming planets, which are actively accreting gas from their environment. The physical and chemical characteristics of these planets remain ambiguous due to ...their unusual spectral appearance compared to more evolved objects. In this work, we report the first detection of PDS 70 b in the Brα and M′ filters with VLT/NACO, a tentative detection of PDS 70 c in Brα, and a reanalysis of archival NACO L′ and SPHERE H23 and K12 imaging data. The near side of the disk is also resolved with the Brα and M′ filters, indicating that scattered light is non-negligible at these wavelengths. The spectral energy distribution (SED) of PDS 70 b is well described by blackbody emission, for which we constrain the photospheric temperature and photospheric radius to Teff = 1193 ± 20 K and R = 3.0 ± 0.2 RJ. The relatively low bolometric luminosity, log(L∕L⊙) = −3.79 ± 0.02, in combination with the large radius, is not compatible with standard structure models of fully convective objects. With predictions from such models, and adopting a recent estimate of the accretion rate, we derive a planetary mass and radius in the range of Mp ≈ 0.5–1.5 MJ and Rp ≈ 1–2.5 RJ, independently of the age and post-formation entropy of the planet. The blackbody emission, large photospheric radius, and the discrepancy between the photospheric and planetary radius suggests that infrared observations probe an extended, dusty environment around the planet, which obscures the view on its molecular composition. Therefore, the SED is expected to trace the reprocessed radiation from the interior of the planet and/or partially from the accretion shock. The photospheric radius lies deep within the Hill sphere of the planet, which implies that PDS 70 b not only accretes gas but is also continuously replenished by dust. Finally, we derive a rough upper limit on the temperature and radius of potential excess emission from a circumplanetary disk, Teff ≲ 256 K and R ≲ 245 RJ, but we do find weak evidence that the current data favors a model with a single blackbody component.
CROCODILE Hayoz, J.; Cugno, G.; Quanz, S. P. ...
Astronomy and astrophysics (Berlin),
10/2023, Letnik:
678
Journal Article
Recenzirano
Context.
The investigation of the atmospheres of closely separated, directly imaged gas giant exoplanets is challenging due to the presence of stellar speckles that pollute their spectrum. To remedy ...this, the analysis of medium- to high-resolution spectroscopic data via cross-correlation with spectral templates (cross-correlation spectroscopy) is emerging as a leading technique.
Aims.
We aim to define a robust Bayesian framework combining, for the first time, three widespread direct-imaging techniques, namely photometry, low-resolution spectroscopy, and medium-resolution cross-correlation spectroscopy in order to derive the atmospheric properties of close-in directly imaged exoplanets. Current atmospheric characterisation frameworks are indeed either not compatible with all three observing techniques or they lack the commitment to efficient sampling strategies that allow high-dimensional forward models.
Methods.
Our framework
CROCODILE
(cross-correlation retrievals of directly imaged self-luminous exoplanets) naturally combines the three techniques by adopting adequate likelihood functions. To validate our routine, we simulated observations of gas giants similar to the well-studied
β
Pictoris b planet and we explored the parameter space of their atmospheres to search for potential biases.
Results.
We obtain more accurate measurements of atmospheric properties when combining photometry, low- and medium-resolution spectroscopy into atmospheric retrievals than when using the techniques separately as is usually done in the literature. Indeed, the combined fit is, on average, 20% more accurate than fitting only medium-resolution cross-correlation spectroscopy. We find that medium-resolution (
R
≈ 4000)
K
-band cross-correlation spectroscopy alone is not suitable to constrain the atmospheric properties of our synthetic datasets; however, this problem disappears when simultaneously fitting photometry throughout the
Y
and
M
bands and low-resolution (
R
≈ 60) spectroscopy between the
Y
and
H
bands. Our thorough testing demonstrates that free chemistry is a suitable forward model to retrieve the atmospheric thermal and chemical properties of cloudless gas giants at chemical equilibrium.
Conclusions.
CROCODILE
provides a robust statistical framework to interpret medium-resolution spectroscopic data of close-in directly imaged exoplanets, where speckles originating from stellar stray light render the extraction of the continuum difficult. Our framework allows the atmospheric characterisation of directly imaged exoplanets using the high-quality spectral data that will be provided by the new generation of instruments such as the Enhanced Resolution Imager and Spectrograph (ERIS) at the Very Large Telescope, the Mid-Infrared Instrument (MIRI) aboard the
James Webb
Space Telescope, and in the future the Mid-infrared ELT Imager and Spectrograph (METIS) at the Extremely Large Telescope.
