37 research outputs found
The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope
We present the scientific motivation and conceptual design for the recently
funded Habitable-zone Planet Finder (HPF), a stabilized fiber-fed near-infrared
(NIR) spectrograph for the 10 meter class Hobby-Eberly Telescope (HET) that
will be capable of discovering low mass planets around M dwarfs. The HPF will
cover the NIR Y & J bands to enable precise radial velocities to be obtained on
mid M dwarfs, and enable the detection of low mass planets around these stars.
The conceptual design is comprised of a cryostat cooled to 200K, a dual
fiber-feed with a science and calibration fiber, a gold coated mosaic echelle
grating, and a Teledyne Hawaii-2RG (H2RG) NIR detector with a 1.7m cutoff.
A uranium-neon hollow-cathode lamp is the baseline wavelength calibration
source, and we are actively testing laser frequency combs to enable even higher
radial velocity precision. We will present the overall instrument system design
and integration with the HET, and discuss major system challenges, key choices,
and ongoing research and development projects to mitigate risk. We also discuss
the ongoing process of target selection for the HPF survey.Comment: 14 pages, 9 figures. To appear in the proceedings of the SPIE 2012
Astronomical Instrumentation and Telescopes conferenc
Towards Space-like Photometric Precision from the Ground with Beam-Shaping Diffusers
We demonstrate a path to hitherto unachievable differential photometric
precisions from the ground, both in the optical and near-infrared (NIR), using
custom-fabricated beam-shaping diffusers produced using specialized
nanofabrication techniques. Such diffusers mold the focal plane image of a star
into a broad and stable top-hat shape, minimizing photometric errors due to
non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and
telescope-induced variable aberrations seen in defocusing. This PSF reshaping
significantly increases the achievable dynamic range of our observations,
increasing our observing efficiency and thus better averages over
scintillation. Diffusers work in both collimated and converging beams. We
present diffuser-assisted optical observations demonstrating
ppm precision in 30 minute bins on a nearby bright star
16-Cygni A (V=5.95) using the ARC 3.5m telescope---within a factor of 2
of Kepler's photometric precision on the same star. We also show a transit of
WASP-85-Ab (V=11.2) and TRES-3b (V=12.4), where the residuals bin down to
ppm in 30 minute bins for WASP-85-Ab---a factor of 4 of
the precision achieved by the K2 mission on this target---and to 101ppm for
TRES-3b. In the NIR, where diffusers may provide even more significant
improvements over the current state of the art, our preliminary tests have
demonstrated ppm precision for a star on the 200"
Hale Telescope. These photometric precisions match or surpass the expected
photometric precisions of TESS for the same magnitude range. This technology is
inexpensive, scalable, easily adaptable, and can have an important and
immediate impact on the observations of transits and secondary eclipses of
exoplanets.Comment: Accepted for publication in ApJ. 30 pages, 20 figure
Long-term operation of a laser frequency comb with the Habitable Zone Planet Finder
Laser frequency combs are an ideal calibration source for precision astronomical spectrographs. We report on the demonstrated long term operation of a laser frequency comb that we designed and built as the primary calibrator for the Habitable Zone Planet Finder (HPF). The core technology of the comb is based on robust, polarization maintaining fiber coupled electro-optic modulators and broadband supercontinuum generation spanning 700-1600 nm in an efficient silicon nitride waveguide. The comb is continuously maintained on and ready to use, and since May 2018 the laser frequency comb has had a total uptime of 97%
A Prograde, Low-Inclination Orbit for the Very Hot Jupiter WASP-3b
We present new spectroscopic and photometric observations of the transiting
exoplanetary system WASP-3. Spectra obtained during two separate transits
exhibit the Rossiter-McLaughlin (RM) effect and allow us to estimate the
sky-projected angle between the planetary orbital axis and the stellar rotation
axis, lambda = 3.3^{+2.5}_{-4.4} degrees. This alignment between the axes
suggests that WASP-3b has a low orbital inclination relative to the equatorial
plane of its parent star. During our first night of spectroscopic measurements,
we observed an unexpected redshift briefly exceeding the expected sum of the
orbital and RM velocities by 140 m/s. This anomaly could represent the
occultation of material erupting from the stellar photosphere, although it is
more likely to be an artifact caused by moonlight scattered into the
spectrograph.Comment: 23 pages, 4 figures, Accepted for publication in The Astrophysical
Journal, Replacement includes revised citation
Solar Contamination in Extreme Precision Radial Velocity Measurements: Deleterious Effects and Prospects for Mitigation
Solar contamination, due to moonlight and atmospheric scattering of sunlight,
can cause systematic errors in stellar radial velocity (RV) measurements that
significantly detract from the ~10cm/s sensitivity required for the detection
and characterization of terrestrial exoplanets in or near Habitable Zones of
Sun-like stars. The addition of low-level spectral contamination at variable
effective velocity offsets introduces systematic noise when measuring
velocities using classical mask-based or template-based cross-correlation
techniques. Here we present simulations estimating the range of RV measurement
error induced by uncorrected scattered sunlight contamination. We explore
potential correction techniques, using both simultaneous spectrometer sky
fibers and broadband imaging via coherent fiber imaging bundles, that could
reliably reduce this source of error to below the photon-noise limit of typical
stellar observations. We discuss the limitations of these simulations, the
underlying assumptions, and mitigation mechanisms. We also present and discuss
the components designed and built into the NEID precision RV instrument for the
WIYN 3.5m telescope, to serve as an ongoing resource for the community to
explore and evaluate correction techniques. We emphasize that while "bright
time" has been traditionally adequate for RV science, the goal of 10cm/s
precision on the most interesting exoplanetary systems may necessitate access
to darker skies for these next-generation instruments