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"Dunham, Edward"
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Kepler-16: A Transiting Circumbinary Planet
by
Winn, Joshua N.
,
Ford, Eric B.
,
Borucki, William J.
in
Astronomical transits
,
Astronomy
,
Average linear density
2011
We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.
Journal Article
Science Commissioning of NIHTS: The Near-infrared High Throughput Spectrograph on the Lowell Discovery Telescope
2021
The Near-Infrared High Throughput Spectrograph (NIHTS) is in operation on the 4.3 m Lowell Discovery Telescope (LDT) in Happy Jack, AZ. NIHTS is a low-resolution spectrograph ( R ∼ 200) that operates from 0.86 to 2.45 microns. NIHTS is fed by a custom dichroic mirror which reflects near-infrared wavelengths to the spectrograph and transmits the visible to enable simultaneous imaging with the Large Monolithic Imager (LMI), an independent visible wavelength camera. The combination of premier tracking and acquisition capabilities of the LDT, a several arcminutes field of view on LMI, and high spectral throughput on NIHTS enables novel studies of a number of astrophysical and planetary objects including Kuiper Belt Objects, asteroids, comets, low mass stars, and exoplanet hosts stars. We present a summary of NIHTS operations, commissioning, data reduction procedures with two approaches for the correction of telluric absorption features, and an overview of select science cases that will be pursued by Lowell Observatory, Northern Arizona University, and LDT partners.
Journal Article
A closely packed system of low-mass, low-density planets transiting Kepler-11
2011
When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary systems. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47 days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.
Edge-on view of Kepler-11 planetary system
NASA's Kepler mission, a space observatory designed to detect and study extrasolar planets that transit across the disk of their host star, has hit the jackpot with the discovery of a six-planet system orbiting a Sun-like star now named Kepler-11. Five of the planets have orbital periods of between 10 and 47 days, and these are among the smallest for which size and mass have both been measured. The sixth and outermost transiting planet has been less well characterized thus far. Only one other star has more than one confirmed transiting planet (Kepler-9, which has three). This newly discovered system resembles our own Solar System in being close to coplanar, but Kepler-11's planets orbit much closer to their star. Kepler is due to continue to return data on Kepler-11 and its planets for some time yet, and it should provide many valuable constraints on models of the formation and evolution of solar systems in general.
When an extrasolar planet passes in front of its star (transits), its radius can be measured from the decrease in starlight and its orbital period from the time between transits. This study reports Kepler spacecraft observations of a single Sun-like star that reveal six transiting planets, five with orbital periods between 10 and 47 days plus a sixth one with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases.
Journal Article
Kepler-9: A System of Multiple Planets Transiting a Sun-Like Star, Confirmed by Timing Variations
by
Fressin, Francois
,
Steffen, Jason H
,
Hartman, Joel D
in
Astronomical photometry
,
Astronomical transits
,
Astronomy
2010
The Kepler spacecraft is monitoring more than 150,000 stars for evidence of planets transiting those stars. We report the detection of two Saturn-size planets that transit the same Sun-like star, based on 7 months of Kepler observations. Their 19.2- and 38.9-day periods are presently increasing and decreasing at respective average rates of 4 and 39 minutes per orbit; in addition, the transit times of the inner body display an alternating variation of smaller amplitude. These signatures are characteristic of gravitational interaction of two planets near a 2:1 orbital resonance. Six radial-velocity observations show that these two planets are the most massive objects orbiting close to the star and substantially improve the estimates of their masses. After removing the signal of the two confirmed giant planets, we identified an additional transiting super-Earth-size planet candidate with a period of 1.6 days.
Journal Article
Wide Angle Telescope Transit Search (WATTS): A Low-Elevation Component of the TrES Network
by
Mandushev, Georgi I.
,
Dunham, Edward W.
,
Kowalczyk, Michael
in
Astronomical photometry
,
Astronomy
,
Earth, ocean, space
2010
The Wide Angle Telescope Transit Search (WATTS) is a low-elevation small aperture, wide-field(5.5° × 5.5°)
(
5.5
°
×
5.5
°
)
, transit search instrument capable of achieving the photometric precision needed to detect giant extrasolar planets. The system is designed to simultaneously observe tens of thousands of stars with
R
R
magnitudes between 10 and 13. In just over one year of operation, WATTS has completed five observing campaigns. During this period, 20 candidates have been identified from WATTS data. As the fourth component of the TrES network, WATTS significantly increases the efficiency of the survey when data are combined.
