Planet detection and characterization through high contrast imaging Raffaele Gratton INAF – Osservatorio Astronomico di Padova La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014

Content The difficulty of HCI Extrasolar planets may be detected in HCI! Struggling against speckles: the principles of HCI High contrast imagers: first and second gen’s What we can do with HCI? – Detection – Characterization Photometry Astrometry Spectroscopy La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014

Problematic Planets are faint and close … = 1 billion 10 6 = 1 million Reflected lightThermal emission But better for young giant planets Contrast ~10 6 in NIR

Required high contrast performances are equivalent to those required to see a moth flying around a street-lamp from a satellite at 500 km height

Fomalhaut< 3 M J 120 AU HR8799 b7 M J 68 AU HR8799 c10 M J 38 AU HR8799 d10 M J 24 AU Systems with quite large mass ratio are being discovered…

Fomalhaut< 3 M J 120 AU HR8799 b7 M J 68 AU HR8799 c10 M J 38 AU HR8799 d10 M J 24 AU Systems with quite large mass ratio are being discovered…

First generation HCI These discoveries were made using first generation HCI systems such as NACO, NIRC, or Hi-CIAO These instruments used moderately high order AO systems (<200 actuators, sampling the pupil at ~50 cm  SR(H)~0.5) available since early 2000s, and were not specially designed to fully exploit the potential of HCI La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014

State-of-the-art HCI Combines various techniques to provide high contrast imaging, with excellent stellar PSF suppression and stability: –a high density high frequency AO system that corrects turbulence and static optical aberrations (WFE~100 nm, SR(H)~0.9, 5-σ contrast at 0.5 arcsec: ~10 -3 ) –coronagraphy (gain by a factor of 10) –differential imaging, in which images at different wavelengths or polarization states are observed simultaneously (further gain by a factor of 100)

Angular Differential Imaging ADI exploits the fact that the field and the pupil rotate with respect to each other In pupil stabilized mode, most speckles are caused by instrumental artifacts and are locked up in the pupil plane, whereas the object of interest, a companion or a disk, will rotate as the field rotates (see video_adi.avi )video_adi.avi This allows distinguishing the stellar halo from the object (provided instrument is stable)

Spectral deconvolution Simultaneous observation of several monochromatic images can be used to reduce the impact of speckles (Sparks and Ford, 2002) For a given observation, the location of a companion around a star is constant while the location of speckles from the star increases with wavelength and their intensity decreases (see video_spectrum.avi ) video_spectrum.avi For a wide enough wavelength range this allows subtraction of the speckles. This process is known as spectral deconvolution (Thatte et al. 2007)

High contrast imaging pillars High-order AO: Contrast ~10 3 Coronagraphy: Contrast ~10 4 Differential imaging: Contrast ~10 6

First and second generation HCI La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014 NACO SPHERE

Second generation (XAO based) HCI InstrumentTelescopeYear of operation Wavelength range (µm) IFS P1640Palomar Yes LMIRCamLBT No CLIO2Magellan No GPIGemini South Yes SPHEREVLT UT Yes Hi-CIAO upgrade Subaru2014Y-KYes La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014

What is SPHERE? SPHERE is the new high contrast imager for the VLT SPHERE is the new high contrast imager for the VLT It just passed commissioning and is offered in P95 It just passed commissioning and is offered in P95 SPHERE also provides narrow-field (few arcsec), very high quality diffraction-limited imaging over the wavelength range micron SPHERE also provides narrow-field (few arcsec), very high quality diffraction-limited imaging over the wavelength range micron It requires a bright NGS (I<14-16) It requires a bright NGS (I<14-16)

First new detection with SPHERE: HR7581B (an M dwarf companion to a K-giant)

Photometric accuracy: <0.02 mag La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014

Spectra of HR8799 planets (Pueyo et al. 2014) La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014 See talk by Anne-Lise Maire

Comparison between transmission and high contrast imaging spectra Transmission spectrum HD (Pont et al. 2013) High contrast imaging spectrum HR8799c (Pueyo et al. 2014) La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014

Astrometry of HR8799 planets (Pueyo et al. 2014) La ricerca sui pianeti extrasolari in Italia, Roma, 5-7 novembre 2014