Context. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) will give access to mid-infrared (mid-IR) spectra (5–28 microns) ...while retaining spatial information. With the unparalleled sensitivity of JWST and the MIRI detectors, the MRS has the potential to revolutionise our understanding of giant exoplanet atmospheres. Aims. Molecular mapping is a promising detection and characterisation technique used to study the spectra of directly imaged exoplanets. We aim to examine the feasibility and application of this technique to MRS observations. Methods. We used the instrument simulator MIRISIM to create mock observations of resolved star and exoplanet systems. As an input for the simulator, we used stellar and planet parameters from literature, with the planet spectrum being modelled with the radiative transfer code petitRADTRANS. After processing the raw data with the JWST pipeline, we high pass filter the data to account for the stellar point spread function, and used a forward modelling approach to detect the companions and constrain the chemical composition of their atmospheres through their molecular signatures. Results. We identified limiting factors in spectroscopic characterisation of directly imaged exoplanets with the MRS and simulated observations of two representative systems, HR8799 and GJ504. In both systems, we could detect the presence of multiple molecules that were present in the input model of their atmospheres. We used two different approaches with single molecule forward models, used in literature, that are sensitive to detecting mainly H2O, CO, CH4, and NH3, and a log-likelihood ratio test that uses full atmosphere forward models and is sensitive to a larger number of less dominant molecular species. Conclusions. We show that the MIRI MRS can be used to characterise widely separated giant exoplanets in the mid-IR using molecular mapping. Such observations would provide invaluable information for the chemical composition of the atmosphere, complementing other JWST observing modes, as well as ground-based observations.
Context.
Direct imaging has made significant progress over the past decade, in part thanks to a new generation of instruments and excellent adaptive optic systems, but also thanks to advanced ...post-processing techniques. The combination of these two factors allowed the detection of several giant planets with separations as close as 0.2 arcsec with contrasts typically reaching 9–10 magnitudes at nearinfrared wavelengths. Observing strategies and data rates vary depending on the instrument and the wavelength, with
L-
and
M
-band observations yielding tens of thousands of images to be combined.
Aims.
We present a new approach, tailored for VLT/NaCo observations performed with the Annular Groove Phase Mask (AGPM) coronagraph, but that can be applied to other instruments using similar coronagraphs. Our pipeline aims to improve the post-processing of the observations on two fronts: identifying the location of the star behind the AGPM to better align the science frames and performing frame selection.
Methods.
Our method relies on finding the position of the AGPM in the sky frame observations, and correlating it with the circular aperture of the coronagraphic mask. This relationship allows us to retrieve the location of the AGPM in the science frames. We are then able to model the torus shape visible in the sky-subtracted science frames, as a combination of negative and positive 2D Gaussian functions. The model provides additional information that is useful to design our frame selection criteria.
Results.
We tested our pipeline on three targets (
β
Pictoris, R CrA, and HD 34282), two of which have companions at intermediate and close separations, and the third hosts a bright circumstellar disk. We find that the centering of the science frames has a significant impact on the signal-to-noise ratio (S/N) of the companions. Our results suggest that the best reduction is achieved when performing the principal component analysis centered on the location of the AGPM and derotating the frames centered at the location of the star before collapsing the final datacube. We improved the S/N of companions around
β
Pictoris and R CrA by 24 ± 3% and 117 ± 11% respectively, compared to other state-of-the-art reductions. We find that the companion position for all the centering strategies are consistent within 3
σ
. Finally, we find that even for NaCo observations with tens of thousands of frames, frame selection yields just marginal improvement for point sources, but may improve the final images for objects with extended emission such as disks.
Conclusions.
We propose a novel approach to identify the location of the star behind a coronagraph even when it cannot easily be determined by other methods. We led a thorough study on the importance of frame selection, concluding that the improvements are marginal in most cases, but may yield better contrast in some specific cases. Our approach can be applied to the wealth of archival NaCo data and, assuming that the field of view includes the edges of the coronagraphic mask, its implementation can be adapted to other instruments with coronagraphs similar to the AGPM used on NaCo (e.g., Keck/NIRC2, LBT/LMIRCam).
Aims.
