17 research outputs found
CHIRON - A Fiber Fed Spectrometer for Precise Radial Velocities
The CHIRON optical high-resolution echelle spectrometer was commissioned at
the 1.5m telescope at CTIO in 2011. The instrument was designed for high
throughput and stability, with the goal of monitoring radial velocities of
bright stars with high precision and high cadence for the discovery of low-mass
exoplanets. Spectral resolution of R=79,000 is attained when using a slicer
with a total (including telescope and detector) efficiency of 6% or higher,
while a resolution of R=136,000 is available for bright stars. A fixed spectral
range of 415 to 880 nm is covered. The echelle grating is housed in a vacuum
enclosure and the instrument temperature is stabilized to +-0.2deg. Stable
illumination is provided by an octagonal multimode fiber with excellent
light-scrambling properties. An iodine cell is used for wavelength calibration.
We describe the main optics, fiber feed, detector, exposure-meter, and other
aspects of the instrument, as well as the observing procedure and data
reduction.Comment: 15 pages, 10 figures. Accepted by PAS
Fiber scrambling for high-resolution spectrographs. I. Lick Observatory
In this paper, we report all results obtained with a fiber scrambler on the
Hamilton spectrograph at Lick Observatory. We demonstrate an improvement in the
stability of the instrumental profile using this fiber scrambler. Additionally,
we present data obtained with a double scrambler that further improves the
stability of the instrument by a factor 2. These results show that errors
related to the coupling between the telescope and the spectrograph are the
dominant source of instrumental profile variability at Lick Observatory. In
particular, we show a strong correlation between instrumental profile
variations and hour angle, most likely due to pointing-dependent illumination
of the spectrograph optics
A High Eccentricity Component in the Double Planet System Around HD 163607 and a Planet Around HD 164509
We report the detection of three new exoplanets from Keck Observatory. HD
163607 is a metal-rich G5IV star with two planets. The inner planet has an
observed orbital period of 75.29 0.02 days, a semi-amplitude of 51.1
1.4 \ms, an eccentricity of 0.73 0.02 and a derived minimum mass of
\msini = 0.77 0.02 \mjup. This is the largest eccentricity of any known
planet in a multi-planet system. The argument of periastron passage is 78.7
2.0; consequently, the planet's closest approach to its parent
star is very near the line of sight, leading to a relatively high transit
probability of 8%. The outer planet has an orbital period of 3.60 0.02
years, an orbital eccentricity of 0.12 0.06 and a semi-amplitude of 40.4
1.3 \ms. The minimum mass is \msini = 2.29 0.16 \mjup. HD 164509 is
a metal-rich G5V star with a planet in an orbital period of 282.4 3.8
days and an eccentricity of 0.26 0.14. The semi-amplitude of 14.2
2.7 \ms\ implies a minimum mass of 0.48 0.09 \mjup. The radial velocities
of HD 164509 also exhibit a residual linear trend of -5.1 0.7 \ms\ per
year, indicating the presence of an additional longer period companion in the
system. Photometric observations demonstrate that HD 163607 and HD 164509 are
constant in brightness to sub-millimag levels on their radial velocity periods.
This provides strong support for planetary reflex motion as the cause of the
radial velocity variations.Comment: 10 pages, 8 figures, accepted to Ap
HARPS3 for a Roboticized Isaac Newton Telescope
We present a description of a new instrument development, HARPS3, planned to
be installed on an upgraded and roboticized Isaac Newton Telescope by end-2018.
HARPS3 will be a high resolution (R = 115,000) echelle spectrograph with a
wavelength range from 380-690 nm. It is being built as part of the Terra
Hunting Experiment - a future 10 year radial velocity measurement programme to
discover Earth-like exoplanets. The instrument design is based on the
successful HARPS spectrograph on the 3.6m ESO telescope and HARPS-N on the TNG
telescope. The main changes to the design in HARPS3 will be: a customised fibre
adapter at the Cassegrain focus providing a stabilised beam feed and on-sky
fibre diameter ~ 1.4 arcsec, the implementation of a new continuous flow
cryostat to keep the CCD temperature very stable, detailed characterisation of
the HARPS3 CCD to map the effective pixel positions and thus provide an
improved accuracy wavelength solution, an optimised integrated polarimeter and
the instrument integrated into a robotic operation. The robotic operation will
optimise our programme which requires our target stars to be measured on a
nightly basis. We present an overview of the entire project, including a
description of our anticipated robotic operation.Comment: 13 pages, 8 figures, SPIE conference proceeding
Planet Hunters: The First Two Planet Candidates Identified by the Public using the Kepler Public Archive Data
Planet Hunters is a new citizen science project, designed to engage the
public in an exoplanet search using NASA Kepler public release data. In the
first month after launch, users identified two new planet candidates which
survived our checks for false- positives. The follow-up effort included
analysis of Keck HIRES spectra of the host stars, analysis of pixel centroid
offsets in the Kepler data and adaptive optics imaging at Keck using NIRC2.
Spectral synthesis modeling coupled with stellar evolutionary models yields a
stellar density distribution, which is used to model the transit orbit. The
orbital periods of the planet candidates are 9.8844 \pm0.0087 days (KIC
10905746) and 49.7696 \pm0.00039 (KIC 6185331) days and the modeled planet
radii are 2.65 and 8.05 R\oplus. The involvement of citizen scientists as part
of Planet Hunters is therefore shown to be a valuable and reliable tool in
exoplanet detection.Comment: Submitted to MNRAS, added 1 line to table
M2K: II. A Triple-Planet System Orbiting HIP 57274
Doppler observations from Keck Observatory have revealed a triple planet
system orbiting the nearby mid-type K dwarf, HIP 57274. The inner planet, HIP
57274b, is a super-Earth with \msini\ = 11.6 \mearth (0.036 \mjup), an orbital
period of 8.135 0.004 d, and slightly eccentric orbit .
We calculate a transit probability of 6.5% for the inner planet. The second
planet has \msini\ = 0.4 \mjup\ with an orbital period of 32.0 d in
a nearly circular orbit, and . The third planet has \msini\
= 0.53 \mjup\ with an orbital period of 432 d (1.18 years) and an
eccentricity . This discovery adds to the number of super
Earth mass planets with \msini < 12 \mearth\ that have been detected with
Doppler surveys. We find that 56 % super-Earths are members of
multi-planet systems. This is certainly a lower limit because of observational
detectability limits, yet significantly higher than the fraction of Jupiter
mass exoplanets, %, that are members of Doppler-detected,
multi-planet systems.Comment: 11 figures, submitte to ApJ on Sept 10, 201
Design of the CHIRON high-resolution spectrometer at CTIO
Small telescopes coupled to high resolution spectrometers are powerful tools for Doppler planet searches. They allow for high cadence observations and flexible scheduling; yet there are few such facilities. We present an innovative and inexpensive design for CHIRON, a high resolution (R∼80.000) Echelle spectrometer for the 1.5m telescope at CTIO. Performance and throughput are very good, over the whole spectral range from 410 to 870nm, with a peak efficiency of 15% in the iodine absorption region. The spectrograph will be fibre-fed, and use an iodine cell for wavelength calibration. An image slicer permits a moderate beam size. We use commercially available, high performance optical components, which is key for quick and efficient implementation. We discuss the optical design, opto-mechanical tolerances and resulting image quality.7 page(s