Hot Stellar Populations in Globular Clusters: a Photometrist's View

We briefly review the recent results on hot horizontal-branch stars in globular clusters. Since the first Ivanfest, in 1992, there have been a number of new observational lines of evidence which have allowed significant progress in our understanding of blue-tail stars, though new, even more intriguing questions arise. Despite this progress, we still do not know the answer to the main question: why are there blue-HB-tail stars? The new photometric data bases collected in the last few years, and the forthcoming multi-fiber observational campaigns on 10m-class telescopes, might be the key to solve this puzzle. We will show an example of how these data bases can disclose important properties of blue HB stars.Comment: 12 pages, 5 figures, A.S.P. Conf. Ser., in press in Vol. 296, 200

Sensitivity to sgoldstino states at the future linear e+e−e^+e^- and photon colliders

Sensitivity to the supersymmetric scalar states $\phi$ at the future linear $e^+e^-$ and photon colliders is discussed. In particular it is illustrated a search strategy for massive sgoldstinos, the supersymmetric partners of the goldstino

The Contributions of Interactive Binary Stars to Double Main Sequence Turn-Offs and Dual Red Clump of Intermediate-Age Star Clusters

Double or extended main-sequence turn-offs (DMSTOs) and dual red clump (RC) were observed in intermediate-age clusters, such as in NGC 1846 and 419. the DMSTOs are interpreted as that the cluster has two distinct stellar popula- tions with differences in age of about 200-300 Myr but with the same metallicity. The dual RC is interpreted as a result of a prolonged star formation. Using a stellar population-synthesis method, we calculated the evolutions of binary-star stellar population (BSP). We found that binary interactions and merging can reproduce the dual RC in the color-magnitude diagrams of an intermediate-age cluster, whereas in actuality only a single population exists. Moreover, the binary interactions can lead to an extended MSTO rather than DMSTOs. However, the rest of main sequence, subgiant branch and first giant branch are hardly spread by the binary interactions. Part of the observed dual RC and extended MSTO may be the results of binary interactions and merger.Comment: 10 pages, 2 figures; accepted by ApJ

Standard Model Higgs search at LEP in channels other than four jets

The LEP centre of mass energy has been increased since 1996 in the aim of producing the Higgs boson. The SM Higgs boson search has been pursued in the four LEP collaborations exploiting final states with higher branching ratios. In the following we discuss the search in final states with two jets and missing energy or charged leptons.Comment: Proceedings of Moriond QCD, 17-24 march 200

Photometric catalog of nearby globular clusters (I)

We present the first part of the first large and homogeneous CCD color-magnitude diagram (CMD) data base, comprising 52 nearby Galactic globular clusters (GGC) imaged in the V and I bands using only two telescopes (one for each hemisphere). The observed clusters represent 75% of the known Galactic globulars with (m-M)v<=16.15 mag, cover most of the globular cluster metallicity range (-2.2 <= [Fe/H] <= -0.4), and span Galactocentric distances from ~1.2 to ~18.5 kpc. In this paper, the CMDs for the 39 GGCs observed in the southern hemisphere are presented. The remaining 13 northern hemisphere clusters of the catalog are presented in a companion paper. For four clusters (NGC 4833, NGC 5986, NGC 6543, and NGC 6638) we present for the first time a CMD from CCD data. The typical CMD spans from the 22nd V magnitude to the tip of the red giant branch. Based on a large number of standard stars, the absolute photometric calibration is reliable to the ~0.02 mag level in both filters. This catalog, because of its homogeneity, is expected to represent a useful data base for the measurement of the main absolute and relative parameters characterizing the CMD of GGCs.Comment: 34 pages, 108 figures, Astronomy & Astrophysics Supplement Series, in press. Full resolution figures can be obtained from the authors upon reques

High resolution kinematics of galactic globular clusters. II. On the significance of velocity dispersion measurements

Small number statistics may heavily affect the structure of the broadening function in integrated spectra of galactic globular cluster centers. As a consequence, it is a priori unknown how closely line broadening measure- ments gauge the intrinsic velocity dispersions at the cores of these stel- lar systems. We have tackled this general problem by means of Monte Carlo simulations. An examination of the mode and the frequency distribution of the measured values of the simulations indicates that the low value measured for the velocity dispersion of M30 (Zaggia etal 1992) is likely a reliable estimate of the velocity dispersion at the center of this cluster. The same methodology applied to the case of M15 suggests that the steep inward rise of the velocity dispersion found by Peterson, Seitzer and Cudworth (1989) is real, although less pronounced. Large-aperture observa- tions are less sensitive to statistical fluctuations, but are unable to detect strong variations in the dispersion wich occur within the aperture itself.Comment: 6 pages, 8 figures upon request, Latex A&A style version 3.0, DAPD-20