Speckle statistics in adaptive optics images at visible wavelengths

Stangalini, M.; Pedichini, Fernando; Ambrosino, Filippo; Centrone, Mauro; Moro, D. Del

doi:10.1117/12.2232377

Cited by 4 publications

(3 citation statements)

References 39 publications

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“…This timescale is by far longer than the typical timescale of atmospheric turbulence (a few ms). Indeed, Stangalini et al (2016) have deeply analyzed the decorrelation timescales of adaptive optic residual aberrations using on-sky data, and found them to be of the order of 10-20 ms at visible wavelengths (∼630 nm). This is consistent with independent works in the literature (see, for example, Davis & Tango 1996).…”

Section: Discussionmentioning

confidence: 99%

Polarized Kink Waves in Magnetic Elements: Evidence for Chromospheric Helical Waves

Stangalini

Giannattasio

Erdélyi

et al. 2017

ApJ

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In recent years, new high spatial resolution observations of the Sunʼs atmosphere have revealed the presence of a plethora of small-scale magnetic elements down to the resolution limit of the current cohort of solar telescopes (∼100-120 km on the solar photosphere). These small magnetic field concentrations, due to the granular buffeting, can support and guide several magnetohydrodynamic wave modes that would eventually contribute to the energy budget of the upper layers of the atmosphere. In this work, exploiting the high spatial and temporal resolution chromospheric data acquired with the Swedish 1m Solar Telescope, and applying the empirical mode decomposition technique to the tracking of the solar magnetic features, we analyze the perturbations of the horizontal velocity vector of a set of chromospheric magnetic elements. We find observational evidence that suggests a phase relation between the two components of the velocity vector itself, resulting in its helical motion.

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Section: Discussionmentioning

confidence: 99%

Polarized Kink Waves in Magnetic Elements: Evidence for Chromospheric Helical Waves

Stangalini

Giannattasio

Erdélyi

et al. 2017

ApJ

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“…In reality, the turbulence is not Kolmogorovic, the atmospheric turbulence evolves, and there are often multiple turbulence layers with different wind speeds and directions (Roddier et al 1982;Macintosh et al 2005). Other high speed processes such as dome seeing, telescope vibrations from wind buffeting, or the AO loop itself can further complicate the speckle temporal power spectrum density (PSD) (Stangalini et al 2016). This may result in a faster speckle decorrelation time, a temporal PSD described by multiple exponential timescales, or possibly a dependence on the position in the focal plane.…”

Section: Modeling the Stellar Speckle Intensitymentioning

confidence: 99%

Stochastic Speckle Discrimination with Time-tagged Photon Lists: Digging below the Speckle Noise Floor

Walter¹,

Bockstiegel²,

Brandt³

et al. 2019

PASP

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We present an algorithm that uses the distribution of photon arrival times to distinguish speckles from incoherent sources, like planets and disks, in high contrast images. Using simulated data, we show that our approach can overcome the noise limit from fluctuating speckle intensity. The algorithm is likely to be most advantageous when a coronagraph limits the coherent diffraction pattern in the image plane but the intensity is still strongly modulated by fast-timescale uncorrected stellar light, for example from atmospheric turbulence. These conditions are common at small inner working angles and will allow probing of exoplanet populations at smaller angular separations. The technique requires a fast science camera that can temporally resolve the speckle fluctuations, and the detection of many photons per speckle decorrelation time. Since the algorithm directly extracts the incoherent light, standard differential imaging post-processing techniques can be performed afterwards to further boost the signal.

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“…Furthermore, models of exoplanet atmospheres (Marley et al 1999;Fortney et al 2008;Marley & Sengupta 2011) show that at wavelengths shorter than 650 nm the planet albedo increases, and thus the probability of their detection is maximized. More recently, a large effort has been made to design two high contrast imagers at LBT, SHARK-VIS, and SHARK-NIR, exploiting FLAO at visible and infrared wavelengths, respectively (Farinato et al 2014(Farinato et al , 2015Stangalini et al 2014). These imagers have been conceived to minimize non-common-path aberration (NCPA).…”

Section: Introductionmentioning

confidence: 99%

High Contrast Imaging in the Visible: First Experimental Results at the Large Binocular Telescope

Pedichini

Stangalini

Ambrosino

et al. 2017

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In 2014 February, the System for High contrast And coronography from R to K at VISual bands (SHARK-VIS) Forerunner, a high contrast experimental imager operating at visible wavelengths, was installed at the Large Binocular Telescope (LBT). Here we report on the first results obtained by recent on-sky tests. These results show the extremely good performance of the LBT Extreme Adaptive Optics (ExAO) system at visible wavelengths, both in terms of spatial resolution and contrast achieved. Similarly to what was done by Amara & Quanz (2012), we used the SHARK-VIS Forerunner data to quantitatively assess the contrast enhancement. This is done by injecting several different synthetic faint objects in the acquired data and applying the angular differential imaging (ADI) technique. A contrast of the order of 5×10 −5 is obtained at 630 nm for angular separations from the star larger than 100 mas. These results are discussed in light of the future development of SHARK-VIS and compared to those obtained by other high contrast imagers operating at similar wavelengths.

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Speckle statistics in adaptive optics images at visible wavelengths

Cited by 4 publications

References 39 publications

Polarized Kink Waves in Magnetic Elements: Evidence for Chromospheric Helical Waves

Polarized Kink Waves in Magnetic Elements: Evidence for Chromospheric Helical Waves

Stochastic Speckle Discrimination with Time-tagged Photon Lists: Digging below the Speckle Noise Floor

High Contrast Imaging in the Visible: First Experimental Results at the Large Binocular Telescope

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