15 research outputs found
A New Analysis of the Exoplanet Hosting System HD 6434
The current goal of exoplanetary science is not only focused on detecting but
characterizing planetary systems in hopes of understanding how they formed,
evolved, and relate to the Solar System. The Transit Ephemeris Refinement and
Monitoring Survey (TERMS) combines both radial velocity (RV) and photometric
data in order to achieve unprecedented ground-based precision in the
fundamental properties of nearby, bright, exoplanet-hosting systems. Here we
discuss HD 6434 and its planet, HD 6434b, which has a M_p*sin(i) = 0.44 M_J
mass and orbits every 22.0170 days with an eccentricity of 0.146. We have
combined previously published RV data with new measurements to derive a
predicted transit duration of ~6 hrs, or 0.25 days, and a transit probability
of 4%. Additionally, we have photometrically observed the planetary system
using both the 0.9m and 1.0m telescopes at the Cerro Tololo Inter-American
Observatory, covering 75.4% of the predicted transit window. We reduced the
data using the automated TERMS Photometry Pipeline, developed to ensure
consistent and accurate results. We determine a dispositive null result for the
transit of HD 6434b, excluding the full transit to a depth of 0.9% and grazing
transit due to impact parameter limitations to a depth of 1.6%Comment: 9 pages, 5 figures, 3 tables, accepted to A
On the measurement of intensity correlations from laboratory and astronomical sources with SPADs and SNSPDs
We describe the performance of detector modules containing silicon single photon avalanche photodiodes (SPADs) and superconducting nanowire single photon detectors (SNSPDs) to be used for intensity interferometry. The SPADs are mounted in fiber-coupled and free-space coupled packages. The SNSPDs are mounted in a small liquid helium cryostat coupled to single mode fiber optic cables which pass through a hermetic feed-through. The detectors are read out with microwave amplifiers and FPGA-based coincidence electronics. We present progress on measurements of intensity correlations from incoherent sources including gas-discharge lamps and stars with these detectors. From the measured laboratory performance of the correlation system, we estimate the sensitivity to intensity correlations from stars using commercial telescopes and larger existing research telescopes. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
The HD 192263 system: planetary orbital period and stellar variability disentangled
As part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS), we
present new radial velocities and photometry of the HD 192263 system. Our
analysis of the already available Keck-HIRES and CORALIE radial velocity
measurements together with the five new Keck measurements we report in this
paper results in improved orbital parameters for the system. We derive
constraints on the size and phase location of the transit window for HD
192263b, a Jupiter-mass planet with a period of 24.3587 \pm 0.0022 days. We use
10 years of Automated Photoelectric Telescope (APT) photometry to analyze the
stellar variability and search for planetary transits. We find continuing
evidence of spot activity with periods near 23.4 days. The shape of the
corresponding photometric variations changes over time, giving rise to not one
but several Fourier peaks near this value. However, none of these frequencies
coincides with the planet's orbital period and thus we find no evidence of
star-planet interactions in the system. We attribute the ~23-day variability to
stellar rotation. There are also indications of spot variations on longer (8
years) timescales. Finally, we use the photometric data to exclude transits for
a planet with the predicted radius of 1.09 RJ, and as small as 0.79 RJ.Comment: 9 pages, 6 tables, 6 figures; accepted to Ap
TERMS Photometry of Known Transiting Exoplanets
The Transit Ephemeris Refinement and Monitoring Survey (TERMS) conducts
radial velocity and photometric monitoring of known exoplanets in order to
refine planetary orbits and predictions of possible transit times. This effort
is primarily directed towards planets not known to transit, but a small sample
of our targets consist of known transiting systems. Here we present precision
photometry for 6 WASP planets acquired during their transit windows. We perform
a Markov Chain Monte Carlo (MCMC) analysis for each planet and combine these
data with previous measurements to redetermine the period and ephemerides for
these planets. These observations provide recent mid-transit times which are
useful for scheduling future observations. Our results improve the ephemerides
of WASP-4b, WASP-5b and WASP-6b and reduce the uncertainties on the mid-transit
time for WASP-29b. We also confirm the orbital, stellar and planetary
parameters of all 6 systems.Comment: 12 pages; 6 figures; 9 tables; accepted for publication in AJ; two
references updated and minor improvements made to match the version to be
publishe
Improved Orbital Parameters and Transit Monitoring for HD 156846b
HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a
period of 359.55 days. The pericenter passage at a distance of 0.16 AU is
nearly aligned to our line of sight, offering an enhanced transit probability
of 5.4% and a potentially rich probe of the dynamics of a cool planetary
atmosphere impulsively heated during close approach to a bright star (V = 6.5).
