Context. Transition disks offer the extraordinary opportunity to look for newly born planets and to investigate the early stages of planet formation. Aim. In this context we observed the Herbig A5 ...star MWC 758 with the L′-band vector vortex coronagraph installed in the near-infrared camera and spectrograph NIRC2 at the Keck II telescope, with the aim of unveiling the nature of the spiral structure by constraining the presence of planetary companions in the system. Methods. Our high-contrast imaging observations show a bright (ΔL′ = 7.0 ± 0.3 mag) point-like emission south of MWC 758 at a deprojected separation of ~20 au (r = 0.′′111 ± 0.′′004) from the central star. We also recover the two spiral arms (southeast and northwest), already imaged by previous studies in polarized light, and discover a third arm to the southwest of the star. No additional companions were detected in the system down to 5 Jupiter masses beyond 0.′′6 from the star. Results. We propose that the bright L′-band emission could be caused by the presence of an embedded and accreting protoplanet, although the possibility of it being an asymmetric disk feature cannot be excluded. The spiral structure is probably not related to the protoplanet candidate, unless on an inclined and eccentric orbit, and it could be due to one (or more) yet undetected planetary companions at the edge of or outside the spiral pattern. Future observations and additional simulations will be needed to shed light on the true nature of the point-like source and its link with the spiral arms.
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We present 17 transit light curves of the ultrashort period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a ...high-precision reference epoch for transit timing studies. The time of the reference transit mid-point is now measured to an accuracy of 4.8 s, versus 67.4 s in the discovery paper, aiding future searches for orbital decay. With the help of published spectroscopic measurements and theoretical stellar models, we determine the physical properties of the system to high precision and present a detailed error budget for these calculations. The planet has a Roche lobe filling factor of 0.58, leading to a significant asphericity; we correct its measured mass and mean density for this phenomenon. A high-resolution Lucky Imaging observation shows no evidence for faint stars close enough to contaminate the point spread function of WASP-103. Our data were obtained in the Bessell RI and the SDSS griz passbands and yield a larger planet radius at bluer optical wavelengths, to a confidence level of 7.3σ. Interpreting this as an effect of Rayleigh scattering in the planetary atmosphere leads to a measurement of the planetary mass which is too small by a factor of 5, implying that Rayleigh scattering is not the main cause of the variation of radius with wavelength.
ABSTRACT An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L′-band ...observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP 79124, which had previously been detected by means of interferometry. With HIP 79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L′ band versus H band, this new coronagraphic capability will enable high-contrast, small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics coronagraphs.
Context. The circumstellar disk of the Herbig Fe star HD 142527 is host to several remarkable features including a warped inner disk, a 120 au-wide annular gap, a prominent dust trap and several ...spiral arms. A low-mass companion, HD 142527 B, was also found orbiting the primary star at ~14 au. Aims. This study aims to better characterize this companion, which could help explain its impact on the peculiar geometry of the disk. Method. We observed the source with VLT/SINFONI in H + K band in pupil-tracking mode. Data were post-processed with several algorithms based on angular differential imaging (ADI). Results. HD 142527 B is conspicuously re-detected in most spectral channels, which enables us to extract the first medium-resolution spectrum of a low-mass companion within 0.″1 from its central star. Fitting our spectrum with both template and synthetic spectra suggests that the companion is a young M2.5 ± 1.0 star with an effective temperature of 3500 ± 100 K, possibly surrounded with a hot (1700 K) circum-secondary environment. Pre-main sequence evolutionary tracks provide a mass estimate of 0.34 ± 0.06 M⊙, independent of the presence of a hot environment. However, the estimated stellar radius and age do depend on that assumption; we find a radius of 1.37 ± 0.05 R⊙ (resp. 1.96 ± 0.10 R⊙) and an age of 1.8-0.5+1.2 1.8 − 0.5 + 1.2 $ 1.8_{-0.5}^{+1.2} $ Myr (resp. 0.75 ± 0.25 Myr) in the case of the presence (resp. absence) of a hot environment contributing in H + K. Our new values for the mass and radius of the companion yield a mass accretion rate of 4.1–5.8 × 10−9 M⊙ yr−1 (2–3% that of the primary). Conclusions. We have constrained the physical properties of HD 142527 B, thereby illustrating the potential for SINFONI+ADI to characterize faint close-in companions. The new spectral type makes HD 142527 B a twin of the well-known TW Hya T Tauri star, and the revision of its mass to higher values further supports its role in shaping the disk.
