Pengcheng Guo

The First Extrasolar Planet Discovered with a New-Generation High-Throughput Doppler Instrument

We report the detection of the first extrasolar planet, ET-1 (HD 102195b), using the Exoplanet Tracker (ET), a new-generation Doppler instrument. The planet orbits HD 102195, a young star with solar metallicity that may be part of the local association. The planet imparts radial velocity variability to the star with a semiamplitude of 63.4 ± 2.0 m s-1 and a period of 4.11 days. The planetary minimum mass (m sin i) is 0.488MJ ± 0.015MJ. The planet was initially detected in the spring of 2005 with the Kitt Peak National Observatory (KPNO) 0.9 m coude feed telescope. The detection was confirmed by radial velocity observations with the ET at the KPNO 2.1 m telescope and also at the 9 m Hobby-Eberly Telescope (HET) with its High Resolution Spectrograph. This planetary discovery with a 0.9 m telescope around a V = 8.05 magnitude star was made possible by the high throughput of the instrument: 49% measured from the fiber output to the detector. The ETs interferometer-based approach is an effective method for planet detection. In addition, the ET concept is adaptable to multiple-object Doppler observations or very high precision observations with a cross-dispersed echelle spectrograph to separate stellar fringes over a broad wavelength band. In addition to spectroscopic observations of HD 102195, we obtained brightness measurements with one of the automated photometric telescopes at Fairborn Observatory. Those observations reveal that HD 102195 is a spotted variable star with an amplitude of ~0.015 mag and a 12.3 ± 0.3 day period. This is consistent with spectroscopically observed Ca II H and K emission levels and line-broadening measurements but inconsistent with rotational modulation of surface activity as the cause of the radial velocity variability. Our photometric observations rule out transits of the planetary companion.

MARVELS-1b: A Short-period, Brown Dwarf Desert Candidate from the SDSS-III Marvels Planet Search

We present a new short-period brown dwarf (BD) candidate around the star TYC 1240-00945-1. This candidate was discovered in the first year of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the Sloan Digital Sky Survey (SDSS) III, and we designate the BD as MARVELS-1b. MARVELS uses the technique of dispersed fixed-delay interferometery to simultaneously obtain radial velocity (RV) measurements for 60 objects per field using a single, custom-built instrument that is fiber fed from the SDSS 2.5 m telescope. From our 20 RV measurements spread over a ~370 day time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 2.533 ± 0.025 km s^(–1), period P = 5.8953 ± 0.0004 days, and eccentricity consistent with circular. Independent follow-up RV data confirm the orbit. Adopting a mass of 1.37 ± 0.11 M_☉ for the slightly evolved F9 host star, we infer that the companion has a minimum mass of 28.0 ± 1.5 M_(Jup), a semimajor axis 0.071 ± 0.002 AU assuming an edge-on orbit, and is probably tidally synchronized. We find no evidence for coherent intrinsic variability of the host star at the period of the companion at levels greater than a few millimagnitudes. The companion has an a priori transit probability of ~14%. Although we find no evidence for transits, we cannot definitively rule them out for companion radii ≲ R_(Jup).

Eclipsing Binary Science via the Merging of Transit and Doppler Exoplanet Survey Data—A Case Study with the MARVELS Pilot Project and SuperWASP

Exoplanet transit and Doppler surveys discover many binary stars during their operation that can be used to conduct a variety of ancillary science. Specifically, eclipsing binary stars can be used to study the stellar mass-radius relationship and to test predictions of theoretical stellar evolution models. By cross-referencing 24 binary stars found in the MARVELS Pilot Project with SuperWASP photometry, we find two new eclipsing binaries, TYC 0272-00458-1 and TYC 1422-01328-1, which we use as case studies to develop a general approach to eclipsing binaries in survey data. TYC 0272-00458-1 is a single-lined spectroscopic binary for which we calculate a mass of the secondary and radii for both components using reasonable constraints on the primary mass through several different techniques. For a primary mass of M_1 = 0.92 ± 0.1 M_☉, we find M_2 = 0.610 ± 0.036 M_☉, R_1 = 0.932 ± 0.076 R_☉, and R_2 = 0.559 ± 0.102 R_☉, and find that both stars have masses and radii consistent with model predictions. TYC 1422-01328-1 is a triple-component system for which we can directly measure the masses and radii of the eclipsing pair. We find that the eclipsing pair consists of an evolved primary star (M_1 = 1.163 ± 0.034 M_☉, R_1 = 2.063 ± 0.058 R_☉) and a G-type dwarf secondary (M_2 = 0.905 ± 0.067 M_☉, R_2 = 0.887 ± 0.037 R_☉). We provide the framework necessary to apply this analysis to much larger data sets.

A fiber feed system for a multiple object Doppler instrument at Sloan Telescope

A fiber feed system has been developed to allow a new generation multiple object Doppler instrument, called the WM Keck Exoplanet Tracker, simultaneously tracking 59 stars for high precision radial velocity measurements for planet detection, and switching among over 500 targets per night. The system includes 27 plug fiber bundles and 3 instrument fiber bundles, and each fiber bundle includes 22 fibers. Individual fibers of a plug fiber bundle are plugged to a plate to receive star lights, and then they are grouped together to form a compact 22-fiber connector. An instrument fiber bundle with a matching fiber bundle connector can connect and disconnect with the plug fiber bundle. The 45 m long instrument fiber bundles deliver the light from the telescope to an environment controlled instrument room in distance. We characterizes the light loses including the position and pointing error of plug connectors, the fiber end reflection, fiber misalignment at the mating connectors, focal ratio degradation and fiber absorption through the long fiber link. All fiber bundles are tested and average total throughput of 61% is achieved.

A New Generation Multi-object High Throughput Doppler Instrument for a Planet Survey at the SDSS Telescope

We report the design of a new generation multi-object high throughput Doppler instrument and first light results at the Sloan Digital Sky Survey (SDSS) telescope. This instrument, capable of simultaneously monitoring 60 stars for planet detection, is called the W.M. Keck Exoplanet Tracker (or Keck ET) thanks to the generous gift from the W.M. Keck Foundation. It is designed for a planet survey around hundreds of thousands of stars with V =8-13 for detecting tens of thousands of planets in 2006-2020. The Doppler precision is between 3-25 m/s depending on the star magnitude. We also report a new planet detected with a prototype single object version ET instrument at the KPNO Coude Feed/2.1 m telescopes. The extrasolar planet, ET-1 (HD 102195b), has a minimum mass of 0.49 Jupiter masses and orbits a V = 8.1 G8V star with a 4.1 day period. The planet was identified using the Coude Feed 0.9 meter telescope in spring 2005. This is the first time an extrasolar planet around a star fainter than V=8 magnitude has been discovered with an under 1 meter size astronomical telescope and Doppler instrument. This planet discovery is possible due to the extremely high throughput of the instrument, 49% measured from the fiber output end to the detector.