To understand how the multitude of planetary systems that have been discovered come to be, we need to study systems at different evolutionary stages, with different central stars but also in ...different environments. The most challenging environment for planet formation may be the harsh UV radiation field of nearby massive stars which quickly erodes disks by external photo-evaporation. We observed the AT Pyx system, located in the head of a cometary globule in the Gum Nebula, to search for signs of ongoing planet formation.
Methods.
We used the extreme adaptive optics imager VLT/SPHERE in Dual Beam Polarization Imaging Mode in
H
-band as well as in IRDIFS Extended mode (
K12
-band imaging and Y-H integral field spectroscopy) to observe AT Pyx in polarized light and total intensity. Additionally, we employed VLT/NACO to observe the system in the
L
-band.
Results.
We resolve the disk around AT Pyx for the first time in scattered light across multiple wavelengths in polarized light and total intensity. We find an extended (≥126 au) disk, with an intermediate inclination of between 35° and 42°. The disk shows a complex substructure and we identify two or possibly three spiral-like features. Depending on the precise geometry of the disk (which we cannot unambiguously infer from our data), the disk may be eccentric with an eccentricity of ~0.16 or partially self-shadowed. The spiral features and possible eccentricity are both consistent with signatures of an embedded gas giant planet with a mass of ~1
M
Jup
. Our own observations can rule out brown dwarf companions embedded in the resolved disk, but are nevertheless not sensitive enough to confirm or rule out the presence of a gas giant.
Conclusions.
AT Pyx is the first disk to be spatially resolved in a cometary globule in the Gum Nebula. By comparison with disks in the Orion Nebula Cluster we note that the extension of the disk may be exceptional for this environment if the external UV radiation field is indeed comparable to other cometary globules in the region. The signposts of ongoing planet formation are intriguing and need to be followed up with either higher sensitivity or at different wavelengths.
Context
. Within the NaCo-ISPY exoplanet imaging program, we aim at detecting and characterizing the population of low-mass companions at wide separations (≳10 AU), focusing in particular on young ...stars either hosting a known protoplanetary disk or a debris disk.
Aims
. R CrA is one of the youngest (1–3 Myr) and most promising objects in our sample because of two previous studies that suggested the presence of a close companion. Our aim is to directly image and characterize the companion for the first time.
Methods
. We observed R CrA twice with the NaCo instrument at the Very Large Telescope (VLT) in the
L
′ filter with a one year time baseline in between. The high-contrast imaging data were reduced and analyzed and the companion candidate was detected in both datasets. We used artificial negative signals to determine the position and brightness of the companion and the related uncertainties.
Results
. The companion is detected at a separation of 196.8 ± 4.5/196.6 ± 5.9 mas (18.7 ± 1.3/18.7 ± 1.4 AU) and position angle of 134.7 ± 0.5 ° /133.7 ± 0.7° in the first/second epoch observation. We measure a contrast of 7.29 ± 0.18/6.70 ± 0.15 mag with respect to the primary. A study of the stellar proper motion rejects the hypothesis that the signal is a background object. The companion candidate orbits in the clockwise direction and, if on a face-on circular orbit, its period is ∼43 − 47 yr. This value disagrees with the estimated orbital motion and therefore a face-on circular orbit may be excluded. Depending on the assumed age, extinction, and brightness of the primary, the stellar companion has a mass between 0.10 ± 0.02
M
⊙
and 1.03
−0.18
+0.20
M
⊙
range, if no contribution from circumsecondary material is taken into account.
Conclusions
. As already hypothesized by previous studies, we directly detected a low-mass stellar companion orbiting the young Herbig Ae/Be star R CrA. Depending on the age assumptions, the companion is among the youngest forming companions imaged to date, and its presence needs to be taken into account when analyzing the complex circumstellar environment of R CrA.
LaryngoPharyngeal Reflux (LPR) is characterized by symptoms, signs, and/or tissue damage
resulting from the aggression of the gastrointestinal contents in the upper airways. The Reflux Finding
Score ...(RFS) assesses the laryngeal signs through laryngoscopy. The Reflux Symptom Index (RSI) scores
the LPR symptoms. The objective of this real-world study was to compare RFS with RSI in a cohort of
Italian LPR patients. Globally, 3932 patients with LPR were evaluated and RFS and RSI were assessed in
all subjects. A moderate correlation was found between RSI and RFS (r=0.484, p<0.0001). In conclusion,
the RSI and RFS can easily be included in the LPR work-up as objective and consistent parameters,
with low cost and high practicality. Based on these clinical outcomes, the specialist can easily use these
tests in clinical practice.
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