Astrophysics
N-body simulations were conducted of pairs of galaxies with a 3:1 mass ratio on parabolic orbits, in order to quantify the effect of dynamical friction. The effects of varying the ratio of the dark matter halo size to the distance of…
A modification to the absolute magnitude calibration for W~UMa-type systems, taking into account differences in metal abundances, is derived on the basis of contact binary systems recently discovered in metal-poor clusters. A preliminary…
Infrared surveys provide essential insights on galaxy evolution. If near-IR studies suggest mild evolution of stellar populations with cosmic time, indications of a substantial evolution have been seen in the far-IR, although the available…
The present understanding of type Ib/c supernovae and their connection to interacting binaries is reviewed. The problems of the classification and the lack of well-observed events exclude direct inference of progenitor characteristics. The…
Attempts to measure the optical depth due to a diffuse intergalactic medium (IGM) in the spectra of high redshift quasars (GP test) within the ESO key program on the intergalactic medium are reviewed. It is shown that there is no evidence…
Observational constraints on standard CDM spectra and perturbation spectra with broken scale invariance are discussed.
Wray 977, the B supergiant companion of the X-ray pulsar GX301-2, should be classified as B1~Ia+, based on a comparison of its optical spectrum to that of zeta1 Sco, a well-known B hypergiant and ONE OF THE BRIGHTEST STARS IN THE GALAXY.…
Low-mass binary millisecond pulsars (LMBPs) are born with very small orbital eccentricities, typically of order $e_i\sim10^{-6}$--$10^{-3}$. In globular clusters, however, higher eccentricities $e_f\gg e_i$ can be induced by dynamical…
Along with data on radial velocities, more and more data on proper motions of individual stars in globular clusters are becoming available. Their usage was until now rather limited. It was mostly restricted to determining cluster membership…
The status of the Agape experiment to detect Machos in the direction of the andromeda galaxy is presented.
We present the redshift data for a survey of galaxies selected from the data base of the Infrared Astronomical Satellite (IRAS). This survey extends the 1.936 Jy sample of Strauss et al. (1992) from a flux limit of 1.936 Jy at 60 microns to…
We study the distribution of low-redshift Ly$\alpha$ clouds in a CDM model using numerical simulations including photoionization and cooling of the baryonic component. The ionizing background is found to be efficient enough to keep most of…
This is an introduction to accretion disk theory, with emphasis on aspects relevant for X-ray Binaries and Cataclysmic Variables. The text corrects some mistakes in an earlier version, which appeared in 'Lives of Neutron Stars', A. Alpar,…
This paper presents an angular correlation analysis of the Green Bank 4.85 GHz radio catalog (Gregory \& Condon 1991) of 54,579 sources (S \gsim 25 mJy). The Green Bank catalog is found to be complete to S $\geq$ 35 mJy over 20$^{\circ}…
During the course of a gravitational lensing survey of distant, X-ray selected, EMSS clusters of galaxies, we have studied 6 X-ray luminous (Lx > 5x10^44 h_{50}^{-2} erg s^{-1}) clusters at redshifts exceeding z=0.5. All of these clusters…
We present the rotation curves (RCs) of 967 spiral galaxies, obtained by folding and deprojecting the raw optical data by Mathewson et al. (1992). Out of these, we have identified 80 excellent RCs and 820 fair RCs. The 80 excellent RCs are…
Whatever the ultimate energy source of gamma-ray bursts turns out to be, the resulting sequence of physical events is likely to lead to a fairly generic, almost unavoidable scenario: a relativistic fireball that dissipates its energy after…
77 W~UMa-type systems to $I=18$ mag in one of the 21 fields of OGLE have been assessed in terms of utility for extraction of astrophysical information from time-independent data such as colors, periods, maximum magnitudes, and variability…
We have obtained images of the eclipsing pulsar binary PSR~B1957+20 using the Planetary Camera of the Hubble Space Telescope. The high spatial resolution of this instrument has allowed us to separate the pulsar system from a nearby…
The classic question regarding Lyman-alpha forest clouds is whether they are confined by the pressure of a hot, diffuse surrounding medium, or by the gravity of dark matter mini-halos. This paper reviews these basic models for forest…