Period changes in six semi-detached Algol-type binaries

Six semi-detached Algol-type binaries lacking a period analysis were chosen to test for a presence of a third body. The O-C diagrams of these binaries were analyzed with the least-squares method by using all available times of minima. Also fourteen new minima, obtained from our observations, were included in the present research. The light-time effect was adopted as a main factor for the detailed description of the long-term period changes. Third bodies were found with orbital periods from 46 up to 84 years, and eccentricities from 0.0 to 0.78 for the selected binaries. The mass functions and the minimal masses of such bodies were also calculated.Comment: 14 pages, 8 figure

V2051 Ophiuchi after superoutburst : out-of-plane material and the superhump light source

Aims. We performed a detailed spectroscopic analysis of the dwarf nova V2051 Oph at the end of its 1999 superoutburst. We studied and interpreted the simultaneous behaviour of various emission lines. Methods. We obtained high-resolution echelle spectroscopic data at ESO’s NTT with EMMI, covering the spectral range of 4000–7500 Å. The analysis was performed using standard IRAF tools. The indirect imaging technique of Doppler tomography was applied, in order to map the accretion disc and distinguish between the different emission sources. Results. The spectra are characterised by strong Balmer emission, together with lines of He i and the iron triplet Fe ii 42. All lines are double-peaked, but the blue-to-red peak strength and central absorption depth vary. The primary’s velocity was found to be 84.9 kms−1. The spectrograms of the emission lines reveal the prograde rotation of a disc-like emitting region and, for the Balmer and He i lines, an enhancement of the red-wing during eclipse indicates a bright spot origin. The modulation of the double-peak separation shows a highly asymmetric disc with non-uniform emissivity. This is confirmed by the Doppler maps, which apart from the disc and bright spot emission also indicate an additional region of enhanced emission in the 4th quadrant (+Vx, −Vy), which we associate with the superhump light source. Given the behaviour of the iron triplet and its distinct differences from the rest of the lines, we attribute its existence to an extended gas region above the disc. Its origin can be explained through the fluorescence mechanism

Scattering of 99-MeV 6-Li Ions

This work was supported by National Science Foundation Grant PHY 75-00289 and Indiana Universit

Large-Angle Proton-Nucleus Elastic Scattering

This work was supported by the National Science Foundation Grants NSF PHY 78-22774 A03, NSF PHY 81-14339, and by Indiana Universit

A photometric and spectroscopic study of the cataclysmic variable SX Leonis Minoris in quiescence and superoutburst

We present CCD imaging, CCD photometry on long and short timescales, and time-resolved spectroscopy of SX LMi, a new SU Ursae Majoris type dwarf nova. The quiescent optical spectrum shows broad double-peaked Balmer, He I, and He II emission lines, similar to other quiescent dwarf novae. Absorption lines from a late-type secondary are not detected. Time-resolved spectra obtained in quiescence reveal radial velocity variations of the Balmer emission lines on a period of 0.06717 +/- 0.00011 days, or 96.72 +/- 0.16 minutes, with only a slight possibility of a daily cycle-count error. Optical photometry obtained between 1987 and 1991 shows flickering with a peak-to-peak amplitude of 0.18 mag. The binary orbital period can sometimes be seen in the photometric record. Long-term photometric monitoring for a three-year period between 1992 October and 1995 June shows seven well-defined outbursts and marginally detects a few others. The outburst interval varies between 34 and 64 days. During the 1994 December outburst, optical photometric observations show that SX LMi exhibited superhumps with a period of 0.06893 +/- 0.00012 days, which is 2.6 percent +/- 0.2 percent longer than the orbital period, as expected for a normal SU UMa star at this period. Spectra obtained during superoutburst show dramatic variations in the emission-line profiles on timescales of 10 minutes. Profile fits indicate that underlying absorption contributes to the shape of the Balmer emission-line profiles during superoutburst as in other dwarf novae in outburst or superoutburst. Direct images in good seeing show a ~D19 mag companion star from SX LMi

Optical Model Analysis of Elastic Deuteron Scattering at 80 MeV

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Optical potential for <SUP>6</SUP>Li+<SUP>28</SUP>Si elastic scattering at 154 MeV

The differential cross section angular distribution for 6Li elastic scattering from 28Si was measured at 154 MeV lab energy for center-of-mass angles up to 66&#176;. The data exhibit forward-angle diffractive structure and a large-angle falloff similar to that of refractive nuclear scattering. An optical-model analysis with Woods-Saxon form factors and standard fitting criterion yields a broad continuum of admissible real central potential depths |V|~120-200 MeV rather than the multitude of discrete parameter families encountered at lower bombarding energies. The best fit to the data selects a |V| near 160 MeV. A Woods-Saxon squared form factor as well as a microscopic folding-model potential have also been investigated in fitting the data

The Optical Potential for 99 MeV 6-Li Scattering

This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit

Deuteron Elastic Scattering Cross-Section and Vector Analyzing Power Measurements for 58-Ni and 208-Pb at 79.5 MeV

Supported by the National Science Foundation and Indiana Universit