We present observations of the young multiple system UX Tauri to look for circumstellar disks and for signs of dynamical interactions. We obtained SPHERE/IRDIS deep differential polarization images ...in the
J
and
H
bands. We also used ALMA archival CO data. Large extended spirals are well detected in scattered light coming out of the disk of UX Tau A. The southern spiral forms a bridge between UX Tau A and C. These spirals, including the bridge connecting the two stars, all have a CO (3–2) counterpart seen by ALMA. The disk of UX Tau C is detected in scattered light. It is much smaller than the disk of UX Tau A and has a major axis along a different position angle, suggesting a misalignment. We performed
PHANTOM
SPH hydrodynamical models to interpret the data. The scattered light spirals, CO emission spirals and velocity patterns of the rotating disks, and the compactness of the disk of UX Tau C all point to a scenario in which UX Tau A has been perturbed very recently (∼1000 years) by the close passage of UX Tau C.
Context.
The nearby and young
β
Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was ...recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution.
Aims.
We aim to further constrain the orbital and physical properties of
β
Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system.
Methods.
We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry.
Results.
The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the H
IPPARCOS
distance. We note that despite these low fitting error bars, the eccentricity of
β
Pictoris c might still be over-estimated. If no prior is provided on the mass of
β
Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of
β
Pictoris b, we find a solution in the 10–11
M
Jup
range. Conversely,
β
Pictoris c’s mass is well constrained, at 7.8 ± 0.4
M
Jup
, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the
β
Pictoris system. The absolute astrometry H
IPPARCOS
-
Gaia
data are consistent with the solutions presented here at the 2
σ
level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5
M
Jup
closer than 3 au, and more massive than 3.5
M
Jup
between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1–2
M
Jup
.
Conclusions.
Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of
β
Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of
β
Pictoris b.
First light of the VLT planet finder SPHERE Zurlo, A.; Vigan, A.; Galicher, R. ...
Astronomy and astrophysics (Berlin),
03/2016, Letnik:
587, Številka:
A57
Journal Article, Web Resource
Recenzirano
Odprti dostop
Context. The planetary system discovered around the young A-type HR 8799 provides a unique laboratory to: a) test planet formation theories; b) probe the diversity of system architectures at these ...separations, and c) perform comparative (exo)planetology.Aims. We present and exploit new near-infrared images and integral-field spectra of the four gas giants surrounding HR 8799 obtained with SPHERE, the new planet finder instrument at the Very Large Telescope, during the commissioning and science verification phase of the instrument (July–December 2014). With these new data, we contribute to completing the spectral energy distribution (SED) of these bodies in the 1.0–2.5 μm range. We also provide new astrometric data, in particular for planet e, to further constrain the orbits.Methods. We used the infrared dual-band imager and spectrograph (IRDIS) subsystem to obtain pupil-stabilized, dual-band H2H3 (1.593 μm, 1.667 μm), K1K2 (2.110 μm, 2.251 μm), and broadband J (1.245 μm) images of the four planets. IRDIS was operated in parallel with the integral field spectrograph (IFS) of SPHERE to collect low-resolution (R ~ 30), near-infrared (0.94–1.64 μm) spectra of the two innermost planets HR 8799 d and e. The data were reduced with dedicated algorithms, such as the Karhunen-Loève image projection (KLIP), to reveal the planets. We used the so-called negative planets injection technique to extract their photometry, spectra, and measure their positions. We illustrate the astrometric performance of SPHERE through sample orbital fits compatible with SPHERE and literature data.Results. We demonstrated the ability of SPHERE to detect and characterize planets in this kind of systems, providing spectra and photometry of its components. The spectra improve upon the signal-to-noise ratio of previously obtained data and increase the spectral coverage down to the Y band. In addition, we provide the first detection of planet e in the J band. Astrometric positions for planets HR 8799 bcde are reported for the epochs of July, August, and December 2014. We measured the photometric values in J, H2H3, K1K2 bands for the four planets with a mean accuracy of 0.13 mag. We found upper limit constraints on the mass of a possible planet f of 3–7 MJup . Our new measurements are more consistent with the two inner planets d and e being in a 2d:1e or 3d:2e resonance. The spectra of HR 8799 d and e are well matched by those of L6-8 field dwarfs. However, the SEDs of these objects are redder than field L dwarfs longward of 1.6 μm.
