Christ Ftaclas - Academia.edu (original) (raw)

Papers by Christ Ftaclas

The Procyon binary system consists of an F5 IV-V primary and a white dwarf secondary in an approx... more The Procyon binary system consists of an F5 IV-V primary and a white dwarf secondary in an approximately 40-year orbit. The mass of the F5 primary as determined from stellar evolution theory does not agree with the value derived astrometrically by K. Aa. Strand in 1951, nor with a more recent determination by A. W. Irwin et al. in 1992

Ground-based and Airborne Instrumentation for Astronomy II, 2008

CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida for the... more CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida for the 10-meter Gran Telescopio Canarias (GTC) on La Palma. CanariCam has four science modes that provide the GTC community with an especially powerful research tool for imaging, grating spectroscopy, coronagraphy, and dual-beam polarimetry. Instrument commissioning in the laboratory at the University of Florida indicates that all modes perform as required, and the next step is on-telescope commissioning. After commenting on the instrument status, we will review key features of each of these science modes, with emphasis on illustrating each mode with science examples that put the system performance, particularly the anticipated sensitivity, into perspective.

The Astrophysical Journal, 2013

The Astrophysical Journal, 2001

We present ground-based near-infrared (H-band) imaging of the circumstellar disk around the nearb... more We present ground-based near-infrared (H-band) imaging of the circumstellar disk around the nearby classical T Tauri star TW Hydrae. The scattered light image shows a face-on disk with radius 4 arcseconds (corresponding to 225 AU) and a morphology which agrees with recent images from the Hubble Space Telescope and the Very Large Array. The best fit power-law for the disk's radial surface brightness profile obeys the law r −3.3±0.3 . We use our image and published continuum flux densities to derive properties of the disk with a simple model of emission from an optically thick, flat disk. The best-fit values for disk mass and inner radius are 0.03 M ⊙ and 0.3 AU; best-fit values for temperature, density, and grain opacity power law exponents (q, p, and β) are 0.7, 1.3, and 0.9, respectively. These properties are similar to those of disks around classical T Tauri stars located in more distant molecular clouds. Because of TW Hydrae's nearby location and pole-on orientation, it is a uniquely favorable object for future studies of radial disk structure at the classical T Tauri stage.

Jovian Planet Finder (JPF) employs an optical coronagraphic telescope with supersmooth optics and... more Jovian Planet Finder (JPF) employs an optical coronagraphic telescope with supersmooth optics and high throughput to obtain unprecedented contrast near bright point sources. For example, JPF is natural background limited for stars fainter than V = 7.5 at all field angles, and for 5th mag stars beyond 3 arcsec. This capability will be applied to the detection of Exo-Jovian Planets

Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby pl... more Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby planetary systems and their evolutionary stages from formation as young stellar objects to their demise as planetary nebulae. During a three-year science mission, Eclipse will directly detect and characterize jovian planets, zodiacal dust structures, and brown dwarf companions associated with stars in the solar neighborhood;

Eclipse is a proposed NASA Discovery-class mission to perform a direct imaging survey of nearby p... more Eclipse is a proposed NASA Discovery-class mission to perform a direct imaging survey of nearby planetary systems, including a complete survey for jovian-sized planets orbiting 5 AU from all stars of spectral types A-K within 15 pc of the Sun. Eclipse is a coronagraphic space telescope concept for high-contrast visible wavelength imaging and spectrophotometry. Its optical design incorporates a telescope

Eclipse is a proposed NASA Discovery mission to perform a sensitive imaging survey of nearby plan... more Eclipse is a proposed NASA Discovery mission to perform a sensitive imaging survey of nearby planetary systems, including a survey for jovian-sized planets orbiting Sun-like stars to distances of 15 pc. Eclipse is a space telescope concept for high-contrast visible wavelength imaging and spectrophotometry. Its design incorporates a telescope with an unobscured aperture of 1.8 meters, a coronagraphic camera for

Ground-based and Airborne Instrumentation for Astronomy V, 2014

ABSTRACT The Hokupa’a-85 curvature adaptive optics system components have been adapted to create ... more ABSTRACT The Hokupa’a-85 curvature adaptive optics system components have been adapted to create a new AO-corrected coud´e instrument at the 3.67m Advanced Electro-Optical System (AEOS) telescope. This new AO-corrected optical path is designed to deliver an f/40 diffraction-limited focus at wavelengths longer than 800nm. A new EMCCD-based dual-beam imaging polarimeter called InnoPOL has been designed and is presently being installed behind this corrected f/40 beam. The InnoPOL system is a flexible platform for optimizing polarimetric performance using commercial solutions and for testing modulation strategies. The system is designed as a technology test and demonstration platform as the coud´e path is built using off-the-shelf components wherever possible. Models of the polarimetric performance after AO correction show that polarization modulation at rates as slow as 200Hz can cause speckle correlations in brightness and focal plane location sufficient enough to change the speckle suppression behavior of the modulators. These models are also verified by initial EMCCD scoring camera data at AEOS. Substantial instrument trades and development efforts are explored between instrument performance parameters and various polarimetric noise sources.

Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby pl... more Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby planetary systems and their evolutionary stages from formation as young stellar objects to their demise as planetary nebulae. During a three-year survey of stars in the solar neighborhood, Eclipse will directly detect and characterize jovian-mass planets orbiting AFGK stars to 10 pc, zodiacal dust structures

The Mauna Kea Observatory offers a unique opportunity to build a large and sensitive interferomet... more The Mauna Kea Observatory offers a unique opportunity to build a large and sensitive interferometer. Seven telescopes have diameters larger than 3 meters and are or may be equipped with adaptive optics systems to correct phase perturbations induced by atmospheric turbulence. The maximum telescope separation of 800 meters can provide an angular resolution as good as 0.25 milli-arcseconds in the

Eclipse is a proposed NASA Discovery mission for direct imaging of planetary systems orbiting nea... more Eclipse is a proposed NASA Discovery mission for direct imaging of planetary systems orbiting nearby stars. The mission concept is based on an actively corrected coronagraphic space telescope for high-contrast visible wavelength imaging and spectrophotometry. Eclipse imagery provides billion-to-one suppression of diffracted and scattered starlight in the field of view between 0.25 and 1.5 arcseconds from a target star, a

We present results of a direct imaging search for extrasolar planets around two of the nearest, y... more We present results of a direct imaging search for extrasolar planets around two of the nearest, youngest stars, Beta Pictoris (12 Myrs, 19.4 pc) and TW Hydrae (8 Myrs, 54 pc), using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South 8-meter Telescope. The NICI instrument obtains high-contrast images of bright stars by combining a high-order curvature AO system with simultaneous

We review the basic approach of curvature adaptive optics (AO) and show how its many advantages a... more We review the basic approach of curvature adaptive optics (AO) and show how its many advantages arise. A curvature wave front sensor (WFS) measures exactly what a curvature deformable mirror (DM) generates. This leads to the computational and operational simplicity of a nearly diagonal control matrix. The DM automatically reconstructs the wave front based on WFS curvature measurements. Thus, there

Adaptive Optics Systems, 2008

The goal of this project is to achieve exquisite image quality over the largest possible field of... more The goal of this project is to achieve exquisite image quality over the largest possible field of view, with a goal of a FWHM of not more than 0.3" over a square degree field in the optical domain. The narrow PSF will allow detection of fainter sources in reasonable exposure times. The characteristics of the turbulence of Mauna Kea, a very thin ground layer with excellent free seeing allows very wide fields to be corrected by GLAO and would make such an instrument unique. The Ground Layer AO module uses a deformable mirror conjugated to the telescope pupil. Coupled with a high order WFS, it corrects the turbulence common to the entire field. Over such large fields the probability of finding sufficiently numerous and bright natural guide sources is high, but a constellation of laser beacons could be considered to ensure homogeneous and uniform image quality. The free atmosphere seeing then limits the image quality (50% best conditions: 0.2" to 0.4"). This can be further improved by an OTCCD camera, which can correct local image motion on isokinetic scales from residual high altitude tip-tilt. The advantages of the OTCCD are not limited to improving the image quality: a Panstarrs1 clone covers one square degree with 0.1" sampling, in perfect accordance with the scientific requirements. The fast read time (6 seconds for 1.4 Gpixels) also leads to an improvement of the dynamic range of the images. Finally, the guiding capabilities of the OTCCD will provide the overall (local and global) tip-tilt signal.

Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation, 2003

Eclipse is a proposed Discovery-class mission to perform a sensitive imaging survey of nearby pla... more Eclipse is a proposed Discovery-class mission to perform a sensitive imaging survey of nearby planetary systems, including a complete survey for Jupiter-sized planets orbiting 5 AU from all stars of spectral types A-K to distances of 15 pc. Eclipse is a coronagraphic space telescope concept designed for high-contrast visible wavelength imaging and spectrophotometry. Its optical design incorporates essential elements: a

Adaptive Optics Systems, 2008

We discuss observing strategy for the Near Infrared Coronagraphic Imager (NICI) on the 8-m Gemini... more We discuss observing strategy for the Near Infrared Coronagraphic Imager (NICI) on the 8-m Gemini South telescope. NICI combines a number of techniques to attenuate starlight and suppress superspeckles: 1) coronagraphic imaging, 2) dual channel imaging for Spectral Differential Imaging (SDI) and 3) operation in a fixed Cassegrain rotator mode for Angular Differential Imaging (ADI). NICI will be used both in service mode and for a dedicated 50 night planet search campaign. While all of these techniques have been used individually in large planet-finding surveys, this is the first time ADI and SDI will be used with a coronagraph in a large survey. Thus, novel observing strategies are necessary to conduct a viable planet search campaign.

Adaptive Optics Systems, 2008

We present the coronagraphic and adaptive optics performance of the Gemini-South Near-Infrared Co... more We present the coronagraphic and adaptive optics performance of the Gemini-South Near-Infrared Coronagraphic Imager (NICI). NICI includes a dual-channel imager for simultaneous spectral difference imaging, a dedicated 85element curvature adaptive optics system, and a built-in Lyot coronagraph. It is specifically designed to survey for and image large extra-solar gaseous planets on the Gemini Observatory 8-meter telescope in Chile. We present the on-sky performance of the individual subsystems along with the end-to-end contrast curve. These are compared to our model predictions for the adaptive optics system, the coronagraph, and the spectral difference imaging.

Ground-based and Airborne Instrumentation for Astronomy II, 2008

The Near-Infrared Coronagraphic Imager (NICI) is a high-contrast AO imager at the Gemini South te... more The Near-Infrared Coronagraphic Imager (NICI) is a high-contrast AO imager at the Gemini South telescope. The camera includes a coronagraphic mask and dual channel imaging for Spectral Differential Imaging (SDI). The instrument can also be used in a fixed Cassegrain Rotator mode for Angular Differential Imaging (ADI). While coronagraphy, SDI, and ADI have been applied before in direct imaging searches for exoplanets. NICI represents the first time that these 3 techniques can be combined. We present preliminary NICI commissioning data using these techniques and show that combining SDI and ADI results in significant gains.

The Procyon binary system consists of an F5 IV-V primary and a white dwarf secondary in an approx... more The Procyon binary system consists of an F5 IV-V primary and a white dwarf secondary in an approximately 40-year orbit. The mass of the F5 primary as determined from stellar evolution theory does not agree with the value derived astrometrically by K. Aa. Strand in 1951, nor with a more recent determination by A. W. Irwin et al. in 1992

Ground-based and Airborne Instrumentation for Astronomy II, 2008

CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida for the... more CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida for the 10-meter Gran Telescopio Canarias (GTC) on La Palma. CanariCam has four science modes that provide the GTC community with an especially powerful research tool for imaging, grating spectroscopy, coronagraphy, and dual-beam polarimetry. Instrument commissioning in the laboratory at the University of Florida indicates that all modes perform as required, and the next step is on-telescope commissioning. After commenting on the instrument status, we will review key features of each of these science modes, with emphasis on illustrating each mode with science examples that put the system performance, particularly the anticipated sensitivity, into perspective.

The Astrophysical Journal, 2013

The Astrophysical Journal, 2001

We present ground-based near-infrared (H-band) imaging of the circumstellar disk around the nearb... more We present ground-based near-infrared (H-band) imaging of the circumstellar disk around the nearby classical T Tauri star TW Hydrae. The scattered light image shows a face-on disk with radius 4 arcseconds (corresponding to 225 AU) and a morphology which agrees with recent images from the Hubble Space Telescope and the Very Large Array. The best fit power-law for the disk's radial surface brightness profile obeys the law r −3.3±0.3 . We use our image and published continuum flux densities to derive properties of the disk with a simple model of emission from an optically thick, flat disk. The best-fit values for disk mass and inner radius are 0.03 M ⊙ and 0.3 AU; best-fit values for temperature, density, and grain opacity power law exponents (q, p, and β) are 0.7, 1.3, and 0.9, respectively. These properties are similar to those of disks around classical T Tauri stars located in more distant molecular clouds. Because of TW Hydrae's nearby location and pole-on orientation, it is a uniquely favorable object for future studies of radial disk structure at the classical T Tauri stage.

