14 research outputs found
Data Reduction Pipeline for the CHARIS Integral-Field Spectrograph I: Detector Readout Calibration and Data Cube Extraction
We present the data reduction pipeline for CHARIS, a high-contrast
integral-field spectrograph for the Subaru Telescope. The pipeline constructs a
ramp from the raw reads using the measured nonlinear pixel response, and
reconstructs the data cube using one of three extraction algorithms: aperture
photometry, optimal extraction, or fitting. We measure and apply both
a detector flatfield and a lenslet flatfield and reconstruct the wavelength-
and position-dependent lenslet point-spread function (PSF) from images taken
with a tunable laser. We use these measured PSFs to implement a -based
extraction of the data cube, with typical residuals of ~5% due to imperfect
models of the undersampled lenslet PSFs. The full two-dimensional residual of
the extraction allows us to model and remove correlated read noise,
dramatically improving CHARIS' performance. The extraction produces a
data cube that has been deconvolved with the line-spread function, and never
performs any interpolations of either the data or the individual lenslet
spectra. The extracted data cube also includes uncertainties for each spatial
and spectral measurement. CHARIS' software is parallelized, written in Python
and Cython, and freely available on github with a separate documentation page.
Astrometric and spectrophotometric calibrations of the data cubes and PSF
subtraction will be treated in a forthcoming paper.Comment: 18 pages, 15 figures, 3 tables, replaced with JATIS accepted version
(emulateapj formatted here). Software at
https://github.com/PrincetonUniversity/charis-dep and documentation at
http://princetonuniversity.github.io/charis-de
The Optical Design of CHARIS: An Exoplanet IFS for the Subaru Telescope
High-contrast imaging techniques now make possible both imaging and
spectroscopy of planets around nearby stars. We present the optical design for
the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a
lenslet-based, cryogenic integral field spectrograph (IFS) for imaging
exoplanets on the Subaru telescope. The IFS will provide spectral information
for 138x138 spatial elements over a 2.07 arcsec x 2.07 arcsec field of view
(FOV). CHARIS will operate in the near infrared (lambda = 1.15 - 2.5 microns)
and will feature two spectral resolution modes of R = 18 (low-res mode) and R =
73 (high-res mode). Taking advantage of the Subaru telescope adaptive optics
systems and coronagraphs (AO188 and SCExAO), CHARIS will provide sufficient
contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets.
CHARIS will undergo CDR in October 2013 and is projected to have first light by
the end of 2015. We report here on the current optical design of CHARIS and its
unique innovations.Comment: 15 page
GPI 2.0: Upgrades to the IFS including new spectral modes
The Gemini Planet Imager (GPI) is a high-contrast imaging instrument designed
to directly image and characterize exoplanets. GPI is currently undergoing
several upgrades to improve performance. In this paper, we discuss the upgrades
to the GPI IFS. This primarily focuses on the design and performance
improvements of new prisms and filters. This includes an improved
high-resolution prism which will provide more evenly dispersed spectra across
y, J, H and K-bands. Additionally, we discuss the design and implementation of
a new low-resolution mode and prism which allow for imaging of all four bands
(y, J, H and K-bands) simultaneously at R=10. We explore the possibility of
using a multiband filter which would block the light between the four spectral
bands. We discuss possible performance improvements from the multiband filter,
if implemented. Finally we explore the possibility of making small changes to
the optical design to improve the IFS's performance near the edge of the field
of view.Comment: 8 pages, 5 figures, Proc. of SPIE Paper No. 11447-41
GPI 2.0: Upgrades to the IFS including new spectral modes
The Gemini Planet Imager (GPI) is a high-contrast imaging instrument designed to directly image and characterize exoplanets. GPI is currently undergoing several upgrades to improve performance. In this paper, we discuss the upgrades to the GPI IFS. This primarily focuses on the design and performance improvements of new prisms and filters. This includes an improved high-resolution prism which will provide more evenly dispersed spectra across y, J, H and K-bands. Additionally, we discuss the design and implementation of a new low-resolution mode and prism which allow for imaging of all four bands (y, J, H and K-bands) simultaneously at R≈10. We explore the possibility of using a multiband filter which would block the light between the four spectral bands. We discuss possible performance improvements from the multiband filter, if implemented. Finally we explore the possibility of making small changes to the optical design to improve the IFS’s performance near the edge of the field of view
