A&A 644, A13 (2020) The circumstellar disk of PDS 70 hosts two forming planets, which are
actively accreting gas from their environment. In this work, we report the
first detection of PDS 70 b in the ...Br$\alpha$ and $M'$ filters with VLT/NACO, a
tentative detection of PDS 70 c in Br$\alpha$, 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 Br$\alpha$ and $M'$ filters, indicating that scattered
light is non-negligible at these wavelengths. The spectral energy distribution
of PDS 70 b is well described by blackbody emission, for which we constrain the
photospheric temperature and photospheric radius to $T_\mathrm{eff}=1193 \pm
20$ K and $R=3.0 \pm 0.2$ $R_\mathrm{J}$. The relatively low bolometric
luminosity, $\log(L/L_\odot) = -3.79 \pm 0.02$, 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
$M_\mathrm{p}\approx 0.5-1.5$ $M_\mathrm{J}$ and $R_\mathrm{p}\approx 1-2.5$
$R_\mathrm{J}$, 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. Finally, we derive a rough
upper limit on the temperature and radius of potential excess emission from a
circumplanetary disk, $T_\mathrm{eff}\lesssim256$ K and $R\lesssim245$
$R_\mathrm{J}$, but we do find weak evidence that the current data favors a
model with a single blackbody component.
We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a \(<\)20 M\(_\mathrm{Jup}\) widely separated (\(\sim\)8\arcsec, a = 150 au), young, planetary-mass ...companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799 c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color-magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256~b with \textit{JWST}'s NIRSpec IFU and MIRI MRS modes for coverage from 1 \(\mu\)m to 20 \(\mu\)m at resolutions of \(\sim\)1,000 - 3,700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the \textit{JWST} spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion.
We know little about the outermost exoplanets in planetary systems, because our detection methods are insensitive to moderate-mass planets on wide orbits. However, debris discs can probe the ...outer-planet population, because dynamical modelling of observed discs can reveal properties of perturbing planets. We use four sculpting and stirring arguments to infer planet properties in 178 debris-disc systems from the ISPY, LEECH and LIStEN planet-hunting surveys. Similar analyses are often conducted for individual discs, but we consider a large sample in a consistent manner. We aim to predict the population of wide-separation planets, gain insight into the formation and evolution histories of planetary systems, and determine the feasibility of detecting these planets in the near future. We show that a `typical' cold debris disc likely requires a Neptune- to Saturn-mass planet at 10-100 au, with some needing Jupiter-mass perturbers. Our predicted planets are currently undetectable, but modest detection-limit improvements (e.g. from JWST) should reveal many such perturbers. We find that planets thought to be perturbing debris discs at late times are similar to those inferred to be forming in protoplanetary discs, so these could be the same population if newly formed planets do not migrate as far as currently thought. Alternatively, young planets could rapidly sculpt debris before migrating inwards, meaning that the responsible planets are more massive (and located further inwards) than debris-disc studies assume. We combine self-stirring and size-distribution modelling to show that many debris discs cannot be self-stirred without having unreasonably high masses; planet- or companion-stirring may therefore be the dominant mechanism in many (perhaps all) debris discs. Finally, we provide catalogues of planet predictions, and identify promising targets for future planet searches.
The unprecedented medium-resolution (R~1500-3500) near- and mid-infrared (1-18um) spectrum provided by JWST for the young (140+/-20Myr) low-mass (12-20MJup) L-T transition (L7) companion VHS1256b ...gives access to a catalogue of molecular absorptions. In this study, we present a comprehensive analysis of this dataset utilizing a forward modelling approach, applying our Bayesian framework, ForMoSA. We explore five distinct atmospheric models to assess their performance in estimating key atmospheric parameters: Teff, log(g), M/H, C/O, gamma, fsed, and R. Our findings reveal that each parameter's estimate is significantly influenced by factors such as the wavelength range considered and the model chosen for the fit. This is attributed to systematic errors in the models and their challenges in accurately replicating the complex atmospheric structure of VHS1256b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances M/H and C/O, often employed as indicators of formation history, remains challenging. Nevertheless, the pioneering case of JWST's data for VHS1256b has paved the way for future acquisitions of substellar spectra that will be systematically analyzed to directly compare the properties of these objects and correct the systematics in the models.
