Abstract
Directly imaging exoplanets is challenging because quasi-static phase aberrations in the pupil plane (speckles) can mimic the signal of a companion at small angular separations. Kernel ...phase, which is a generalization of closure phase (known from sparse aperture masking), is independent of pupil plane phase noise to second order and allows for a robust calibration of full pupil, extreme adaptive optics observations. We applied kernel phase combined with a principal component based calibration process to a suitable but not optimal, high cadence, pupil stabilized L’-band ($3.8\, {\mu \rm m}$) data set from the ESO archive. We detect eight low-mass companions, five of which were previously unknown, and two have angular separations of ∼0.8–1.2 λ/D (i.e. ∼80–$110\, \text{mas}$), demonstrating that kernel phase achieves a resolution below the classical diffraction limit of a telescope. While we reach a 5σ contrast limit of ∼1/100 at such angular separations, we demonstrate that an optimized observing strategy with more diversity of PSF references (e.g. star-hopping sequences) would have led to a better calibration and even better performance. As such, kernel phase is a promising technique for achieving the best possible resolution with future space-based telescopes (e.g. James Webb Space Telescope), which are limited by the mirror size rather than atmospheric turbulence, and with a dedicated calibration process also for extreme adaptive optics facilities from the ground.
Brown dwarfs exhibit patchy or spatially varying banded cloud structures that are inferred through photometric and spectroscopic variability modeling techniques. However, these methods are ...insensitive to rotationally invariant structures, such as the bands seen in Jupiter. Here, we present H-band Very Large Telescope/NaCo linear polarization measurements of the nearby Luhman 16 L/T transition binary, which suggest that Luhman 16A exhibits constant longitudinal cloud bands. The instrument was operated in pupil tracking mode, allowing us to unambiguously distinguish between a small astrophysical polarization and the ∼2% instrumental linear polarization. We measure the degree and angle of linear polarization of Luhman 16A and B to be pA = 0.031% 0.004% and A = −32° 4°, and pB = 0.010% 0.004% and , respectively. Using known physical parameters of the system, we demonstrate that an oblate homogeneous atmosphere cannot account for the polarization measured in Luhman 16A, but could be responsible for that of the B component. Through a nonexhaustive search of banded cloud morphologies, we demonstrate a two-banded scenario that can achieve a degree of linear polarization of p = 0.03% and conclude that the measured polarization of the A component must be predominantly due to cloud banding. For Luhman 16B, either oblateness or cloud banding could be the dominant source of the measured polarization. The misaligned polarization angles of the two binary components tentatively suggest spin-orbit misalignment. These measurements provide new evidence for the prevalence of cloud banding in brown dwarfs while at the same time demonstrating a new method-complementary to photometric and spectroscopic variability methods-for characterizing the cloud morphologies of substellar objects without signs of variability.
We present high-contrast observations of the circumstellar environment of the Herbig Ae/Be star HD 100546. The final 3.8 mu m image reveals an emission source at a projected separation of 0".48 + or ...- 0".04 (corresponding to ~47 + or - 4 AU) at a position angle of 8degrees.9 + or - 0degrees.9. The emission appears slightly extended with a point source component with an apparent magnitude of 13.2 + or - 0.4 mag. The position of the source coincides with a local deficit in polarization fraction in near-infrared polarimetric imaging data, which probes the surface of the well-studied circumstellar disk of HD 100546. This suggests a possible physical link between the emission source and the disk. Assuming a disk inclination of ~47degrees, the de-projected separation of the object is degrees68 AU. Assessing the likelihood of various scenarios, we favor an interpretation of the available high-contrast data with a planet in the process of forming. Follow-up observations in the coming years can easily distinguish between the different possible scenarios empirically. If confirmed, HD 100546 "b" would be a unique laboratory to study the formation process of a new planetary system, with one giant planet currently forming in the disk and a second planet possibly orbiting in the disk gap at smaller separations.
We present the first observational evidence for a circumplanetary disk (CPD) around the protoplanet PDS 70 b, based on a new spectrum in the K-band acquired with Very Large Telescope/SINFONI. We ...tested three hypotheses to explain the spectrum: atmospheric emission from the planet with either (1) a single value of extinction, (2) a variable extinction, and (3) a combined atmospheric and CPD model. Goodness-of-fit indicators favor the third option, suggesting that circumplanetary material contributes excess thermal emission-most prominent at λ 2.3 m. Inferred accretion rates (∼10−7.8-10−7.3 MJ yr−1) are compatible with observational constraints based on the H and Brγ lines. For the planet, we derive an effective temperature of 1500-1600 K, surface gravity , radius ∼1.6RJ, mass ∼10MJ, and possible thick clouds. Models with variable extinction lead to slightly worse fits. However, the amplitude (ΔAV 3 mag) and timescale of variation ( years) required for the extinction would also suggest circumplanetary material.
