Steven S. Vogt

The Population of Weak Mg II Absorbers. I. A Survey of 26 QSO HIRES/Keck Spectra* **

We present a search for weak Mg II absorbers [those with Wr(2796) (2796)=0.02 A and that this is primarily a high-metallicity selection effect ([Z/Z☉] ≥ -1). This implies that Mg II absorbing structures figure prominently as tracers of sub-LLS environments where gas has been processed by stars. We compare the number density of Wr(2796) ≥ 0.02 A absorbers with that of both high and low surface brightness galaxies and find a fiducial absorber size of 35 h-1-63 h-1 kpc, depending upon the assumed galaxy population and their absorption properties. The individual absorbing clouds have Wr(2796) ≤ 0.15 A, and their narrow (often unresolved) line widths imply temperatures of ~25,000 K. We measured Wr(1548) from C IV in Faint Object Spectrograph/Hubble Space Telescope archival spectra and, based upon comparisons with Fe II, found a range of ionization conditions (low, high, and multiphase) in absorbers selected by weak Mg II.

Statistical Properties of Extrasolar Planets

The emerging statistical properties from the first 50 extrasolar planets are startlingly different from the picture that was imagined prior to 1995. About 0.75% of nearby solar type stars harbor jovian planets in 3 to 5 day circular orbits. Another ∽7% of stars have jupiter–mass companions orbiting in eccentric orbits within 3.5 AU. The mass distribution of substellar companions rises abruptly near 5 M Jup and continues increasing down to the detection limit near 1 M Jup -Orbital eccentricities correlate positively with semimajor axes, even for planets beyond the tidal circularization zone within 0.1 AU, distinguishing planets from binary stars. The planet bearing stars are metal–rich relative to both nearby stars and to the Sun. Analogs of Solar System planets have not been detected to date as they require precision of 3 m s −1 maintained for more than a decade.

The automated planet finder at Lick Observatory

By July 2014, the Automated Planet Finder (APF) at Lick Observatory on Mount Hamilton will have completed its first year of operation. This facility combines a modern 2.4m computer-controlled telescope with a flexible development environment that enables efficient use of the Levy Spectrometer for high cadence observations. The Levy provides both sub-meter per second radial velocity precision and high efficiency, with a peak total system throughput of 24%. The modern telescope combined with efficient spectrometer routinely yields over 100 observations of 40 stars in a single night, each of which has velocity errors of 0.7 to 1.4 meters per second, all with typical seeing of < 1 arc second full-width-half-maximum (FWHM). The whole observing process is automated using a common application programming interface (API) for inter-process communication which allows scripting to be done in a variety of languages (Python, Tcl, bash, csh, etc.) The flexibility and ease-of-use of the common API allowed the science teams to be directly involved in the automation of the observing process, ensuring that the facility met their requirements. Since November 2013, the APF has been routinely conducting autonomous observations without human intervention.

Silicon Photodiode Array Detectors For High Resolution Spectroscopy At Lick Observatory

This paper describes the design and performance of two unintensified Reticon photodiode array detectors for high resolution spectroscopy with the Shane 3-meter telescope at Lick Observatory. Reticon arrays of 2 x 936 and 1 x 1872 formats were chosen for the initial installation. The remaining optical and mechanical components of the system were designed to allow easy addition of charge coupled devices (CCDs) as they become available. Detailed descriptions are given of cooling techniques, temperature control, and signal processing electronics which represent major improvements in performance and simplicity of operation over many previous Reticon systems. Both Reticon arrays are in routine operation for high resolution spectroscopy at Lick, and their performance is illustrated by astronomical observations obtained for several on-going research programs.

Achieving autonomous data flow of the Automated Planet Finder (APF)

The Automated Planet Finder (APF) is a dedicated, ground-based precision radial velocity facility located at Lick Observatory, operated by University of California Observatories (UCO), atop Mt. Hamilton in California. The 2.4-m telescope and accompanying high-resolution echelle spectrograph were specifically designed for the purpose of detecting planets in the liquid water habitable zone of low-mass stars. The telescope is operated every night (weather permitting) to achieve meaningful signal-to-noise gains from high cadence observing and to avoid the aliasing problems inherent to planets whose periods are close to the lunar month. To take full advantage of the consistent influx of data it is necessary to analyze each nights results before designing the next evenings target list. To address this requirement, we are in the process of developing a fully automated reduction pipeline that will take each nights data from raw FITS files to final radial velocity values and integrate those values into a master database. The database is then accessed by the publicly available Systemic console, a general-purpose software package for the analysis and combined multiparameter fitting of Doppler radial velocity observations. As each stellar system is updated, Systemic evaluates the probability that a planetary signal is present in the data, and uses this value, along with other considerations such as the stars brightness and chromospheric activity level, to assign it a priority rating for future observations. When the telescope is once again on sky it determines the optimal targets to observe in real time using an in-house dynamic scheduler.

Planetary Messages in the Doppler Residuals

The Doppler residuals to the Keplerian ts for extrasolar planets reveal important properties of the planets and host stars. Stellar magnetic elds modify the photospheric velocity elds, causing Doppler uctuations with unknown time scales. This Doppler jitter, seen prominently in the magnetic stars Epsilon Eridani and Boo A, compromises the detectability of planets. The Doppler residuals during the transit of HD209458 reveal that the planet orbits in the same direction as the star spins. Moreover, the transit path across the star is nearly parallel to the stellar equator. Most interestingly, the Doppler residuals of known planets often reveal additional coherent variations, probably caused by additional companions. Both 55 Cancri and HD168443 reveal such coherent Doppler residuals. Another ve planet{bearing stars observed at Lick show trends in the Doppler residuals indicating the presence of additional companions. Remarkably, about half of the known extrasolar planets reveal such coherent variations. This suggests that stars with planets have a high occurrence rate of harboring more distant companions, planetary or otherwise.