Astrophysics
The passage from angular to spatial correlations, in the case of spatial clustering length depending on the average distance between nearby objects is studied. We show that, in a number of cases, the scaling law of angular correlation…
In October 1997 daily monitoring observations of the Crab pulsar at 327 MHz and 610 MHz with an 85ft telescope in Green Bank, WV showed a jump in the dispersion by 0.12 cm^{-3} pc. Pulses were seen simultaneously at both old and new…
It is generally believed that cosmological Gamma Ray Bursts (GRBs) are produced by the deceleration of relativistic objects with Lorentz factor (Gamma) >~ 100. We study the possibility that some GRBs are produced along with relativistic…
We present the target selection, observations, and data reduction and analysis process for a program aimed at discovering numerous, weak (equivalent width < 100 mA) Lya absorption lines in the local Universe (0.003 < z < 0.069). The purpose…
We revisited the BeppoSAX observation of SAX J0635+0533, suggested as a possible counterpart to the gamma-ray source 2EG J0635+0521. We have discovered a 33.8 ms pulsation from the source and derived an improved position, consistent with…
We review observational tests for the homogeneity of the Universe on large scales. Redshift and peculiar velocity surveys, radio sources, the X-Ray Background, the Lyman-alpha forest and the Cosmic Microwave Background are used to set…
We derive an expression for the angular power spectrum of cosmic microwave background anisotropies due to gravity waves generated by a stochastic magnetic field and compare the result with current observations; we take into account the…
The redshifts of the gravitational lens galaxies in MG1131+0456 and B1938+666 are 0.844 and 0.881 respectively. Both are early-type galaxies lying at the redshifts predicted by assuming that they are early-type galaxies with old stellar…
A Square Kilometer Array radio telescope will detect tens of thousands of galaxies per square degree in the 21cm emission line of neutral hydrogen. The telescope will be sensitive to ordinary galaxy populations at redshifts z>3 when the…
It may prove useful in cosmology to understand the behavior of the energy distribution in a scalar field that interacts only with gravity and with itself by a pure quartic potential, because if such a field existed it would be…
A combination of Hubble Space Telescope (HST) WFPC2 and NICMOS images are used to investigate the gas/dust and stellar structure inside the central 300 pc of the nearby active galaxy NGC 4303. The NICMOS H-band (F160W) image reveals a…
We consider a network of topological defects which can partly decay into neutrinos, photons, baryons, or Cold Dark Matter. We find that the degree-scale amplitude of the cosmic microwave background (CMB) anisotropies as well as the shape of…
An initially highly biased value of the spatial correlation function, which decreases with time up to a transition redshift z_t ~ 1-2, was predicted theoretically at least as early as 1993, and shown to be consistent with the HDF-N angular…
In this paper, the historical infrared (JHK) data compiled from the published literature are presented here for 30 blazars. Maximum near-IR variations are found and compared with the optical ones. For the color-magnitude relation, some…
Relativistic plasma masers operating on the anomalous cyclotron-Cherenkov resonance and the Cherenkov-drift resonance are capable of explaining the main observational characteristics of pulsar radio emission. Both electromagnetic…
Galaxy clusters are sources of gravitational radiation. The main aim of this paper is to give numerical estimates and theoretical description of the relevant features of the gravitational radiation coming from an appropriate spatial…
We present the first medium-resolution ($R\sim 600$) mid-infrared (8-13.3\micron) spectra of 11 Be stars. A large number of lines are observed and identified in these spectra, including, as an example, 39 hydrogen recombination lines in the…
We present HI data cubes of four low-luminosity early-type galaxies which are currently forming stars. These galaxies have absolute magnitudes in the range M_B=-17.9 to -19.9 (H_o=50 km/s/Mpc). Their HI masses range between a few times 10^8…
The Northern Sky Optical Cluster Survey is a project to create an objective catalog of galaxy clusters over the entire high-galactic-latitude Northern sky, with well understood selection criteria. We use the object catalogs generated from…
The evolution of a system consisting of a protoplanetary disc with two embedded Jupiter sized planets is studied numerically. The disc is assumed to be flat and non-self gravitating, which is modeled by the planar (two-dimensional)…