We present new radial velocity (RV) and photometric measurements of this star
as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). The
RV measurements from Keck-HIRES reduce the predicted transit time uncertainty
to 20 minutes, an order of magnitude improvement over the ephemeris from the
discovery paper. We photometrically monitored a predicted transit window under
relatively poor photometric conditions, from which our non-detection does not
rule out a transiting geometry. We also present photometry that demonstrates
stability at the millimag level over its rotational timescale.Comment: 7 pages, 4 figures, accepted for publication in Ap
Stellar variability of the exoplanet hosting star HD 63454
Of the hundreds of exoplanets discovered using the radial velocity (RV) technique, many are orbiting close to their host stars with periods less than 10 days. One of these, HD 63454, is a young active K dwarf which hosts a Jovian planet in a 2.82 day period orbit. The planet has a 14% transit probability and a predicted transit depth of 1.2%. Here we provide a re-analysis of the RV data to produce an accurate transit ephemeris. We further analyze 8 nights of time series data to search for stellar activity both intrinsic to the star and induced by possible interactions of the exoplanet with the stellar magnetospheres. We establish the photometric stability of the star at the 3 mmag level despite strong CaII emission in the spectrum. Finally, we rule out photometric signatures of both star-planet magnetosphere interactions and planetary transit signatures. From this we are able to place constraints on both the orbital and physical properties of the planet
A Search for the Transit of HD 168443b: Improved Orbital Parameters and Photometry
The discovery of transiting planets around bright stars holds the potential
to greatly enhance our understanding of planetary atmospheres. In this work we
present the search for transits of HD 168443b, a massive planet orbiting the
bright star HD 168443 V=6.92 with a period of 58.11 days. The high eccentricity
of the planetary orbit e=0.53 significantly enhances the a-priori transit
probability beyond that expected for a circular orbit, making HD 168443 a
candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey
(TERMS). Using additional radial velocities from Keck-HIRES, we refined the
orbital parameters of this multi-planet system and derived a new transit
ephemeris for HD 168443b. The reduced uncertainties in the transit window make
a photometric transit search practicable. Photometric observations acquired
during predicted transit windows were obtained on three nights. CTIO 1.0 m
photometry acquired on 2010 September 7 had the required precision to detect a
transit but fell just outside of our final transit window. Nightly photometry
from the T8 0.8 m Automated Photometric Telescope (APT) at Fairborn
Observatory, acquired over a span of 109 nights, demonstrates that HD 168443 is
constant on a time scale of weeks. Higher-cadence photometry on 2011 April 28
and June 25 shows no evidence of a transit. We are able to rule out a
non-grazing transit of HD 168443b.Comment: Accepted in ApJ. 25 pages. 8 Figure
Host star properties and transit exclusion for the HD 38529 planetary system
The transit signature of exoplanets provides an avenue through which characterization of exoplanetary properties may be undertaken, such as studies of mean density, structure, and atmospheric composition. The Transit Ephemeris Refinement and Monitoring Survey is a program to expand the catalog of transiting planets around bright host stars by refining the orbits of known planets discovered with the radial velocity technique. Here we present results for the HD 38529 system. We determine fundamental properties of the host star through direct interferometric measurements of the radius and through spectroscopic analysis. We provide new radial velocity measurements that are used to improve the Keplerian solution for the two known planets, and we find no evidence for a previously postulated third planet. We also present 12 years of precision robotic photometry of HD 38529 that demonstrate the inner planet does not transit and the host star exhibits cyclic variations in seasonal mean brightness with a timescale of approximately six years
SmallSat interferometry for THz astrophysics
While great strides have been made in far-infrared astrophysics with the NASA Spitzer and ESA Herschel missions, subarcsecond spatial resolution from space is still beyond the reach of current technologies. The Atacama Large Millimeter Array has produced stunning images from the ground of planetary systems in the process of formation but cannot observe the key molecules of water or O-2, due to the presence of Earth's atmosphere. The concept presented here will enable interferometric imaging with sub-arcsecond resolution of water and other key far infrared molecular species from space at a cost far lower than the flagship class interferometric missions previously proposed (i.e. ESA's ESPRIT). We present a concept for a far infrared interferometer based on a constellation of CubeSat antenna elements with a central ESPA-class correlator satellite optimized for the imaging of water in protoplanetary systems. Such a mission would produce groundbreaking images of newly forming planetary systems in a key astrophysical and astrobiological tracer, the 557 GHz ground state line of water. By leveraging recent developments in CubeSat technology, inflatable reflectors, miniaturized receiver systems and low power CMOS digital electronics, such a mission could be implemented at an Explorer level budget. In addition to the proposed astrophysics application, the developments proposed here could also find application in planetary science (FIR spectroscopy of comets and small bodies) and Earth observing (high resolution imaging of Earth from geostationary orbit).NASA [NNX16AT65A]; JPL award [SP.17.0001.003]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
A Search for the Transit of HD 168443b: Improved Orbital Parameters and Photometry
The discovery of transiting planets around bright stars holds the potential to greatly enhance our understanding of planetary atmospheres. In this work we present the search for transits of HD 168443b, a massive planet orbiting the bright star HD 168443 (V = 6.92) with a period of 58.11 days. The high eccentricity of the planetary orbit (e = 0.53) significantly enhances the a priori transit probability beyond that expected for a circular orbit, making HD 168443 a candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey. Using additional radial velocities from Keck High Resolution Echelle Spectrometer, we refined the orbital parameters of this multi-planet system and derived a new transit ephemeris for HD 168443b. The reduced uncertainties in the transit window make a photometric transit search practicable. Photometric observations acquired during predicted transit windows were obtained on three nights. Cerro Tololo Inter-American Observatory 1.0 m photometry acquired on 2010 September 7 had the required precision to detect a transit but fell just outside of our final transit window. Nightly photometry from the T8 0.8 m automated photometric telescope at Fairborn Observatory, acquired over a span of 109 nights, demonstrates that HD 168443 is constant on a timescale of weeks. Higher-cadence photometry on 2011 April 28 and June 25 shows no evidence of a transit. We are able to rule out a non-grazing transit of HD 168443b