Jovian Planet Finder (JPF) employs an optical coronagraphic telescope with supersmooth optics and... more Jovian Planet Finder (JPF) employs an optical coronagraphic telescope with supersmooth optics and high throughput to obtain unprecedented contrast near bright point sources. For example, JPF is natural background limited for stars fainter than V = 7.5 at all field angles, and for 5th mag stars beyond 3 arcsec. This capability will be applied to the detection of Exo-Jovian Planets

Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby pl... more Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby planetary systems and their evolutionary stages from formation as young stellar objects to their demise as planetary nebulae. During a three-year science mission, Eclipse will directly detect and characterize jovian planets, zodiacal dust structures, and brown dwarf companions associated with stars in the solar neighborhood;

Eclipse is a proposed NASA Discovery-class mission to perform a direct imaging survey of nearby p... more Eclipse is a proposed NASA Discovery-class mission to perform a direct imaging survey of nearby planetary systems, including a complete survey for jovian-sized planets orbiting 5 AU from all stars of spectral types A-K within 15 pc of the Sun. Eclipse is a coronagraphic space telescope concept for high-contrast visible wavelength imaging and spectrophotometry. Its optical design incorporates a telescope

Eclipse is a proposed NASA Discovery mission to perform a sensitive imaging survey of nearby plan... more Eclipse is a proposed NASA Discovery mission to perform a sensitive imaging survey of nearby planetary systems, including a survey for jovian-sized planets orbiting Sun-like stars to distances of 15 pc. Eclipse is a space telescope concept for high-contrast visible wavelength imaging and spectrophotometry. Its design incorporates a telescope with an unobscured aperture of 1.8 meters, a coronagraphic camera for

Ground-based and Airborne Instrumentation for Astronomy V, 2014

ABSTRACT The Hokupa’a-85 curvature adaptive optics system components have been adapted to create ... more ABSTRACT The Hokupa’a-85 curvature adaptive optics system components have been adapted to create a new AO-corrected coud´e instrument at the 3.67m Advanced Electro-Optical System (AEOS) telescope. This new AO-corrected optical path is designed to deliver an f/40 diffraction-limited focus at wavelengths longer than 800nm. A new EMCCD-based dual-beam imaging polarimeter called InnoPOL has been designed and is presently being installed behind this corrected f/40 beam. The InnoPOL system is a flexible platform for optimizing polarimetric performance using commercial solutions and for testing modulation strategies. The system is designed as a technology test and demonstration platform as the coud´e path is built using off-the-shelf components wherever possible. Models of the polarimetric performance after AO correction show that polarization modulation at rates as slow as 200Hz can cause speckle correlations in brightness and focal plane location sufficient enough to change the speckle suppression behavior of the modulators. These models are also verified by initial EMCCD scoring camera data at AEOS. Substantial instrument trades and development efforts are explored between instrument performance parameters and various polarimetric noise sources.

Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby pl... more Eclipse is a proposed Discovery mission to perform the first sensitive imaging study of nearby planetary systems and their evolutionary stages from formation as young stellar objects to their demise as planetary nebulae. During a three-year survey of stars in the solar neighborhood, Eclipse will directly detect and characterize jovian-mass planets orbiting AFGK stars to 10 pc, zodiacal dust structures

The Mauna Kea Observatory offers a unique opportunity to build a large and sensitive interferomet... more The Mauna Kea Observatory offers a unique opportunity to build a large and sensitive interferometer. Seven telescopes have diameters larger than 3 meters and are or may be equipped with adaptive optics systems to correct phase perturbations induced by atmospheric turbulence. The maximum telescope separation of 800 meters can provide an angular resolution as good as 0.25 milli-arcseconds in the

Eclipse is a proposed NASA Discovery mission for direct imaging of planetary systems orbiting nea... more Eclipse is a proposed NASA Discovery mission for direct imaging of planetary systems orbiting nearby stars. The mission concept is based on an actively corrected coronagraphic space telescope for high-contrast visible wavelength imaging and spectrophotometry. Eclipse imagery provides billion-to-one suppression of diffracted and scattered starlight in the field of view between 0.25 and 1.5 arcseconds from a target star, a

We present results of a direct imaging search for extrasolar planets around two of the nearest, y... more We present results of a direct imaging search for extrasolar planets around two of the nearest, youngest stars, Beta Pictoris (12 Myrs, 19.4 pc) and TW Hydrae (8 Myrs, 54 pc), using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South 8-meter Telescope. The NICI instrument obtains high-contrast images of bright stars by combining a high-order curvature AO system with simultaneous