We present orbital fits and dynamical masses for HIP 113201AB and HIP 36985AB, two M1 + mid-M dwarf binary systems monitored as part of the SPHERE-SHINE survey. To robustly determine the age of both ...systems via gyrochronology, we undertook a photometric monitoring campaign for HIP 113201 and GJ 282AB, the two wide K star companions to HIP 36985, using the 40 cm Remote Observatory Atacama Desert telescope. Based on this monitoring and gyrochronological relationships, we adopt ages of 1.2 ± 0.1 Gyr for HIP 113201AB and 750 ± 100 Myr for HIP 36985AB. These systems are sufficiently old that we expect that all components of these binaries have reached the main sequence. To derive dynamical masses for all components of the HIP 113201AB and HIP 36985AB systems, we used parallel-tempering Markov chain Monte Carlo sampling to fit a combination of radial velocity, direct imaging, and
Gaia
and
HIPPARCOS
astrometry. Fitting the direct imaging and radial velocity data for HIP 113201 yields a primary mass of 0.54 ± 0.03
M
⊙
, fully consistent with its M1 spectral type, and a secondary mass of 0.145 ±
M
⊙
. The secondary masses derived with and without including
HIPPARCOS
-
Gaia
data are all considerably more massive than the 0.1
M
⊙
mass estimated from the photometry of the companion. Thus, the dynamical impacts of this companion suggest that it is more massive than expected from its photometry. An undetected brown dwarf companion to HIP 113201B could be a natural explanation for this apparent discrepancy. At an age >1 Gyr, a 30
M
Jup
companion to HIP 113201B would make a negligible (<1%) contribution to the system luminosity but could have strong dynamical impacts. Fitting the direct imaging, radial velocity, and
HIPPARCOS
-
Gaia
proper motion anomaly for HIP 36985AB, we find a primary mass of 0.54 ± 0.01
M
⊙
and a secondary mass of 0.185 ± 0.001
M
⊙
, which agree well with photometric estimates of component masses, the masses estimated from
M
K
– mass relationships for M dwarf stars, and previous dynamical masses in the literature.
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.
Aims
. To date, infrared interferometry at best achieved contrast ratios of a few times 10
−4
on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast observations, ...enabling the direct observation of exoplanets. We demonstrate the technique on HR 8799, a young planetary system composed of four known giant exoplanets.
Methods
. We used the GRAVITY fringe tracker to lock the fringes on the central star, and integrated off-axis on the HR 8799 e planet situated at 390 mas from the star. Data reduction included post-processing to remove the flux leaking from the central star and to extract the coherent flux of the planet. The inferred
K
band spectrum of the planet has a spectral resolution of 500. We also derive the astrometric position of the planet relative to the star with a precision on the order of 100
μ
as.
Results
. The GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital solutions. A small adjustment of a few degrees to the orbital inclination of HR 8799 e can resolve the tension, implying that the orbits are close to, but not strictly coplanar. The spectrum, with a signal-to-noise ratio of ≈5 per spectral channel, is compatible with a late-type L brown dwarf. Using Exo-REM synthetic spectra, we derive a temperature of 1150 ± 50 K and a surface gravity of 10
4.3 ± 0.3
cm s
2
. This corresponds to a radius of 1.17
−0.11
+0.13
R
Jup
and a mass of 10
−4
+7
M
Jup
, which is an independent confirmation of mass estimates from evolutionary models. Our results demonstrate the power of interferometry for the direct detection and spectroscopic study of exoplanets at close angular separations from their stars.
Context.
In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand ...their formation and evolution mechanisms, in 2015 we initiated the SPHERE infrared survey for exoplanets (SHINE), a systematic direct imaging survey of young, nearby stars that is targeted at exploring their demographics.
Aims.
We aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. Combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.
Methods.
In this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars that are representative of the full SHINE sample. Observations were conducted in a homogeneous way between February 2015 and February 2017 with the dedicated ground-based VLT/SPHERE instrument equipped with the IFS integral field spectrograph and the IRDIS dual-band imager, covering a spectral range between 0.9 and 2.3 μm. We used coronographic, angular, and spectral differential imaging techniques to achieve the best detection performances for this study, down to the planetary mass regime.
Results.
We processed, in a uniform manner, more than 300 SHINE observations and datasets to assess the survey typical sensitivity as a function of the host star and of the observing conditions. The median detection performance reached 5
σ
-contrasts of 13 mag at 200 mas and 14.2 mag at 800 mas with the IFS (
YJ
and
YJH
bands), and of 11.8 mag at 200 mas, 13.1 mag at 800 mas, and 15.8 mag at 3 as with IRDIS in
H
band, delivering one of the deepest sensitivity surveys thus far for young, nearby stars. A total of sixteen substellar companions were imaged in this first part of SHINE: seven brown dwarf companions and ten planetary-mass companions.These include two new discoveries, HIP 65426 b and HIP 64892 B, but not the planets around PDS70 that had not been originally selected for the SHINE core sample. A total of 1483 candidates were detected, mainly in the large field of view that characterizes IRDIS. The color-magnitude diagrams, low-resolution spectrum (when available with IFS), and follow-up observations enabled us to identify the nature (background contaminant or comoving companion) of about 86% of our subsample. The remaining cases are often connected to crowded-field follow-up observations that were missing. Finally, even though SHINE was not initially designed for disk searches, we imaged twelve circumstellar disks, including three new detections around the HIP 73145, HIP 86598, and HD 106906 systems.
