Paul B. Etzel

New rotational velocities for eclipsing binaries, and a comparison of spectroscopic and photometric rotations

Rotational velocities are determined spectroscopically for 38 eclipsing binaries, including many long-period, nominally semidetached, systems. We note that spectroscopic rotations may differ from rotations derived from light-curve modeling using the Wilson-Devinney program. In direct-impact mass-transferring systems, or in most systems with periods smaller than about 7 days, observations suggest that the two rotations are usually about the same. In cases where the stream misses the gainer and an accretion disk forms, however, photometric rotation estimates often exceed spectroscopic determinations. The possible physical significance of this situation is briefly discussed. Doubt is cast on the likelihood that the rotation of the hot component of U Sge has changed detectably in the last 30 years

Basic stellar parameter determination for active cool eclipsing binaries

We examine procedures for the determination of reliable parameter sets characterizing stars in short period eclipsing binary systems of later dwarf, generally sunlike, spectral types. These stars have magnetodynamically active components and form a useful “extension to the solar laboratory”. Their much more rapid rotation than that of the Sun implies correspondingly enhanced indications of activity-particularly with relatively large maculation effects in broadband data.We concentrate on five such systems, for which we discuss new data and analyses-CG Cyg, ER Vul, YY Gem, BH Vir and UV Psc. Our main aim is to enable more reliable absolute comparisons between the basic properties of such stars and the Sun. Some indications of the ages of these binaries can also provide further pointers to the relative importance of different parameters (e.g. rotation, age, etc.), in determining stellar activity.

Cool-star photometric activity in six totally-eclipsing Algol binaries

We summarize results of an intermediate-band five-color photometric program that monitored the cool subgiant stars in six totally-eclipsing Algol binaries for intervals of 7 to 14 years. Brightness changes occurred in all of these stars, whose orbital periods range from 0.97 to 9.48 days. Analysis of conspicuous variations in RW Tau shows that they are consistent with changes in total area (or temperature) of cool star spots. These brightness fluctuations grow with increasing rotational velocity or decreasing orbital period, suggesting that rotationally-induced magnetic activity may be responsible for these variations

Final assembly of the ULTRA 1-m carbon fiber optical telescope

Presented is a poster presentation relating to the final assembly and testing of the Ultra Lightweight Telescope for Research in Astronomy, ULTRA [1]. The program is a 3-year Major Research Instrumentation (MRI) program funded by NSF. Objectives are to demonstrate carbon fiber reinforced plastic (CFRP) composite mirrors for ground-based optical telescopes. Presented will be final assembly of the telescope including the unique features of the system including the 27 kg primary mirror, hexapod secondary mirror control, motorized iris for the primary mirror cover. Also presented are results of the optical testing of the 0.4m mirrors used as developmental optics in the program.

Mass Transfer Variations in UX Monocerotis: Eight Years of Automated Photometric Monitoring

We analyze eight years (1999-2007) of automated photometric observations of the active Algol binary UX Monocerotis to search for mass transfer bursts similar to those seen in U Cephei. The largest photometric anomaly is the mean gainer luminosity difference between the stream-impact hemisphere and the opposite hemisphere. We find an updated Wilson-Devinney solution for earlier six-color observations. The UX Mon donor star fills its Roche lobe and the gainer nearly fills its rotational lobe. Instead of isolated bursts of the U Cep type, we found nearly continuous brightness fluctuations likely produced by variable mass transfer. We discuss implications for mass transfer.

WW Andromedae: photometric and spectroscopic solutions for a peculiar eclipsing binary

We present and analyze intermediate-band uvbyI (Kron) photometry and CCD spectroscopy of the poorly known long-period system WW And. Early visual photometry suggested a totally eclipsing geometry, while our new data clearly show shallower partial eclipses. Double-peaked Hα emission is prominent at all orbital phases and times, indicating the presence of a permanent accretion disk around the hotter mass-gaining star. Photometric and radial-velocity solutions with the new Wilson code yield estimates of absolute system parameters. These simultaneous multicolor photometric solutions suggest that the cool star does not quite fill its Roche lobe, and that mass transfer in this binary probably occurs by some mechanism other than lobe overflow. WW And may share with RW Per a historical trend of gradually decreasing primary eclipse depth

Current Status of the EBOP Code

The efficient light-curve synthesis computer code EBOP is described. The model is purposely tied to light-curve defmed parameters rather than “astrophysical” ones. The major applications of the model during the past 10 years have been to well-detached eclipsing systems where proximity effects are minimal. Such systems provide well-defined stellar parameters because of their simplicity. Astrophysical parameters can be inferred from empirically calibrated surface fluxes and standardized colors of the components. Improvements to the code have been implemented and others are planned, largely as a result of continued use and suggestions by the astronomical community.

Progress in the ULTRA 1-m ground-based telescope

We present the technical status of the Ultra Lightweight Telescope for Research in Astronomy (ULTRA) program. The program is a 3-year Major Research Instrumentation (MRI) program funded by NSF. The MRI is a collaborative effort involving Composite Mirror Applications, Inc. (CMA), University of Kansas, San Diego State University and Dartmouth College. Objectives are to demonstrate the feasibility of carbon fiber reinforced plastic (CFRP) composite mirror technology for ground-based optical telescopes. CMA is spearheading the development of surface replication techniques to produce the optics, fabricating the 1m glass mandrel, and constructing the optical tube assembly (OTA). Presented will be an overview and status of the 1-m mandrel fabrication, optics development, telescope design and CFRP telescope fabrication by CMA for the ULTRA Telescope.

S Cancri: new multicolor photometric observations and solutions, and spectroscopic observations

We discuss new intermediate-band photometric and spectroscopic observations of the totally eclipsing binary system S Cancri, and new photometric solutions using the 1992 version of the Wilson-Devinney code, updated with modern stellar atmospheres subroutines. We demonstrate that this aged Algol is probably now a detached system, helping to explain its relative inactivity. The effect of a thin extended atmosphere around the cool star is evident in ultraviolet solutions. We also present spectroscopic evidence of this extended atmosphere. A lack of photometric complications at longer wavelengths make S Cnc a prime candidate for a more precise determination of its fundamental stellar properties

New six-color intermediate-band photometry and photometric solutions for U Cephei

We describe new six-color intermediate-band photometric observations of U Cephei, obtained during an interval of consistently low mass-transfer activity. We use the new Wilson eclipsing binary computer program to obtain several photometric solutions, which incorporate the rapid rotation of the hot star. Residual trends for solutions using all observations show the absorbing effect of the stream between phases 0.7 and 0.96. A second set of solutions, omitting data in this phase range, leads to more satisfactory results. Our photometric mass ratio is somewhat smaller than the spectroscopic values found by both Batten and Tomkin. Differences between our solutions and those of Rafert and Markworth are probably due to residual contamination of light curves by circumstellar matter