BVRI Photometry of the CX Cephei System (WR 151)

We have obtained 699 new BVRI observations of the O5 + WN5 eclipsing binary system CX Cephei (WR 151), plus 126 more observations in V only. Our light curves are consistent with previous studies, showing a primary minimum (where the O5 star is eclipsed) of approximately 0.1 mag depth and a much smaller secondary minimum with an approximately 0.03 mag depth. Using the PHOEBE interface to the Wilson-Devinney computer code, we were able to obtain a reasonably satisfactory fit to these data, ignoring any possible contribution from atmospheric eclipse phenomena. The best-fit solution has i = 61.1° and results in masses of 36.8 M_☉ for the O5 star and 26.4 M_☉ for the Wolf-Rayet (WR) star. The binary system is detached. There is an asymmetry in the light curve, suggesting that the “leading side” of the O5 star (or the trailing side of the WR star) is brighter than vice versa. We also observed some features in the light curve that were persistent, but which we could not model.0 - C residuals relative to the PHOEBE fit reveal time variations with a total range of approximately 12% of the flux. Comparing our data with those of Lipunova & Cherpashchuk (1982), we find that the secondary minimum is less prominent today than it was in the 1980s. We were able to revise their period estimate to 2.12691 days

Distance to U Pegasi by the DDE Algorithm

A distance is found for the W UMa type binary U Pegasi, with a newly modified version of the Wilson-Devinney program (W-D) that makes use of the direct distance estimation (DDE) algorithm. The reported distance of d = 123.6pc is an average based on solutions for B and V data and a primary star temperature of 5800K. Standardized light curves (not differential), radial velocities, and a spectroscopic primary star temperature are input to the pro- gram. Differential corrections were performed for each light curve band along with the velocities for two primary temperatures that span 100K. Log10d is a model parameter like many others that are adjustable in W-D. The eclipsing binary distance agrees with the Hipparcos parallax distance and is more precise.Comment: 2 pages, 1 table, International Conference: Binaries - Key to Comprehension of the Universe, Brno, Czech Republic June 8-12, 200

The V471 Tauri System: A Multi-datatype Probe

V471 Tauri, a white dwarf--red dwarf eclipsing binary in the Hyades, is well known for stimulating development of common envelope theory, whereby novae and other cataclysmic variables form from much wider binaries by catastrophic orbit shrinkage. Our evaluation of a recent imaging search that reported negative results for a much postulated third body shows that the object could have escaped detection or may have actually been seen. The balance of evidence continues to favor a brown dwarf companion about 12 AU from the eclipsing binary. A recently developed algorithm finds unified solutions from three datatypes. New radial velocities (RVs) of the red dwarf and BV RCIC light curves are solved simultaneously along with white dwarf and red dwarf RVs from the literature, uvby data, the MOST mission light curve, and 40 years of eclipse timings. Precision-based weighting is the key to proper information balance among the various datasets. Timewise variation of modeled starspots allows unified solution of multiple data eras. Light curve amplitudes strongly suggest decreasing spottedness from 1976 to about 1980, followed by approximately constant spot coverage from 1981 to 2005. An explanation is proposed for lack of noticeable variation in 1981 light curves, in terms of competition between spot and tidal variations. Photometric spectroscopic distance is estimated. The red dwarf mass comes out larger than normal for a K2V star, and even larger than adopted in several structure and evolution papers. An identified cause for this result is that much improved red dwarf RVs curves now exist

A BVRcIc Survey of W Ursae Majoris Binaries

We report on a BVRcIc survey of field W Ursae Majoris binary stars and present accurate colors for 606 systems that have been observed on at least three photometric nights from a robotic observatory in southern Arizona. Comparison with earlier photometry for a subset of the systems shows good agreement. We investigate two independent methods of determining the interstellar reddening, although both have limitations that can render them less effective than desired. A subset of 101 systems shows good agreement between the two reddening methods.Comment: 10 pages, 6 figures, accepted for publication in A

KOI-142, the King of Transit Variations, is a Pair of Planets near the 2:1 Resonance

The Transit Timing Variations (TTVs) can be used as a diagnostic of gravitational interactions between planets in a multi-planet system. Many Kepler Objects of Interest (KOIs) exhibit significant TTVs, but KOI-142.01 stands out among them with an unrivaled, 12-hour TTV amplitude. Here we report a thorough analysis of KOI-142.01's transits. We discover periodic Transit Duration Variations (TDVs) of KOI-142.01 that are nearly in phase with the observed TTVs. We show that KOI-142.01's TTVs and TDVs uniquely detect a non-transiting companion with a mass 0.7 that of Jupiter (KOI-142c). KOI-142.01's mass inferred from the transit variations is consistent with the measured transit depth, suggesting a Neptune class planet (KOI-142b). The orbital period ratio P_c/P_b=2.03 indicates that the two planets are just wide of the 2:1 resonance. The present dynamics of this system, characterized here in detail, can be used to test various formation theories that have been proposed to explain the near-resonant pairs of exoplanets

Observational Studies of Early-type Binary Stars: MP Centauri

We present photometric and spectroscopic data on the early-type binary MP Centauri. The photometric data are analyzed simultaneously with radial velocities to derive preliminary absolute dimensions for the binary components. Analysis of the spectra shows that the stars rotate synchronously and that the line of sight to the system crosses two kinematically sharp and well-separated interstellar reddening sources. It is shown that MP Cen consists of a B3 primary with M_1 = 11.4 +/- 0.4 M_sun, R_1 = 7.7 +/- 0.1 R_sun and a lobe-filling B6-B7 secondary with M_2 = 4.4 +/- 0.2 M_sun, R_2 = 6.6 +/- 0.1 R_sunComment: Accepted for publication in the MNRA

The Ultraviolet Follow-On Observatory (UFO)

Prime Solutions Group, Inc. (PSG) in partnerships with Southwest Research Institute (SwRI), the University of Colorado at Boulder, the University of Illinois, and the Astronomy Association of Arizona (AAA) are proposing the development, launch and operation of a 12U CubeSat mission for stellar astronomy. The stellar observatory mission will consist of a space-based UV/optical telescope system designated as the Ultraviolet Follow-on Observatory (UFO). This proposed CubeSat will be a 12U system housing a 250mm telescope and designed for a four-year plus mission timeline in high Earth orbit. A camera capturing simultaneous UV/optical observations will first be developed and tested on a ground-based telescope before being designed and integrated into the CubeSat. UFO will follow in the footsteps of the successful launch and operation of the Colorado Ultraviolet Transit Experiment (CUTE) and the planned launch of the Star-Planet Activity Research CubeSat (SPARCS) which are paving the way for this new era in CubeSat space-based astronomy. The operation of UFO (240nm to 390nm (UVC, UVB, UVA)) will expand on these missions. This will demonstrate that small telescope observations in the ultraviolet frequency can provide valuable data to the astronomical science community and will help fill a critical need in the observational ultraviolet astronomy gap until NASA’s Large UV/Optical/IR Surveyor (LUVOIR) mission launches in the early 2040s timeframe