We present the first multi-wavelength, high-contrast imaging study confirming the protoplanet embedded in the disk around the Herbig Ae/Be star HD 100546. The object is detected at L' (~3.8 mu m) and ...M' (~4.8 mu m), but not at Ks (~2.1 mu m), and the emission consists of a point source component surrounded by spatially resolved emission. For the point source component we derive apparent magnitudes of L' = 13.92 + or - 0.10 mag, M' = 13.33 + or - 0.16 mag, and Ks > 15.43 + or - 0.06 mag (3sigma limit), and a separation and position angle of (0.457 + or - 0.014)" and (8.4 + or -1.4)degrees, and (0.472 + or - 0.014)" and (9.2 + or - 1.4)degrees in L' and M', respectively. We demonstrate that the object is co-moving with HD 100546 and can reject any (sub-)stellar fore-/background object. Fitting a single-temperature blackbody to the observed fluxes of the point source component yields an effective temperature of T sub(eff) = 932 super(+193) sub(-202) K and a radius for the emitting area of R = 6.9 super(+2.7) sub(-2.9)R sub(Jupiter). The best-fit luminosity is L = (2.3 super(+0.6) sub(-0.4)) times 10 super(-4) L sub(middot in circle). We quantitatively compare our findings with predictions from evolutionary and atmospheric models for young, gas giant planets, discuss the possible existence of a warm, circumplanetary disk, and note that the deprojected physical separation from the host star of (53 + or - 2) AU poses a challenge to standard planet formation theories. Considering the suspected existence of an additional planet orbiting at ~13-14 AU, HD 100546 appears to be an unprecedented laboratory to study the formation of multiple gas giant planets empirically.
Background
Dual-mobility (DM) cups were introduced to minimize the risk of THA dislocation. The overall rate of dislocation of DM cups (including both large and small articulations) is controversial ...and ranges from 0% to 5% in previous studies.
Questions/purposes
We therefore recorded (1) the dislocation rate, (2) loosening and osteolysis, and (3) subsequent related revisions with DM cups.
Methods
Between 1998 and 2003, 2480 primary THAs with DM cups were undertaken in 2179 patients. The mean age was 69 years (range, 19–94 years). This group underwent specific clinical and radiographic evaluation at a minimum followup of 0.17 years (mean, 7 years; range, 0.17–11 years) to assess dislocation, reoperation, osteolysis, and cup fixation.
Results
There were 22 dislocations (0.88%): 15 dislocations of large articulations (0.6%), with two (0.08%) recurring but only one requiring revision (0.04%), and seven intraprosthetic small articulation dislocations (0.28%), all needing revision surgery. At last followup, mean Harris hip score was 91 (range, 60–100); 2439 cups (98%) showed no signs of loosening; and 141 patients (145 hips) had osteolysis (6%). Osteolysis and cup loosening were more frequent in patients younger than 50 years at the time of surgery. The 10-year survivorship considering revision for any reason was 93% (95% CI, 91%–95%).
Conclusions
DM cups had a low dislocation rate in primary THA, with a limited frequency of adverse effects. We recommend DM cups to minimize dislocation in populations at high risk for instability, but they should be avoided in younger, active patients at higher risk for osteolysis.
Level of Evidence
Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
Context.
The detection of radio emissions from exoplanets will open up a vibrant new research field. Observing planetary auroral radio emission is the most promising method to detect exoplanetary ...magnetic fields, the knowledge of which will provide valuable insights into the planet’s interior structure, atmospheric escape, and habitability.
Aims.
We present LOFAR (LOw-Frequency ARray) Low Band Antenna (LBA: 10–90 MHz) circularly polarized beamformed observations of the exoplanetary systems 55 Cancri,
υ
Andromedae, and
τ
Boötis. All three systems are predicted to be good candidates to search for exoplanetary radio emission.
Methods.
We applied the
BOREALIS
pipeline that we have developed to mitigate radio frequency interference and searched for both slowly varying and bursty radio emission. Our pipeline has previously been quantitatively benchmarked on attenuated Jupiter radio emission.
Results.
We tentatively detect circularly polarized bursty emission from the
τ
Boötis system in the range 14–21 MHz with a flux density of ~890 mJy and with a statistical significance of ~3
σ
. For this detection, we do not see any signal in the OFF-beams, and we do not find any potential causes which might cause false positives. We also tentatively detect slowly variable circularly polarized emission from
τ
Boötis in the range 21–30 MHz with a flux density of ~400 mJy and with a statistical significance of >8
σ
. The slow emission is structured in the time-frequency plane and shows an excess in the ON-beam with respect to the two simultaneous OFF-beams. While the bursty emission seems rather robust, close examination casts some doubts on the reality of the slowly varying signal. We discuss in detail all the arguments for and against an actual detection, and derive methodological tests that will also apply to future searches. Furthermore, a ~2
σ
marginal signal is found from the
υ
Andromedae system in one observation of bursty emission in the range 14–38 MHz and no signal is detected from the 55 Cancri system, on which we placed a 3
σ
upper limit of 73 mJy for the flux density at the time of the observation.
Conclusions.
Assuming the detected signals are real, we discuss their potential origin. Their source probably is the
τ
Boötis planetary system, and a possible explanation is radio emission from the exoplanet
τ
Boötis b via the cyclotron maser mechanism. Assuming a planetary origin, we derived limits for the planetary polar surface magnetic field strength, finding values compatible with theoretical predictions. Further observations with LOFAR-LBA and other low-frequency telescopes, such as NenuFAR or UTR-2, are required to confirm this possible first detection of an exoplanetary radio signal.
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