23 research outputs found
ALICE Data Release: A Revaluation of HST-NICMOS Coronagraphic Images
The Hubble Space Telescope NICMOS instrument was used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets and disks studies. As part of the Archival Legacy Investigations of Circumstellar Environments program, we have consistently reprocessed a large fraction of the NICMOS coronagrahic archive using advanced starlight subtraction methods. We present here the high-level science products of these re-analyzed data, which we delivered back to the community through the Mikulski Archive for Space Telescopes: doi:10.17909/T9W89V. We also present the second version of the HCI-FITS format (for High-Contrast Imaging FITS format), which we developed as a standard format for data exchange of imaging reduced science products. These re-analyzed products are openly available for population statistics studies, characterization of specific targets, or detected point-source identification
ALICE Data Release: A Revaluation of HST-NICMOS Coronagraphic Images
The Hubble Space Telescope NICMOS instrument was used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets and disks studies. As part of the Archival Legacy Investigations of Circumstellar Environments program, we have consistently reprocessed a large fraction of the NICMOS coronagrahic archive using advanced starlight subtraction methods. We present here the high-level science products of these re-analyzed data, which we delivered back to the community through the Mikulski Archive for Space Telescopes: doi:10.17909/T9W89V. We also present the second version of the HCI-FITS format (for High-Contrast Imaging FITS format), which we developed as a standard format for data exchange of imaging reduced science products. These re-analyzed products are openly available for population statistics studies, characterization of specific targets, or detected point-source identification
Archival Legacy Investigations of Circumstellar Environments: Overview and First Results
We are currently conducting a comprehensive and consistent re-processing of
archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction
methods, entitled the Archival Legacy Investigations of Circumstellar
Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400
targets has already produced numerous new detections of previously unidentified
point sources and circumstellar structures. We present five newly spatially
resolved debris disks revealed in scattered light by our analysis of the
archival data. These images provide new views of material around young
solar-type stars at ages corresponding to the period of terrestrial planet
formation in our solar system. We have also detected several new candidate
substellar companions, for which there are ongoing followup campaigns (HST/WFC3
and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are
directly applicable to future missions (JWST, AFTA coronagraph) we emphasize
the importance of devising optimal PSF subtraction methods for upcoming
coronagraphic imaging missions. We describe efforts in defining direct imaging
high-level science products (HLSP) standards that can be applicable to other
coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager),
and future space instruments (e.g., JWST). ALICE will deliver a first release
of HLSPs to the community through the MAST archive at STScI in 2014.Comment: Proceedings of the SPIE, 9143-199. 17 pages, 11 figure
Five Debris Disks Newly Revealed in Scattered Light from the HST NICMOS Archive
We have spatially resolved five debris disks (HD 30447, HD 35841, HD 141943,
HD 191089, and HD 202917) for the first time in near-infrared scattered light
by reanalyzing archival Hubble Space Telescope (HST)/NICMOS coronagraphic
images obtained between 1999 and 2006. One of these disks (HD 202917) was
previously resolved at visible wavelengths using HST/Advanced Camera for
Surveys. To obtain these new disk images, we performed advanced point-spread
function subtraction based on the Karhunen-Loeve Image Projection (KLIP)
algorithm on recently reprocessed NICMOS data with improved detector artifact
removal (Legacy Archive PSF Library And Circumstellar Environments Legacy
program). Three of the disks (HD 30447, HD 35841, and HD 141943) appear
edge-on, while the other two (HD 191089 and HD 202917) appear inclined. The
inclined disks have been sculpted into rings; in particular, the disk around HD
202917 exhibits strong asymmetries. All five host stars are young (8-40 Myr),
nearby (40-100 pc) F and G stars, and one (HD 141943) is a close analog to the
young sun during the epoch of terrestrial planet formation. Our discoveries
increase the number of debris disks resolved in scattered light from 19 to 23
(a 21% increase). Given their youth, proximity, and brightness (V = 7.2 to