We present multi-epoch observations of the RY~Tau jet for H\(\alpha\) and \ion{Fe}{2} 1.644 \micron~emission lines obtained with Subaru/SCExAO+VAMPIRES, Gemini/NIFS, and Keck/OSIRIS in 2019--2021. ...These data show a series of four knots within 1\(\arcsec\) consistent with the proper motion of \(\sim\)0\farcs3~yr\(^{-1}\), analogous to the jets associated with another few active T-Tauri stars. However, the spatial intervals between the knots suggest the time intervals of the ejections of about 1.2, 0.7, and 0.7 years, significantly shorter than those estimated for the other stars. These H\(\alpha\) images contrast with the archival VLT/SPHERE/ZIMPOL observations from 2015, which showed only a single knot-like feature at \(\sim0\farcs25\). The difference between the 2015 and 2019--2021 epochs suggests an irregular ejection interval within the six-year range. Such variations of the jet ejection may be related to a short-term (\(<\)1 year) variability of the mass accretion rate. We compared the peaks of the H\(\alpha\) emissions with the ZIMPOL data taken in 2015, showing the brighter profile at the base (\(<0\farcs3\)) than the 2020--2021 VAMPIRES profiles due to time-variable mass ejection rates or the heating-cooling balance in the jet. The observed jet knot structures may be alternatively attributed to stationary shocks, but a higher angular resolution is required to confirm its detailed origin.
GQ Lup B is a young and accreting, substellar companion that appears to drive a spiral arm in the circumstellar disk of its host star. We report high-contrast imaging observations of GQ Lup B with ...VLT/NACO at 4-5 \(\mu\)m and medium-resolution integral field spectroscopy with VLT/MUSE. The optical spectrum is consistent with an M9 spectral type, shows characteristics of a low-gravity atmosphere, and exhibits strong H\(\alpha\) emission. The \(H-M'\) color is \(\gtrsim\)1 mag redder than field dwarfs with similar spectral types and a detailed analysis of the spectral energy distribution (SED) from optical to mid-infrared wavelengths reveals excess emission in the \(L'\), NB4.05, and \(M'\) bands. The excess flux is well described by a blackbody component with \(T_\mathrm{disk} \approx 460\) K and \(R_\mathrm{disk} \approx 65\,R_\mathrm{J}\) and is expected to trace continuum emission from small grains in a protolunar disk. We derive an extinction of \(A_V \approx 2.3\) mag from the broadband SED with a suspected origin in the vicinity of the companion. We also combine 15 yr of astrometric measurements and constrain the mutual inclination with the circumstellar disk to \(84 \pm 9\) deg, indicating a tumultuous dynamical evolution or a stellar-like formation pathway. From the measured H\(\alpha\) flux and the estimated companion mass, \(M_\mathrm{p} \approx 30\,M_\mathrm{J}\), we derive an accretion rate of \(\dot{M} \approx 10^{-6.5}\,M_\mathrm{J}\,\mathrm{yr}^{-1}\). We speculate that the disk is in a transitional stage in which the assembly of satellites from a pebble reservoir has opened a central cavity while GQ Lup B is in the final stages of its formation.
Abbreviated. We aim to identify new low-mass companions to young stars using the astrometric measurements provided by the Gaia space mission and complementary VLT/SPHERE data. We identify companion ...candidates from a sample of K-type, pre-main sequence stars in the Scorpius Centaurus association using the early version of the third data release of the Gaia space mission. Based on the provided positions, proper motions, and magnitudes, we identify all objects within a predefined radius whose differential proper motions are consistent with a gravitationally bound system. We derive companion masses through comparison with evolutionary tracks. For seven identified companion candidates we use additional data collected with VLT/SPHERE and VLT/NACO to assess the accuracy of the properties of the companions based on Gaia photometry alone. We identify 110 comoving companions that have a companionship likelihood of more than \(95\,\%\). We identify ten especially intriguing companions that have masses in the brown dwarf regime down to \(20\,M_\mathrm{Jup}\). Our high-contrast imaging data confirm both astrometry and photometric masses derived from Gaia alone. We discover a new brown dwarf companion, TYC 8252-533-1 B, with a projected separation of approximately \(570\,\mathrm{au}\) from its Sun-like primary. SED modeling provides a companion mass of \(52^{+17}_{-11}\,M_\mathrm{Jup}\). We show that the Gaia database can identify low-mass companions at wide separations from their host stars. For K-type Sco-Cen members Gaia can detect sub-stellar objects at projected separations larger than \(300\,\mathrm{au}\) and is sensitivity limited beyond \(1,000\,\mathrm{au}\) with a lower mass limit down to \(20\,M_\mathrm{Jup}\). A similar analysis of other star-forming regions could significantly enlarge the sample size of such objects and test formation and evolution theories of planetary systems.