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We report 13 high-precision light curves of eight transits of the exoplanet WASP-52 b, obtained by using four medium-class telescopes, through different filters, and adopting the defocussing ...technique. One transit was recorded simultaneously from two different observatories and another one from the same site but with two different instruments, including a multiband camera. Anomalies were clearly detected in five light curves and modelled as star-spots occulted by the planet during the transit events. We fitted the clean light curves with the JKTEBOP code, and those with the anomalies with the PRISM+GEMC codes in order to simultaneously model the photometric parameters of the transits and the position, size and contrast of each star-spot. We used these new light curves and some from the literature to revise the physical properties of the WASP-52 system. Star-spots with similar characteristics were detected in four transits over a period of 43 d. In the hypothesis that we are dealing with the same star-spot, periodically occulted by the transiting planet, we estimated the projected orbital obliquity of WASP-52 b to be ... = 3 Math Processing Error...8 plus or minus 8 Math Processing Error...4. We also determined the true orbital obliquity, ... = 20... plus or minus 50..., which is, although very uncertain, the first measurement of ... purely from star-spot crossings. We finally assembled an optical transmission spectrum of the planet and searched for variations of its radius as a function of wavelength. Our analysis suggests a flat transmission spectrum within the experimental uncertainties. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
We present broad-band photometry of 11 planetary transits of the hot Jupiter WASP-74 b, using three medium-class telescopes and employing the telescope-defocusing technique. Most of the ...transits were monitored through I filters and one was simultaneously observed in five optical (U, g′, r′, i′, z′) and three near-infrared (J, H, K) passbands, for a total of 18 light curves. We also obtained new high-resolution spectra of the host star. We used these new data to review the orbital and physical properties of the WASP-74 planetary system. We were able to better constrain the main system characteristics, measuring smaller radius and mass for both the hot Jupiter and its host star than previously reported in the literature. Joining our optical data with those taken with the HST in the near infrared, we built up an observational transmission spectrum of the planet, which suggests the presence of strong optical absorbers, as TiO and VO gases, in its atmosphere.
We present new ground-based, multi-colour, broad-band photometric measurements of the physical parameters, transmission and emission spectra of the transiting extrasolar planet WASP-19b. The ...measurements are based on observations of eight transits and four occultations through a Gunn i filter using the 1.54-m Danish Telescope, 14 transits through an R
c
filter at the Perth Exoplanet Survey Telescope (PEST) observatory and one transit observed simultaneously through four optical (Sloan g
′, r
′, i
′, z
′) and three near-infrared (J, H, K) filters, using the Gamma Ray Burst Optical and Near-Infrared Detector (GROND) instrument on the MPG/ESO 2.2-m telescope. The GROND optical light curves have a point-to-point scatter around the best-fitting model between 0.52 and 0.65 mmag rms. We use these new data to measure refined physical parameters for the system. We find the planet to be more bloated (R
b = 1.410 ± 0.017R
Jup; M
b = 1.139 ± 0.030M
Jup) and the system to be twice as old as initially thought. We also used published and archived data sets to study the transit timings, which do not depart from a linear ephemeris. We detected an anomaly in the GROND transit light curve which is compatible with a spot on the photosphere of the parent star. The starspot position, size, spot contrast and temperature were established. Using our new and published measurements, we assembled the planet's transmission spectrum over the 370-2350 nm wavelength range and its emission spectrum over the 750-8000 nm range. By comparing these data to theoretical models we investigated the theoretically predicted variation of the apparent radius of WASP-19b as a function of wavelength and studied the composition and thermal structure of its atmosphere. We conclude that: (i) there is no evidence for strong optical absorbers at low pressure, supporting the common idea that the planet's atmosphere lacks a dayside inversion; (ii) the temperature of the planet is not homogenized, because the high warming of its dayside causes the planet to be more efficient in re-radiating than redistributing energy to the night side; (iii) the planet seems to be outside of any current classification scheme.