We review the basic approach of curvature adaptive optics (AO) and show how its many advantages a... more We review the basic approach of curvature adaptive optics (AO) and show how its many advantages arise. A curvature wave front sensor (WFS) measures exactly what a curvature deformable mirror (DM) generates. This leads to the computational and operational simplicity of a nearly diagonal control matrix. The DM automatically reconstructs the wave front based on WFS curvature measurements. Thus, there

Adaptive Optics Systems, 2008

The goal of this project is to achieve exquisite image quality over the largest possible field of... more The goal of this project is to achieve exquisite image quality over the largest possible field of view, with a goal of a FWHM of not more than 0.3" over a square degree field in the optical domain. The narrow PSF will allow detection of fainter sources in reasonable exposure times. The characteristics of the turbulence of Mauna Kea, a very thin ground layer with excellent free seeing allows very wide fields to be corrected by GLAO and would make such an instrument unique. The Ground Layer AO module uses a deformable mirror conjugated to the telescope pupil. Coupled with a high order WFS, it corrects the turbulence common to the entire field. Over such large fields the probability of finding sufficiently numerous and bright natural guide sources is high, but a constellation of laser beacons could be considered to ensure homogeneous and uniform image quality. The free atmosphere seeing then limits the image quality (50% best conditions: 0.2" to 0.4"). This can be further improved by an OTCCD camera, which can correct local image motion on isokinetic scales from residual high altitude tip-tilt. The advantages of the OTCCD are not limited to improving the image quality: a Panstarrs1 clone covers one square degree with 0.1" sampling, in perfect accordance with the scientific requirements. The fast read time (6 seconds for 1.4 Gpixels) also leads to an improvement of the dynamic range of the images. Finally, the guiding capabilities of the OTCCD will provide the overall (local and global) tip-tilt signal.

Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation, 2003

Eclipse is a proposed Discovery-class mission to perform a sensitive imaging survey of nearby pla... more Eclipse is a proposed Discovery-class mission to perform a sensitive imaging survey of nearby planetary systems, including a complete survey for Jupiter-sized planets orbiting 5 AU from all stars of spectral types A-K to distances of 15 pc. Eclipse is a coronagraphic space telescope concept designed for high-contrast visible wavelength imaging and spectrophotometry. Its optical design incorporates essential elements: a

Adaptive Optics Systems, 2008

We discuss observing strategy for the Near Infrared Coronagraphic Imager (NICI) on the 8-m Gemini... more We discuss observing strategy for the Near Infrared Coronagraphic Imager (NICI) on the 8-m Gemini South telescope. NICI combines a number of techniques to attenuate starlight and suppress superspeckles: 1) coronagraphic imaging, 2) dual channel imaging for Spectral Differential Imaging (SDI) and 3) operation in a fixed Cassegrain rotator mode for Angular Differential Imaging (ADI). NICI will be used both in service mode and for a dedicated 50 night planet search campaign. While all of these techniques have been used individually in large planet-finding surveys, this is the first time ADI and SDI will be used with a coronagraph in a large survey. Thus, novel observing strategies are necessary to conduct a viable planet search campaign.

Adaptive Optics Systems, 2008

We present the coronagraphic and adaptive optics performance of the Gemini-South Near-Infrared Co... more We present the coronagraphic and adaptive optics performance of the Gemini-South Near-Infrared Coronagraphic Imager (NICI). NICI includes a dual-channel imager for simultaneous spectral difference imaging, a dedicated 85element curvature adaptive optics system, and a built-in Lyot coronagraph. It is specifically designed to survey for and image large extra-solar gaseous planets on the Gemini Observatory 8-meter telescope in Chile. We present the on-sky performance of the individual subsystems along with the end-to-end contrast curve. These are compared to our model predictions for the adaptive optics system, the coronagraph, and the spectral difference imaging.

Ground-based and Airborne Instrumentation for Astronomy II, 2008

The Near-Infrared Coronagraphic Imager (NICI) is a high-contrast AO imager at the Gemini South te... more The Near-Infrared Coronagraphic Imager (NICI) is a high-contrast AO imager at the Gemini South telescope. The camera includes a coronagraphic mask and dual channel imaging for Spectral Differential Imaging (SDI). The instrument can also be used in a fixed Cassegrain Rotator mode for Angular Differential Imaging (ADI). While coronagraphy, SDI, and ADI have been applied before in direct imaging searches for exoplanets. NICI represents the first time that these 3 techniques can be combined. We present preliminary NICI commissioning data using these techniques and show that combining SDI and ADI results in significant gains.