A&A 631, A84 (2019) H$\alpha$ is a powerful tracer of accretion and chromospheric activity, which
has been detected in the case of young brown dwarfs and even recently in
planetary mass companions ...(e.g. PDS70 b and c). H$\alpha$ detections and
characterisation of brown dwarf and planet companions can further our knowledge
of their formation and evolution, and expanding such a sample is therefore our
primary goal. We used the Zurich IMaging POLarimeter (ZIMPOL) of the SPHERE
instrument at the Very Large Telescope (VLT) to observe the known
$38-72$M$_{\mathrm{J}}$ companion orbiting PZ Tel, obtaining simultaneous
angular differential imaging observations in both continuum and narrow
H$\alpha$ band. We detect H$\alpha$ emission from the companion, making this
only the second H$\alpha$ detection of a companion using the SPHERE instrument.
We used our newly added astrometric measurements to update the orbital analysis
of PZ Tel B, and we used our photometric measurements to evaluate the H$\alpha$
line flux. Given the estimated bolometric luminosity, we obtained an H$\alpha$
activity (log$\mathrm{(L_{H\alpha}/L_{bol}})$) between $-4.16$ and $-4.31$. The
H$\alpha$ activity of PZ Tel B is consistent with known average activity levels
for M dwarf of the same spectral type. Given the absence of a known gaseous
disk and the relatively old age of the system (24 Myr), we conclude that the
H$\alpha$ emission around PZ Tel B is likely due to chromospheric activity.
We present JWST Early Release Science (ERS) coronagraphic observations of the
super-Jupiter exoplanet, HIP 65426 b, with the Near-Infrared Camera (NIRCam)
from 2-5 $\mu$m, and with the Mid-Infrared ...Instrument (MIRI) from 11-16 $\mu$m.
At a separation of $\sim$0.82" (86$^{+116}_{-31}$ au), HIP 65426 b is clearly
detected in all seven of our observational filters, representing the first
images of an exoplanet to be obtained by JWST, and the first ever direct
detection of an exoplanet beyond 5 $\mu$m. These observations demonstrate that
JWST is exceeding its nominal predicted performance by up to a factor of 10,
depending on separation and subtraction method, with measured 5$\sigma$
contrast limits of $\sim$1$\times10^{-5}$ and $\sim$2$\times10^{-4}$ at 1" for
NIRCam at 4.4 $\mu$m and MIRI at 11.3 $\mu$m, respectively. These contrast
limits provide sensitivity to sub-Jupiter companions with masses as low as
0.3$M_\mathrm{Jup}$ beyond separations of $\sim$100 au. Together with existing
ground-based near-infrared data, the JWST photometry are well fit by a BT-SETTL
atmospheric model from 1-16 $\mu$m, and span $\sim$97% of HIP 65426 b's
luminous range. Independent of the choice of model atmosphere we measure an
empirical bolometric luminosity that is tightly constrained between
$\mathrm{log}\!\left(L_\mathrm{bol}/L_{\odot}\right)$=-4.31 to $-$4.14, which
in turn provides a robust mass constraint of 7.1$\pm$1.2 $M_\mathrm{Jup}$. In
totality, these observations confirm that JWST presents a powerful and exciting
opportunity to characterise the population of exoplanets amenable to
high-contrast imaging in greater detail.
We observed the planet-hosting system PDS 70 with the James Webb Interferometer, JWST's Aperture Masking Interferometric (AMI) mode within NIRISS. Observing with the F480M filter centered at 4.8 ...\(\mu\)m, we simultaneously fit a geometric model to the outer disk and the two known planetary companions. We re-detect the protoplanets PDS 70 b and c at an SNR of 21 and 11, respectively. Our photometry of both PDS 70 b and c provide evidence for circumplanetary disk emission through fitting SED models to these new measurements and those found in the literature. We also newly detect emission within the disk gap at an SNR of \(\sim\)4, at a position angle of \(207^{+11}_{-10}\) degrees, and an unconstrained separation within \(\sim\)200 mas. Follow-up observations will be needed to determine the nature of this emission. We place a 5\(\sigma\) upper limit of \(\Delta\)mag = 7.56 on the contrast of the candidate PDS 70 d at 4.8 \(\mu\)m, which indicates that if the previously observed emission at shorter wavelengths is due to a planet, this putative planet has a different atmospheric composition than PDS 70 b or c. Finally, we place upper limits on emission from any additional planets in the disk gap. We find an azimuthally averaged 5\(\sigma\) upper limit of \(\Delta\)mag \(\approx\) 7.5 at separations greater than 125 mas. These are the deepest limits to date within \(\sim\)250 mas at 4.8 \(\mu\)m and the first space-based interferometric observations of this system.
