A. Pavlov

Bio: A. Pavlov is an academic researcher from Max Planck Society. The author has contributed to research in topics: Exoplanet & Integral field spectrograph. The author has an hindex of 16, co-authored 47 publications receiving 1608 citations.

SPHERE: A ‘Planet Finder’ Instrument for the VLT

Abstract: Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also one of the most challenging areas in modern astronomy. The challenge consists in the very large contrast between the host star and the planet, larger than 12.5 magnitudes at very small angular separations, typically inside the seeing halo. The whole design of a "Planet Finder" instrument is therefore optimized towards reaching the highest contrast in a limited field of view and at short distances from the central star. Both evolved and young planetary systems can be detected, respectively through their reflected light and through the intrinsic planet emission. We present the science objectives, conceptual design and expected performance of the SPHERE instrument.

Three radial gaps in the disk of TW Hydrae imaged with SPHERE

Abstract: We present scattered light images of the TW Hya disk performed with SPHERE in PDI mode at 063, 079, 124 and 162 micron We also present H2/H3-band ADI observations Three distinct radial depressions in the polarized intensity distribution are seen, around 85, 21, and 6~au The overall intensity distribution has a high degree of azimuthal symmetry; the disk is somewhat brighter than average towards the South and darker towards the North-West The ADI observations yielded no signifiant detection of point sources in the disk Our observations have a linear spatial resolution of 1 to 2au, similar to that of recent ALMA dust continuum observations The sub-micron sized dust grains that dominate the light scattering in the disk surface are strongly coupled to the gas We created a radiative transfer disk model with self-consistent temperature and vertical structure iteration and including grain size-dependent dust settling This method may provide independent constraints on the gas distribution at higher spatial resolution than is feasible with ALMA gas line observations We find that the gas surface density in the "gaps" is reduced by 50% to 80% relative to an unperturbed model Should embedded planets be responsible for carving the gaps then their masses are at most a few 10 Mearth The observed gaps are wider, with shallower flanks, than expected for planet-disk interaction with such low-mass planets If forming planetary bodies have undergone collapse and are in the "detachted phase" then they may be directly observable with future facilities such as METIS at the E-ELT

Performance of the VLT Planet Finder SPHERE - II. Data analysis and results for IFS in laboratory

Abstract: Aims. We present the performance of the Integral Field Spectrograph (IFS) of SPHERE, the high-contrast imager for the ESO VLT telescope designed to perform imaging and spectroscopy of extrasolar planets, obtained from tests performed at the Institut de Planetologie et d'Astrophysique de Grenoble facility during the integration phase of the instrument. Methods. The tests were performed using the instrument software purposely prepared for SPHERE. The output data were reduced applying the SPHERE data reduction and handling software, adding an improved spectral deconvolution procedure. To this aim, we prepared an alternative procedure for the spectral subtraction exploiting the principal component analysis algorithm. Moreover, a simulated angular differential imaging procedure was also implemented to estimate how the instrument performed once this procedure was applied at telescope. The capability of the IFS to faithfully retrieve the spectra of the detected faint companions was also considered. Results. We found that the application of the updated version of the spectral deconvolution procedure alone, when the algorithm throughput is properly taken into account, gives us a 5 sigma limiting contrast of the order of 5 x 10(-6) or slightly better. The further application of the angular differential imaging procedure on these data should allow us to improve the contrast by one order of magnitude down to around 7x10(-7) at a separation of 0.3 arcsec. The application of a principal component analysis procedure that simultaneously uses spectral and angular data gives comparable results. Finally, we found that the reproducibility of the spectra of the detected faint companions is greatly improved when angular differential imaging is applied in addition to the spectral deconvolution.

SPHERE data reduction and handling system: overview, project status, and development

Abstract: TheSPHEREprojectisaESOsecondgenerationinstrumentwhichaimstodetectgiantextra-solarplanetsinthevicinityofbrightstars andto characterisethe objects foundthroughspectroscopicandpolarimetricobservations.TechnicaltolerancesarethetightesteverforaninstrumentinstalledattheVLT,andSPHEREdemandsaratheruniqueDRHsoftwarepackagetoaccompany the data from the observation preparation to the search for planetary signals. This paper addresses the currentstatus of the data reduction and handling system (DRHS) for the SPHERE instruments. It includes descriptions of thecalibration and science data, reduction steps and their data products. The development strategy for creating of a coherentsoftware that allows to achieve high observationefciency is briey discussed.Keywords: SPHERE, data reduction,pipelines, planet nding 1. INTRODUCTION SPHERE ( S pectro- P olarimetric H igh-contrast E xoplanetResearch)is a projecttoequiptheVLTwith asecond-generationinstrument capable of delivering true images of true extrasolar planets.