Conclusions.
Nowadays, direct imaging provides a unique opportunity to probe the outer part of exoplanetary systems beyond 10 au to explore planetary architectures, as highlighted by the discoveries of: one new exoplanet, one new brown dwarf companion, and three new debris disks during this early phase of SHINE. It also offers the opportunity to explore and revisit the physical and orbital properties of these young, giant planets and brown dwarf companions (relative position, photometry, and low-resolution spectrum in near-infrared, predicted masses, and contrast in order to search for additional companions). Finally, these results highlight the importance of finalizing the SHINE systematic observation of about 500 young, nearby stars for a full exploration of their outer part to explore the demographics of young giant planets beyond 10 au and to identify the most interesting systems for the next generation of high-contrast imagers on very large and extremely large telescopes.
HIP 65426 b is a recently discovered exoplanet imaged during the course of the SPHERE-SHINE survey. Here we present new L′ and M′ observations of the planet from the NACO instrument at the VLT from ...the NACO-ISPY survey, as well as a new Y –H spectrum and K-band photometry from SPHERE-SHINE. Using these data, we confirm the nature of the companion as a warm, dusty planet with a mid-L spectral type. From comparison of its SED with the BT-Settl atmospheric models, we derive a best-fit effective temperature of Teff = 1618 ± 7 K, surface gravity log g = 3.78−0.03+0.04 $\log g\,{=}\,3.78^{+0.04}_{-0.03}$logg = 3.78−0.03+0.04 and radius R = 1.17 ± 0.04RJ (statistical uncertainties only). Using the DUSTY and COND isochrones we estimate a mass of 8 ± 1MJ. Combining the astrometric measurements from our new datasets and from the literature, we show the first indications of orbital motion of the companion (2.6σ significance)and derive preliminary orbital constraints. We find a highly inclined orbit ( i = 1.07−10+13 $i\,{=}\,107^{+13}_{-10}$i = 107−10+13 deg) with an orbital period of 800−400+1200 $800^{+1200}_{-400}$800−400+1200 yr. We also report SPHERE sparse aperture masking observations that investigate the possibility that HIP 65426 b was scattered onto its current orbit by an additional companion at a smaller orbital separation. From this data we rule out the presence of brown dwarf companions with masses greater than 16 MJ at separations larger than 3 AU, significantly narrowing the parameter space for such a companion.
Context.
HD 72946 is a bright and nearby solar-type star hosting a low-mass companion at long period (
P
∼ 16 yr) detected with the radial velocity (RV) method. The companion has a minimum mass of ...60.4 ± 2.2
M
J
and might be a brown dwarf. Its expected semi-major axis of ∼243 mas makes it a suitable target for further characterization with high-contrast imaging, in particular to measure its inclination, mass, and spectrum and thus definitely establish its substellar nature.
Aims.
We aim to further characterize the orbit, atmosphere, and physical nature of HD 72946B.
Methods.
We present high-contrast imaging data in the near-infrared with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. We also use proper motion measurements of the star from H
IPPARCOS
and
Gaia
.
Results.
The SPHERE data reveal a point source with a contrast of ∼9 mag at a projected separation of ∼235 mas. No other point sources are detected in the field of view. By jointly fitting the RV, imaging, and proper motion data, we constrain all the orbital parameters of HD 72946B and assess a dynamical mass of 72.4 ± 1.6
M
J
and a semi-major axis of 6.456.45
+0.08
−0.07
au. Empirical comparison of its SPHERE spectrum to template dwarfs indicates a spectral type of L5.0 ± 1.5. The
J
–
H
3 color is close to the expectations of the DUSTY models and suggests a cloudy atmosphere. Comparison with atmospheric models of the spectrophotometry suggests an effective temperature of ∼1700 K. The bolometric luminosity (log(
L
/
L
⊙
) = −4.11 ± 0.10 dex) and dynamical mass of HD 72946B are more compatible with evolutionary models for an age range of ∼0.9−3 Gyr. The formation mechanism of the companion is currently unclear as the object appears slightly away from the bulk of model predictions. HD 72946B is currently the closest benchmark brown dwarf companion to a solar-type star with imaging, RV, and proper motion measurements.
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.
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