Library of high-resolution UES echelle spectra of F, G, K and M field dwarf stars

We present a library of Utrecht echelle spectrograph (UES) observations of a sample of F, G, K and M field dwarf stars covering the spectral range from 4800 AA to 10600 AA with a resolution of 55000. These spectra include some of the spectral lines most widely used as optical and near-infrared indicators of chromospheric activity such as H_beta, Mg I b triplet, Na I D_1, D_2, He I D_3, H_alpha, and Ca II IRT lines, as well as a large number of photospheric lines which can also be affected by chromospheric activity. The spectra have been compiled with the aim of providing a set of standards observed at high-resolution to be used in the application of the spectral subtraction technique to obtain the active-chromosphere contribution to these lines in chromospherically active single and binary stars. This library can also be used for spectral classification purposes. A digital version with all the spectra is available via ftp and the World Wide Web (WWW) in both ASCII and FITS formats.Comment: Latex file with 5 figures using l-aa.sty and psfig.sty. Full postscript (text and figures) available at http://www.ucm.es/OTROS/Astrof/fgkmsl/UESfgkmsl.html Accepted for publication in: Astronomy and Astrophysics Supplement

DNA polymerases required for repair of UV-induced damage in Saccharomyces cerevisiae

The ability of yeast DNA polymerase mutant strains to carry out repair synthesis after UV irradiation was studied by analysis of postirradiation molecular weight changes in cellular DNA. Neither DNA polymerase alpha, delta, epsilon, nor Rev3 single mutants evidenced a defect in repair. A mutant defective in all four of these DNA polymerases, however, showed accumulation of single-strand breaks, indicating defective repair. Pairwise combination of polymerase mutations revealed a repair defect only in DNA polymerase delta and epsilon double mutants. The extent of repair in the double mutant was no greater than that in the quadruple mutant, suggesting that DNA polymerases alpha and Rev3p play very minor, if any, roles. Taken together, the data suggest that DNA polymerases delta and epsilon are both potentially able to perform repair synthesis and that in the absence of one, the other can efficiently substitute. Thus, two of the DNA polymerases involved in DNA replication are also involved in DNA repair, adding to the accumulating evidence that the two processes are coupled

Color identification testing device

Testing device, which determines ability of a technician to identify color-coded electric wires, is superior to standard color blindness tests. It tests speed of wire selection, detects partial color blindness, allows rapid testing, and may be administered by a color blind person

Multiwavelength analysis of the young open cluster NGC 2362

We present a multiwavelength analysis of the young open cluster NGC 2362. UBVRcIc CCD photometric observations, together with available data in the Chandra data base, near infrared data from the Two Micron All Sky Survey (2MASS), and recently published Halpha spectroscopy were used to get information about the evolutionary stage of the cluster and the main physical properties of its stellar content. Cluster membership is estimated for every individual star by means of ZAMS and isochrone fitting. The cluster is confirmed to host a richly populated pre-main sequence (PMS), and to contain a large amount of X-ray emitting stars, which reach from the PMS members of GK spectral type, up to the most luminous OB type main sequence (MS) members. The PMS cluster members show no significant age spread, and the comparison to both PMS and post-MS isochrones suggests a younger age for the more massive MS than for lower mass PMS members. The analysis allows to asses the validity of currently used pre-main sequence evolutionary models, and supports the suggestion of a well defined positive correlation of the X-ray emission from PMS stars with their bolometric luminosity. Clear differences are found on the other hand, between the X-ray activity properties of MS and PMS cluster members, both in the relation between X-ray luminosity and bolometric luminosity, and in spectral properties as well.Comment: 1 gzipped file: 1 tex file with 9 pages text. 5 ps files with figures. Submitted to Astrophysical Journa

Constraints to the Masses of Brown Dwarf Candidates from the Lithium Test

We present intermediate dispersion (0.7-2.2 \AA ~pix$^{-1}$) optical spectroscopic observations aimed at applying the ``Lithium Test'' to a sample of ten brown dwarf candidates located in the general field, two in young open clusters, and two in close binaries. We find evidence for strong Li depletion in all of them, and thus infer lower mass limits of 0.065~M$_\odot$, depending only slightly ($\pm$0.005~M$_\odot$) on the interior models. None of the field brown dwarf candidates in our sample appears to be a very young (age $<$~10$^8$~yr) substellar object. For one of the faintest proper motion Pleiades members known (V=20.7) the Li test implies a mass greater than $\sim$0.08~M$_\odot$, and therefore it is not a brown dwarf. From our spectra we estimate spectral types for some objects and present measurements of Halpha emission strengths and radial velocities. Finally, we compare the positions in the H-R diagram of our sample of brown dwarf candidates with the theoretical region where Li is expected to be preserved (Substellar Lithium Region). We find that certain combinations of temperature calibrations and evolutionary tracks are consistent with the constraints imposed by the observed Li depletion in brown dwarf candidates, while others are not.Comment: 20 pp.; 4 figs, available under request; plain LaTeX, ApJ in press, OACatania-94-00