Performance of the VLT Planet Finder SPHERE - I. Photometry and astrometry precision with IRDIS and IFS in laboratory

Abstract: Context. The new planet finder for the Very Large Telescope (VLT), the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), just had its first light in Paranal. A dedicated instrument for the direct detection of planets, SPHERE, is composed of a polametric camera in visible light, the Zurich IMager POLarimeter (ZIMPOL), and two near-infrared sub-systems: the Infra-Red Dual-beam Imager and Spectrograph (IRDIS), a multi-purpose camera for imaging, polarimetry, and long-slit spectroscopy, and the integral field spectrograph (IFS), an integral field spectrograph. Aims. We present the results obtained from the analysis of data taken during the laboratory integration and validation phase, after the injection of synthetic planets. Since no continuous field rotation could be performed in the laboratory, this analysis presents results obtained using reduction techniques that do not use the angular differential imaging (ADI) technique. Methods. To perform the simulations, we used the instrumental point spread function (PSF) and model spectra of L and T-type objects scaled in contrast with respect to the host star. We evaluated the expected error in astrometry and photometry as a function of the signal to noise of companions, after spectral differential imaging (SDI) reduction for IRDIS and spectral deconvolution (SD) or principal component analysis (PCA) data reductions for IFS. Results. We deduced from our analysis, for example, that β Picb, a 12 Myr old planet of ~10 MJup and semi-major axis of 9-10 AU, would be detected with IRDIS with a photometric error of 0.16 mag and with a relative astrometric position error of 1.1 mas. With IFS, we could retrieve a spectrum with error bars of about 0.15 mag on each channel and astrometric relative position error of 0.6 mas. For a fainter object such as HR 8799d, a 13 MJup planet at a distance of 27 AU, IRDIS could obtain a relative astrometric error of 3 mas.

The Occurrence and Architecture of Exoplanetary Systems

Abstract: The basic geometry of the Solar System—the shapes, spacings, and orientations of the planetary orbits—has long been a subject of fascination as well as inspiration for planet-formation theories. For exoplanetary systems, those same properties have only recently come into focus. Here we review our current knowledge of the occurrence of planets around other stars, their orbital distances and eccentricities, the orbital spacings and mutual inclinations in multiplanet systems, the orientation of the host star's rotation axis, and the properties of planets in binary-star systems.

The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview

Abstract: We introduce the Disk Substructures at High Angular Resolution Project (DSHARP), one of the initial Large Programs conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The primary goal of DSHARP is to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution (similar to 0.'' 035, or 5 au, FWHM) observations of their 240 GHz (1.25 mm) continuum emission. These data provide a first homogeneous look at the small-scale features in disks that are directly relevant to the planet formation process, quantifying their prevalence, morphologies, spatial scales, spacings, symmetry, and amplitudes, for targets with a variety of disk and stellar host properties. We find that these substructures are ubiquitous in this sample of large, bright disks. They are most frequently manifested as concentric, narrow emission rings and depleted gaps, although large-scale spiral patterns and small arc-shaped azimuthal asymmetries are also present in some cases. These substructures are found at a wide range of disk radii (from a few astronomical units to more than 100 au), are usually compact (less than or similar to 10 au), and show a wide range of amplitudes (brightness contrasts). Here we discuss the motivation for the project, describe the survey design and the sample properties, detail the observations and data calibration, highlight some basic results, and provide a general overview of the key conclusions that are presented in more detail in a series of accompanying articles. The DSHARP data-including visibilities, images, calibration scripts, and more-are released for community use at https://almascience.org/alma-data/lp/DSHARP.

Detection and characterization of exoplanets and disks using projections on karhunen-loève eigenimages

Abstract: We describe a new method to achieve point-spread function (PSF) subtractions for high-contrast imaging using principal component analysis that is applicable to both point sources or extended objects (disks). Assuming a library of reference PSFs, a Karhunen–Lo` eve transform of these references is used to create an orthogonal basis of eigenimages on which the science target is projected. For detection this approach provides comparable suppression to the Locally Optimized Combination of Images (LOCI) algorithm, albeit with increased robustness to the algorithm parameters and speed enhancement. For characterization of detected sources, the method enables forward modeling of astrophysical sources. This alleviates the biases in the astrometry and photometry of discovered faint sources, which are usually associated with LOCI-based PSF subtractions schemes. We illustrate the algorithm performance using archival Hubble Space Telescope images, but the approach may also be considered for ground-based data acquired with angular differential imaging or integral-field spectrographs.

SPHERE: A ‘Planet Finder’ Instrument for the VLT

Abstract: Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also one of the most challenging areas in modern astronomy. The challenge consists in the very large contrast between the host star and the planet, larger than 12.5 magnitudes at very small angular separations, typically inside the seeing halo. The whole design of a "Planet Finder" instrument is therefore optimized towards reaching the highest contrast in a limited field of view and at short distances from the central star. Both evolved and young planetary systems can be detected, respectively through their reflected light and through the intrinsic planet emission. We present the science objectives, conceptual design and expected performance of the SPHERE instrument.

The Exoplanet Handbook

Abstract: 1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.