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New Elements for 80 Eclipsing Binaries IV.
This research presents new elements for 80 eclipsing binaries found withthe help of the ASAS-3, Hipparcos and NSVS databases.
| ASCA Deep Survey in the Lockman Hole Field
We present the results of deep observations of the Lockman Hole fieldwith the ASCA SIS, covering 926 arcmin2 in the 1-7keV energyrange, with a sensitivity 3-5 times deeper than the previous ASCA largerarea surveys. Utilizing the results of the ROSAT Ultra Deep survey, wehave detected 32, 25, and 15 sources in the 1-7, 1-2, and 2-7keV bands,and only 4, 4, and 1 sources remain unidentified, respectively. Theaverage hardness of the sources detected in the 1-7keV band with fluxesof between 10-14 and 10-13erg cm -2s-1 corresponds to a photon index of 1.65 +/- 0.10. Type-2AGNs show significantly harder spectra than type-1s, which can beexplained by absorption column densities of NH simeq1022-23 cm-2 at the source redshifts. Fifteensources are detected in the hard-band (2-7keV), consisting of six type-1AGNs, six type-2 AGNs, one star, one cluster of galaxies, and oneunidentified source. Type-2 AGNs make up a major part of hard X-raypopulations in the 2-7keV band at a flux level of 3 ×10-14 erg cm -2 s-1 (2-7 keV). Theredshift distributions of type-1 and type-2 AGNs suggest a lack of highluminosity (optically-defined) type-2 AGNs with intrinsic NH< 1023 cm-2 , in the redshift range z gtsim 1-2and/or with intrinsic luminosities larger than 3 ×1044erg s-1 (2-10keV at source frame).
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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