128 research outputs found
Development of a New, Precise Near-infrared Doppler Wavelength Reference: A Fiber Fabry-Perot Interferometer
We present the ongoing development of a commercially available Micron Optics
fiber-Fabry Perot Interferometer as a precise, stable, easy to use, and
economic spectrograph reference with the goal of achieving <1 m/s long term
stability. Fiber Fabry-Perot interferometers (FFP) create interference patterns
by combining light traversing different delay paths. The interference creates a
rich spectrum of narrow emission lines, ideal for use as a precise Doppler
reference. This fully photonic reference could easily be installed in existing
NIR spectrographs, turning high resolution fiber-fed spectrographs into precise
Doppler velocimeters. First light results on the Sloan Digital Sky Survey III
(SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE)
spectrograph and several tests of major support instruments are also presented.
These instruments include a SuperK Photonics fiber supercontinuum laser source
and precise temperature controller. A high resolution spectrum obtained using
the NIST 2-m Fourier transform spectrometer (FTS) is also presented. We find
our current temperature control precision of the FFP to be 0.15 mK,
corresponding to a theoretical velocity stability of 35 cm/s due to temperature
variations of the interferometer cavity.Comment: 16 pages, 11 figures. To appear in the proceedings of the SPIE 2012
Astronomical Instrumentation and Telescopes conferenc
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
A comprehensive radial velocity error budget for next generation Doppler spectrometers
We describe a detailed radial velocity error budget for the NASA-NSF Extreme
Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet
Investigations with Doppler spectroscopy). Such an instrument performance
budget is a necessity for both identifying the variety of noise sources
currently limiting Doppler measurements, and estimating the achievable
performance of next generation exoplanet hunting Doppler spectrometers. For
these instruments, no single source of instrumental error is expected to set
the overall measurement floor. Rather, the overall instrumental measurement
precision is set by the contribution of many individual error sources. We use a
combination of numerical simulations, educated estimates based on published
materials, extrapolations of physical models, results from laboratory
measurements of spectroscopic subsystems, and informed upper limits for a
variety of error sources to identify likely sources of systematic error and
construct our global instrument performance error budget. While natively
focused on the performance of the NEID instrument, this modular performance
budget is immediately adaptable to a number of current and future instruments.
Such an approach is an important step in charting a path towards improving
Doppler measurement precisions to the levels necessary for discovering
Earth-like planets.Comment: 20 pages, 12 figures, published in Proc. of SPIE Astronomical
Telescopes + Instrumentation 201
Improving the Thermal Stability of a CCD Through Clocking
Modern precise radial velocity spectrometers are designed to infer the
existence of planets orbiting other stars by measuring few-nm shifts in the
positions of stellar spectral lines recorded at high spectral resolution on a
large-area digital detector. While the spectrometer may be highly stabilized in
terms of temperature, the detector itself may undergo changes in temperature
during readout that are an order of magnitude or more larger than the other
opto-mechanical components within the instrument. These variations in detector
temperature can translate directly into systematic measurement errors. We
explore a technique for reducing the amplitude of CCD temperature variations by
shuffling charge within a pixel in the parallel direction during integration.
We find that this "dither clocking" mode greatly reduces temperature variations
in the CCDs being tested for the NEID spectrometer. We investigate several
potential negative effects this clocking scheme could have on the underlying
spectral data.Comment: Submitted to JATIS, special issue from the ISPA 2018 conference. 11
pages, 9 figure
The PuZZling Li-Rich Red Giant Associated With NGC 6819
A Li-rich red giant (RG) star (2M19411367+4003382) recently discovered in the direction of NGC 6819 belongs to the rare subset of Li-rich stars that have not yet evolved to the luminosity bump, an evolutionary stage where models predict Li can be replenished. The currently favored model to explain Li enhancement in first-ascent RGs like 2M19411367+4003382 requires deep mixing into the stellar interior. Testing this model requires a measurement of C-12/C-13, which is possible to obtain from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra. However, the Li-rich star also has abnormal asteroseismic properties that call into question its membership in the cluster, even though its radial velocity and location on color-magnitude diagrams are consistent with membership. To address these puzzles, we have measured a wide array of abundances in the Li-rich star and three comparison stars using spectra taken as part of the APOGEE survey to determine the degree of stellar mixing, address the question of membership, and measure the surface gravity. We confirm that the Li-rich star is a RG with the same overall chemistry as the other cluster giants. However, its log g is significantly lower, consistent with the asteroseismology results and suggestive of a very low mass if the star is indeed a cluster member. Regardless of the cluster membership, the C-12/C-13 and C/N ratios of the Li-rich star are consistent with standard first dredge-up, indicating that Li dilution has already occurred, and inconsistent with internal Li enrichment scenarios that require deep mixing.National Science Foundation AST1109888NSF AST-1358862, AST 1109718, AST 1312863Alfred P. Sloan FoundationNational Science FoundationU.S. Department of Energy Office of ScienceUniversity of ArizonaBrazilian Participation GroupBrookhaven National LaboratoryCarnegie Mellon UniversityUniversity of FloridaFrench Participation GroupGerman Participation GroupHarvard UniversityInstituto de Astrofisica de CanariasMichigan State/NotreDame/JINA Participation GroupJohns Hopkins UniversityLawrence Berkeley National LaboratoryMax Planck Institute for AstrophysicsMax Planck Institute for Extraterrestrial PhysicsNew Mexico State UniversityNew York UniversityOhio State UniversityPennsylvania State UniversityUniversity of PortsmouthPrinceton UniversitySpanish Participation GroupUniversity of TokyoUniversity of UtahVanderbilt UniversityUniversity of VirginiaUniversity of WashingtonYale UniversityNational Aeronautics and Space AdministrationTwo Micron All Sky SurveyUniversity of MassachusettsInfrared Processing and Analysis Center/California Institute of TechnologyU.S. Government NAG W-2166Astronom
Evidence for He I 10830 \AA~ absorption during the transit of a warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone Planet Finder
Understanding the dynamics and kinematics of out-flowing atmospheres of hot
and warm exoplanets is crucial to understanding the origins and evolutionary
history of the exoplanets near the evaporation desert. Recently, ground based
measurements of the meta-stable Helium atom's resonant absorption at 10830
\AA~has become a powerful probe of the base environment which is driving the
outflow of exoplanet atmospheres. We report evidence for the He I 10830 \AA~in
absorption (equivalent width \AA) in the exosphere of
a warm Neptune orbiting the M-dwarf GJ 3470, during three transits using the
Habitable Zone Planet Finder (HPF) near infrared spectrograph. This marks the
first reported evidence for He I 10830 \AA\, atmospheric absorption for a
planet orbiting an M-dwarf. Our detected absorption is broad and its
blueshifted wing extends to -36 km/sec, the largest reported in the literature
to date. We modelled the state of Helium atoms in the exosphere of GJ3470b
based on assumptions on the UV and X-ray flux of GJ 3470, and found our
measurement of flux-weighted column density of meta-stable state Helium
, derived from our transit
observations, to be consistent with model, within its uncertainties. The
methodology developed here will be useful to study and constrain the
atmospheric outflow models of other exoplanets like GJ 3470b which are near the
edge of the evaporation desert.Comment: Accepted in Ap
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%
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