CHARIS Science: Performance Simulations for the Subaru Telescope's Third-Generation of Exoplanet Imaging Instrumentation
We describe the expected scientific capabilities of CHARIS, a high-contrast
integral-field spectrograph (IFS) currently under construction for the Subaru
telescope. CHARIS is part of a new generation of instruments, enabled by
extreme adaptive optics (AO) systems (including SCExAO at Subaru), that promise
greatly improved contrasts at small angular separation thanks to their ability
to use spectral information to distinguish planets from quasistatic speckles in
the stellar point-spread function (PSF). CHARIS is similar in concept to GPI
and SPHERE, on Gemini South and the Very Large Telescope, respectively, but
will be unique in its ability to simultaneously cover the entire near-infrared
, , and bands with a low-resolution mode. This extraordinarily broad
wavelength coverage will enable spectral differential imaging down to angular
separations of a few , corresponding to 0.\!\!''1. SCExAO
will also offer contrast approaching at similar separations,
0.\!\!''1--0.\!\!''2. The discovery yield of a CHARIS survey will
depend on the exoplanet distribution function at around 10 AU. If the
distribution of planets discovered by radial velocity surveys extends unchanged
to 20 AU, observations of 200 mostly young, nearby stars targeted
by existing high-contrast instruments might find 1--3 planets. Carefully
optimizing the target sample could improve this yield by a factor of a few,
while an upturn in frequency at a few AU could also increase the number of
detections. CHARIS, with a higher spectral resolution mode of , will
also be among the best instruments to characterize planets and brown dwarfs
like HR 8799 cde and And b.Comment: 13 pages, 7 figures, proceedings from SPIE Montrea
The TEMPO Survey I: Predicting Yields of the Transiting Exosatellites, Moons, and Planets from a 30-day Survey of Orion with the Nancy Grace Roman Space Telescope
We present design considerations for the Transiting Exosatellites, Moons, and
Planets in Orion (TEMPO) Survey with the Nancy Grace Roman Space Telescope.
This proposed 30-day survey is designed to detect a population of transiting
extrasolar satellites, moons, and planets in the Orion Nebula Cluster (ONC).
The young (1-3 Myr), densely-populated ONC harbors about a thousand bright
brown dwarfs (BDs) and free-floating planetary-mass objects (FFPs). TEMPO
offers sufficient photometric precision to monitor FFPs with for transiting satellites. The survey is also capable of detecting
FFPs down to sub-Saturn masses via direct imaging, although follow-up
confirmation will be challenging. TEMPO yield estimates include 14 (3-22)
exomoons/satellites transiting FFPs and 54 (8-100) satellites transiting BDs.
Of this population, approximately of companions would be "super-Titans"
(Titan to Earth mass). Yield estimates also include approximately
exoplanets transiting young Orion stars, of which will orbit
mid-to-late M dwarfs and approximately ten will be proto-habitable zone,
terrestrial () exoplanets. TEMPO would
provide the first census demographics of small exosatellites orbiting FFPs and
BDs, while simultaneously offering insights into exoplanet evolution at the
earliest stages. This detected exosatellite population is likely to be markedly
different from the current census of exoplanets with similar masses (e.g.,
Earth-mass exosatellites that still possess H/He envelopes). Although our yield
estimates are highly uncertain, as there are no known exoplanets or exomoons
analogous to these satellites, the TEMPO survey would test the prevailing
theories of exosatellite formation and evolution, which limit the certainty
surrounding detection yields.Comment: Submitted to PAS
Formation, Habitability, and Detection of Extrasolar Moons
The diversity and quantity of moons in the Solar System suggest a manifold population of natural satellites exist around extrasolar planets. Of peculiar interest from an astrobiological perspective, the number of sizable moons in the stellar habitable zones may outnumber planets in these circumstellar regions. With technological and theoretical methods now allowing for the detection of sub-Earth-sized extrasolar planets, the first detection of an extrasolar moon appears feasible. In this review, we summarize formation channels of massive exomoons that are potentially detectable with current or near-future instruments. We discuss the orbital effects that govern exomoon evolution, we present a framework to characterize an exomoon's stellar plus planetary illumination as well as its tidal heating, and we address the techniques that have been proposed to search for exomoons. Most notably, we show that natural satellites in the range of 0.1 - 0.5 Earth mass (i) are potentially habitable, (ii) can form within the circumplanetary debris and gas disk or via capture from a binary, and (iii) are detectable with current technology