We present new photometric observations of H1413+117 acquired during seasons between 2001 and 2008 in order to estimate the time delays between the lensed quasar images and to characterize at best ...the on-going micro-lensing events. We propose a highly performing photometric method called the adaptive point spread function fitting and have successfully tested this method on a large number of simulated frames. This has enabled us to estimate the photometric error bars affecting our observational results. We analysed the V- and R-band light curves and V-R colour variations of the A-D components which show short- and long-term brightness variations correlated with colour variations. Using the ... and dispersion methods, we estimated the time delays on the basis of the R-band light curves over the seasons between 2003 and 2006. We have derived the new values: ...tAB = -17.4 plus or minus 2.1, ...tAC = -18.9 plus or minus 2.8 and ...tAD = 28.8 plus or minus 0.7 d using the ... method (B and C are leading, D is trailing) with 1s confidence intervals. We also used available observational constraints (resp. the lensed image positions, the flux ratios in mid-IR and two sets of time delays derived in the present work) to update the lens redshift estimation. We obtained zl=1.95... which is in good agreement with previous estimations. We propose to characterize two kinds of micro-lensing events: micro-lensing for the A, B, C components corresponds to typical variations of ~10-4 mag d-1 during all the seasons, while the D component shows an unusually strong micro-lensing effect with variations of up to ~10-3 mag d-1 during 2004 and 2005. (ProQuest: ... denotes formulae/symbols omitted.)
Considering a small misalignment between a point-like source, a singular isothermal ellipsoid deflector and an observer, we derive to first order simple relations between the model parameters and the ...lensed image positions, and an expression for the time delay between pairs of opposed images which is analogue to the one previously derived for the case of ε − γ models. Combined with the first-order astrometric relations, we retrieve a simple expression for the time delays, in agreement with Witt, Mao & Keeton, which solely depends on the lensed image positions. The real advantage of using the first-order equations when dealing with symmetric gravitational lens systems is to directly test the validity of the adopted lens model without having to perform any accurate numerical fit. In this paper, we present in detail the calculations which lead to those relations between the singular isothermal ellipsoid lens model parameters and the lensed image positions. In addition, we model the well-known Einstein cross Q2237+0305 with three families of models: ε − γ, singular isothermal ellipsoid and non-singular isothermal ellipsoid plus shear, using a genetic algorithm from the Qubist Optimization Toolbox. We conclude that although the non-singular isothermal ellipsoid plus shear model shows the best agreement between the calculated and the observed image positions (〈Δx〉 = 0.0026 arcsec), the more simple singular isothermal ellipsoid also leads to quite satisfactory and acceptable results (〈Δx〉 = 0.0059 arcsec).
Knowing that the gravitational lens deflection angle can be expressed as the convolution product between the dimensionless surface mass density
and a simple function of the scaled impact parameter ...vector
, we make use of the Fourier transform to derive its analytical expression for the case of mass distributions presenting a homoeoidal symmetry. For this family of models, we obtain the expression of the two components of the deflection angle in the form of integrals performed over the radial coordinate ρ. In the limiting case of axially symmetric lenses, we obviously retrieve the well-known relation
. Furthermore, we derive explicit solutions for the deflection angle characterized by dimensionless surface mass density profiles such as
; corresponding to the non-singular isothermal ellipsoid model for the particular case ν = 1/2. Let us insist that all these results are obtained without using the complex formalism introduced by Bourassa and Kantowski. Further straightforward applications of this Fourier approach are suggested in the conclusions of this work.
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