Journal Article
PSST: The Planet Search Survey Telescope
by
Mandushev, Georgi I.
,
Taylor, Brian W.
,
Dunham, Edward W.
in
Astronomical photometry
,
Astronomical transits
,
Eclipsing binary stars
2004
The Planet Search Survey Telescope is an automated small‐aperture CCD imaging photometer designed to search for transits by extrasolar planets across the disks of their parent stars. It simultaneously observes thousands of stars with apparentRmagnitudes between 10 and 13 in a field approximately
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. Stars in this brightness range are well within the capability of the high‐precision radial velocity systems that have successfully detected over 100 extrasolar planets to date. The combination of the photometric transit depth and radial velocity amplitude can provide both the radius of the planet and a good estimate of its mass, since the orbit is nearly edge‐on. As a result, estimates of the planet’s density and other parameters can be obtained.
Journal Article
Kepler Planet-Detection Mission: Introduction and First Results
2010
The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.
Journal Article
The TESS Mission Target Selection Procedure
by
Winn, Joshua N.
,
Paegert, Martin
,
Rinehart, S. A.
in
Algorithms
,
Exoplanets
,
Statistical analysis
2021
We describe the target selection procedure by which stars are selected for 2 minute and 20 s observations by TESS. We first list the technical requirements of the TESS instrument and ground systems processing that limit the total number of target slots. We then describe algorithms used by the TESS Payload Operation Center (POC) to merge candidate targets requested by the various TESS mission elements (the Target Selection Working Group, TESS Asteroseismic Science Consortium, and Guest Investigator office). Lastly, we summarize the properties of the observed TESS targets over the two-year primary TESS mission. We find that the POC target selection algorithm results in 2.1–3.4 times as many observed targets as target slots allocated for each mission element. We also find that the sky distribution of observed targets is different from the sky distributions of candidate targets due to technical constraints that require a relatively even distribution of targets across the TESS fields of view. We caution researchers exploring statistical analyses of TESS planet-host stars that the population of observed targets cannot be characterized by any simple set of criteria applied to the properties of the input Candidate Target Lists.
Journal Article
The TESS Mission Target Selection Procedure
by
Winn, Joshua N.
,
Paegert, Martin
,
Rinehart, S. A.
in
Astronomical Instrumentation, Telescopes, Observatories, and Site Characterization
2021
We describe the target selection procedure by which stars are selected for 2 minute and 20 s observations by TESS. We first list the technical requirements of the TESS instrument and ground systems processing that limit the total number of target slots. We then describe algorithms used by the TESS Payload Operation Center (POC) to merge candidate targets requested by the various TESS mission elements (the Target Selection Working Group, TESS Asteroseismic Science Consortium, and Guest Investigator office). Lastly, we summarize the properties of the observed TESS targets over the two-year primary TESS mission. We find that the POC target selection algorithm results in 2.1–3.4 times as many observed targets as target slots allocated for each mission element. We also find that the sky distribution of observed targets is different from the sky distributions of candidate targets due to technical constraints that require a relatively even distribution of targets across the TESS fields of view. We caution researchers exploring statistical analyses of TESS planet-host stars that the population of observed targets cannot be characterized by any simple set of criteria applied to the properties of the input Candidate Target Lists.
Journal Article
Searching for NEOs using Lowell observatorys Discovery Channel Telescope (DCT)
by
Dunham, Edward W.
,
Bowell, Edward
,
Millis, Robert L.
in
Astronomy
,
Astrophysics
,
Collaboration
2006
We discuss the potential contribution of the Discovery Channel Telescope (or a clone) to a detection program aimed at discovering 90% of potentially hazardous objects (PHOs) larger than 140 m in diameter. Three options are described, each involving different levels of investment. We believe that LSST, Pan-STARRS, and DCT, working in a coordinated fashion, offer a cost-effective, low-risk way to accomplish the objectives of the extended NEO search program.
Journal Article