8.5), these targets are excellent candidates for follow-up investigations of
planet formation at visible wavelengths using the HST/STIS coronagraph, at
near-infrared wavelengths with the Gemini Planet Imager (GPI) and Very Large
Telescope (VLT)/SPHERE, and at thermal infrared wavelengths with the James Webb
Space Telescope NIRCam and MIRI coronagraphs.Comment: 6 pages, 1 figure, 1 tabl
Debris Disk Color with the Hubble Space Telescope
Multi-wavelength scattered light imaging of debris disks may inform dust
properties including typical size and mineral composition. Existing studies
have investigated a small set of individual systems across a variety of imaging
instruments and filters, calling for uniform comparison studies to
systematically investigate dust properties. We obtain the surface brightness of
dust particles in debris disks by post-processing coronagraphic imaging
observations, and compare the multi-wavelength reflectance of dust. For a
sample of resolved debris disks, we perform a systematic analysis on the
reflectance properties of their birth rings. We reduced the visible and
near-infrared images of 23 debris disk systems hosted by A through M stars
using two coronagraphs onboard the Hubble Space Telescope: the STIS instrument
observations centering at 0.58 m, and the NICMOS instrument at 1.12 m
or 1.60 m. For proper recovery of debris disks, we used classical
reference differential imaging for STIS, and adopted non-negative matrix
factorization with forward modeling for NICMOS. By dividing disk signals by
stellar signals to take into account of intrinsic stellar color effects, we
systematically obtained and compared the reflectance of debris birth rings at
~90 deg scattering angle. Debris birth rings typically exhibit a blue color at
~90 deg scattering angle. As the stellar luminosity increases, the color tends
to be more neutral. A likely L-shaped color-albedo distribution indicates a
clustering of scatterer properties. The observed color trend correlates with
the expected blow-out size of dust particles. The color-albedo clustering
likely suggests different populations of dust in these systems. More detailed
radiative transfer models with realistic dust morphology will contribute to
explaining the observed color and color-albedo distribution of debris systems.Comment: 17 pages, 8 figures, 3 tables. A&A accepte
An Exo-Kuiper Belt with an Extended Halo around HD 191089 in Scattered Light
We have obtained Hubble Space Telescope STIS and NICMOS and Gemini/GPI scattered-light images of the HD 191089 debris disk. We identify two spatial components: a ring resembling the Kuiper Belt in radial extent (FWHM ∼ 25 au, centered at ∼46 au) and a halo extending to ∼640 au. We find that the halo is significantly bluer than the ring, consistent with the scenario that the ring serves as the birth ring for the smaller dust in the halo. We measure the scattering phase functions in the 30°-150° scattering-angle range and find that the halo dust is more forward- and backward-scattering than the ring dust. We measure a surface density power-law index of -0.68 ± 0.04 for the halo, which indicates the slowdown of the radial outward motion of the dust. Using radiative transfer modeling, we attempt to simultaneously reproduce the (visible) total and (near-infrared) polarized intensity images of the birth ring. Our modeling leads to mutually inconsistent results, indicating that more complex models, such as the inclusion of more realistic aggregate particles, are needed
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
ALICE Data Release: A Revaluation of HST -NICMOS Coronagraphic Images
International audienceThe Hubble Space Telescope NICMOS instrument was used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets and disks studies. As part of the Archival Legacy Investigations of Circumstellar Environments program, we have consistently reprocessed a large fraction of the NICMOS coronagrahic archive using advanced starlight subtraction methods. We present here the high-level science products of these re-analyzed data, which we delivered back to the community through the Mikulski Archive for Space Telescopes: doi:10.17909/T9W89V. We also present the second version of the HCI-FITS format (for High-Contrast Imaging FITS format), which we developed as a standard format for data exchange of imaging reduced science products. These re-analyzed products are openly available for population statistics studies, characterization of specific targets, or detected point-source identification
Time-Resolved Doubly-Stimulated Two-Photon Emission In Gallium Arsenide
We perform degenerate pump-probe experiments at 1700 nm on GaAs with an additional 780 nm excitation pulse generating free carriers. An increased normalized transmission of the probe is observed, indicative of doubly-stimulated two-photon emission. © OSA 2013