Search

We use photometric and spectroscopic observations of four detached eclipsing binaries in the globular cluster NGC 3201 to derive masses, radii, and luminosities of the component stars. Spanning across almost three magnitudes in the colour–magnitude diagram, the components offer a unique possibility to test the theory of stellar evolution. Their masses, radii, and luminosities range from 0.66 to 0.84 M⊙, 0.68 to 2.46 R⊙, and 0.38 to 5.56 L⊙, respectively. The distance to the cluster measured from the distance moduli of the component stars amounts to 4.54$^{+0.11}_{-0.14}$ kpc and agrees with the recent estimate based on Gaia parallaxes. By comparing the M − R and M − L diagrams of the component stars and the colour–magnitude diagram of NGC 3201 to Dartmouth model isochrones, we estimate the most probable age of the cluster to be 11.5 ± 0.5 Gyr. This estimate is based on three binaries only, as the fourth one seems to evolve along a different path, probably due to non-standard chemical composition and/or history. We confirm the tendency, observed in earlier CASE papers, for the age indicated by the M − R diagram to be younger than that implied by the colour–magnitude diagram.

We report on the discovery of eleven multimode SX Phoenicis--type blue stragglers in the field of the southern globular cluster NGC 3201. In these variables both radial and non-radial modes are excited. For three variables the derived period ratio is close to that observed in SX Phoenicis itself, suggesting that these stars are pulsating in the fundamental and the first-overtone radial modes. Using the McNamara (1997) period-luminosity relation we have estimated the apparent distance modulus to NGC 3201 to be 14.08$\pm0.06\pm0.1$mag., Comment: 10 pages, requires mn2e.cls,contact the first author at batka@camk.edu.pl for high-resolution figures

ABSTRA C T We report the results of a CCD search for short-period variables in the field of a southern globular cluster NGC 6362. We identified 19 new candidate variables, five of which are cluster RR Lyraes, four are probable SX Phe-type stars and eight are eclipsing binaries. Of the discovered binaries, three are EA-type systems, two of which are located on the cluster CMD in the turn-off region and the third 1 mag above the turn-off point, in the yellow straggler region. Five other systems are of W UMa type, three of which are foreground objects and two are likely cluster members. The remaining two candidates exhibit a modulation of the brightness level with an amplitude of 0.1‐0.2 mag; further observations are needed to reveal the nature of their variability. Phased VI light curves for 20 variables (18 RR Lyrae stars and two blue stragglers) located in the central region of the cluster are presented.

We present CCD BVI photometry for Be 33, a previously unstudied open cluster located toward the Galactic Anticentre. The radial extent of the cluster is about 4 arcmin, and it contains about 285 stars with V < 20.5 mag. Examination of the derived colour-magnitude diagrams shows that Be 33 is a strongly reddened object, with an age slightly lower than the age of the Hyades. Its apparent distance modulus is (m − M) V ≃ 14.7, and its reddening is E(B − V) ≃ 0.6 for an assumed metallicity equal to the solar value. Comparison of the cluster colour-magnitude diagram with isochrones published by Bertelli et al. suggests that in fact Be 33 has a metallicity significantly lower than solar

We report the results of a CCD search for short-period variables in the field of the old open cluster Berkeley 39. Twelve variables were discovered among ≃ 2000 stars with I>20.0. We argue that all or almost all discovered variables are members of Be 39. Eleven variables are contact binaries (W UMa-type systems) with periods ranging from 0.225 to 0.546 d. The twelfth variable is probably an eclipsing binary with a period of the order of 1 d. Four variables are located among the blue stragglers on the cluster colour-magnitude diagram. The distribution of binaries along this diagram (a 5-mag spread) favours the theory that the Berkeley 39 W UMa-type systems have been formed mainly through the mechanism of magnetic braking

A rapid screening method, employing a gas chromatographic technique with electron capture detection, has been developed for t h e analysis of organochlorine pesticide residues in hard red spring wheat. Ground wheat is extracted by ball-milling with an ethyl etherhexane (3 + 97) extractant. After filtration, the extract is cleaned up on a partially deactivated Florisil column, using a single eluting system, ethyl ether-hexane (1 + 99). The eluate i s concentrated before gas chromatographic analysis. Sixteen organochlorine pesticide chemicals were recovered in excess of 80% from wheat samples fortified at 0.010 and 0.200 ppm. Organochlorine pesticide residues were recovered by the rapid method from 18 samples with field-incurred residues as efficiently as by t he Bertuzzi et al. method. Organochlorine pesticide residues were also recovered by t h e rapid method from 4 samples with field-incurred residues and from 2 wheat samples, spiked at 0.500 ppm as efficiently as by the total extraction method of Mumma et al. The rapid method offers a savings in time and solvents over.the Bertuzzi et al. method for the determination of organochlorine pesticide residues in wheat.